Assertion: Mylein sheath insulates the nerve fibre and prevents i

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 Multiple Choice QuestionsMultiple Choice Questions

221.

Which of the following is the part of mid brain of rabbit?

  • Diencephalon

  • Cerebrum

  • Corpora quadrigemina

  • None of the above


222.

Now-a-days cornea transplantation is very popular. The reason is that it

  • is easy to preserve

  • transplanted very easily

  • can be easily obtained

  • does not link with blood supply and immune system


223.

Unidirectional transmission of a nerve impulse through nerve fibre is due to the fact that

  • nerve fibre is insulated by a medullary sheath

  • sodium pump starts operating only at the cyton and then continues into the nerve fibre

  • neurotransmitters are released by dendrites and not by axon endings

  • neurotransmitters are released by the axon endings and not by dendrites.


224.

Cornea transplant in humans is almost never rejected. This is because

  • it is composed of enucleated cells

  • it is a non-living layer

  • its cells are least penetrable by bacteria

  • it has no blood supply


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225.

Assertion : All motor neurons are efferent neurons.

Reason : Motor neurons conduct nerve impulses from the spinal cord to the brain.

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

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

  • If assertion is true but reason is false.

  • If both assertion and reason are false


226.

Given is the diagrammatic representation of the sectional view of cochlea. Select the correct option regarding it.

  • A - Organ of corti-responsible for maintenance of balance of the body and posture.

  • B- Scala vestibuli-filled with perilymph that ends at the oval window.

  • C- Scala tympani-terminates at the round window which opens to the middle ear.

  • D- Basilar membrane - nerve impulses are generated against it.


227.

Assertion: The optic nerves leave the eye at the point called blind spot.

Reason: Only cone are densely packed at the blind spot, hence is the name.

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

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

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


228.

Which of the following is correctly labelled

  • A: Reissner's membrane

  • B: Scala vestibuli

  •  C : Basilar membrane

  • D: Tectorial membrane


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229.

The release of chemical messenger from synaptic vesicles is under the influence of these ion(s).

  • Cl- 

  • Fe and S2+

  • Ca2+

  • Mg2+ and Sr2+


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230.

Assertion: Mylein sheath insulates the nerve fibre and prevents its depolarisation.

Reason: Nerve impulses are conducted more rapidly in non - myelinated nerve fibres than in myelinated ones.

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

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

  • If assertion is true but reason is false.

  • If both assertion and reason are false


C.

If assertion is true but reason is false.

In non-myelinated nerve fibres, the ionic changes are repeated over the membrane all along the length of the fibre. So, the action potential flows all along the membrane over the entire length of the fibre. But in myelinated fibres, the ionic changes and the consequent depolarisation can take place only at the nodes of Ranvier free from myelin sheath, because the myelin sheath between the nodes insulates the fibre and prevents its depolarisation. So, the action potential in effect jumps from one node to the next.This is called saltatory conduction of nerve impulses. Because of this, nerve impulses do not have to run all along the myelinated nerve fibre. This is why nerve impulses are conducted far more rapidly in myelinated fibres than in the non - myelinated ones.


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