School Science Lessons Animal physiology
2011-01-31 SP
Please send comments to: J.Elfick@uq.edu.au Table of contents 9.45.7 Body temperature, diurnal variation 9.5.1 Ear and hearing, balance 9.5.2 Eyes and sight 4.2.11 Glycemic index (GI) 9.5.3 Nose and smelling, taste, flavour 9.4.0 Respiration, aerobic respiration 9.242.0 Respiration, (EAR) and (CPR) 9.5.7 Respiration, humans 9.5.8 Respiration, small animals and plants 6.14 Shakir strip, (Test for malnourished child) 9.5.4 Touch and feeling 9.5.10 Urine tests 9.5.5 Voice and speaking
9.4.0 Respiration, aerobic
respiration 5.17 Body temperature (Primary) 9.239.1 Breath, simulated diaphragm breathing 9.241 Breath volume 5.15 Breathing in and out (Primary) 3.37 Carbon dioxide and respiration 9.238 Elimination of wastes when we breathe 5.18 Feel your pulse (Primary) 4.2.1 Feel your pulse, Human pulse rate,
recording and averaging 20.0.9 Henry's law and decompression
sickness, the bends 9.239.2 Hiccups 4.20 Measure chest expansion (Primary) 9.240 Measure oxygen absorbed in the lungs 4.240 Model lungs 4.229.1 Mountain sickness and hyperventilation 9.237 Oxygen content of inhaled and exhaled air 9.5.7 Respiration, humans 8.6.5 Respiration is a form of combustion 9.10.0 Respiration of organisms 9.239 Respiration rate of humans, respiratory rate
and heart ate 4.244 Scuba diving and Boyle's law 9.239.1 Simulated diaphragm breathing 6.16 Volume of air breathed out (Primary) 9.242.0 Respiration, (EAR)
and (CPR) 9.242.3 Cardiopulmonary resuscitation (CPR),
Adult 9.242.4 Cardiopulmonary resuscitation (CPR),
Child (aged 1-8) 9.242.5 Cardiopulmonary resuscitation (CPR),
Infant (under 1 year) 9.242.1 Expired air resuscitation (EAR), Adult 9.242.2 Expired air resuscitation (EAR), Infant
(under 1 year), and Child (aged 1 to 8) 9.5.1 Ear and hearing, balance 26.6.3 Binaural hearing 9.247 Direction of sound heard 26.6.4 Direction of sound, direction judgement
of the ear 4.101 Ear and hearing 1.16 Hearing sounds game (Primary) 26.6.2 Human ear, how the ear works, model of the
ear 26.6.5 Range of hearing 9.5.2 Eyes and sight See pdf: Anaglyphic 3D Glasses 28.12.5 Astigmatism 28.12.3 Blind spot 28.12.7 Chromatic aberration of the eye 28.12.18 Colour blindness 9.248 Distance of object seen 5.2 Eye damage, Serious eye damage
/ eye irritation 28.12.0 Eye, structure and physiology 28.12.6 Eyeglasses 9.250 Examine your eyes 5.19 Eyesight test (Primary) 28.12.10 Fluorescence of retina 6.15 How far you can see (Primary) 28.12.4 Inversion of image on the retina 28.12.11 Jarring the eye 28.12.13 Mach disc 28.12.14 Most sensitive to green light 2.17 Move your eyes (Primary) 9.254 Optical illusions 28.12.8 Resolving power of the eye 28.12.9 Retinal fatigue colour 28.1.1.1 Stroboscope 28.12.12 Subjectivity of colours 28.12.16 Square that isn't there 28.12.2 Water flask model of the eye 9.5.3 Nose and smelling, taste,
flavour 9.245 Sense of smell, the olfactory system 9.246 Sense of taste, the gustatory system 2.18 Smelling game (Primary) 19.4 2 5 Sweeteners phenylalanine
and aspartame 19.4.2.4 Sweetness, relative sweetness
of some artificial sweeteners 19.3.1 Taste, smell, flavour 9.5.4 Touch and feeling 1.18 Feelie bag game (Primary) 9.244 Sense of feeling temperature 9.243 Sense of touch 1.17 Touch and feel game (Primary) 9.219 Women feel colder then men 9.5.5 Voice and speaking 4.102 Voice and speaking 26.6.0 Ear, voice, hearing, voice, audible limits 26.6.14 How the voice is produced, music perception
and the voice 26.6.15 Sing and whistle octaves 4.2.11 Glycemic index (GI)
Glycemia refers to the rise in blood sugar. GI is a ranking of carbohydrates
in food depending on their immediate effects on blood sugar levels. Carbohydrates
that breakdown rapidly during digestion and release glucose quickly into
the blood have a high GI Carbohydrates with a low GI are called "smart
carbs". Low GI diets help people with type 1 and type 2 diabetes, pregnancy
diabetes, overweight, excess abdominal fat, too high blood glucose levels,
high levels of triglycerides and low levels of HDL cholesterol ("good cholesterol").
GI values: high GI = 70+, medium GI = 59-69, low GI = <55. Glycemic
load = GI X grams of carbohydrate per nominal serving size / 100, e.g.
apple GI = 40, GL = (40 X15) / 100 g = 6, potato GI = 90 GL = (90 X 20) /
100 = 18. 4.101 Ear and hearing See 4.244 Scuba diving and Boyle's
law, overexpansion syndrome See diagram 26.197: Vertical section of human
ear
1. Eardrum, 2. Incus, stapes, malleus, 3. Auditory nerve, 4. ear canal,
5. Middle ear, 6. Inner ear, circulatory canals, cochlea, 7. Eustachian tube
1. A sound wave is a longitudinal wave so it consists of alternating
compression and rarefaction, i.e. particles closer together and farther
apart. A sound wave can pass through the ear canal of the outer ear to reach
the sensitive eardrum, tympanic membrane, and causing it vibrate at the same
frequency. The eardrum is attached to the bones of the middle ear, the ossicles.
The hammer (malleus) connects the eardrum to the anvil (incus) that connects
to the stirrup (stapes) that connects to the oval window of the middle ear.
These bones transmit vibration from the eardrum to fluid in the cochlea, the
portion of the inner ear responsible for hearing. It looks like a snail's
shell. These vibrations in the inner ear cause nerve impulses to be transmitted
to the brain by the auditory nerve. The bones of the skull can also transmit
vibrations. You hear a sound if the waves reach the cochlea by either route.
When a sound reaches your two ears, you can distinguish the direction from
which it comes. If it comes from straight ahead, the vibrations reach both
ears simultaneously and with the same strength. However, if the source of
sound is on one side, one ear is farther away from it and receives the sound
waves less strongly and with a slight delay. The eardrum must be protected.
A perforated eardrum can lead to serious infection. Never use a bobby pin
or cotton buds to clean the ear. When the ear canal gets blocked with wax,
treat it with medical ear drops. Do not hit anyone on the ear! The eardrum
can become perforated if the outer ear is hit with the open palm of the hand
2. Besides the cochlea, the inner ear also contains three small semicircular
canals to maintain balance. Movement of fluid in the semicircular canals
sends messages to the brain about the speed of rotation of the head and
the direction of movement of the head, e.g. nodding or looking behind. Spinning
the whole body causes giddiness, vertigo. To experience extreme vertigo,
mark a cross on the floor, bend the body at right angles, rotate the body
with one eye looking down at the cross. Be careful! This movement may cause
nausea.
3. The Eustachian tube extends from the middle ear to the nasopharynx.
Usually it is closed. It can open to let air pass and equalize the pressure
between the middle ear and the atmosphere, causing a small "pop" sound.
This happens during change of height in an aircraft or during mountain travel.
People, and especially babies, with eustachian tubes blocked with mucus experience
pain when an aircraft changes height. To balance the pressure in the middle
ear with the outside pressure, hold the nose shut and blow softly or blow
the nose or chew chewing gum . During flight, the air pressure in a commercial
aircraft is usually regulated to the pressure at 2000 metres above ground.
4. In the ear, the three circular canals filled with fluid are set at
angles to each other such that any movement of the head sets off nervous
impulses according to different combinations of sensation from them to
allow the brain to interpret the signals and maintain balance. This action
is similar to the way a gyroscope can keeps a forward motion in a constant
direction.
