NEET Biology: Human Physiology · Chapter 5

Neural Control and Coordination

What to remember

A neuron at rest is polarised: the outside of the membrane is positive and the inside is negative. The resting potential is about -70 mV, kept by the Na⁺/K⁺ pump, which moves 3 Na⁺ out and 2 K⁺ in using ATP.
An action potential has three phases: depolarisation (Na⁺ rushes in), repolarisation (K⁺ moves out) and return to the resting state. It travels along the axon and crosses a synapse by a neurotransmitter in chemical synapses.
The human brain has three main parts: the forebrain (cerebrum, thalamus, hypothalamus), the midbrain (corpora quadrigemina) and the hindbrain (pons, cerebellum, medulla). The hypothalamus controls body temperature, hunger, thirst and hormones; the cerebellum controls balance and posture; the medulla controls heartbeat, breathing and reflexes such as vomiting.
A reflex arc is the pathway of a reflex: receptor → sensory (afferent) neuron → spinal cord (CNS) → motor (efferent) neuron → effector. The knee jerk is a two-neuron reflex.

Neural system in animals and in humans

All animals need to detect changes and respond. In simple animals such as Hydra, the neural system is a network of neurons spread through the body (a nerve net). In flatworms such as planaria, there is a simple brain and nerve cords. In insects, there is a brain and a ventral nerve cord with ganglia. In vertebrates, the neural system is highly developed, with a brain, a spinal cord and nerves.

The human neural system has two divisions.

Central neural system (CNS): the brain and the spinal cord. It is the site of information processing and control.
Peripheral neural system (PNS): all the nerves that connect the CNS to the body.

The nerve fibres of the PNS are of two types.

Afferent fibres carry impulses from tissues and organs to the CNS.
Efferent fibres carry regulatory impulses from the CNS to the peripheral tissues.

The PNS is divided into two parts.

Somatic neural system: relays impulses from the CNS to skeletal muscles. It controls voluntary actions.
Autonomic neural system (ANS): relays impulses from the CNS to involuntary organs and smooth muscles of the body. It has two parts, the sympathetic and the parasympathetic. The part of the neural system that includes nerves, ganglia and plexuses of the internal organs is called the visceral nervous system.

Feature	Sympathetic	Parasympathetic
Overall effect	Prepares the body for stress (fight or flight)	Restores the body to rest and digestion
Heart rate	Increases	Decreases
Pupil	Dilates	Constricts
Digestive activity	Decreases	Increases
Bronchi	Dilate	Constrict

The neuron: structure and types

The neuron is the structural and functional unit of the neural system. A neuron has three main parts.

Part	Description	Function
Cell body (cyton)	Contains cytoplasm, nucleus and Nissl's granules (granular bodies)	Metabolic centre; Nissl's granules are rough ER with ribosomes, used in protein synthesis
Dendrites	Short, branched fibres that project from the cell body, also containing Nissl's granules	Carry impulses towards the cell body
Axon	A long fibre that ends in a branched structure, each branch ending in a bulb-like synaptic knob that holds synaptic vesicles	Carries impulses away from the cell body to a synapse or to an effector

Synaptic vesicles contain chemicals called neurotransmitters.

Types of neurons by the number of axons and dendrites

Type	Structure	Location
Multipolar	One axon and two or more dendrites	Cerebral cortex
Bipolar	One axon and one dendrite	Retina of the eye
Unipolar	Cell body with one axon only	Embryonic stage (in the adult, found in a few places such as the sensory neurons of the dorsal root ganglia)

Types of axons by covering

Myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. Myelinated fibres are found in spinal and cranial nerves. Impulses jump from node to node, so conduction is faster.
Non-myelinated nerve fibres are enclosed by a Schwann cell that does not form a myelin sheath around the axon. They are commonly found in autonomic and somatic neural systems.

Generation and conduction of a nerve impulse

A nerve impulse is a wave of change in the electrical potential of the membrane. It is carried by neurons, which are excitable cells because their membrane is polarised.

