10th Science Unit 15 Nervous System Book Back Answers
10th Science Unit 15 Nervous System book back answers for all 49 questions in the 2026-27 Samacheer Kalvi (Tamil Nadu) textbook.
This unit looks at how our body senses changes around it and reacts to them. You will study the neuron and its parts, neuroglia and nerve fibres, the types of neurons, and how a nerve impulse travels across a synapse. Book-back questions ask you to name parts, tell types apart, explain impulse transmission, and describe reflex action and brain functions.
Answers at a glance
I. Choose the correct answer
II. Fill in the blanks
III. State whether true or false, if false write the correct statement
IV. Match the following
- Q1A - Cyton, B - Forebrain, C - Hindbrain, D - Peripheral Nervous system
I. Choose the correct answer
Bipolar neurons have one axon and one dendron arising from the cyton.
The textbook states they are found in the retina of the eye and the olfactory epithelium of nasal chambers.
a) retina of eye
The brain is the controlling centre of all body activities.
The cerebral cortex handles sensory perception, language, thinking, memory and decision making.
c) brain
The reflex arc is the pathway of the impulse: receptor → sensory neuron → spinal cord (relay neuron) → motor neuron → effector muscle.
So it begins at the receptor and ends at the muscle, passing through the spinal cord.
d) receptor, spinal cord, muscle
Dendrites transmit impulse ________ cell body and axon transmit impulse ________ cell body.
Dendrites conduct nerve impulses towards the cyton (cell body).
The axon carries impulses away from the cyton.
b) towards, away from
The three meninges are duramater, arachnoid membrane and piamater.
Duramater (dura: tough) is the outermost thick fibrous membrane.
c) duramater
There are ________ pairs of cranial nerves and ________ pairs of spinal nerves.
In man there are 12 pairs of cranial nerves arising from the brain.
There are 31 pairs of spinal nerves arising from the spinal cord.
a) 12, 31
The neurons which carries impulse from the central nervous system to the muscle fibre.
Motor or efferent neurons carry impulses from the central nervous system to effector organs such as muscle fibre or gland.
Afferent (sensory) neurons do the opposite — they carry impulses to the CNS.
c) efferent neuron
The cerebrum is divided into right and left hemispheres by the median cleft.
The two hemispheres are interconnected by a thick band of nerve fibres called corpus callosum.
c) corpus callosum
The myelin sheath covering the axon breaks at intervals by depressions called Nodes of Ranvier.
Hence they occur on axons, not on dendrites or cyton.
b) axons
Medulla oblongata has cardiac, respiratory and vasomotor centres.
It also regulates vomiting and salivation.
a) medulla oblongata
A neuron has dendrites, an axon and a neurilemma (Schwann cell layer over the myelin sheath).
Sarcolemma is the membrane of a muscle cell, so nerve cells do not possess it.
b) sarcolemma
A person who met with an accident lost control of body temperature, water balance, and hunger. Which of the following part of brain is supposed to be damaged?
Hypothalamus controls involuntary functions like hunger, thirst, water balance and acts as the thermoregulatory centre.
Loss of temperature control, water balance and hunger points to damage of the hypothalamus.
d) hypothalamus
II. Fill in the blanks
The neuron or nerve cell is the structural and functional unit of the nervous system.
It measures over 100 mm in length, making it the longest cell of the human body.
Neuron (nerve cell)
In myelinated neurons the axon is covered by a myelin sheath.
The myelin sheath acts as an insulator and ensures rapid transmission of nerve impulses.
Myelinated
A change in the environment that causes an animal to react is called ________ .
A change in the environmental condition detected by receptors in the body is a stimulus.
Light, heat, sound, touch and pressure are examples of stimuli.
Stimulus
Dendrites are the numerous branched cytoplasmic processes projecting from the cell body.
They conduct nerve impulses towards the cyton, while the axon carries impulses away from it.
Dendrites
The autonomic nervous system regulates the internal visceral organs.
It works through two antagonistic (opposite) components that maintain a steady state.
Sympathetic and parasympathetic nervous systems
The cyton has a nucleus, Nissl's granules, mitochondria, ribosomes, lysosomes and endoplasmic reticulum.
But neurons lack centrosome, so they do not have the ability to divide.
Centrosome (hence neurons cannot divide)
Cerebrospinal fluid (CSF) surrounds the brain and fills the central canal of the spinal cord.
Besides acting as a shock absorber and supplying nutrients, it maintains a constant pressure inside the cranium.