5. Earwax that lubricates the ear canal is a mixture of cerumen, skin
cells, bits of hairs and substances caught in the wax. Cerumen is a secretion
produced by the sebaceous glands in the outer ear canal. Cerumen may be
"dry" or "wet", with Asians having dry cerumen and Europeans having wet
cerumen. The colour of cerumen may vary from grey (dry) to light brown (wet).
With age, wet cerumen darkens and becomes less liquid. 4.102 Voice and speaking See diagram 26.198: Voice
1. vocal cords, 2. epiglottis, 3. during ordinary breathing, 4. during
speaking, 5. larynx
Mouth, teeth, tongue, throat and lungs are all used in the production
of the voice. The sound is produced by vibrations of two thin sheets of
membrane, the vocal cords, stretched across the sound chamber, the larynx.
The larynx is the upper end of the windpipe and is near the base of the
tongue. A trapdoor of cartilage, the epiglottis, automatically drops down
over the larynx when you swallow, so that no food can enter the windpipe.
When the vocal cords are stretched by the contraction of certain muscles
in the throat, a narrow slit forms between them. It is when the air is forced
through this narrow slit that the cords are forced to vibrate. This sets
the air vibrating in the windpipe, lungs, mouth and nasal cavities. 5.19 Eyesight test See diagram: 28.1.1.6: Eyesight test
Be able to test your eyesight.
This lesson is designed to give children experience in measuring eyesight
and comparing the eyesight of different children. It is different from the
eyesight test used by doctors. Use the "E" chart over the page. Cut out a
big "E" from a piece of cardboard or tell the children to cut out the big
"E" during the lesson or the children can make an "E" shape with their fingers.
1. Draw a line on the floor five metres from the teacher's chair and parallel
to the front of the teacher's desk. Stand on the line facing you. Show the
chart. Point to the top E. The child has to hold the E in the same position
or make the same E shape with the hand.
2. What is the lowest line in the chart where the child can see the
positions of the E? If you can see the bottom line, you should move one
metre away and start again. If you can't see the bottom line, you should
move one metre closer.
3. Test all the children again. Which child has the best eyesight?
4. Do the test again with one eye closed, then test the other eye. Is
one eye stronger than the other?
Extra Activity: Draw a chart of white E's on a black background. Are they
easier to see or harder to see than the black E's? 6.14 Shakir strip, (Test for
malnourished child) See diagram 9.236: Shakir strip See 15.05: Electrolytes in the blood
and urine
Be able to discover malnourished small children by measuring their arms
with the Shakir strip.
Use The Shakir strip.
People who do not have enough food or do not have the correct amounts
of energy food, growth food, and healthy food are said to be malnourished.
Malnourishment of young children, especially after weaning, can be very
dangerous. They may get sick and die or they cannot learn much when they
go to school. It is not easy to tell whether a child is really undernourished
or has a temporary sickness. This problem has been solved by the Shakir
strip used in many countries. When babies are about one year old, they have
much fat under the skin of their arms. When you are five, this fat is not
there but there is much more muscle. This means that the circumference of
the upper arm is almost the same between the ages of one and five. If you
measure the middle of the upper arm of children between the ages of one and
five, you can find the malnourished children. Instead of a tape measure you
can use a piece of string or a strip of material that does not stretch, e.g.
old x-ray film.
1.1 Children between the ages of one and five should not be malnourished
otherwise they may get sick and die. Malnourished children may not learn
much when they grow up.
1.2 Doctors have found a way to tell if children are malnourished by
using a marked tape called the Shakir strip. It is one cm wide. The circumference
of the upper arm is as follows:
Shakir Strip
Circumference of Upper Arm
Colour Zone
Health of Child
Greater than 135 cm
green zone
Healthy child, not malnourished
Between 125 and 135 cm
yellow zone
Child probably malnourished
Less than 125 cm
red zone
Child certainly malnourished
1.3 Cut a strip of paper the length of the page and one cm wide. At six
cm from one end mark 0 cm. Then mark it at 12. 5 and 13. 5 cm. Colour 0 to
12. 5 cm red, 12. 5 to 13. 5 cm yellow and more than 13. 5 cm green. Give
the children a cardboard toilet roll centre or a thin tube to measure. Are
they correct?
1.4 Take the Shakir strip home and measure the arms of all the children
with age one to five years. If you find any children in the yellow or red
measurement, you should tell the teacher the next day.
Extra Activity: Why may recently weaned children or animals be malnourished?
[There is no suitable food for them or mothers do not prepare proper food.]
Do a class or community experiment on this for one to five year old
children and then record a graph to compare malnutrition rates.
2.1 Be able to take care of younger children with diarrhoea by replacing
water lost because of dehydration.
(in many areas, diarrhoea is the most common cause of death in small
children, and is specially frequent in babies between six months and two
years. It is more common and dangerous in children who are malnourished.
Bottle fed babies have diarrhoea more often than breast fed babies. Diarrhoea
can be prevented by: breast feeding babies for as long as possible, good
nutrition and cleanliness. If you are a good teacher, you can teach your
children how to care for younger children with diarrhoea. Use sugar, salt,
water, spoons, cups.
2.2 How to give the drink, coconut water or "special drink": Start giving
the drink when diarrhoea begins. A child should drink for each time a stool
is passed. If the child vomits up the drink, keep giving more. A little of
it will stay in the stomach. Give it in sips every two or three minutes. If
the child does not want to drink, gently insist that the child tries to drink
something. Keep giving the drink every two or three minutes, day and night
until the child urinates normally, every two or three hours. Older children
and their mother can take turns through the night.
Warning signs: Take the child with diarrhoea to the Health Centre if
the child shows any signs of dehydration, cannot drink or will not drink,
makes no urine for six hours, has diarrhoea too often so cannot drink one
glass per stool, has blood in the stool, diarrhoea lasts more than two days.
2.3 Diarrhoea means frequent watery stools. Often children with diarrhoea
also have vomited and have a swollen belly with cramps. The stools smell
different from normal stools (toilet).
2.4 Children die of diarrhoea usually because their bodies lose too
much water. This loss of water is called dehydration. All living things
contain much water. For example, if you bring two cut plants to school,
and put one in water and the other not, you will see that one will wilt.
A baby with diarrhoea loses water like the wilted plant.
2.5 Signs of dehydration: 5.1 almost no urine that is dark yellow, 5.2
dry mouth, 5.3 sunken tearless eyes, 5.4 sunken soft spot (fontanelle) on
top of baby's head, 5.5 skin loses its stretching. If you lift up the skin
and you can still see the fold after you let go, the child is dehydrated.
2.6 The most important part of treatment is to replace the water lost
through diarrhoea and vomiting. Medicines are often not very effective but
coconut water puts water back into the child. Also children with diarrhoea
must be given food, if they can take it, to help their bodies fight the
sickness. 5. The Special Drink: Make the Special Drink from sugar, salt
and water. Mix: sugar + salt + water. Use one level teaspoon of sugar and
add a little salt at the end of the spoon in one glass of water. Before
giving the drink taste it, it should be no more salty then tears. Let the
children make the Special Drink and taste it.
Extra Activity: Visit a Health Centre to see how children are treated
for diarrhoea and dehydration. 6.15 How far you can see
Be able to test their eyes to find out if they can see things near and
far.
Use Various objects, e.g. books, windows, trees
In the human eye the distance between the lens and the screen [the retina.]
remains the same whether you try to see things near or far. What changes is
the shape of the lens controlled by muscles in your eye.
1. Look outside the classroom at something far away. Hold up one finger
20 cm in front of your eyes but keep looking at the distant object. Can you
see the distant object clearly? [Yes.] Can you see your finger clearly? [Not
at first.] Can you feel any movement in your eyes? [Yes.] Is the distant object
clear now that the finger is clear? [If you keep looking at your finger then
the distant object will not be clear.]
2. Hold a printed page at arms length. Bring the book closer and closer
until it is just too close to read the letters. Measure the distance from
the book to the eyes with a ruler and record it in your notebook. Move the
book away from the eyes until it is just too far to read the letters. Measure
the distance and record.
3. Compare the distance recorded with other children. Are they all the
same? [No, the answers should vary.]
