in the resting state the inyerior o

in the resting state the inyerior of the nerve cell and is proceses are rich in potassium ions and low in so dium ions whereas on their exterior the concentration of these ions is reversed because of this unequal distribution of ions, togther with the fact that the membrane in its resting state is much more permeable to potassium than sodium ions,the nerve has a resting potential of approximately 70 mv, the outside being electrically positive with respect the interior
A nerve impulse is created by the temporary depolarization of the nerve membrane Channels in the membrane open up to allow the flow of sodium ions into the cell with a second set of channels allowing for the outward flow of potassium ions from the cell after a slight delay A wave of depolarization is conducted over the whole surface of the neuron from the point at which it was originally generated In myelinated nerve fibers the nerve impulse jumps quickly from one node of Ranvier to the next The conduction velocity of nerve impulses along myelinated fiber is up to 25 times greater than along unmyelinated fibers of similar diameter.
the ionic exchange across the nerve membrane to produce a nerve impulse is a relativeiy simple biochemical mechanism. it is altered little during the normal aging process. in normal older people there is no significant change in the conduction velocity along a specified portion of a nerve trunk when compared to that found in younger adults. in the elderly, as in younger persons if a reduction in conduction velocity is found some narrowing of the fider or some impairment of blood flow to the nerve sheath or some degree of demyelination of the fiber should be suspected