Cerebrospinal fluid (CSF)
The cerebral cortex is extremely folded.
The elevations are called gyri and the depressions between them are called sulci.
These folds increase the surface area of the cerebrum.
Gyri and sulci
The part of human brain which acts as relay center is ________ .
The thalamus lies in the cerebral medulla.
It is a major conducting centre for sensory and motor signalling and acts as a relay centre.
Thalamus
III. State whether true or false, if false write the correct statement
Dendrons are the longest fibres that conducts impulses away from the cell body.
Dendrites (dendrons) are short, branched processes that conduct impulses towards the cyton.
The axon is the single long fibre that carries impulses away from the cell body.
False – Axons are the longest fibres that conduct impulses away from the cell body.
The central nervous system consists only of the brain and the spinal cord.
The sympathetic system, along with the parasympathetic system, forms the autonomic nervous system.
False – Sympathetic nervous system is a part of the autonomic nervous system.
Hypothalamus lies at the base of the thalamus.
It acts as the thermoregulatory (temperature control) centre and also controls hunger, thirst, sleep and water balance.
True
Cerebrum is the largest part of the brain, forming nearly two-third of it.
Its cerebral cortex is responsible for sensory perception and control of voluntary functions, thinking, memory and reasoning.
True
Nerve fibres are myelinated or non-myelinated based on the presence of myelin sheath.
Myelinated fibres form the white matter and non-myelinated fibres form the grey matter of the brain.
True
Meninges are the three connective tissue membranes – duramater, arachnoid and piamater.
They cover and protect only the brain and the spinal cord (CNS), not all the nerves of the body.
False – The brain and spinal cord are covered and protected by meninges.
CSF is a lymph-like watery fluid that surrounds the brain and fills the central canal of the spinal cord.
Its functions include supplying nutrients to the brain, removing wastes, absorbing shocks and maintaining constant pressure inside the cranium.
True
Reflex arc is the pathway taken by a nerve impulse to accomplish a reflex action: receptor → sensory neuron → spinal cord → motor neuron → effector.
Since the impulse need not travel to the brain, the response is rapid and automatic, as in withdrawing the hand from a hot pan.
True
Pons is a bridge of nerve fibres connecting the lobes of the cerebellum and relays signals between cerebellum, spinal cord, midbrain and cerebrum.
It controls respiration and the sleep cycle.
True
IV. Match the following
| Column I | Column II |
|---|---|
| A. Nissil's granules | Forebrain |
| B. Hypothalamus | Peripheral Nervous system |
| C. Cerebellum | Cyton |
| D. Schwann cell | Hindbrain |
A. Nissl's granules – Cyton: the cell body (cyton) has abundant neuroplasm containing large granular bodies called Nissl's granules.
B. Hypothalamus – Forebrain: the forebrain consists of cerebrum and diencephalon, which has the dorsal thalamus and ventral hypothalamus.
C. Cerebellum – Hindbrain: the hindbrain is formed of three parts — cerebellum, pons and medulla oblongata.
D. Schwann cell – Peripheral Nervous system: Schwann cells form the neurilemma around the myelinated nerve fibres of the peripheral nerves.
A - Cyton, B - Forebrain, C - Hindbrain, D - Peripheral Nervous system
V. Understand the assertion statement. Justify the reason given and choose the correct choice
Assertion: Cerebrospinal fluid is present throughout the central nervous system. Reason: Cerebrospinal fluid has no such functions.
The assertion is true: cerebrospinal fluid surrounds and protects the brain within the skull and also fills the central canal of the spinal cord, so it is present throughout the central nervous system.
The reason is false: CSF has many important functions — it acts as a shock absorber, supplies nutrients to the brain, removes wastes and maintains a constant pressure inside the cranium.
Hence the assertion alone is correct while the reason is wrong.
a) Assertion is correct and reason is wrong
Assertion: Corpus callosum is present in space between the duramater and piamater. Reason: It serves to maintain the constant intracranial pressure.
The assertion is wrong: corpus callosum is not present between the meninges. It is the thick band of nerve fibres that interconnects the right and left cerebral hemispheres.
The structure present in the space between the duramater and piamater (around the brain) is the cerebrospinal fluid.
The reason is correct as a statement, because the fluid filling this space (CSF) is responsible for maintaining a constant pressure inside the cranium.
