A. Action potentials occur ____________________________. in the unmyelinated reg

Question

A. Action potentials occur ____________________________.

in the unmyelinated regions of an axon

in myelinated regions of an axon

in both unmyelinated and myelinated regions of an axon and the dendrites

B. Demyelinating diseases cause a(n) ______________ in the conduction velocity of action potentials.

increase

decrease

C. If demyelination occurs, why don’t action potentials occur at regions of the axon that were previously myelinated?

A much thinner plasma membrane is present within these regions of the axon.

These regions lack the appropriate concentration of voltage-gated sodium channels.

These regions contain too high of a concentration of voltage-gated sodium channels to work appropriately.

A much thicker plasma membrane is present within these regions of the axon.

Explanation / Answer

A. Action potentials occur in both mylienatedand unmyelinated regions of axon and dendrites.

It is a brief electrical signal that travels along axon and dedrites at a great speed which causes the depolarisation.

B. Demyelinating disesases cause decrease in conduction velocity of action potentials because it damages the myelin sheath of brain and spinal cord causing neurological problems.

C. If demyelination occurs, action potential does not occur at the previously myelinated regions of axon because these regions lack appropriate concentration of voltage gated sodium channels (vgsc).

These concentrations play a very important role in action potential generation and hence transmission of nerve impulses

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