Resting potential. A neuron at rest has no impulse. The axon membrane is more permeable to K⁺ and nearly impermeable to Na⁺. It is also impermeable to negatively charged proteins inside the axoplasm. As a result, the axoplasm has a high concentration of K⁺ and negatively charged proteins and a low concentration of Na⁺. The fluid outside the axon has a low concentration of K⁺, a high concentration of Na⁺ and a low concentration of proteins. These ionic gradients are maintained by the sodium-potassium pump, which moves 3 Na⁺ outwards for every 2 K⁺ it moves into the cell. The outer surface of the membrane is positively charged and the inner surface is negatively charged. The membrane is then said to be polarised. The electrical potential difference across the resting membrane is called the resting potential.

Action potential. When a stimulus is applied at a site on the polarised membrane, the membrane at that site becomes freely permeable to Na⁺. Na⁺ moves in rapidly. The polarity of the membrane is reversed: the outer surface becomes negative and the inner surface becomes positive. This is depolarisation. The electrical potential difference across the membrane at this site is the action potential, which is the nerve impulse.

Repolarisation. Soon after, the membrane becomes impermeable to Na⁺ and more permeable to K⁺. K⁺ diffuses outside. The resting potential is restored at the site. This is repolarisation. The Na⁺/K⁺ pump then restores the original ionic distribution.

Conduction. At the site of an action potential (say site A), the outer surface is negative and the inner surface is positive. At the next site (site B), the outer surface is still positive and the inner surface is negative. Current flows from site B to site A on the outer surface and from site A to site B on the inner surface. This depolarises site B, so the impulse moves forward along the axon in one direction. The sequence is: resting (polarised) → depolarised → repolarised.

Stage	Ion movement	Membrane (outside / inside)
Resting	K⁺ leak out slightly; Na⁺ nearly blocked	Positive / negative
Depolarisation	Na⁺ enters	Negative / positive
Repolarisation	K⁺ leaves	Positive / negative

Transmission of impulses across a synapse

A nerve impulse is transmitted from one neuron to another through junctions called synapses. A synapse is formed by the membranes of the pre-synaptic neuron and the post-synaptic neuron, which may or may not be separated by a gap called the synaptic cleft.

Electrical synapses: the membranes of the pre- and post-synaptic neurons are in very close contact. Electrical current flows directly from one neuron to the next. Transmission is very similar to conduction along a single axon and is faster. Electrical synapses are rare in our system.
Chemical synapses: the membranes are separated by a fluid-filled synaptic cleft. Neurotransmitters carry the message across.

Mechanism at a chemical synapse. When an impulse (action potential) arrives at the axon terminal, it stimulates the movement of synaptic vesicles towards the membrane. They fuse with the plasma membrane and release their neurotransmitter into the synaptic cleft. The neurotransmitter binds to specific receptors on the post-synaptic membrane. This opens ion channels and allows the entry of ions, which generates a new potential in the post-synaptic neuron. The new potential may be excitatory (excitatory post-synaptic potential) or inhibitory (inhibitory post-synaptic potential). Acetylcholine is a well-known neurotransmitter.

Central neural system: the brain

The brain is the central information processing organ of the body. It is protected by the skull and covered by three membranes called meninges.

Meninx	Position
Dura mater	Outermost, tough
Arachnoid	Middle, thin and web-like
Pia mater	Innermost, thin, in contact with the brain tissue

The brain has three major parts: the forebrain, the midbrain and the hindbrain.

Forebrain consists of the cerebrum, thalamus and hypothalamus.

Cerebrum forms the major part of the human brain. A deep cleft divides it into two cerebral hemispheres, which are connected by a thick band of nerve fibres called the corpus callosum. The outer layer of the cerebrum is the cerebral cortex, which is grey (grey matter) because of the cell bodies of neurons. It is folded, which increases its surface area. The cortex has motor areas, sensory areas and association areas. Association areas are neither clearly sensory nor motor. They are responsible for complex functions such as intersensory association, memory and communication. Inner to the cortex are layers of myelinated fibres that give the white matter its colour.
Thalamus is the major coordinating centre for sensory and motor signals.
Hypothalamus lies at the base of the thalamus. It contains centres that control body temperature, eating and drinking. It also contains several groups of neurosecretory cells that secrete hormones called hypothalamic hormones.
Limbic system: the inner part of the cerebral hemispheres and a group of associated deeper structures (amygdala, hippocampus and others) form a complex called the limbic lobe or limbic system. Along with the hypothalamus, it is involved in the regulation of sexual behaviour, expression of emotional reactions (excitement, pleasure, fear, rage) and motivation.