Hence only the reason is correct.
b) Reason is correct and the assertion is wrong
VI. Short answer questions
A stimulus is any change in the environmental condition that is detected by the receptors present in the body.
Living organisms respond to stimuli such as light, heat, cold, sound, smell, taste, touch, pressure, pain or the force of gravity.
Example: when we touch a hot object, heat is the stimulus and withdrawal of the hand is the response.
Stimulus is a change in the environmental condition detected by receptors of the body, to which the organism responds (e.g., heat, light, sound).
The hind brain is formed of three parts.
Cerebellum – coordinates voluntary movements and maintains body balance.
Pons – a bridge of nerve fibres connecting the lobes of cerebellum; controls respiration and sleep cycle.
Medulla oblongata – has cardiac, respiratory and vasomotor centres; regulates vomiting and salivation.
Hind brain consists of cerebellum, pons and medulla oblongata.
The brain is lodged in the bony cavity of the skull (cranium), which protects it from injury.
It is covered by three connective tissue membranes called meninges – duramater (outer, thick fibrous), arachnoid membrane (middle, thin vascular, web-like cushion) and piamater (inner, thin delicate, richly supplied with blood).
Meningeal membranes protect the brain from mechanical injury.
The brain is suspended in cerebrospinal fluid (CSF), which acts as a shock absorber and maintains constant pressure inside the cranium.
The brain is protected by the bony skull, the three meninges (duramater, arachnoid and piamater) and the cerebrospinal fluid.
Conditioned (acquired) reflexes are the result of practice and learning, and need conscious training effort.
Example: playing a harmonium by striking a particular key on seeing a music note.
Playing harmonium by striking a particular key on seeing a music note is an example of conditioned reflex.
The hypothalamus lies at the base of the thalamus in the forebrain.
It controls the secretion of hormones from the anterior pituitary gland.
Thus it forms an important link between the nervous system and the endocrine system.
Hypothalamus acts as the link between the nervous system and the endocrine system.
A reflex is a response that occurs automatically without consciousness.
The pathway taken by the nerve impulse to accomplish a reflex action is called the reflex arc.
It is formed of receptor → sensory (afferent) neuron → spinal cord (relay neuron) → motor (efferent) neuron → effector such as a muscle.
Reflex arc is the pathway taken by a nerve impulse to accomplish a reflex action: receptor → sensory neuron → spinal cord → motor neuron → effector.
VII. Differentiate between
Voluntary actions: actions performed consciously, under the control of our will, and monitored by the brain (mainly the cerebrum and cerebellum). Example: walking, writing, speaking.
Involuntary actions: actions that occur automatically without our consciousness or will; they are controlled by the spinal cord, medulla oblongata and the autonomic nervous system. Example: heart beat, breathing, digestion, withdrawal of hand from a hot pan (reflex).
Control centre: voluntary actions are decided by the thinking part of the brain, whereas involuntary actions need no thinking and are mostly reflex or visceral activities.
Speed: voluntary actions are comparatively slow as the brain takes decision; involuntary actions such as reflexes are very rapid and protect the body.
Voluntary actions are conscious, willed actions controlled by the brain (e.g., writing), while involuntary actions are automatic, unconscious actions controlled by the spinal cord, medulla and autonomic nervous system (e.g., heart beat, reflexes).
Medullated (myelinated) nerve fibre: the axon is covered with a myelin sheath; non-medullated (non-myelinated) nerve fibre: the axon is not covered by a myelin sheath.
Nodes of Ranvier: medullated fibres show depressions called Nodes of Ranvier where the myelin sheath breaks at intervals; such nodes are absent in non-medullated fibres.
Impulse conduction: myelin sheath acts as an insulator and ensures rapid transmission of nerve impulses, so medullated fibres conduct faster than non-medullated fibres.
Occurrence: medullated fibres form the white matter of the brain and spinal cord, while non-medullated fibres form the grey matter.
Medullated fibres have a myelin sheath with Nodes of Ranvier, conduct impulses rapidly and form white matter; non-medullated fibres lack myelin sheath and nodes, conduct slowly and form grey matter.
VIII. Long answer questions
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Definition: A neuron (nerve cell) is the structural and functional unit of the nervous system. It is the longest cell of the human body, over 100 mm long, and is specialised to detect, receive and transmit stimuli as electrical impulses.
Parts: A neuron typically consists of three basic parts — cyton, dendrites and axon.
