Biology

Nervous System and Neurons

1,224 Questions

The nervous system and neurons section covers the structural and functional aspects of the human nervous system. Topics include nerve fibers, the myelin sheath, and sympathetic nervous system functions. This material is crucial for general science preparation in various competitive exams.

Neuron structureMyelin sheath productionSympathetic nervous systemCranial and spinal nervesParasympathetic functions

Nervous System and Neurons Questions

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

End plate junction is present between

  1. Neuron and striated muscle

  2. Neuron and neuron

  3. Muscle and muscle

  4. Both (b) and (c)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • The site of chemical communication between a nerve fibre and a muscle cell is called the end plate junction or neuromuscular junction.
  • The neuromuscular junction is analogous to the synapse between two neurons. 
  • A nerve fibre divides into many terminal branches; each terminal ends on a region of muscle fibre called the end plate. Embedded in the end plate are thousands of receptors. 
  • So, the correct option is 'Neuron and Striated muscle'.
Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

The myelin sheath around the axon is produced by which type of neurogical cells?

  1. Satellite glial cells

  2. Radial glial cells

  3. Dendrocytes

  4. Schwann cells
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation


  1. Myelin sheath is formed by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system. 
  2. These cells wrap layer upon layer of their own plasma membrane in a tight spiral around axon. 
  3. The insulating layer checks the leakage of charge and lesser stoppage points (nodes of Ranvier) leading to acceleration of the conduction and conservation of the metabolic energy.
So, the correct option is 'Schwann cells'.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

During depolarisation of neuron

  1. $K^+$ channels remain open
  2. N$a^+$ gets inside through ion channels
  3. N$a^+$ gets outside through ion channels

  4. All the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During depolarization, voltage-gated sodium channels open, allowing sodium ions to rush into the neuron, which makes the interior less negative.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

An investigator places an isolated neuron in a calcium-free medium, gives the neuron a suprathreshold stimulus and then performs an assay to test whether neurotransmitter is released into the medium. Which of the following outcomes would you predict?

  1. No neurotransmitter is detected since influx of calcium into the synaptic knob is required for neurotransmitter release.

  2. No neurotransmitter is detected since influx of calcium is required in order for the neuron to conduct an action potential.

  3. Neurotransmitter is detected since calcium is not required for action potential conduction and the initial stimulus was suprathreshold.

  4. We cannot predict the outcome without knowing whether the neuron was myelinated or non-myelinated.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Calcium influx into the synaptic terminal is essential for the exocytosis of neurotransmitter vesicles. Without extracellular calcium, the neurotransmitter cannot be released even if the action potential reaches the terminal.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Synaptic vesicles are

  1. at the ends of dendrites and axons

  2. at the ends of axons only

  3. along the length of all long fibres

  4. all of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a neuron, synaptic vesicles store various neurotransmitter that is released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagation nerve impulses between neurons and are constantly recreated by the cell.

So, the correct option is 'at the ends of axons only'.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Assertion : Myelinated nerve fibre are enveloped with Schwann cells, which form a myelin sheath around the axon
Reason : Unmyelinated nerve fibre is not enclosed by a Shwann cell and hence does not form a myelin sheath around the axon

  1. If both assertion and reason are true and the reason is the correct explanation of the assertion

  2. If both assertion and reason are true but reason is not the correct explanation of the assertion

  3. If assertion is true but reason is false

  4. If both assertion and reason are false
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The myelinated nerve fibers contain a myelin sheath surrounding the axons of nerve cells. While in unmyelinated nerve fibre is not enclosed by a Schwann cell and hence does not form a myelin sheath around the axon.

So the correct option is "Both Assertion and Reason are correct but the reason is not the correct explanation of assertion".

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

The .................... of the neuron secretes the substance named neurotransmitter.

  1. Axon

  2. Dendron

  3. Schwann cell

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The axon of the neuron secretes the substance named neurotransmitter to communicate with next dendrite.

Neurotransmitters are the brain chemicals that communicate information throughout our brain and body.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

The role of the axon is to

  1. Integrate signals from the dendrites

  2. Release neurotransmitter

  3. Conduct the impulse to the synaptic terminal

  4. Synthesize cellular components
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
An axon also known as a nerve fibre, is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body. The function of the axon is to transmit information to different neurons, muscles and glands. The space between two neuron is known as synapse. The nerve impulse is transmitted towards the synaptic terminal from the dendron.
Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

In comparison with other cells, nerve cells show a higher degree of

  1. Metabolism

  2. Growth

  3. Contractility

  4. Irritability
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Irritability or excitability is the ability of nerve cells to respond to environmental stimulus. Primary function of nerve cells is to generate sensory input in response to external and internal stimuli followed by integration of sensory information to generate motor output. Thus, nerve cells exhibit higher rate of irritability as compared to other cell types. 