4. Judging distance game
One child of each pair puts a hand over one eye. The other child holds
up one finger about 40 cm in front of the partner's eyes. The child with one
eye covered has to place the tip of one fingers on top of the finger that
the partner is holding up. [This is difficult to do because you need both
eyes to judge distances.] Uncover your eyes and try again. [It should be
easy for them with both eyes open.] Partners swap places and repeat the activity.
What conclusion? [We need both eyes to judge distance correctly.]
9.5.7 Respiration, humans See 12.3.0: Properties of acids
H2O (l) <--> H+ (aq) + OH- (aq)
2H+ (aq) + CO32- (aq) <--> H2CO3
(aq) carbonic acid
CO2 + H2O <--> H3O+
+ HCO3-
HCO3- + H2O <--> H3O+
+ CO32-
Add one drop of sodium carbonate solution, Na2CO3.10H2O,
to a test-tube full of water. Shake the test-tube then pour out the contents
leaving 2 cm depth. Add one drop of phenolphthalein solution. The solution
in the test-tube turns red. Blow through a straw or glass tube into the
solution in the test-tube. The red colour disappears because the carbon dioxide
gas in the breath has formed carbonic acid in water and neutralized the sodium
carbonate solution. 9.5.8 Respiration,
small animals and plants See diagram 9.155: Respiration of soaked peas
| See diagram 9.3.61: Respiration of grasshopper
1. Attach a 50 cm3 syringe to a 1 cm3 pipette, as
in the diagram. The sodium hydroxide solution absorbs carbon dioxide released
during respiration. Change in air pressure inside the syringe is caused
by the consumption of oxygen by the organism and is shown by change of the
water level in the pipette. The rise in the water level per unit time indicates
the rate of respiration of the organism. A steady drop of the liquid level
in the pipette indicates a leak in the apparatus. When testing green plants,
cover the syringe with aluminium foil to exclude light. When the meniscus
reaches the upper part of the pipette, move it down again by adjusting
the position of the plunger. To correct for changes in air volume inside
the syringe because of change in room temperature during the experiment,
use a control identical to the experiment except for the organism. Then any
difference between the readings of the two sets of apparatus is because of
respiration of the organism.
2. Put a grasshopper in a closed jar containing absorbent paper soaked
in 0.5% potassium hydroxide solution. Use a two-holes stopper with a fine
bore glass tube and graph paper or ruler behind it to measure the movement
of a drop of coloured water through the tube. Keep the organism off the absorbent
paper by adding crumpled paper or tying the moist paper on a string attached
to a drawing pin stuck in the underside of the stopper. The grasshopper
breathes in oxygen and breathes out carbon dioxide absorbed by the potassium
hydroxide solution causing the coloured drop to move. Record the movement
of the coloured drop at regular intervals. Observe the distribution and
movement of spiracles on the grasshopper. 9.5.10 Urine tests See 19.1.20.4: Prepare artificial
urine sample
If testing human urine, the medical interpretation can only be done
by an experienced medical practitioner. Some school systems do not allow
use of human urine in a school laboratory.
1. Quantity
700 to 2 500 mL per day
Less: during the night, after small intake of food or drink, after sweating
on a hot day, after diarrhoea decreases salts and water in the body, vomiting,
fever, kidney diseases, obstruction in urinary tract.
More: during the day, after large intake of food or drink, on a cold
day, after kidney failure. 2. Colour and odour
Urine has a yellow-amber colour and is clear and transparent when first
voided but the colour darkens on standing, caused by oxidation of colourless
urobilinogen to coloured urobilin. Red-brown colour caused by urochrome
and uroerythrin pigments. Colour may be changed by eating beetroot (red),
rhubarb (orange tint), tetracyclines (yellow), methylene blue (green), some
bacterial infections (green tint), vitamin B tablets (vivid yellow). Clouded
urine caused by some bacterial infections and possibly some foods.
Transparent at body temperature but may precipitate ureates when cooled.
Pus, bacteria and phosphates may cause cloudiness. 3. Odour
Aromatic odour but distinct odour if asparagus is consumed, and an acetone
odour if diabetic ketoacidosis (fatty acids breaking down to form ketone bodies). 4. Specific gravity (relative density)
Usually 1.003 to 1.030. Lower if excessive drinking of water, diabetes
insipidus, renal failure. Higher if dehydration, heart failure, high level
of glucose (glycosuria). Freezing point can be used to measure concentration
of solute particles per unit of solvent. The highest concentration occurs
in the first urine passed on rising in the morning. 5. pH
Usually acid, pH 4.5 to 8. 6. Protein
Normally < 100 mg/24 hours. Less protein after exercise, inflammation,
kidney infection. Tests for protein with Albustix commercial reagent strip
16.6.8
7. Tests for protein with the boiling test
If urine sample is alkaline use litmus paper and add drops of 10% acetic
acid until urine is pH 5. Hold test-tube at an angle and heat the top of
the solution to boiling then view against a dark background. Cloudy solution
shows presence of of protein or phosphates because urine is more alkaline
after boiling because of loss of carbon dioxide. Add 10% acetic acid, if
precipitate disappears cloudiness caused by phosphates, if precipitate stays
cloudiness caused by proteins. 8. Glucose
Should be none but present if diabetes mellitus or excess corticosteroid
hormones (Cushing's disease)
Tests for sugar, Benedict's tests for reducing sugars 9.141
Tests for glucose 19.1.20.4
Tests for glucose and starch with "Testape" 9.182
Should be no ketones.
9.45.7 Body temperature,
diurnal variation
Body temperature is an example of a circadian rhythm, regular cyclic
activity about 24 hours long and the regulator of the sleep wake cycle.
In a healthy person average temperature for healthy adults is 36.3°C to 37.1°C
for males, 36.5°C to 37.3°C for females, with the highest temperatures between
6.00 a.m. and 6.00 p.m. and lowest temperatures between 2.00 a.m. and 6.00
a.m. An oral temperature between 35.9°C and 37.5°C is usually considered
normal. Body temperature is sensitive to hormone level in the female. Blood
vessels in the skin expand to carry the excess heat to the skin surface.
Also, evaporating sweat cools the body as sweat absorbs the heat of vaporization.
Blood vessels in the skin contract to reduce loss of heat. Also, involuntary
shivering, contraction of the muscles, generates more heat. A rectal or
ear temperature is 0.3°C to 0.6°C higher than an oral temperature reading.
An armpit temperature is 0.3°C to 0.6°C lower than an oral temperature reading.
The forehead temperature is the same temperature as the arterial blood supply
under the skin. It is said to be more accurate that ear temperature because
the position of the probe in the ear canal in sequential readings is usually
inconsistent. The forehead thermometer scans the forehead area for the temporal
artery by positioning the probe flush on the centre of the forehead, midway
between the eyebrow and the hairline. Fever is present if rectum temperature
or ear temperature > 38.0°C, mouth temperature > 37.5°C, under the
arm > 37.2°C.
A lady on a diet finds that after eating her body temperature drops and
she feels very cold. She probably experiences what doctors call a post-prandial
effect to a rush of blood to the stomach leaving the skin feeling cool
as blood carrying body heat is shunted away from below the skin. So she should
eat her meals slowly. Similarly, she should not go swimming straight after
consuming a heavy meal because the skeletal muscles may be starved of enough
oxygen for rapid contraction to cause cramps and death by drowning.
1. Measure the temperature under your tongue every hour and draw a graph
of the results.
2. Note the changes in your body at high ambient temperature
2.1 Capillaries in the skin swell (vasodilation) to release more heat.
2.2 The arrector pili muscles in the skin pull the hairs to make them
lay flat down on the surface of the skin and allow air to circulate freely
over the skin.
2.3 Sweat glands secret sweat onto the skin surface where the latent
heat of vaporization of water is lost.
Animals, e.g. dogs, can lose heat by panting. Can you lose heat by panting?
3. Note the change in your body at low ambient temperature
3.1 Capillaries in the skin constrict (vasoconstriction) to release less
heat.
3.2 The arrector pili muscles in the skin pull the hairs up to not allow
air to circulate freely over the skin. This action of the arrector pili
muscles causes "goose pimples". Animals can increase the thickness of their
coats and birds can ruffle their feathers.
3.3 The sweat glands stop secreting and the hypothalamus of the brain
sends messages to internal muscles to contract violently and cause shivering.