Cyton (cell body or perikaryon): It has a central nucleus with abundant cytoplasm called neuroplasm. The cytoplasm contains large granular bodies called Nissl's granules along with mitochondria, ribosomes, lysosomes and endoplasmic reticulum. Neurons do not have the ability to divide.
Neurofibrils: Several neurofibrils present in the cytoplasm of the cyton help in the transmission of nerve impulses to and from the cell body.
Dendrites: These are numerous branched cytoplasmic processes projecting from the surface of the cell body. They conduct nerve impulses towards the cyton, and their branching increases the surface area for receiving signals from other nerve cells.
Axon: It is a single, elongated, slender projection which carries impulses away from the cyton. Its plasma membrane is the axolemma and its cytoplasm is the axoplasm. The end of the axon terminates as fine branches ending in knob-like swellings called synaptic knobs.
Myelin sheath and neurilemma: The axon may be covered by a protective myelin sheath, which is further covered by a layer of Schwann cells called neurilemma. The myelin sheath acts as an insulator and ensures rapid transmission of nerve impulses.
Nodes of Ranvier: The myelin sheath breaks at intervals by depressions called Nodes of Ranvier; the region between two nodes is called the internode.
Synapse: The junction between the synaptic knob of the axon of one neuron and the dendron of the next neuron is the synaptic junction, where neurotransmitters are released to pass information.
Diagram: Draw an elongated cell — label cyton with nucleus and Nissl's granules, branched dendrites at one end, a long axon with myelin sheath, neurilemma, Nodes of Ranvier, and the axon terminals with synaptic knobs (as in Fig. 15.1).
A neuron has a cyton (with nucleus, neuroplasm and Nissl's granules), branched dendrites that carry impulses towards the cyton, and a single axon (with axolemma, myelin sheath, neurilemma, Nodes of Ranvier and synaptic knobs) that carries impulses away from the cyton.
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Protection: The brain is the controlling centre of all body activities. It lies in the bony cavity of the skull and is covered by three meninges — duramater (outermost, thick, fibrous), arachnoid membrane (middle, thin, vascular, web-like cushion) and piamater (innermost, thin, delicate, richly supplied with blood). It is also suspended in cerebrospinal fluid, which acts as a shock absorber.
Main parts: The human brain is formed of three main parts — forebrain, midbrain and hindbrain.
Forebrain — Cerebrum: It is the largest portion, forming nearly two-thirds of the brain. It is divided into right and left cerebral hemispheres by a deep median cleft, and the two hemispheres are joined by a thick band of nerve fibres called corpus callosum. The outer cerebral cortex is grey matter, folded into gyri with depressions called sulci; the inner cerebral medulla is white matter. Each hemisphere has frontal, parietal, temporal and occipital lobes. It is responsible for thinking, intelligence, consciousness, memory, imagination, reasoning and willpower.
Forebrain — Thalamus: Present in the cerebral medulla, it is a major conducting centre for sensory and motor signalling and acts as a relay centre.
Forebrain — Hypothalamus: It lies at the base of the thalamus and controls involuntary functions like hunger, thirst, sleep, sweating, sexual desire, anger, fear, water balance and blood pressure. It is the thermoregulatory centre and controls the secretion of hormones from the anterior pituitary, thus linking the nervous and endocrine systems.
Midbrain: It lies between the thalamus and hindbrain. Its dorsal portion has four rounded bodies called corpora quadrigemina which control visual and auditory (hearing) reflexes.
Hindbrain — Cerebellum: The second largest part of the brain, formed of two large hemispheres and a middle vermis. It coordinates voluntary movements and maintains body balance and posture.
Hindbrain — Pons: A bridge of nerve fibres connecting the lobes of the cerebellum. It relays signals between the cerebellum, spinal cord, midbrain and cerebrum, and controls respiration and the sleep cycle.
Hindbrain — Medulla oblongata: The posterior-most part of the brain, connecting the spinal cord with other parts of the brain. It has cardiac, respiratory and vasomotor centres controlling heart beat, respiration and contraction of blood vessels, and it also regulates vomiting and salivation.
Diagram: Draw the L.S. of the human brain and label cerebrum, corpus callosum, ventricles, thalamus, hypothalamus, pituitary gland, midbrain, cerebellum, pons and medulla oblongata (as in Fig. 15.5).
The brain, protected by the skull, meninges and CSF, consists of the forebrain (cerebrum for thinking and memory, thalamus as relay centre, hypothalamus for involuntary functions), midbrain (visual and auditory reflexes) and hindbrain (cerebellum for balance, pons for respiration and sleep, medulla for heart beat, respiration and vomiting).
