1970-04-23 — Page 23

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Reflex action

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70英文中學會考試題預習專欄

堅道英文書院主編

(二十五)

BIOLOGY (25)

生物科

Answers to the questions of Last week

Answer

1.

2. (B)

5. (c)

(E)

6. (D)

·9. (D).

10. (D)

11.

13. (E).

8. (a) 12. (A)

14. (D) 18. (D)

15. (0) 19.

16. (B)

20. (B)

Answer II

(a) (i) Olfactory lobe - It transmits nerve impulses

from the nose to the cerebrum. ie. it is concerned with the sense of smell.

(ii) Cerebrum

-

It, being the centre of co-ordina- tion, centrols all the voluntary actions and is responsible for intelligence and sensation (feeling).

(iii) Cerebellum - It controls and co-ordinates the balanoing organa and the muscles, thus making precise and accurate movements possible, e.g. controls the antagonistic musoles like the tricep and the bicep muscles of the arm. (iv) Medulla oblongata - It is the centre of

involuntary action (reflex action), thus controlling the heart-beat, blood vessels, secretion of glands and breathing movements.

A reflex aetion is involuntary and

automatio action or response to a stimulus, by. an organ or system of organs, which does not physiologically under the control of the brain. Examples of reflex action are knee jerking. winking, sneezing, and coughing ato.

In order to understand thoroughly how the refier sotion works, it is better to study ane of such reflex aotione, e.g. a knee jerk reflex, as follows a

Grey matter

Spinal Cord (V.S.)..

Motor fibre

extensor

Flexor

·Muscle

Position

of flexion

Position

of extension

White matter

Ganglion -Afferent fibre

from extensor

Extensor

muscle

-Patellar Tendon

Diagram to illustrate Knee jerk. Note: that patella ligament is tendon of extensor muscle and is attached to tibia, below knee,

When the right leg is crossed over and suspended above the left leg and struck gently with a rubber hammer just the portion below the patella (knee oap) of the right leg will automatically jerk forwards, and upwards by such a reflex action.

How such a reflex action works can be traced as follows:- When we tap on the portion below the patella, we are initiating an impulse (or a stimulus) to the receptor organ of the nerve fibre in the tendon of the muscles. This impulse-

travela" along the sensory fibre in the nerve, which runs to the spinal cord, entering through the dorsal root. When this impulse reaches the spinal cord it intensifies when crossing a synapse and becomes an impulse in a motor fibre. This motor impulse leaves the spinal cord through the ventral root and passes the motor fibre to the effector organ in the extensor muscles of the thigh. By means of this stimulation the muscles are caused to contract. So the contracting. muscles extend the leg,

The central nervous system, ne Drain AIBO Depones Consolous of the tap by the rubber A hammer and the, reflex action happens, but it tAKOS no part in the physiologisal response. i.e. the reflex action is only controlled by the spinal cord (peripheral nervous system).

(0) Dimwinotion or keflex Boviem from Voluntary

actions

(1) It is an action that

resulte when e

sensation or

stimulation passes. over a reflex arc to the peripheral organ which is thus stimulated to action without the aid of volition or in many cases without even entering conscious. ness, i.e. without transmitting up to the cerebrum.

(2) quick, automatic,

involuntary action.

(3) Simple rasponse.

(4) For example, knos

jerk reflex by tapping the part below the patella, the gotion of kioking up the lower leg takes placs at once.

Questions for this week

Voluntary action

(1) It is an action that

results when a sensation or

stimulation transmits from the peripheral receptor organ through the sensory fibres to the cerebruma and eventually out through the motor fibres of the brain and the spinal cord respectively and back to activate the receptor organ with the aid of volition, consciousness, alalysis, selection: and decision,

(2) Slow, steady

decisive, voluntary action.

(3) Complicated response.

(4) For example, the

action of retreat from the place with danger with conscious nase, 1.0, by walking away from danger after consideration.

Choose the best answer from each of the following questions or statemento.