The oxygen consumption increases 2 to 5 times and the internal organs are
warmed.
Hypothermia begins when body temperature drops to 35°C when normal metabolism
slows until the internal organs no longer function and the person dies.
9.219 Women feel colder then
men
Women feel the cold more than men but their bodies are better at conserving
heat when the weather turns colder. Women are usually smaller so they
have a higher surface area to volume ratio than men and thus shed heat
faster. Heat generation is proportional to volume (radius3)
but heat dissipation is proportional to skin surface area (radius2).
The smaller your size, the lower your heat generation to heat dissipation
ratio, and the colder you are. So a woman with a higher surface area to volume
ratio than a man, will lose heat more quickly and feel colder. Women usually
have a slightly lower metabolic rate because of their typically smaller size,
so they generate less heat. Men have more heat-generating muscle mass. The
more muscle, the more blood flow and warmth. Women have a higher percentage
of body fat but that does not insulate them. Women usually have less insulating
fat on the upper body and around the waist but more padding on hips and thighs.
Men may have extra fat around the waist and upper torso, where it may help
insulate vital organs and prevent the core temperature from decreasing. Women
have less vigorous blood circulation to arms and legs, so their hands and
feet are often the first to feel the cold.
Deposits of fat that push against the connective tissue mainly in the
thighs and nearby regions to form a dimpled surface commonly called cellulite.
It occurs mainly in older women and is difficult to remove without persistent
dieting. Cellulite is indicated by pinched skin of the upper thigh that
appears lumpy.
Women can shut off the the blood flow to the skin and extremities to maintain
their core temperature at 37oC.
Most of the temperature sensors are in the skin so we feel cold if the
extremities are cold no matter the temperature of the internal organs.
The average woman has 20 to 25% body fat but the average man has about 15%
body fat. A woman has a more even distribution of body fat so a man will
tend not experience such a change in temperature. So women feel cold before
men do. The hands and feet of women are colder. For example one report
states that the hand temperature of women are about 2.9oC lower but their core body temperature
is about 0.4oC higher. Women have less muscle mass than men
so they need a more efficient technique to protect their core body temperature.
Also, the core body temperature of women changes during the menstrual cycle.
People who feel cold all the time could be suffering from hypothyroidism,
or diabetes, or anaemia.
9.237 Oxygen content of inhaled
and exhaled air
Compare the oxygen content of inhaled and exhaled air with a burning
candle. Candles can only burn in the presence of oxygen. The more oxygen
present, the longer they burn. Fix a candle into a candle holder. Light
the candle and put it quickly into a glass container and at the same time
cover the glass container with a glass disk. Insert a glass tube in the glass
container and again cover it with a glass disk. Exhale through the glass
tube 20 times so that only exhaled air remains in the vessel. Take out the
glass tube, introduce the candle holder with the burning candle and immediately
cover the glass container. Note how long the candle burns. Use the data to
compare the oxygen content of inhaled and exhaled air. 9.238 Elimination of wastes
when we breathe See diagram 3.34.1: Limewater tests for carbon
dioxide
1. Use a rubber bulb to pump air into a beaker containing limewater.
Note the change in the limewater
2. Fit a short glass tube into the bore of a stopper that can fit into
the neck of a bottle of aerated water, soda water. Attach rubber tubing
to the glass tube. Fit the stopper into the neck of an opened bottle of aerated
water. Put the other end of the rubber tubing into a beaker of limewater.
Warm the bottle of aerated water with the hands. Note the change in the
limewater. The aerated water contains carbon dioxide that forms bubbles and
escapes when the bottle is opened.
3. Blow exhaled air into the limewater. Note the change in the limewater. 9.239 Respiration rate of
humans, respiratory rate and heart rate See diagram 9.239: Feel the pulse See 3.4.6: Gas or vapour inhalation,
EAR, CPR
Heartburn (pyrosis) has nothing to do with the heart. It is a burning
feeling behind the breastbone and sometimes acid or bitter taste in the
mouth caused by regurgitation of stomach contents after a heavy meal.
1. The respiratory rate is the number of breaths per minute. Measure
it by observing the chest rising and falling with every breath. Rest for
ten minutes and measure the respiratory rate again. Normal values for resting
persons, per minute: 3 months 30-50, 10 years 18-30, adult 8-18.
2. After ten minutes rest, measure the heart rate by feeling the pulse.
The heart rate is the number of beats per minute, bpm. Put the forearm on
the desk, palm up with the wrist on the edge of the desk and hand in the
air. Press the four fingers of the other hand down on the side of the wrist.
Keep still and feel the pulse. Feel the pulse in the radial artery on the
palm side of the wrist in the same direction as the thumb. Start counting
the pulse. Note the number of beats per minute. It is from 60 to 100, usually
about 70. Do ten knee bends and measure the activity pulse. The pulse rate
tells us how fast the blood is pumped around the body. After ten minutes
rest, measure the recovery pulse. Note whether the pulse has returned to
the original resting pulse. If a student is sick or just had a big meal,
the pulse increases. During sleep the respiratory rate is slower. The best
resting pulse is taken when awakening in the morning. Normal values for resting
persons, per minute: 3 months 70-170, 10 years 70-110, adult 50-95.
3. Roll up some paper to make a tight tube. Hold it against the chest
of another student. Press the ear against the other end. Hear the heart
pumping the blood. The doctor uses a stethoscope instead of a paper tube
for listening to the different sounds in the body, auscultation.
Commercial stethoscope, nurses type, flat 9.239.1 Breath, simulated
diaphragm breathing See diagram 9.242: Simulated diaphragm | See diagram 9.240: V.S. Lungs and a bronchiole
Breathing movements cause the change of air in the lungs necessary for
breathing, because the lungs have no muscles and cannot inhale or exhale
air by themselves.
1. Breathe deeply in an out. Note that the volume of the chest cavity
changes in two ways.
1.1 When you inhale, the thorax expands to produce decreased pressure
in the airtight chest cavity that causes air to flow into the lungs. When
you exhale, the thorax contracts to decrease the size of the chest cavity,
compress the elastic lung tissue and force air out of the lungs. The thorax
rises and falls because of the action of the muscles between the ribs.
In this way you can increase breathing to allow stronger bodily activity.
1.2 In diaphragm breathing, abdominal breathing, the diaphragm rises
and falls because of the action of the diaphragm muscle controlled by the
respiratory centre. At rest, or during with low bodily activity, breathing
acts mainly in this manner.
2. Show the mechanism of diaphragm breathing. Pull a rubber balloon over
each of the two ends of the glass Y-tube. Smear the ends of the glass tube
with glycerine. Pass the long limb of the Y-tube from below through the
neck of a 5 litre polystyrene large jar and through a hole in a rubber stopper
lubricated with glycerine. Use a rubber cloth with a loop on one side to
close the opening at the base of the large jar so that the loop remains
outside. Secure the rubber cloth to the large jar with a clamping ring. Press
the rubber stopper firmly into the neck of the large jar. Grab the model
by the neck in one hand, and pass the other hand through the loop. Move the
rubber cloth up and down to simulate the breathing rhythm. Draw down the
rubber cloth to inflate the balloons. Push the rubber cloth upwards to collapse
the balloons. If the rubber cloth is drawn downwards, the volume in the large
jar outside the rubber balloons increases. A decrease in pressure occurs
which is immediately equalized by the flow of air into the elastic balloons
so they expand. When you press the rubber cloth upwards, the volume in the
large jar outside the rubber balloons decreases to produce excess pressure
that forces air out of the elastic balloons that then collapse. 9.239.2 Hiccups
If the diaphragm is irritated by eating too quickly, drinking too much
alcoholic drinks or carbonated drinks, or swallowing too much air, it may
go into spasms that bounce air off the vocal cords. We call the movement
and the sound "hiccups". In a healthy person, hiccups will gradually lessen
and stop but immediate remedies include taking 10 sips of water, blowing
into a paper bag and holding the breath to increase the concentration of carbon
dioxide in the blood. 9.240 Measure oxygen absorbed
in the lungs See diagram 9.240: Lungs and alveoli
Air breathed in: O2 21%, CO2 0.04%, Moisture 2%
(varies)
Air breathed out: O2 16%, CO2 4.0%, Moisture 5%
(varies)
1. Immerse a large jar so that the water level coincides with the 5 litre
mark. The large jar then contains 5 litres of air, inhalation air. Insert
a burning candle into the large jar. Be careful! Melting wax from a burning
candle can cause severe skin burns. Use safety glasses and insulated, heat-proof
gloves. Close the neck of the large jar immediately. Record the burning
time of the candle. For example, the candle was extinguished after 90 seconds.