Midbrain is located between the thalamus and hypothalamus of the forebrain and the pons of the hindbrain. A canal called the cerebral aqueduct passes through it. The dorsal portion has four round swellings called corpora quadrigemina. The midbrain and hindbrain form the brain stem.

Hindbrain consists of the pons, cerebellum and medulla oblongata.

Pons consists of fibre tracts that interconnect different regions of the brain.
Cerebellum has a very convoluted surface to provide additional space for many more neurons.
Medulla oblongata is connected to the spinal cord. It contains centres that control respiration, cardiovascular reflexes and gastric secretions.

Brain part	Main function
Cerebrum	Intelligence, memory, voluntary action, speech
Thalamus	Relay and coordination of sensory and motor signals
Hypothalamus	Temperature, hunger, thirst, hormone release
Limbic system	Emotions, motivation, sexual behaviour
Corpora quadrigemina	Visual and auditory reflex centres
Pons	Links brain regions
Cerebellum	Balance, posture, coordination of movement
Medulla oblongata	Breathing, heartbeat, gastric secretion

Reflex action and reflex arc

The neural system provides the ability to sense a stimulus and act. The action of the effector organ is called the response. A reflex action is an involuntary, quick and automatic response to a stimulus, controlled by the spinal cord or the brain stem without the need for thought. Examples: pulling the hand away from a hot object, sneezing and the knee jerk.

The pathway of a reflex action is the reflex arc.

Stimulus → receptor → afferent (sensory) neuron → dorsal root of the spinal cord → interneuron in the CNS → efferent (motor) neuron through the ventral root → effector (muscle or gland) → response.

In the knee jerk, a tap on the tendon below the kneecap stretches the receptor in the muscle. A sensory neuron carries the impulse to the spinal cord. It synapses directly with a motor neuron, and the thigh muscle contracts. Only two neurons are involved, so it is a monosynaptic reflex. A reflex arc usually has a sensory neuron and a motor neuron. Many reflex arcs have an additional interneuron.

NEET traps

1. Resting potential: outside positive, inside negative. During depolarisation this is reversed.
2. The pump moves 3 Na⁺ out and 2 K⁺ in, not 2 out and 3 in.
3. Depolarisation is Na⁺ entry; repolarisation is K⁺ exit.
4. Afferent means towards the CNS (sensory). Efferent means away from the CNS (motor).
5. The somatic system controls voluntary skeletal muscle; the autonomic system controls involuntary organs.
6. Bipolar neurons are in the retina; multipolar neurons are in the cerebral cortex; unipolar neurons are found in the embryo.
7. Myelin is made by Schwann cells in the PNS, and conduction in myelinated fibres is faster because the impulse jumps between nodes of Ranvier.
8. The corpus callosum joins the two cerebral hemispheres; the corpora quadrigemina are four swellings in the midbrain. Do not mix the names.
9. The hypothalamus controls temperature and hunger; the medulla controls breathing and heartbeat; the cerebellum controls balance.
10. Meninges from outside to inside: dura mater, arachnoid, pia mater.

One-liners

1. The neuron is the structural and functional unit of the neural system.
2. Nissl's granules are found in the cell body and dendrites, not in the axon.
3. Synaptic vesicles are found in the synaptic knob.
4. The resting potential is about -70 mV inside relative to outside.
5. The Na⁺/K⁺ pump uses ATP.
6. The membrane at rest is more permeable to K⁺ than to Na⁺.
7. The action potential is the nerve impulse.
8. Electrical synapses are faster but rare in humans.
9. Chemical synapses have a synaptic cleft and neurotransmitters.
10. The cerebral cortex is grey because of the neuron cell bodies.
11. The thalamus is the main coordinating centre for sensory and motor signals.
12. The limbic system is concerned with emotions and motivation.
13. The midbrain and hindbrain (pons, medulla) together form the brain stem.
14. The medulla oblongata continues into the spinal cord.
15. A reflex is an involuntary response; the spinal cord is its centre.

