Myelin: specialized cells called Schwann cells wrapped along the axon.
– Schwann cells are made of lipids and proteins
– many Schwann cells form the myelin sheath affects the speed of conduction of
electrical impulses
Transmission of nerve impulses:
– impulse/signals are brief changes in the distribution of electrical charge across the cell
surface membrane results in action potentials
– caused by the rapid movement of Na+
and K
+
ions into and out of the axon
Resting potential
– inside the axon: slightly negative
– potential difference: -60mV to -70mV (potential inside the axon is less than that outside
the axon)
Neurones, like all cells, have sodium-potassium pumps in their cell surface
membranes. However, in neurones these are especially active. By active transport,
they pump out 3 Na+
ions for every 2 K+
ions brought in.