2. Insert the mouthpiece in the mouth and fill the large jar to the 5
litre mark with exhalation air. With normal breathing this air has only
been in the lungs for a few seconds. Adjust the large jar so that the water
level in it is 3 mm lower than in the tank. Remove the stopper and put the
candle holder with the lighted candle in the large jar. Close the neck of
the large jar immediately. Record the burning time of the candle. The candle
burns for a much shorter period than in experiment 1.
3. Repeat experiment 2 with air retained in the lungs for a longer period
than normal, e.g. 30 seconds, before breathing it out. The candle in the
large jar is extinguished immediately. The longer air remains in the lungs,
the more oxygen is absorbed into the bloodstream. 9.241 Breath volume See diagram 9.241: Volume of air in a breath
1. Fix a glass tube bent at right angles through a one-hole stopper.
Push the stopper into the neck of a large jar. Immerse the large jar in
the water of a fish tank. Connect one end of rubber tubing to the glass
tube. Suck out the residual air in the large jar with a rubber bulb. Close
the stopcock and raise the large jar by 10 cm. Connect the other end of the
rubber tubing to a glass mouthpiece. Take a few normal breaths, in through
the nose and out through the mouth. Blow breaths of air into the large jar.
If two litres of air are blown into the large jar with 6 breaths, the volume
of air expelled per breath is 330 mL.
2. Normal breathing exchanges 200 to 500 mL of air at each breath. Vigorous
inhaling and exhaling exchange 2.5 to 5 litres of air at each breath. This
value is called the vital capacity. measured with a spirometer. After the
most powerful exhalation, about 1 000 mL of air is left in the lungs, the
residual air. The vital capacity + the residual capacity = the total volumetric
capacity of the lungs. Measure the vital capacity with a method similar
to that used for measuring the volume of air in one breath. Breathe in as
much air as possible. Place the glass mouthpiece in the mouth and attempt
to blow all the air out of the lungs with one breath into the large jar.
3. Use the rubber bulb to pass air through limewater. The limewater does
not turn milky. Immerse the large jar in the water and dip the mouthpiece
into limewater so that the air bubbles through the limewater. The limewater
has turned milky, showing the presence of carbon dioxide in exhaled air.
4. Measure the volume of air breathed out. Take a deep breath. Blow air
out slowly into one jar until all the water has been pushed out. Transfer
to the next jar and blow more air out until the lungs are empty. For example,
the volume of the air in a student's lungs may be 1 000 cm³ + 1 000 cm³
+ 200 cm³ = 2 200 cm³. Make air replace water by blowing air into inverted
jars filled with water. Estimate the volume of the lungs by measuring the
volume of air pushed out. Be careful! Do not let students blow so hard
that they feel sick.
5. Measure chest expansion. Use a tape measure to measure the perimeter
of the chest where it is widest. Note the chest measurement after breathing
out. Note the chest measurement after breathing in. Calculate the chest
expansion. Measure again after breathing really hard out and in. Observe
the movement of the ribs when breathing in. Stand up and push one finger
into the stomach, up and under the lower rib. Then breathe in. The diaphragm
muscle pushes the finger down. The volume of the chest increases when the
ribs move up like the handle of a bucket, just when the diaphragm muscle
drops down.
6. Record the breathing rate per minute and chest expansion 1. when sitting
quietly 2. after running. Breathing rate and chest expansion is greater
after running. 9.242.1 Expired air resuscitation
(EAR), Adult
If breathing:
1.0 Clear airway,
1.1 Place patient in recovery position: Patient on back, straighten
both legs, lift one leg at knee to make right angle, one arm across chest,
other arm at right angle to body, roll patient onto side, knee of leg at
right angle touches ground so patient does not roll on face.
1.2 Lift chin and open mouth.
1.3 Use finger to remove any obvious obstruction.
1.4 Tilt head back gently.
1.5 Check breathing for up to 10 seconds..
If not breathing:
2.0 Open airway.
2.1 Turn patient onto back.
2.2 Gently tilt head back.
2.3 Pinch nose closed, using thumb and index finger.
2.4 Open mouth and maintain chin lift.
3.0 Give EAR (mouth-to-mouth resuscitation).
3.1 Take a full breath and place lips on patient's mouth to ensure good
seal.
3.2 Blow steadily into mouth for 1.5 to 2 seconds.
3.3 Watch for chest to rise.
3.4 Take mouth away and watch for chest to fall.
3.5 Take another breath and repeat sequence, to give two effective breaths.
4.0 Check for signs of circulation.
4.1 Look for any movement, including swallowing or breathing.
4.2 Observe colour of skin on face.
4.3 Check pulse at neck or wrist.
4.4 If circulation absent, commence CPR.
4.5 If circulation present, continue EAR at 15 breaths per minute.
4.6 Look for signs of circulation about every minute.
5. Place in recovery position when breathing 5 returns. 9.242.2 Expired air resuscitation
(EAR), Infant (under 1 year), and Child (aged 1 to 8)
If breathing:
1.0 Clear airway.
1.1 Place infant / child in recovery position: Patient on back, straighten
both legs, lift one leg at knee to make right angle, one arm across chest,
other arm at right angle to body, roll patient onto side, knee of leg at
right angle touches ground so patient does not roll on face.
1.2 Lift chin and open mouth.
1.3 Use finger to remove any obvious obstruction.
1.4 Tilt head back very gently.
1.5 Check breathing for up to 10 seconds.
If not breathing.:
2.0 Open airway
2.1 Turn patient onto back
2.2 Tilt head back slightly
2.3 Open mouth and lift chin.
3.0 Give EAR (mouth-to-mouth resuscitation)
3.1 Cover mouth and nose with your mouth
3.2 Give two gentle breaths/puffs into child's /infant's mouth and nose
3.3 Check for signs of circulation: swallowing, breathing, colour of
skin on face and pulse (infant on inside upper arm, child at neck or wrist)
3.4 If circulation absent, commence CPR
3.5 If circulation present, continue EAR at 20 breaths per minute
3.6 Look for signs of circulation about every minute.
4.0 Place in recovery position if breathing returns. 9.242.3 Cardiopulmonary resuscitation
(CPR), Adult
1.0 Position hands for CPR.
1.1 Place patient on back.
1.2 Find groove at neck between collarbones.
1.3 Find lower end of breastbone by running finger along last rib to
centre of body.
1.4 Extend thumbs equal distances to meet in middle of breastbone.
1.5 Keep thumb of one hand in position and place heel of other hand
below it.
1.6 Place heel of other hand on top of first and interlock fingers of
both hands.
2.0 Commence chest compressions.
2.1 Position yourself vertically above patient's chest.
2.2 With your arms straight, press down on breastbone to depress it about
4 to 5 cm.
2.3 Release pressure.
3.0 Continue CPR.
3.1 Complete 15 compressions.
3.2 Give two effective breaths (EAR).
3.3 Continue compressions and breaths in ratio of 15 : 2 at a rate of
4 cycles per minute.
3.4 Check for signs of circulation every minute. 9.242.4 Cardiopulmonary resuscitation
(CPR), Child (aged 1-8)
1. Use heel of one hand over lower half of breastbone to give chest
compressions.
2. Compress chest approximately 1 / 3 depth of chest.
3. Give 1 effective breath (EAR).
4. Continue compressions and breaths in ratio of 5:1 at a rate of 12
cycles per minute. 9.242.5 Cardiopulmonary resuscitation
(CPR), Infant (under 1 year)
1. Place tips of 2 fingers (index and middle) on lower half of breastbone.
2. Compress chest approximately 1 / 3 depth of chest.
3. Give 5 chest compressions in 3 seconds.
4. Give 1 effective breath.
5. Continue compressions and breaths in ratio of 5 : 1 at a rate of 12
cycles per minute.