Practice questions

The sodium-potassium pump of a neuron moves ions across the membrane in which ratio?
1. 3 Na⁺ into the cell and 2 K⁺ out of the cell
2. 2 Na⁺ out of the cell and 3 K⁺ into the cell
3. 3 Na⁺ out of the cell and 3 K⁺ into the cell
4. 3 Na⁺ out of the cell and 2 K⁺ into the cell
Answer
D. 3 Na⁺ out of the cell and 2 K⁺ into the cell
The pump uses ATP to move 3 Na⁺ outwards and 2 K⁺ inwards.
Nissl's granules are found in which parts of a neuron?
1. Axon and synaptic knob
2. Cell body and dendrites
3. Axon only
4. Nodes of Ranvier
Answer
B. Cell body and dendrites
Nissl's granules occur in the cell body and the dendrites, where proteins are made. They are absent from the axon.
Bipolar neurons, with one axon and one dendrite, are found in the
1. embryonic stage
2. spinal cord
3. retina of the eye
4. cerebral cortex
Answer
C. retina of the eye
Bipolar neurons are found in the retina. Multipolar neurons are in the cerebral cortex.
Which of the meninges is the outermost covering of the brain?
1. Dura mater
2. Pia mater
3. Arachnoid
4. Corpus callosum
Answer
A. Dura mater
From outside to inside the meninges are dura mater, arachnoid and pia mater.
The corpus callosum is a thick band of nerve fibres that connects
1. the pons and the medulla
2. the thalamus and the hypothalamus
3. the two cerebral hemispheres
4. the cerebrum and the cerebellum
Answer
C. the two cerebral hemispheres
The corpus callosum joins the right and left cerebral hemispheres.
The corpora quadrigemina are four round swellings found in the
1. forebrain
2. hindbrain
3. spinal cord
4. midbrain
Answer
D. midbrain
Corpora quadrigemina form the dorsal part of the midbrain.
Which part of the brain contains centres that control respiration and cardiovascular reflexes?
1. Medulla oblongata
2. Cerebellum
3. Pons
4. Thalamus
Answer
A. Medulla oblongata
The medulla oblongata has centres for respiration, cardiovascular reflexes and gastric secretion.
Which part of the brain is mainly concerned with balance and posture?
1. Pons
2. Cerebellum
3. Cerebrum
4. Hypothalamus
Answer
B. Cerebellum
The cerebellum, with its convoluted surface, controls balance, posture and coordination of movement.
The movement of which ion into the axon causes depolarisation at the site of a stimulus?
1. Ca²⁺
2. Na⁺
3. Cl⁻
4. K⁺
Answer
B. Na⁺
At the stimulated site the membrane becomes freely permeable to Na⁺, which rushes in and reverses the polarity.
The myelin sheath around an axon of the peripheral nerves is formed by
1. dendrites
2. Nissl's granules
3. synaptic vesicles
4. Schwann cells
Answer
D. Schwann cells
Schwann cells form the myelin sheath around myelinated nerve fibres.
The autonomic neural system relays impulses from the CNS to
1. skeletal muscles only
2. sense organs
3. the spinal cord only
4. involuntary organs and smooth muscles
Answer
D. involuntary organs and smooth muscles
The somatic system supplies skeletal muscles; the autonomic system supplies involuntary organs and smooth muscles.
Which of the following is a function of the hypothalamus?
1. Controlling body temperature, eating and drinking
2. Coordinating voluntary movements
3. Joining the two cerebral hemispheres
4. Regulating breathing and heartbeat
Answer
A. Controlling body temperature, eating and drinking
The hypothalamus has centres for body temperature, eating and drinking and has neurosecretory cells that secrete hypothalamic hormones.
The gaps between two adjacent myelin sheaths along an axon are called
1. synaptic clefts
2. synaptic knobs
3. nodes of Ranvier
4. Nissl's bodies
Answer
C. nodes of Ranvier
Nodes of Ranvier are the uncovered gaps between myelin sheaths; the impulse jumps between them.
The canal that passes through the midbrain is called the
1. synaptic cleft
2. cerebral aqueduct
3. central canal
4. pia canal
Answer
B. cerebral aqueduct
A canal called the cerebral aqueduct passes through the midbrain.
