Question

Some researchers believe that parasympathetic neurons regulate heart rate by impacting 3 channel types in pacemaker cells. Make a numbered list of the channel types. For each, explain which direction the ion moves and why. That is, does it move into or out of the cell, and what are the driving forces? Lastly, summarize the overall effect of parasymp on V_m in pacemaker cells.  

Answer 1

The three channel types of pacemaker cells regulated by the parasympathetic nervous system are, sodium, potassium and calcium channels.

1). Sodium channels: Sodium channels are blocked or the inward movement of sodium ions is decreased by parasympathetic stimulation

2). Potassium channels: Inward movement of potassium ions is increased by parasympathetic stimulation

3).Calcium channels: Inward movement of calcium ions is reduced by parasympathetic stimulation.

As a result, the membrane potential of the pacemaker cells becomes more negative and the cells are less likely to be activated by the impulse and to conduct the impulse because the threshold potential is increased.