6. Check for signs of circulation every minute. 9.243 Sense of touch See diagram 9.243: Touch with dividers
1. Meissner corpuscles are just below the epidermis of the skin and
are sensitive to light touch. They occur mainly in the face, fingertips,
genitals, lips, palms of hands, soles of feet, and tongue. Merkel nerve
endings are in superficial skin layers and fingertip ridges and are sensitive
to pressure. Pacinian corpuscles are deep in the skin, in mesenteries (membranes
connecting the small intestine to the posterior wall of the abdomen) and
around joints and detect vibration and big pressure changes. These mechanoreceptors
are not uniformly distributed in the skin, so some parts of the body are
more sensitive to touch than others. When the skin is touched in two separate
points within a single receptive field, the student will be unable to feel
the two separate points. If the two points touched span more than a single
receptive field then both will be felt. The closer the receptive fields,
the greater the resolution of touch. So mechanoreceptors are more dense
in the fingertips and less dense in the palms of the hands.
2. Investigate the sensitivity to touch of different parts of the body.
Tie a blindfold over the eyes and touch objects with the fingers, e.g. table
top, coins, cup, pins, clothing. Describe the feelings. Repeat the experiment
by touching the same objects with the back of the hand. Describe the feelings
and whether they are the same as before.
3. Tie a blindfold over the eyes and ask another student to touch gently
different parts of the back of the hand with a touching bristle. Note when
and where you feel the touching bristle. Repeat the experiment on the end
of a finger and on the bare forearm. Do not test on other parts of the body.
4. Use a paper clip opened to be V-shaped or a hairpin or two thick
hairs. Start with the points 40 mm apart. Tie a blindfold over the eyes
and ask another student to touch gently different parts of the back of the
hand with only one point or with both points. Point to where the body was
touched and say whether it was one point or two points. Repeat the experiment
by reducing the distance between the points. Note the distance between the
points when a touch with both points feels like a touch with only one point.
When the points touch close together, they feel like one point. Repeat the
experiment on the end of a finger and on the bare forearm. Different parts
of the body have different sensitivity but do not test on other parts of
the body. This experiment was originally done with the points of geometrical
dividers or even two pins but these objects may be too dangerous for school
children to use in this experiment.
5. Feel two noses. Cross the middle finger over the index finger. Close
your eyes. Move the tips of these fingers along your nose with one finger
each side of the nose. When your fingers reach the tip of your nose your fingers
feel further apart and you get the illusion (Aristotle's illusion) that
you have two noses because you brain assumes that your finger tips are in
the usual position. Get the same illusion by holding a marble, pencil,
or another person's finger (dead man's finger) between the crossed fingertips. 9.244 Sense of feeling temperature See diagram 9.244: Feeling temperature
1. Fill three containers with water at 10oC, 20oC
and 30oC. Put the containers in one line on the table. Dip the
left hand in the water at 10oC. Dip the right hand in the water
at 30oC. After two minutes, take both hands out of water and dip
them simultaneously in the middle container 20oC. Compare the
temperature sensations of the right hand and by the left hand. You do not
have an absolute sense of temperature.
2. Use three containers of water, ice water, room temperature water
and hot water. Test the temperature with the end of the elbow to check that
the hot water is not too hot. Hold one hand in the ice water and the other
hand in the hot water for 20 seconds then quickly put both hands in the
water at room temperature. The hand from the ice water feels warmer and the
hand from the hot water feels cooler. 9.245 Sense of smell, the
olfactory system See diagram 1.13: Smelling technique Do not inhale gases directly from a test-tube. Fan the gas towards
the nose with the hand and sniff cautiously. If you detect no odour, move
closer and try again.
1. The olfactory neuroepithelium is located at the upper area of each
nasal chamber. As humans age, the number of olfactory neurones steadily
decreases. The sense of smell is caused by stimulation of the olfactory
receptor cells by volatile chemicals carried as airborne molecules. An odour's
stimulating effectiveness depends on the duration, volume, and velocity
of a sniff. Each olfactory receptor cell is a sensory neurone. The average
nasal cavity contains more than 100 million sensory neurones generated throughout
life by the underlying basal cells. So new receptor cells are generated
every 30-60 days. Humans have many hundreds of different olfactory receptors,
but each neurone expresses only one receptor type, part of an olfactory
"map". An odour activates a set of odour receptors depending on its chemical
composition. The vomeronasal organ (VNO) (Jacobson organ) is a membranous
structure within pits of the anterior nasal septum. Its opening 2 cm from
the nostril is visible in nearly all adult humans. It detects the external
chemical signals called pheromones but these signals are not detected as
perceptible smells by the olfactory system. Pheromones send messages to
all individuals in the species to mediate behaviour, e.g. alarm, food trail
for ants, sex responses and possibly synchronization of menstrual cycles
among women living together.
2. Pour 1 cm of methylated spirit into a small beaker. Hold the beaker
under the nose and note the smell while breathing:
2.1 without inhaling,
2.2. inhaling steadily,
2.3. inhaling with jerky sniffs.
Repeat the experiments with different foodstuffs.
3. Repeat the experiment with one nostril closed. Note whether both
nostrils give the same smell sensation.
4. Test the ability to detect the smell of baby powder, chocolate, cinnamon,
coffee, mothballs, peanut butter, soap, banana, petrol (gasoline) lemon,
onion, paint thinner, pineapple, rose, and turpentine
5. Collect different substances that have different kinds of smell.
Be careful! Do not let students smell volatile liquids, e.g. petrol, methylated
spirit, alcohol, pesticides, correcting fluid and dry-cleaning fluid. A
description of smells may include the following: "fruity" from ripe fruit,
"fragrant" from flowers and perfume, "onion" from onion or garlic, sulfur
from sulfur or volcanic gases, "burning" from burning meat or coffee or
tobacco, "burning feathers' from feathers or silk or wool or rubber or hair,
"sweaty", from sweat, old cheese, and goats, "foul" from rotten meat, rotten
vegetables and faeces. Repeat the experiment with the students blindfolded. 9.246 Sense of taste, the
gustatory system
1. Taste perception occurs in individual taste buds with multiple receptor
cells in each bud. Taste buds are modified epithelial cells, with a life span
of about 10 days and arise continuously from the underlying basal cell layer.
So if you burn your tongue new taste buds can later replace any damaged taste
buds. Taste buds occupy projections embedded in the tongue epithelium called
lingual papillae. A single nerve fibre innervates multiple taste papillae.
A single nerve fibre can respond to different types of tastes, called "broad
tuning". Lingual papillae have 4 forms, each in different areas of the tongue.
Taste buds also occur in the soft palate, epiglottis and larynx, and the pharynx.
2. The five different taste qualities are salty, sweet, sour, bitter,
and umami (savoury taste of monosodium glutamate). There are no "taste
areas" on the tongue. The five taste qualities can be detected in all regions
of the tongue, but certain areas of the tongue have lower thresholds for
each quality. Sweetness is most readily detected at the tip of the tongue.
Salty taste receptors focus on the front and side borders of the tongue.
Sour tastes are best perceived along the lateral border, and bitter sensations
are tasted most in the posterior one third. Another proposed taste quality
is chalky (calcium salts). Salt taste is caused by sodium ions and sour taste
is cause by hydrogen ions in solution. Sweet taste, bitter taste and umami
taste is caused by reactions with proteins on the surface of the taste buds.
3. Never taste a chemical or any substance in the laboratory! Crush
different fruits and vegetables into a pulp using a food chopping mill.
Tie a blindfold over the eyes, taste the different foods and record the
tastes in order of tasting. Repeat the experiment while holding your nose
and breathing only through the mouth. Taste the different foods and record
the tastes in the same order of tasting. If the nose is held tight, no
air can move through the nasal space and you cannot smell anything. You
may notice that different foods taste the same when you have a cold. Flavour
is a mixture of taste, smell and feel of the food in the mouth.
4. Report on the taste sensations of your tongue. Dry the surface of
the tongue with a clean handkerchief, stretch it out as far as possible
and look at the tongue with a mirror to note the many taste buds. Describe
the taste sensation after you place on different parts of the tongue a drop
of the following:
4.1 dilute solution of sucrose, saccharin or aspartame for sweet taste,
4.2 dilute vinegar solution for sour taste,
4.3 dilute table salt solution for salt taste,
4.4 dilute quinine solution (tonic water) or raw almond for bitter taste
4.5 dilute solution of the amino acid monosodium glutamate, MSG, for "umami"
taste.