Which of the following structures is part of the limbic system?
1. Pons
2. Corpora quadrigemina
3. Amygdala
4. Cerebellum
Answer
C. Amygdala
The limbic system includes the inner part of the cerebral hemispheres with the amygdala, hippocampus and related structures.
The brain stem is made up of the
1. midbrain, pons and medulla oblongata
2. cerebrum, thalamus and hypothalamus
3. pons, cerebellum and medulla only
4. cerebrum, cerebellum and pons
Answer
A. midbrain, pons and medulla oblongata
The midbrain together with the pons and medulla of the hindbrain forms the brain stem.
Given below are two statements. Statement I: The resting axon membrane is more permeable to K⁺ than to Na⁺. Statement II: The sodium-potassium pump moves 3 K⁺ out and 2 Na⁺ into the axon. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
Statement I is correct. The pump moves 3 Na⁺ out and 2 K⁺ in, so Statement II is incorrect.
Given below are two statements. Statement I: Electrical synapses conduct impulses faster than chemical synapses. Statement II: Chemical synapses have a fluid-filled synaptic cleft between the two neurons. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
A. Both Statement I and Statement II are correct
Electrical synapses have very close membranes and transmit faster. Chemical synapses are separated by a fluid-filled cleft.
Given below are two statements. Statement I: Afferent fibres carry impulses from the CNS to the tissues and organs. Statement II: Efferent fibres carry regulatory impulses from the CNS to the peripheral tissues. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Afferent fibres carry impulses towards the CNS, so Statement I is incorrect. Statement II is correct.
Which of the following statements are correct? 1. Dendrites carry impulses towards the cell body. 2. Synaptic knobs contain synaptic vesicles with neurotransmitters. 3. Nissl's granules are found in the axon.
1. 1 and 2 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3
Answer
A. 1 and 2 only
Statements 1 and 2 are correct. Nissl's granules are in the cell body and dendrites, not in the axon.
Given below are two statements. Statement I: The cerebral cortex appears grey because of the cell bodies of neurons. Statement II: Association areas of the cortex are purely motor areas. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
Association areas are neither clearly sensory nor motor; they handle memory, communication and association.
Given below are two statements. Statement I: The parasympathetic system increases the heart rate. Statement II: The sympathetic system constricts the bronchi. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
B. Both Statement I and Statement II are incorrect
The sympathetic system increases heart rate and dilates bronchi; the parasympathetic system decreases heart rate and constricts bronchi.
Given below are two statements. Statement I: The pons consists of fibre tracts that interconnect different regions of the brain. Statement II: The medulla oblongata is connected to the spinal cord. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
A. Both Statement I and Statement II are correct
Both are correct descriptions of hindbrain parts.
Which of the following statements are correct about a reflex? 1. The knee jerk involves only a sensory neuron and a motor neuron. 2. A reflex arc runs from receptor to afferent neuron to CNS to efferent neuron to effector. 3. Every reflex action needs conscious thought in the cerebral cortex.
1. 1 only
2. 1 and 2 only
3. 2 and 3 only
4. 1, 2 and 3
Answer
B. 1 and 2 only
Reflexes are involuntary and do not need conscious thought, so statement 3 is wrong.
Given below are two statements. Statement I: Pia mater is the outermost meninx. Statement II: Arachnoid is the thin, web-like middle meninx. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Dura mater is outermost; pia mater is innermost. The arachnoid is the middle layer.