Therefore, the correct answer is option D.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Statements (A, B, C, D) in List I have to be matched with statements (p, q, r, s) in List II.

List I List II
A Cyton p  The body of the nerve cell that contains the organelles.
B Dendrite q Receives the stimuli sent from another nerve or the outside environment.
C Axon r A fatty substance that covers the axon of the nerve cell and speeds.
D Myelin sheath s The long, thin section of the nerve cell where the impulse is transmitted across.

  1. A- p, B- q, C- s, D- r

  2. A- r, B- q, C- s, D- p

  3. A- r, B- s, C- q, D- p

  4. A- r, B- s, C- p, D- q
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cyton is the cell body of the neuron. It contains the nucleus.

Dendrites are the cellular extension from the cyton. They receive stimulus, which may be physical, chemical, mechanical or electrical, and pass it on to the cyton.
Axons are also known as nerve fibres which are a projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body.
Myelin sheath is also known as the medullary sheath. It is the envelope of myelin that surrounds the core of a nerve fiber or axon and that facilitates the transmission of nerve impulses, formed from the cell membrane of the Schwann cell in the peripheral nervous system and from oligodendroglia cells. 
So, the correct answer is option C.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Nerve cells possess
(a) Dendrites
(b) Axon
(c) Sarcolemma
(d) Neurilemma

  1. a, b

  2. a, b, c

  3. a, b, d

  4. a, b, c, d
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Each mammalian neuron consists of a cell body, dendrites, and an axon. The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals. Dendrites extend from the neuron cell body and receive messages from other neurons. 

The dendrites are covered with synapses formed by the ends of axons from other neurons. 
Neurilemma is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. 
The sarcolemma also called the myolemma, is the cell membrane of a striated muscle fiber cell. It is not present in the nerve cells.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Nissl granules are mostly present in 

  1. Axon

  2. Cyton

  3. Dendron

  4. Schwann cells
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A Nissl body is a large granular body found in neurons. These granules are rough endoplasmic reticulum (RER) with rosettes of free ribosomes and are the site of protein synthesis. These are present in cyton of the nerve cell.

So, the correct answer is option B.

Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Which one of the following pairs of structure distinguishes a nerve cell from other types of cell?

  1. Flagellum and medullary sheath

  2. Nucleus and mitochondria

  3. Perikaryon and dendrites

  4. Vacuoles and fibres
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • The structural difference between a neuron and other kinds of cell include the perikaryon and dendrites.
  • The cell body of a neuron, known as perikaryon, has a large and round nucleus. Nissil granules are present in its cytoplasm forming the characteristic feature.
  • While dendrites are branched thread like structure arising from cyton which functions to receive impulses from sensory system and transfer it in form of electrical impulses to other neurons via the Axon.
So, the correct option is 'Perikaryon and Dendrites'.
Multiple choice biology plant and animal tissues nervous system in animals structure of neuron structure and function of neuron

Select the correct statement regarding the Schwann cells.

  1. Surround axon of myelinated nerve fibre

  2. Support muscle fibres

  3. Found in Haversian system of bones

  4. Form basement membrane of epithelium.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Schwann cell, also called neurilemma cell, any of the cells in the peripheral nervous system that produce the myelin sheath around neuronal axons. Myelin, which is a fatty layer that insulates the axon, helps to increase the saltatory conduction of the neuron. 
So, the correct answer is option A.
Multiple choice biology animal behaviour ethology natural selection coordination in human beings- chemical control endocrine system in humans

A frog has its brain crushed, but when pinched on the leg, the leg draws away. It is an example  of 

  1. neurotransmitter induced response

  2. simple reflex

  3. condition reflex

  4. automated motor response.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The action does not involve the brain and is an example of a simple reflex. When the leg of the frog is pinched, the stimulus is received by receptors on the skin that set up a sensory impulse. This impulse is carried to the spinal cord through the dorsal sensory root of a spinal nerve. The spinal cord then transforms the sensory impulse into a motor impulse. This impulse is then transmitted to the leg muscles. The muscles on receiving the impulse contract and the leg is withdrawn to avoid the stimulus. So, the correct option is 'simple reflex'.