You can experience all the qualities of taste in all regions of the
tongue where taste buds occur. Some people experience differences in sensitivity
and people may vary in the number of taste buds in different regions of
the tongue.
5. Put a drop of boiled starch solution on your tongue and let it mix
with the saliva. Leave it there until you can notice a slight change in taste.
The saliva contains an enzyme ptyalin that changes starch to maltose sugar.
It causes the sweet taste. Repeat the experiment with a piece of raw meat
and a piece of pure fat. You do not notice any change of taste because ptyalin
does not act on protein or fat.
9.247 Direction of sound heard
All students form a large circle. One student stands in the middle of
the circle with a blindfold tied over the eyes. Each student in the circle
claps once, one at a time, in any order. After each clap, the blindfolded
student turns in that direction with one arm extended. Record the number
of successful turns and their direction relative to the direction at the
time of the clap. Repeat the experiment with the right ear of the blindfolded
student blocked with cotton wool and with the right index finger pressed
into that ear. Repeat the experiment with the student's left ear blocked
with cotton wool and the left index finger pressed into that ear. Record
the number of successful turns and their direction relative to the direction
at the time of the clap. Examine the records and describe the necessary
conditions to tell the direction of sound correctly. 9.248 Distance of object seen
1. Hold a pencil in each hand horizontally in front of the face with
the points of the pencils 50 cm apart. Move the pencils towards each other
so that the points touch. Repeat the experiment with the right eye closed.
Repeat the experiment with the left eye closed. Describe the necessary conditions
to tell correctly the distance of objects.
2. Look outside the classroom at something far away. Hold up one finger
20 cm in front of the eyes but keep looking at the distant object. Note whether
you can see the distant object clearly. Note whether you can, at the same
time, see the finger clearly. Note whether you feel any movement in your eyes.
Keep looking at the finger and note whether the distant object is clear.
3. Hold a printed page at arms length. Bring the book closer and closer
until it is too close to read the letters. Measure the distance from the book
to the eyes. Move the book away from the eyes until it is too far to read
the letters. Again, measure the distance from the book to the eyes.
4. Work in pairs. One student in a pair puts a hand over one eye. The
other student holds up one finger about 40 cm in front of the partner's
eyes. The student with one eye covered has to place the tip of one finger
on top of the finger that the partner is holding up. Repeat the experiment
with both eyes open. 9.250 Examine your eyes See diagram 28.1.1.6: The eye
If sheep eyes are used for dissection, soak them lens down in 1.0% sodium
chloride solution before freezing, to avoid lens clouding.
1. Work in pairs. Look at the partner's eyes and identify each part
seen.
2. Clap your hands in front of the partner's face. The partner blinks.
3. Tell your partner to watch your finger as you move it towards the nose.
The partner blinks. Repeat the experiment by staring into your partner's eyes
and trying not to blink. The first student to blink loses the game.
4. Tell your partner to walk slowly around you in a big circle. Follow
the partner with your eyes but do not move your head or body. See how long
you can keep your partner in sight. Put your hand up when you can no longer
see your partner.
4. By moving your eyes only and not your head, note how far you can
move your hand up and down in front of your face and keep it in sight.
5. Face your partner with both kneeling on the floor. Put a stone between
you on the floor. Cover your right eye with one hand. Test who can pick up
the stone first.
9.254 Optical illusions See 28.12.16: Square that isn't there | See diagram 9.254: Dark and bright | See diagram 9.254.1: How many boxes?
1. Black and white, dark and bright
Look at the 16 black squares in the diagram and note that the white
bars between the black squares appear whites than where the white bars intersect
where dark areas appear on the intersections. However if you look closely
at the intersections and not at the black squares the dark area disappear.
White contrasted with black appears whiter when we use your peripheral vision.
Look at the black and white discs in the squares. The white discs appear
larger. White objects appear larger when contrasted with a black background.
2. The same drawing of a pile of boxes seen inverted changes the number of
boxes.
3. When observing objects and features of the countryside from the window
of a moving vehicle, closer objects and features appear to move faster than
those further away. Further object have a smaller angular velocity than closer
objects, so they take longer to pass through the field of vision. Look at
text between the V formed by two stretched fingers of your hand flat on the
page. Move your hand across the page and observe the letters closer to the
hand within the V appearing to move faster than the letters between the fingertips. 26.6.0 Ear, voice, hearing, voice, audible limits See diagram 26.6.0: Harmonics
Acoustics, the ear, voice, hearing, voice, audible limits, direction
of sound, sound locator, sound ranging, sense of sound, sound pollution,
explosive sound
The human ear can detect sound waves with frequencies of about 20 to
20,000 hertz. This range is known as "sound", with infrasound below the range
and ultrasound above the range.
Loudness measures the human perception of sound. A sound wave of high
intensity is perceived as louder than a sound wave of lower intensity, but
the sensation of sound is proportional to the logarithm of the sound intensity
for most individuals. Loudness level is defined by a scale corresponding
to the sensation of loudness. The zero on this scale = the sound wave intensity,
Io = 1.00 X 10-12 W / m2, corresponding to the weakest
audible sound. The loudness level, beta, 10 log (I / Io). The decibel (dB)
has no dimensions. Decibel, dB is the logarithmic unit used for human audibility
measurements ranging from 1, just audible, to 120, just causing pain. The
linear scale ranges from 1 to 1012 change in sound pressure. A
doubling of sound pressure corresponds to 6 dB. A doubling of sound loudness
corresponds to a tenfold increase in sound pressure, 20 dB. A different decibel
scale is used for measuring the output of audio amplifiers in terms of intensity.
The normal ear can distinguish intensities down to about 1 dB. Often people
use the word "musical sound" for something they want to hear, and "noise"
for what they do not want to hear. A tuning fork emits an almost pure note
of one frequency. Musical sound is made up of superposition of a set of fundamental
and harmonics with different frequencies and amplitudes according to certain
law. For example, consider two sounds, one a mixture of harmonics (frequencies
related by integer ratios) and the other a mixture of frequencies with no
integer relationship among them. The first sound will result in an identifiable
pitch, that of the fundamental frequency, and is called a musical sound. The
second sound, viz. noise, will have a much different quality, so different
that it may not even have an identifiable pitch. Thus the difference between
music and noise is a gross example of quality. The sound, transitory and declined
quickly is an explosion.
Some animals can hear sounds in the ultrasound range, e.g. dogs, but the
human ear is not able to hear them. Bats use sonar echoes to locate insects
using sounds in the 20 to 50 kHz frequency range. Some insects have developed
bearings in this range so that they can take evasive action. Bats that transmit
at a higher frequency can catch smaller insects than bats that transmit at
lower frequencies. Dolphins use clicks of ultrasounds to locate shoals of
fish.
Echoing ultrasounds are used in underwater sonar and to detect cancers
and check on unborn human foetuses. Different tissues reflect ultrasound
differently so a computer can assemble a picture of the unborn baby.
High amplitude ultrasounds are used to clean metals, to fatigue test
materials and to break up kidney stones. This is similar to loud sounds
causing avalanches on steep slopes. Sonar echoes are used in ships to measure
depth and detect under water objects. ASDIC was an early form of sonar, an
abbreviation for Anti-Submarine Detection Investigation Committee. Short
wave radio listeners use several scales to record the characteristics of
the signal they hear from their loudspeakers and headphones, e.g. "SIO"
Signal strength, Interference and Overall rating, "SINPO" with the addition
of N and P for Noise and Fading.
Pitch of a note
The pitch of a sound is how high or low it sounds. As frequency of the
vibration of particles increases, the pitch of a note is raised. Pitch is
affected by the mass, the length and the tension of the vibrating medium.
The frequency of a vibrating string is inversely proportional to its length.