What will you do if someone pricks your hand with a needle? Elucidate the pathway of response with a neat labelled diagram.
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Response: If someone pricks my hand with a needle, I will withdraw my hand immediately. This is a sudden, automatic response occurring without consciousness, called a reflex action.
Reflex arc: The pathway taken by the nerve impulse to accomplish a reflex action is called the reflex arc. As most reflexes are monitored by the spinal cord, these are also called spinal reflexes.
Step 1 — Stimulus and receptor: The prick (pain) is the stimulus, which is sensed by the pain receptors present in the skin of our hand.
Step 2 — Sensory neuron: The stimulus triggers an impulse in the sensory (afferent) neuron, which conveys the message to the spinal cord.
Step 3 — Spinal cord and relay neuron: The spinal cord interprets the stimulus and the impulse is passed on to the relay (association) neuron, which in turn transmits it to a motor neuron.
Step 4 — Motor neuron: The motor (efferent) neuron carries the command from the spinal cord to the muscles of our arm.
Step 5 — Effector: The muscle of the arm is the effector organ; it contracts and we withdraw our hand immediately from the needle.
Significance: The impulse need not travel to the brain, so the response is very quick and protects the body from injury.
Diagram: Draw the reflex arc showing — receptor in skin → sensory neuron → dorsal root → spinal cord with relay neuron → motor neuron through ventral root → muscle (effector), as in Fig. 15.7.
The hand is withdrawn by a reflex action following the reflex arc: receptor in skin → sensory neuron → spinal cord (relay neuron) → motor neuron → arm muscle (effector) which contracts.
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Position: The spinal cord is a cylindrical structure lying in the neural canal of the vertebral column, which protects it. It is also covered by the three meninges.
Extent: It extends from the lower end of the medulla oblongata to the first lumbar vertebra. Its posterior-most region tapers into a thin, fibrous, thread-like structure called filum terminale.
Central canal: Internally, the spinal cord contains a cavity known as the central canal, which is filled with cerebrospinal fluid.
Grey matter: The grey matter of the spinal cord is 'H' shaped. The upper ends of the letter 'H' form the posterior horns and the lower ends form the anterior horns.
Roots and spinal nerves: A bundle of fibres passes into the posterior horn forming the dorsal or afferent root, and fibres pass outward from the anterior horn forming the ventral or efferent root. These two roots join to form a spinal nerve. There are 31 pairs of spinal nerves.
White matter: The white matter is external in position and has bundles of nerve tracts.
Functions: The spinal cord conducts sensory and motor impulses to and from the brain, and it controls the reflex actions of the body.
Diagram: Draw a T.S. of the spinal cord and label central canal, H-shaped grey matter with dorsal and ventral horns, white matter, dorsal root, ventral root and spinal nerve (as in Fig. 15.6).
The spinal cord is a cylindrical, meninges-covered structure in the neural canal, extending from the medulla oblongata to the first lumbar vertebra, with a CSF-filled central canal, inner H-shaped grey matter, outer white matter and 31 pairs of spinal nerves formed by dorsal and ventral roots; it conducts impulses to and from the brain and controls reflex actions.
Show steps (7)
Reception of stimulus: Information from the environment is detected by receptors located in sense organs such as the eyes, nose and skin. This information is transmitted as an electrical impulse and is received by the dendritic tips of the neuron.
Conduction within a neuron: The impulse travels from the dendrite to the cell body (cyton) and then along the axon to its terminal end.
Release of neurotransmitter: On reaching the axonal end, the impulse causes the nerve endings to release a chemical called a neurotransmitter. The important neurotransmitter released by neurons is acetylcholine.
Crossing the synapse: The neurotransmitter diffuses across the synapse — the junction between the synaptic knob of the axon of one neuron and the dendron of the next neuron.
Starting a new impulse: The chemical starts a similar electrical impulse in the dendrites of the next neuron, which is then carried to its cell body and along its axon. This flow of impulse from the axonal end of one neuron to the dendrite of another through a synapse is called synaptic transmission.
Reaching the CNS and effector: In this way the electrical signal reaches the brain or spinal cord. The response from the brain or spinal cord is similarly passed on to the effector organs such as muscles or glands, which carry out the desired response.
Speed: Each neuron can transmit about 1,000 nerve impulses per second and can make as many as ten thousand synaptic contacts with other neurons.
