Chapter 16: Coordination in humans

Question 1

Components of the CNS (Central nervous system) and PNS (Peripheral nervous system)

Answer 1

CNS: Brain, spinal cord
PNS: Cranial nerves and spinal nerves

Question 2

Cranial nerves VS spinal nerves

Answer 2

Cranial nerves: link effectors and receptors in the head and the neck to the brain
(e.g. optic nerves, auditory nerves)

Spinal nerves link effectors and receptors in the rest of the body to the spinal cord.

Question 3

Withdrawal reflex

Answer 3

• The hand touches a sharp object.
• Pain receptors are simulated and generate nerve impulses.
• Sensory neurone transmits the nerve impulses to interneurone in the spinal cord
• Interneurone relays nerve impulses to the motor neurone
• Motor neurone transmits nerve impulses to the biceps
• Biceps contract and the hand withdraws to prevent further damage

Question 4

The withdrawal reflex does not involve the cereb\rum. Why do we still feel pain?

Answer 4

Nerve impulses are transmitted to the cerebrum via another pathway

// Since this pathway is longer than the reflex arc and involves more synapses, we feel pain after withdrawing the hand

Question 5

Knee jerk reflex

Answer 5

Stretch receptors in the upper leg muscle are stimulated to generate nerve impulses.
Sensory neurone transmits nerve impulses to the spinal cord.
Motor neurone trnasmits nerve impulses to the upper leg muscle.
Upper leg muscle contracts and the leg kicks,

Question 6

The knee jerk reflex does not involve the cerebrum. Why do we still feel pain?

Answer 6

The nerve impulses are transmitted to the brain via another pathway

Question 7

How drugs affect neurotransmission

Answer 7

• One side of cocaine is structurally similar to that of neurotransmitter A (dopamine). (1)
• By binding to the receptor sites of dopamine on the presynaptic neurone, cocaine inhibits the reuptake of dopamine by the presynaptic neurone from the synaptic cleft. (1)
• A much higher concentration of dopamine is maintained in the synaptic cleft. (1)
• Dopamine has a higher chance to bind to the receptors sites on the postsynaptic neurone/ bind at a faster rate. (1)
• The postsynaptic neurone is stimulated continuously to generate nerve impulses at a faster rate for the feeling of pleasure.(1)

Question 8

Why can a nerve impulse be transmitted from neurone X to neurone Y, but not vice versa?

Answer 8

Only neurone Y has dopamine receptors to recognize dopamine which is only released from neurone
X.
There are no dopamine receptors in neurone X. (1)
Thus only neurone Y can generate a nerve impulse upon binding of dopamine receptors with dopamine (1)

Question 9

Defects of neurotransmission at synaptic cleft

Answer 9

(SAME POINT)
- Insufficient amount of vesicles/damaged vesicles at the synaptic knob
OR
- insufficient amount of mitochondria to provide energy for vesicles to synthesise neurotransmitters
//
- Insufficient amount of neurotransmitters is released at the synaptic cleft
- Neurotransmitter is degraded too rapidly
- Insufficient amount of receptors / abnormal or damaged receptors to bind with neurotransmitters

Question 10

Explain the colours of the white matter and the grey matter respectively

Answer 10

Grey matter:
- nuclei of cell bodies are grey,
- accounting for the grey colour of the region

White matter:
- myelin sheath, which is a lipid covering surrounding the axons of sensory and motor neurones
- accounts for the white colour of white matter

Question 11

Functions of the cerebrum, cerebellum and medulla oblongata

Answer 11

Cerebrum
- Site for intelligence
- Controls voluntary actions

Cerebellum
- Coordinates muscular actions for smooth body movements
- Maintain body posture and balance (during movement)

Medulla
- Reflex center for cranial reflex (some reflex actions such as saliva secretion, swallowing, blinking)
- Controls involuntary actions (e.g. peristalsis, breathing, heartbeat)

Question 12

If the function of the cerebellum is affected, difficulties that would be experienced by this patient include: (2022/4c)

Answer 12

Activities related to balance:
* the patient may trip easily while walking
* may experience difficulty in walking
* cannot maintain body balance

Activities related to coordination of movement:
the patient may not be able to:
* walk along a straight line
* perform fine movement
*
* perform movement smoothly

Question 13

https://drive.google.com/drive/folders/1VEbh98OrFgkqr_WqXUKk8IZ5wRXS8qqw

Answer 13

• The presence of infolded membrane/vesicles
• Indicates the fusion of vesicles with the presynaptic membrane of presynaptic neurone A
• to release neurotransmitters to the synaptic cleft for the transmission of nerve impulses
  (3)