Shows hyperpolarisation due to on time closing of Na^+ VCG and K^+ VCG

Question

Show hyperpolarisation due to on time closing of Na⁺ VCG and K⁺ VCG.

Answer 1

Decreased extracellular potassium leads to hyperpolarization:

Lower potassium levels in the extracellular space will cause hyperpolarization of the resting membrane potential. As a result, a greater than normal stimulus is required for depolarization of the membrane in order to initiate an action potential.

The structure of the voltage gated K⁺ channel is that of six transmembrane helices along the lipid bilayer. 

Activation and deactivation of the voltage gated K⁺ channel is triggered by conformational changes in the voltage sensing domain. Specifically,  the S₄ domain moves such that it activates and deactivates the pore. During activation, there is outward S₄ motion, causing tighter VSD-pore linkage. Deactivation is characterized by inward S₄ motion. 

The switch from depolarization into repolarization is dependent on the kinetic mechanisms of both voltage gated K⁺ and Na⁺ channels.

Although both voltage gated Na⁺ and K⁺ channels activate at roughly the same voltage (-50 mV), Na⁺ channels have faster kinetics and activate/deinactivate much more quickly.

Repolarization occurs as the influx of Na⁺ decreases (channels deinactivate) and the efflux of K⁺ ions increases as its channels open.