Question

Consider a typical neuron.

a. What are the critical factors that establish an electrical potential across a neuron cell membrane?

b. Under what conditions will this membrane potential propagate down the length of the neuron?

c. What is the essential difference between myelinated and unmyelinated axons and how does that

affect the propagation of the membrane potential?

Answer 1

Answer a: Action potential is basically change in the electric potential which is associated with the passage of impulse.Action potential in the neurons are basically dependent on two factors as:

1. Type of ion channel(voltage gated sodium or potassium channels)

2. Threshold value ... It is the value of stimulus that has to be just right so that the action potential has to be   generated. This value is around -45mV.

A special type of protein is found in the membrane of our neurons called as voltage gated ion channel which is basically responsible for the action potential to generate.

Answer b: It is basically depolarization which is responsible for the membrane potential propagate down the length of the neuron. Since at the concentration of sodium is high outside the cell membrane which its concentration is low inside of the cell. So in normal condition the outside of cell is positively charged. Now due to any stimulus(by physical, chemical or biological mean) there is generation of electro-chemical gradient means sodium will move down the membrane by voltage gated sodium ion channel. By this again the polarity of membrane changes which is now more positive inside then on outside. This condition is called as depolarization.

Answer c: Myelinated nerve fibers : These are nerve fibers that are covered  by a myelin sheath(acting as insulator). The axons of myelinated is long which is mylinated (insulated) by which it is responsible to sudden response as my myelin there is increase in traveling  speed of information.

Unmyelinated nerve fibers: These are nerve fibers which does not have myelin sheath and also it is contain short nerve axon fiber as it is unmyelinated so the speed of information travel is slow.