Can anyone explain how does impulse travel in our nerves.
My memory is vague but I remember the general principle.
You are talking about how a nerve generates an
action potential. How an impulse travels within our nerves.
The intracelluar milieu of nerve cells contain high concentrations of organic anions and inorganic cations mainly
high K+ and a
lower concentration of N+ and CL-. In the extracellular fluid outside the nerve cell, the concentrations of K+ are low and those of Na+CL- are high...the opposite of the intracellular environment. The result is a difference in potential across the membrane called
resting potential with the
inside of the cell being strongly negative compared with the fluids outside the cell.
During impulse transmission, there is a change in the resting potential and a flow of electric current across the membrane. This is the action potential. It is essentially a very rapid depolarization (decrease in negativity of the inside relative the positive outside) and a somewhat slower repolarization to the resting potential.
At the peak of the action potential the inside of the cell becomes positive with respect to the outside. How does this happen? First, there is an initial inward current due to the influx of Na+ and subsequently an outward current due to migration of the K+ from inside to the outside. This initial depolarization causes Na+ conductance to begin to increase, which depolarizes the membrane further and this increases Na+ conductance and so on. Repolarization then occurs when the K+ efflux restores the internal negativity. These passages of Na+ and K+ are thought to occur through separate channels in the cell membrane. Other ions cross the membrane during the action potential such as Ca++ etc. but that gets more dettailed. Of course, I did not get into the transmission across synapses.
That is a basic description without all the different equations Nernst equation, Donnan equillibrium, crap that I can't remember.