Given below are two statements. Statement I: Impulses travel faster in myelinated fibres than in non-myelinated fibres. Statement II: In myelinated fibres the action potential is generated continuously along the whole length of the membrane. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
Impulses jump from one node of Ranvier to the next, which makes conduction faster.
Assertion (A): The sodium-potassium pump requires ATP. Reason (R): It moves ions against their concentration gradients.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
Movement against a gradient is active transport and needs energy from ATP.
Assertion (A): The medulla oblongata controls breathing and cardiovascular reflexes. Reason (R): The medulla oblongata is a part of the forebrain.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
C. A is true but R is false
The medulla is part of the hindbrain, not the forebrain.
Assertion (A): Unipolar neurons are found in the retina. Reason (R): Bipolar neurons are found in the retina of the eye.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
D. A is false but R is true
The retina contains bipolar neurons; unipolar neurons are found in the embryonic stage.
Assertion (A): The knee jerk is a very quick response. Reason (R): Only a sensory neuron and a motor neuron are involved, with a direct synapse between them.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
With only two neurons and one synapse the pathway is short, so the response is fast.
Assertion (A): Nissl's granules are sites of protein synthesis in a neuron. Reason (R): Nissl's granules are made of rough endoplasmic reticulum with ribosomes.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
Ribosomes on the rough ER make proteins, so the granules are protein-synthesis sites.
Match List I with List II. List I: a. Multipolar neuron b. Bipolar neuron c. Unipolar neuron d. Non-myelinated fibre List II: i. Retina of the eye ii. Embryonic stage iii. Cerebral cortex iv. Autonomic and somatic neural systems
1. a-iii, b-ii, c-i, d-iv
2. a-iii, b-i, c-ii, d-iv
3. a-iv, b-i, c-ii, d-iii
4. a-i, b-iii, c-ii, d-iv
Answer
B. a-iii, b-i, c-ii, d-iv
Multipolar neurons are in the cerebral cortex, bipolar in the retina, unipolar in the embryo; non-myelinated fibres are common in the autonomic and somatic systems.
Match List I with List II. List I: a. Thalamus b. Hypothalamus c. Cerebellum d. Medulla oblongata List II: i. Control of hunger and body temperature ii. Balance and posture iii. Cardiovascular reflexes iv. Relay of sensory and motor signals
1. a-iv, b-i, c-iii, d-ii
2. a-i, b-iv, c-ii, d-iii
3. a-ii, b-i, c-iv, d-iii
4. a-iv, b-i, c-ii, d-iii
Answer
D. a-iv, b-i, c-ii, d-iii
The thalamus relays signals, the hypothalamus controls hunger and temperature, the cerebellum controls balance, and the medulla controls cardiovascular reflexes.
Match List I with List II. List I: a. Resting membrane b. Depolarisation c. Repolarisation d. Sodium-potassium pump List II: i. Na⁺ enters the axon ii. K⁺ leaves the axon iii. 3 Na⁺ out and 2 K⁺ in iv. Outside positive, inside negative
1. a-iv, b-ii, c-i, d-iii
2. a-i, b-iv, c-ii, d-iii
3. a-iii, b-i, c-ii, d-iv
4. a-iv, b-i, c-ii, d-iii
Answer
D. a-iv, b-i, c-ii, d-iii
Resting membrane is positive outside and negative inside; depolarisation is Na⁺ entry; repolarisation is K⁺ exit; the pump moves 3 Na⁺ out and 2 K⁺ in.
Match List I with List II. List I: a. Corpus callosum b. Corpora quadrigemina c. Nissl's granules d. Nodes of Ranvier List II: i. Midbrain ii. Gaps in the myelin sheath iii. Protein synthesis iv. Joins the cerebral hemispheres
1. a-i, b-iv, c-iii, d-ii
2. a-iv, b-i, c-iii, d-ii
3. a-iii, b-i, c-iv, d-ii
4. a-iv, b-i, c-ii, d-iii
Answer
B. a-iv, b-i, c-iii, d-ii
The corpus callosum joins the hemispheres, corpora quadrigemina lie in the midbrain, Nissl's granules make proteins and nodes of Ranvier are gaps in the myelin.
