Question

Describe how each of the conditions at the A-V node below will affect the heart rate

A) Increased sodium permeability

B) Decreased acetylcholine levels

C) Increased norepinephrine levels

D) Increased potassium permeability

E) Increased calcium permeability

Answer 1

A) Increased sodium permeability will change the action potential of the cell from -60mV to -40mV thus causing it to depolarize.

E) Increased calcium permeability will change the action potential of the cell from -40mV to +10mV which depolarizes the cell.

D) Increased potassium permeability will change the action potential of the cell from +10mV to -60mV which repolarizes the cell.

B) Decreased acetylcholine levels cause an increase in the heart rate by increasing the rate of depolarization and increasing the conduction velocity by AV node.

C) Increased norepinephrine levels cause an increase in the heart rate in the same way as it does for decreased acetylcholine levels.