axonal membrane is impermeable to Na+. Then how does it allow 3 Na+ to flow from the axonal membrane?
axonal membrane is impermeable to Na+. Then how does it allow 3 Na+ to flow from the axonal membrane?
At the resting stage (when the neuron is not conducting any impulse), the axonal membrane is comparatively more permeable to potassium ions (K+ ) and nearly impermeable to sodium ions (Na+ ).
As a result of this, the axoplasm inside the axon contains high concentration of K+ and low concentration of Na+.
In contrast, the fluid outside the axon contains a low concentration of K+, a high concentration of Na+ and thus form a concentration gradient.
These ionic gradients across the resting membrane are maintained by the active transport (energy is utilized) of ions by the sodium-potassium pump which transports 3 Na+ outwards for 2 K+ into the cell .3 Na+ are transported outwards for 2 K+ because K+ is more electropositive than Na+. So, the transfer of ions occurs to maintain this ionic gradient. As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarised.
At the resting stage (when the neuron is not conducting any impulse), the axonal membrane is comparatively more permeable to potassium ions (K+ ) and nearly impermeable to sodium ions (Na+ ).
As a result of this, the axoplasm inside the axon contains high concentration of K+ and low concentration of Na+.
In contrast, the fluid outside the axon contains a low concentration of K+, a high concentration of Na+ and thus form a concentration gradient.
These ionic gradients across the resting membrane are maintained by the active transport (energy is utilized) of ions by the sodium-potassium pump which transports 3 Na+ outwards for 2 K+ into the cell .3 Na+ are transported outwards for 2 K+ because K+ is more electropositive than Na+. So, the transfer of ions occurs to maintain this ionic gradient. As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarised.
