The release of chemical messenger from synaptic vesicles is under

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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+


C.

Ca2+

When an impulse arrives at the synaptic knob of the axon, it depolarizes the presynaptic membrane and increases its permeability to calcium ions (Ca2+). Ca2+ ions from the synaptic cleft pass into the synaptic knob via voltage gated channels. Sudden rise in the cytosolic concentration of Ca, causes the release of a chemical, called neurotransmitter substance, from small synaptic vesicles present there into the synaptic cleft by exocytosis through the presynaptic membrane.


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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


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