1. The liquid bathing all the body calle is

(A) plasma

(B) synovial fluid

(C) lymph

Berun

blood

2. Unlike blood, lymph hap

(A) no red blood corpusclea

(B) no white blood

(0) no cells

(D) no nutrients

no serum

Duscles

3. The processes of inspiration are dezoribed 20

the following:

(A) lowering the pressure in the thoracic

cavity

(11) av

contraction of the mugoles of riba and diaphragm

(iii) increasing in the volusa of the thoracio

cavity

(iv) expansion of alveoli

Which of the following is the right sequence?

(4) (1) (41) (17) (111) (3) (11) (111) (1) (10): (iv) (111) (11) (1)

(11) (1) (112) (iv)

The two essential elemento grouth of bones and teeth (A) calcium and irun

B) phosphorus and sulphur (C) calcium and phosphorus

D) iodine and iron

(E) nagnesium and fluorine

required for the

Fats are emulsified in the duodenum

alkaline bile salts do that

(&) they can be changed into fatt ́·änd

glycerol

digestion of fate is accelerated

they can be stored in the form of

tissue.

they can be assimilated

they can be absorbed into the lacteal

6. Similar to the contractile vacuole of Amoeba,

the mammalian kidney functiona

(A) to excrete urea.

(B) to regulate the water balence or the body..

to eliminate nitrogenous wates into the blood

to excrete excess amino-acids in the body to decompose urea

disease called beri-beri is due to (A) insufficient secretion of bile (B) overproduction of gastric

absence of proteins in the diet (D) absence of Vitamin B in the diet (E) absence of calcium in the diet

8. The region between two nerve cells through

which a nervous impulse passes is

a sensory neuron

B a motor neuron

(0) known as synapac

(D

an

axon

9. anglion

autonomic nervous system controls

hearing

seeing

((0) thinking

(D) walking

beating of heart

10. The largest portion of a human brain is the

(A) olfactory lobe

(B) optic lobe.

cerebellum

cerebrum

(F) medulla oblongata

11. Which of the following is a structural and funotional unit of the nervous system of a makmal?

(A) cell body of a nerve call

B) brain

C) a neuron.

(D) a simple reriex aro

spinal cord

12. A bundle of axons is knÖMR

a nerve

(B) a nerve rabre

Can axon brush

D) a dendrite

(E) a dendror

13. Concentration or carbon dioxide in the blood

will stimulate the breathing centre in the

cerebrum

(B) cerebellum

spinal cord.

D) mid-brain

medulla oblongata

Involuntary musole is found in the

(A) finger

(B) leg

(C) stomach

(D) tongua

(B) toe

15. Ciliated cells are important in the human

(A) respiratory system

(B) digestive system

C) skeletal system

(D) muscular system

(E) circulatory systen

10. Waioh part of the following is incorrectly

matched with its function?

Urinary bladder - Stores urine

(B) Liver Stores glycogen

(C) Ovary Stores ova na

D) Gall-bladder Stores pancreatie juice

Epididymis - Stores perme

17. Which statement is incorrect?

(A) The muscular membrane which separates

the thoracic cavity from the abdominal cavity is called the diaphragm (B) The enzyme which is present in saliva and

acts on starch is called ptyalin Sourvy is due to lack of Vitamin B Cellulose will be changed into simple Bugar by the micro-organisme living in the cae cum of a rabbit--

(E) The disease called ricket in due to lack

of calcium in the diat

18. Which one of the following does not an

enzyme for digestion of food?

(A) Trypsinogen

(B) Lipase

(C) Erepsin

Maltage Insulin

19. The Vitamin which helps clotting of blood 18

Vitamin A

(3) Vitamin B.

(C) Vitamin C

Vitamin D

Vitamin K

20. The "white matter of the nervous system of a

mammal is mainly composed of

(A) cell bodies of neurons

(B) ganglia of neurona (C) axons of neurons

(D) dendrons of neurons

(E) dendrites of neurons

11. (a) What do you understand by the term "sense

organs"?

(b) The diagram below is a sectional view of

human eara.

A Sectional View Of Human Ear

(1) Name the parts A to J

B

(11) Give the functions of 0,

HD

II1, (a) Make a clear, fully labelled sectional

diagram to show the structure of a human eye (b) State the functions of the various parts of

the eye."

(o) Give a clear simple alegram to show how the

defect of hypermetropia can be corrected.