Think about the following statements carefully. Are they true or false? Check the answers at the backof the book to get rid of any misconceptions.

1 The erection of hair is a means of heat loss in mammals.

2 A reflex action is an example of feedback control.

3 Reabsorption of glucose by kidney tubules is a homeostatic response.

4 ln cold conditions, vasodilation taking place in the skin of mammals helps toconserve heat.

5 When the glucose level in the blood increases, the body acts to reduce theamount of glucose used for respiration.

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PAPER 1 Multiple Choice Auestions

!nstruction: Answer all questions. For each questionthere are four possible answers, A, B, C and D.

Choose the one you consider conect and record yourchoice in the bracket.

1 Which of the following is not an example ofhomeostasis?

A Passing out more urine after staying in an air-conditioned room

B lncrease and decrease in the blood glucoselevel after a heavy meal

C Change of the colour of urine after takingvitamin tablets

D Passing out more urine after drinking alcohol()

2 What happens when the core temperature ofthe body decreases?

C They absorb more water from thesurrounding tissues.

D They dilate and become wider.

4 The body can regulate both its temperature andthe amount of water in its cells through

A excretionB osmosisC homeostasisD diffusion

5 When the external temperature drops, thefollowing changes may take place in the humanbody.

I Shivering begins.ll The brain detects blood with a lower

temperature.lll The body temperatures falls.lV The body temperature rises.

Which of the following shows the correct orderof the changes?vasodilation decreases

vasoco nstrictio n r ncreases

vasodilation r ncreases

D vasoconstriction decreases

3 What happens to the arterioles near the surfaceof the skin when the body temperature rises?

A They constrict and become narrow.B They absorb more oxygen from the

surrounding tissues.

A

B

c

B il

IV

IV

A

cD

ilt

I

il

ilt

tl

IV

ilt

il

IV

Urine productionSuperficial bloodvessels undergo

First last

171

()

()

()

)(

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Sweat secretion Arterioles in skin

E

6 Which combination of factors helps prevent the 1

loss of heat from the body?

decreases constrict

11 An athlete is running a 1OO-metre race. Whatwill happen to the blood vessels, sweat glandsand the urine production after the race?

A Vasoconstriction

A

B

cD

0cLl,J

FrI()

decreases dilate

7 One structural feature of the skin which doesnot play a part in temperature regulation inmammals is the

A hair erector muscleB malpighian layerC arterioleD sweat gland

8 Homeostasis is best described as

A the control of the concentration of water inblood

B the removal of wastes from the cellsC the maintenance of a stable cellular

environmentD the control of the supply of nutrients to cells

()

9 Which of the following shows the ways inwhich the skin responds when the bodybecomes very cold?

12 When the body temperature rises, which of thefollowing corrective mechanisms would occur?

I lncreased sweatingll Vasodilationlll Decreased metabolic ratelV Contraction of the hair erector muscles

A ll and lV onlyB l, ll and lll onlyC l, lll and lV onlyD l, ll, lll and lV

13 The diagram below shows the regulation ofbody temperature by the hypothalamus.

cold receptors in the skin

body response

Which of the following represent A?

V - Hairs stand on endsW - Lower metabolic rateX - VasodilationY * Shivering

A V andY onlyB WandXonlyC VWandXonlyD W, X andY only

i ncreases

increases

dilate

constrictActive

Active .

lnactive

I n acti ve

I ncreases

Decreases

Decreases

I ncreases

B Vasodilation ,

C Vasoconstriction

D Vasodilation

A Constricted

B Cons-tricted

C Dilated

D Dilated

A dilate

B constrict

C dilate

D constrict

increase sweat production

decrease sweat production

decrease sweat production

increase sweat production

Erect

Erect

Flat

Erect

10 On a hot day, how do the skin structures helpin thermoregulation?

()

Body temperature

Falls

Control centre that maintains body temperature

A

112

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()

()

)

State ofarteiioles

Positionof hair

Sweatproduction

Occurs

Almost ceases

, Occurs

Almost ceases

( )

Arteriolesin skin

Sweat glands

Blood vessels,

Sweat'',{, Urine-,glands' lproduction

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14 The graph below shows the changes in bodytemperature against time.

40 60 B0 100

What causes the changes in body temperatureat phase 'l and phase 2?

Sweating Shivering

Vigorous exercise Sweating .

Shivering Sweating

Vigorous exercise Shivering

(

15 An athlete runs in a 100-metre race. Whathappens to the sweat glands, blood vesselsand body temperature after the race?

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A lnactive

B lnactive

C Active

D

Vasodilation

Vasoconstriction

Vasodilation

High

Low

High

Low

E4,ulc

oActive V-asocon,striction l

(

A

B

cD

PAPER 2 Structured and Free-response Auestions

Section A Structured O,uestions

1 When you enter a room which has a temperature higher than your body temperature, your body willgain heat.

(a) How does your body gain heat in this situation?(b)What physiological effects does a very high temperature have on your body?(c) ln the situation given above, how does your body respond to lower the body temperature?

2 A f ew explorers with a n average mass of 70 kg stayed in a hot deseft for eig ht hours. The averagepercentage body mass lost per hour was 1.5%.

(a) Calculate the total average body mass lost over the eight-hour period.(b) Most of the body mass is lost in the form of water.

(i) Does this loss of body mass help the explorers to survive in the hot desert?(ii) Explain your answer in (bXi).

3 The following organs are considered as homeostatic organs:

(a) Kidney(b) Liver(c) Skin

Briefly describe each organ's role in homeostatic control.

Body ]

temperature l

Sweatglands

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Phase 1

; FhaseBlood yessels

)

)

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4 The table given below shows the volume of water gained and lost per day by a person living in a

tropical climate.

(a) (i) State the form in which water is lost from the lungs.(ii) Name the process that produces water in the body.

(b) (i) With reference to the table above, calculate the total volume of water lost by this personin a day.

(ii) What is the percentage water loss by urine?(c) What is the total volume of water gained in a day?(d) How would the figures of water lost above change in a cold climate?

Section B Free-response Ouestions

5 A man was kept in a room which was maintained at a temperature of 45 "C. After 25 minutes, he drank a

large quantity of ice-cold water. His internal body temperature, rate of sweating and his skin temperaturewere recorded.The results are shown in the table below.

376 . 376 37.6 37.6

20I2bi30_* r -- .l-**tli!37.6'37.6'37.5

r35', 40 45

:37.2 , 37.0 37.2

..:2.5 ' 1.5 2.0

50 55 60 65 80

37.6

4.1

70

37.4 37.6 37.6 , 37.6 ,, 376 376

4.1 4.1 4.1 4.1 4.1

36.8 36.8

3.8

:

36.9 37.2 375.. ....:. ...

3.0 4.0 4.1

i*qtlqit

36.8 36.8 36.8 37.4 37,2 37.0 36.8 36.8 36.8 36.8

(a) Explain why there is a difference between skin temperature and internal body temperature during thefirst 25 minutes of the experiment.

(b)(i) Using the information given in the table, describe the effect of drinking ice-cold water onthe body.

(ii) Explain concisely how the effect in (b)(i) is brought about.(c) How would a steady build-up of humidity in the room affect the man's temperature readings?

6 Horn"ostasis is the maintenance of a constant internal environment for the survival of cells.Thisincludes maintaining the temperature and chemical composition of body fluids at a constantlevel.

A person is exposed to a cold environment of 5 oC for two hours. Describe how the body functions tomaintain a constant body temperature during this time.

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36.8

Water lost {cm3}Water gained {cm3)

Urine Faeces Skin LungsFood Drink Produced in the body

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