Match List I with List II. List I: a. Sympathetic system b. Parasympathetic system c. Somatic system d. Afferent fibres List II: i. Voluntary control of skeletal muscle ii. Rest and digestion iii. Fight or flight iv. Carry impulses towards the CNS
1. a-i, b-iv, c-iii, d-ii
2. a-iii, b-ii, c-iv, d-i
3. a-iii, b-ii, c-i, d-iv
4. a-ii, b-iii, c-i, d-iv
Answer
C. a-iii, b-ii, c-i, d-iv
Sympathetic is fight or flight, parasympathetic is rest and digestion, somatic controls skeletal muscle, and afferent fibres go towards the CNS.
Match List I with List II. List I: a. Forebrain b. Midbrain c. Hindbrain d. Limbic system List II: i. Cerebral aqueduct ii. Pons, cerebellum and medulla iii. Cerebrum, thalamus and hypothalamus iv. Emotions and motivation
1. a-iii, b-ii, c-i, d-iv
2. a-ii, b-i, c-iii, d-iv
3. a-iii, b-i, c-ii, d-iv
4. a-i, b-iii, c-ii, d-iv
Answer
C. a-iii, b-i, c-ii, d-iv
The forebrain has the cerebrum, thalamus and hypothalamus; the midbrain has the cerebral aqueduct; the hindbrain has pons, cerebellum and medulla; the limbic system deals with emotions and motivation.
A person walks with a staggering gait and cannot keep his balance, although his muscles are strong and his intelligence is normal. Which part of the brain is most likely damaged?
1. Corpus callosum
2. Thalamus
3. Pia mater
4. Cerebellum
Answer
D. Cerebellum
The cerebellum controls balance, posture and coordination of movement.
A drug blocks the Na⁺ channels of an axon. What is the most likely effect when the axon is stimulated?
1. The membrane is depolarised permanently
2. No depolarisation occurs and no action potential is generated
3. The pump stops working at once
4. K⁺ enters the axon rapidly
Answer
B. No depolarisation occurs and no action potential is generated
Depolarisation depends on Na⁺ entry. If Na⁺ cannot enter, no action potential is formed.
If the supply of ATP to a neuron is cut off for a long time, what will happen gradually?
1. Myelin will thicken around the axon
2. The axon will produce a stronger action potential
3. The membrane becomes more polarised
4. The Na⁺ and K⁺ gradients maintained by the pump will gradually be lost
Answer
D. The Na⁺ and K⁺ gradients maintained by the pump will gradually be lost
Without ATP, the Na⁺/K⁺ pump cannot restore the ionic gradients that give the resting potential.
A doctor taps the tendon below the kneecap of a patient, but there is no response and the patient feels nothing. Which part of the reflex arc is most likely damaged?
1. Effector muscle only
2. Efferent neuron only
3. Corpus callosum
4. Afferent (sensory) neuron
Answer
D. Afferent (sensory) neuron
Loss of both response and sensation points to the sensory (afferent) pathway carrying the impulse to the spinal cord.
A person sitting in a cold room starts shivering and the body tries to maintain its temperature. Which brain region contains the centre that controls this regulation?
1. Cerebellum
2. Medulla oblongata
3. Hypothalamus
4. Pons
Answer
C. Hypothalamus
The hypothalamus has the centre for body temperature control.
At the peak of an action potential at a site on an axon, the inner surface of the membrane at that site is
1. neutral and the outer surface is positive
2. positively charged and the outer surface is negatively charged
3. negatively charged and the outer surface is positively charged
4. negatively charged and the outer surface is neutral
Answer
B. positively charged and the outer surface is negatively charged
At depolarisation the polarity is reversed: inside positive, outside negative.
In a disease the myelin sheaths around the nerve fibres are damaged. What is the most likely effect?
1. Slower conduction of impulses
2. No resting potential in any neuron
3. Loss of neurotransmitters from synaptic vesicles
4. Faster conduction of impulses
Answer
A. Slower conduction of impulses
Myelin allows impulses to jump from node to node. Loss of myelin slows conduction.

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