QuestionSBA
QuestionChoice
This answer was incorrect as increasing sodium influx would speed up depolarisation and so increase the heart rate.
10026237
c
Vagal activation increases sodium influx into the sinoatrial node cells
QuestionChoice
The pacemaker potential is the section of slow depolarisation between two action potentials. It occurs when the movement of sodium and calcium ions into the nerve cells exceeds the outward movement of potassium ions, causing an overall increase in voltage inside the cells. When the vagus nerve is activated, it increases potassium efflux from the sinoatrial node cells, slowing the pacemaker potential incline. This means it takes longer for the voltage to reach the threshold potential, increasing the length of time between action potentials and so, decreasing the heart rate.
10026235
a
Vagal activation increases potassium efflux from the sinoatrial node cells
QuestionChoice
This answer was incorrect as even though decreasing sodium influx would slow down depolarisation of the pacemaker potential, the vagus nerve does not affect sodium channels.
10026238
d
Vagal activation decreases sodium influx into the sinoatrial node cells
QuestionChoice
This answer was incorrect as increasing calcium influx would speed up depolarisation of the sinoatrial node cells and so increase heart rate.
10026239
e
Vagal activation increases calcium influx into the sinoatrial node cells
QuestionChoice
This answer was incorrect as decreasing potassium efflux would speed up depolarisation of the pacemaker potential and so increase the heart rate.
10026236
b
Vagal activation decreases potassium efflux from the sinoatrial node cells
Concept
Chapter
2693
5884
Autonomic Nervous System
Topic
159
Cardiovascular physiology
17645
What is the mechanism through which vagus nerve activation decreases the heart rate?
a