this is a biophysics problem: The speed of propagation of an action potential ac
ID: 68225 • Letter: T
Question
this is a biophysics problem:
The speed of propagation of an action potential action potential is determined by the space constant ().
What is the strategy by which the squid increases the speed of propagation?
Vertebrate axons have a myelin sheath. What is the effect of the myelin sheath on the space constant of the axon? How does the myelin sheath increase the speed of propagation without increasing the size of the axon?
If T is the duration of an action potential, can you come up with an expression for propagation velocity in terms of and T?
Explanation / Answer
The rate of activity potential transmission depends somewhat on the axon's length consistent, that is the manner by which far down the axon the membrane is depolarized when as activity potential is produced crosswise over one piece of the membrane. There are two approaches to expand the axon's length constant and to enhance the speed of impulse transmission. The primary is to bring down inward resistance, which is expert by making a bigger diameter axon. This strategy is embraced by the squid and different invertebrates that have advanced giant axon. These bigger axons are utilized for mediating escape mechanism for the animal, and it is clearly advantageous to have data go along these axons as quick as would be prudent.
The other mechanism that expand the length steady of an axon and rates activity potential transmission is myelination which is the system of vertebrates. Myelin altogether builds layer resistances (Rm), in this way expanding the length consistent. However when resistance expands, the membrane time consistent ordinarule increment ( t=RC) which implies that it takes more time for the membrane to energize. However, myelin likewise diminishes film capacitance, diminish the tie consistent. As a result, then the time consistent of a myelinated axon is about the same as that of as unmyelinated axon. Myelin decreases membrane capacitance by expanding the thickness of the phospholipid surrpunding the axon.
This like moving the plates of a capacitor separated, which diminishes the capacity of a capacitor to store charge. in this manner after depolarization of the membrane, edge is come to before is a myelinated fibre when contrasted with as unmyelinated one.The increment in Rm of the myelinated axon implies that the voltage created over the membrane because of a set measure of current streaming into the axon is bigger, and since the time steady is about the same in a myelinated and unmyelinated axon of the same size, the membrane achieves spike-terminating edge quicker in the myelinated axon.
Since the speed of such an activity potential is not characterized, we have centered consideration upon the changing speed of the top in the time space. This speed can be communicated
p= lim (x/t)p
where it is understood that subscript p means that Ax and At are chosen as follows: a V/8 t = 0 both at x = xX, t = t1, and at x = xl + Ax, t = t, + At.
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