The frequency will be doubled for a string which is only half as long Frequency
is also increased by an increase in tension. Four times the tension in the
string will double the frequency it vibrates at. In addition frequency varies
inversely as the square root of the string's density. When you increase the
density of the string, you will slow down the vibration rate and decrease
the frequency. Put a small v-shaped piece of paper on a stretched string or
the string of a musical instrument. Pluck the string and note the motion of
the paper V. Decibels and sound pressure for sound pressure range of 0 to
140 decibels.
dB (pressure Ear's response scale) Sound pressure units (Pa)
0 dB: 2 x 10-5 Pa
10 dB: just audible, the sound of falling leaves
20 dB: empty broadcasting studio 2 x 10-4 Pa
30 dB: soft whisper at 5 m
35 dB: quiet library
40 dB: bedroom, no conversation 2 x 10-3 Pa
50 dB: very quiet
55 dB: light traffic at 15 m
60 dB: air conditioning at 6 m. 2 x 10-2 Pa
65 dB: normal conversation
70 dB: light freeway traffic
75 dB: conversation noticeably difficult
80 dB: annoying sound level 2 x 10-1 Pa
85 dB: pneumatic drill at 15 m
90 dB: heavy truck at 15 m
95 dB: very annoying
100 dB: loud shout at 15 m 2
105 dB: jet plane take-off at 600 m
110 dB: riveting gun close by
115 dB: maximum vocal voice without amplification
117 dB: discotheque at full blast
120 dB: jet take-off at 60 m 2 X 10 Pa
130 dB: limit of amplified speech
135 dB: painfully loud
140 dB: on aircraft carrier deck 2 X 102 Pa 26.6.01 Noise exposure thresholds
Noise, dB . . . Time, hours
85 . . . 8
88 . . . 4
91 . . . 2
94 . . . 1
97 . . . 0.5
100 . . 0.25
140 + . no exposure, can cause hearing loss 26.6.2 Human ear, how the ear works, model of the
ear See diagram 26.197: Human ear, vertical section
Air vibrations enter the ear by the auditory passage formed at the base
of the ear by the eardrum membrane. They set the eardrum in motion and, in
doing so, set in motion the system of three little bones attached to it.
By this means they reach a cavity in the bone called the inner ear. One
part of the ear is shaped like a snail shell. Here is found the organ that
receives the sound vibrations and is connected with the brain by the auditory
nerve. Another part of the inner ear includes three small semicircular
canals and serves to maintain equilibrium. It plays no part in hearing. Sound
vibrations are normally transmitted to the snail shell shaped cochlea by the
eardrum and the small bones. This causes a nerve message carried to the brain.
They can also be transmitted by the bones of the skull, and you hear a sound
if the waves reach the cochlea by either route. When a sound reaches your
two ears, you can distinguish the direction from which it comes. If it comes
from straight ahead, the vibrations reach both ears simultaneously and with
the same strength. However if the source of the sound is on one side of us,
one of your ears is further away from it and receives the waves less strongly
and with a slight delay. The pinnae collect the sound and contributes to
your sense of direction. Sound is transmitted from the auditory canal via
the eardrum into the middle ear. In the middle ear small bones act as an
impedance matching mechanism. This maximizes the. amount of signal that is
passed on to the brain. The bones also magnify the vibrations of the eardrum.
The. message is then passed into the cochlea and on to the nerve that takes
the. message to the brain. The auditory canal is a tube of air that is able
to vibrate and is closed at one end by the eardrum. 26.6.3 Binaural hearing
Hold the ends of a long tube to each ear and have someone tap in the centre
and then a few centimetres to each side. 26.6.4 Direction of sound, direction
judgement of the ear
To identify the direction and position of sound cover your eyes with
a piece of black cloth. Other students emit sounds at different positions
at a classroom, e.g. shake a string of keys, rub a piece of paper. Describe
each sound source and its direction and position. Repeat the experiment
with various sound sources emitting the sounds at the same time. Human hearing
can not only identify the directions and positions of a sound sources but
also tell their characters. High frequency location depends on difference
in intensity produced by the shadow of the head. Location of low pitched sounds
depends on phase difference. Use a model stethoscope with one tube longer
than the other. 26.6.5 Range of hearing
The range of human hearing is from about 20 vibrations per second to
about 20, 000 vibrations per second, nearly 10 octaves. Use an oscillator
driving an audio system to show the range of hearing. Use a set of good
speakers. Use whistles, tuning forks to establish upper range of hearing.
The Galton whistle can be adjusted to produce an intense sound into the
ultrasonic range. 26.6.14 How the voice is produced,
music perception and the voice See diagram 26.198: Voice
Mouth, teeth, tongue, throat and lungs are all used in the production
of the voice. The sound is produced by vibrations of two thin sheets of
membrane called the vocal cords, which are stretched across the sound chamber
called the larynx. The larynx is the upper end of the windpipe and is found
well back, at the base of the tongue. The front of the larynx, the "Adam's
apple" is often prominent in males. A trap door of cartilage, the epiglottis,
automatically drops down over the larynx when you swallow, so that no food
will go through the windpipe. When the cords, vocal folds, are stretched
by the contraction of certain muscles in the throat, a narrow slit forms
between them. It is when the air is forced through this narrow slit that
the cords are forced to vibrate. This sets the air vibrating in the windpipe,
lungs, mouth and nasal cavities. The vocal cords located in the throat act
as a double reed and are set in motion by air exhaled from the lungs. The
quality and tone of the sound depends on the size and shape of the resonating
cavities such as the windpipe, the back of the throat, the mouth and other
air filled parts of the head. For the human voice, the vocal cords in the
throat act as a double reed and are set in motion by air exhaled from the
lungs. The quality and tone of the human sound depends on the size and
shape of the resonating cavities such as the windpipe, the back of the
throat, the mouth and other air filled parts of the head. Ventriloquists
speak in the normal manner but with some modification of their speech. They
allow their breath to escape slowly, narrow the glottis at the back of the
throat, open their mouth as little as possible and retract the tongue while
moving only its tip. The resultant pressure on the vocal cords diffuses the
sound so that it appears to be coming from another source. The greater the
pressure on the vocal cords, the greater the deception. Ventriloquists
use a dummy with moving lips to aid in their deception that the sound they
are making is not coming from themselves. Other animals, including lions,
are able to "throw their voices". 28.12.0 The eye, structure and physiology See diagram 28.1.1.6: The eye
Blind spot, binocular vision, defects, spectacles and contact lenses,
persistence of vision 28.12.2 Water flask model of the
eye
A large flask filled with water, fluorescein and with external lenses
make a model of the eye in near-sighted and far-sighted conditions. A spherical
lens filled with milky water represents the eyeball. Use a large lens in
front of the sphere to show inverted image, near sighted and far sighted. 28.12.3 Blind spot
Move a white cross towards a white spot on the blackboard with one eye
closed. 28.12.4 Inversion of image on the
retina
A small tube has three holes in a triangular pattern drilled in one
end and a single hole in the other. Hold the triangular end near the eye
and the pattern appears inverted. 28.12.5 Astigmatism
Look at a chart of radial black lines. 28.12.6 Eyeglasses
Project an image of concentric circles crossed by radial lines. Place
a lens and then a correcting lens over the projection lens. 28.12.7 Chromatic aberration of the
eye
A purple filter is mounted in front of a straight filament lamp. 28.12.8 Resolving power of the eye
The limit of resolving two filaments of an auto headlamp is about 10
m. 28.12.9 Retinal fatigue colour
A red light placed behind a rotating with a slot at the border of half
black and half white appears different colours depending on the direction
of rotation. A disc with a notch half black half white is spun in front
of a red lamp The lamp appears green or red depending on the direction that
the disc spins. A black and white patterned disc appears coloured when rotated. 28.12.10 Fluorescence of retina
Shine an UV source with a visible filter towards the class and notice
the luminous haze that covers the field of view. 28.12.11 Jarring the eye
Stamp your foot while watching a free running oscilloscope. 28.12.12 Subjectivity of colours
A red spot projected on the wall looks orange or brown if it is surrounded
by white or black. 28.12.13 Mach disc
A spinning disc appears to have light and dark rings where it should
be uniform 28.12.14 Most sensitive to green
light
A stick moved up and down in a projected spectrum will appear to bend
at the green light are most sensitive to green light. 28.12.16 Square that is not there See diagram 28.1.1.7: Absent square
1. The human brain tries to make sense of all sense perceptions, even
to "seeing" a square that is not there!
2. A cut-out square in black paper has the illusion of being a white
square on top of black paper. 28.12.18 Colour blindness
Use standard colour blindness slides or charts to test for colour blindness. 28.12.19 Stroboscope
See diagram 28.1.1.1 Stroboscope