An impulse travels as an electrical signal from dendrite → cyton → axon; at the axon terminal it releases a neurotransmitter (acetylcholine) which diffuses across the synapse and starts a fresh electrical impulse in the dendrites of the next neuron — this is synaptic transmission.
Basis of classification: Structurally, neurons are classified according to the number of nerve processes arising from the cyton. They are of three types.
Unipolar neurons: Only one nerve process arises from the cyton, which acts as both axon and dendron. They are found in early embryos but not in adults.
Bipolar neurons: The cyton gives rise to two nerve processes, of which one acts as an axon and the other as a dendron. They are found in the retina of the eye and the olfactory epithelium of the nasal chambers.
Multipolar neurons: The cyton gives rise to many dendrons and one axon. They are found in the cerebral cortex of the brain.
Diagram: Draw the three types side by side and label them unipolar (A), bipolar (B) and multipolar (C), as in Fig. 15.2.
Structurally neurons are of three types — unipolar (one process, in early embryos), bipolar (one axon and one dendron, in retina and olfactory epithelium) and multipolar (many dendrons and one axon, in cerebral cortex).
IX. Higher Order Thinking Skills (HOTS)
'A' is a cylindrical structure that begins from the lower end of medulla and extend downwards. It is enclosed in bony cage 'B' and covered by membranes 'C'. As many as 'D' pairs of nerves arise from the structure 'A'. (i) What is A? (ii) Name (a) bony cage 'B' and (b) membranes 'C' (iii) How much is D?
(i) A is the spinal cord — a cylindrical structure lying in the neural canal, extending from the lower end of the medulla oblongata to the first lumbar vertebra.
(ii) (a) The bony cage B is the vertebral column (its neural canal encloses the spinal cord).
(ii) (b) The membranes C are the meninges — duramater (outermost), arachnoid membrane (middle) and piamater (innermost).
(iii) D = 31 pairs of spinal nerves arise from the spinal cord.
A - spinal cord; B - vertebral column; C - meninges (duramater, arachnoid, piamater); D - 31 pairs of spinal nerves.
Our body contains a large number of cells 'L' which are the longest cells in the body. L has long and short branch called as 'M' and 'N' respectively. There is a gap 'O' between two 'L' cells, through which nerve impulse transfer by release of chemical substance 'P'. (i) Name the cells L (ii) What are M and N? (iii) What is the gap O? (iv) Name the chemical substance P
(i) L is the neuron (nerve cell), the structural and functional unit of the nervous system and the longest cell of the human body (over 100 mm).
(ii) M is the axon — the single, long, slender process that carries impulses away from the cyton; N is the dendrites — short, numerous branched processes that conduct impulses towards the cyton.
(iii) O is the synapse (synaptic junction) — the gap between the synaptic knob of the axon of one neuron and the dendron of the next neuron.
(iv) P is the neurotransmitter, the important one released by neurons being acetylcholine.
L - neuron; M - axon; N - dendrites; O - synapse (synaptic junction); P - neurotransmitter (acetylcholine).
Quick check
Bipolar neurons are found in
Question 1 of 5Show answer
Answer: (1) retina of eye
Bipolar neurons have one axon and one dendron arising from the cyton.
The textbook states they are found in the retina of the eye and the olfactory epithelium of nasal chambers.
There are ________ pairs of cranial nerves and ________ pairs of spinal nerves.
Question 2 of 5Show answer
Answer: (1) 12, 31
In man there are 12 pairs of cranial nerves arising from the brain.
There are 31 pairs of spinal nerves arising from the spinal cord.
Nerve cells do not possess
Question 3 of 5Show answer
Answer: (2) sarcolemma
A neuron has dendrites, an axon and a neurilemma (Schwann cell layer over the myelin sheath).
Sarcolemma is the membrane of a muscle cell, so nerve cells do not possess it.
In reflex action, the reflex arc is formed by
Question 4 of 5Show answer
Answer: (4) receptor, spinal cord, muscle
The reflex arc is the pathway of the impulse: receptor → sensory neuron → spinal cord (relay neuron) → motor neuron → effector muscle.
So it begins at the receptor and ends at the muscle, passing through the spinal cord.
Which nervous band connects the two cerebral hemispheres of brain?
Question 5 of 5Show answer
Answer: (3) corpus callosum
The cerebrum is divided into right and left hemispheres by the median cleft.
The two hemispheres are interconnected by a thick band of nerve fibres called corpus callosum.