Action Potential

Increased Permeability to K⁺ ion

REF: See previous question for explanation

During an  action potential,  the conductance for both sodium and potassium is higher than it is at rest.  However,  the  conductance  for  sodium  is higher than the conductance for potassium during the over shoots. Hence, the transference for potassium is less. Recall that transference is a measure of an ion’s relative conductance: 

TN.  = gN.lCgN. + gK) and TK = gK/(gN.  + gK)

Where T = transference and g = conductance.

The main difference between the nerve and the glial cells are the possession of axons and dendrites and the capacity to generate action potentials.

A i.e. Nerves; B i.e. Muscle; C i.e. Glands

Action potential develops in excitable cells such as nerves (neurons), muscle (skeletal, smooth and cardiac), and other contractile tissues such as few glandsQ. Glial cells such as neuroglial cells do not generate action potential.

D i.e. Threshold stimulus is required

B i.e. Frequency of AP

Ans. C: Sodium ion

Ans. A: Lower extracellular sodium

Conversely, increasing the external K+ concentration decreases the resting membrane potential.

A decrease in extracellular Ca2+ concentration increases the excitability of nerve and muscle cells by decreasing the amount of depolarization necessary to initiate the changes in the Na+ and K+ conductance that produce the action potential. Conversely, an increase in extracellular Ca2+ concentration “stabilizes the membrane” by decreasing excitability