Question

fill in the table below with the requested information for each channel or pump

channel active or passive? Stimulus that opens the channel resulting membrane state: polarization, depolrazation, hyperpolarization, repolarization   

Box 1: VG-NA+

Box 2. CG-K+

Box 3. VG-K+   

Answer 1

Polarisation is the state in which cell is in resting condition that is resting membrane potential is present.In this condition inside of the cell is relatively electronegative.As potassium ion move out of the cell through potassium leacky channels along the the concentration gradient.During this time cell is more permeable to potassium ion.Small part of resting membrane potential is contributed by sodium potassium ATPase pump.Here 3 Na+ goes out of the cell and 2 K+ ion move in to the cell against the concentration gradient using ATP.

Depolarisation  condition occur when the cell is stimulated or excitated and generation of action potential occurs as the Na+ move into the cell through voltage gated Na+ channel,making inside electropositive.After some time when it reaches the maximum action potential, cell starts to repolarise.

During repolarisation voltage gated K+ channel open and K +move out of the cell making the potential negative towards-RMP.

When much of K+ are effluxed out of the cell inside becomes more electro negative than RMP.This is called Hyperpolarisation.Than after some time again resting membrane potential is achived that is cell becomes polarized.

All these occor as a cyclical process.That is polarization_depolarization_repolarization_hyperpolarization_polarization.

That is during polarization_concentration gradient based k+ channels.(k+leaky channels)_passive.

Also active channel_Na-k ATPase pump is operated.

Depolarisation(voltage gated Na+channels)_channels open or close according to membrane potential.These are passive channels as Na move along the concentration gradient.

Repolarization(voltage gated potassium channels open)_passive channel as k+ move along concentration gradient.

Hyperpolarization_voltage gated k+ channels open)_passive.