QuestionSBA
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. Adrenaline binds to beta-1 receptors causing increased calcium influx, hence speeding up the depolarisation of the pacemaker potential. This reduces the time taken for the cell to reach threshold potential. It occurs through L-type calcium channels.
10026240
a
Adrenaline binds to beta-1 receptors causing increased calcium influx through L-type calcium channels into the sinoatrial node cells
QuestionChoice
The binding of adrenaline to Beta-1 receptors increases calcium influx, not efflux. Increasing the calcium efflux would slow down the depolarisation of the pacemaker potential, reducing the heart rate. Furthermore, the movement of calcium during the pacemaker potential is through L-type calcium channels, not T-type.
10026242
c
Adrenaline binds to beta-1 receptors causing increased calcium efflux through T-type calcium channels into the sinoatrial node cells
QuestionChoice
Whilst adrenaline does indeed increase calcium influx, this is not done primarily via binding to beta-2 receptors. Beta-2 receptors are found mainly in vascular and bronchial smooth muscle. Whilst they are present in cardiac muscle, they are considerably less numerous and functionally important at that site than beta-1 receptors. Furthermore, the movement of calcium during the pacemaker potential is through L-type calcium channels, not T-type,
10026243
d
Adrenaline binds to beta-2 receptors causing increased calcium influx through T-type calcium channels into the sinoatrial node cells
QuestionChoice
Whilst adrenaline does indeed increase calcium influx through L-type calcium channels, this is not done primarily via binding to beta-2 receptors. Beta-2 receptors are found mainly in vascular and bronchial smooth muscle. Whilst they are present in cardiac muscle, they are considerably less numerous and functionally important at that site than beta-1 receptors.
10026241
b
Adrenaline binds to beta-2 receptors causing increased calcium influx through L-type calcium channels into the sinoatrial node cells
QuestionChoice
Whilst adrenaline does bind to beta-1 receptors, this does not affect potassium movement. Instead, adrenaline binding results in increased calcium influx into sinoatrial node cells, hence speeding up the depolarisation of the pacemaker potential, reducing the time taken for the cell to reach threshold potential. Furthermore, increasing potassium efflux would slow down the depolarisation of the pacemaker potential, reducing the heart rate.
10026244
e
Adrenaline binds to beta-1 receptors causing increased potassium efflux out of the sinoatrial node cells
Concept
Chapter
2693
5884
Autonomic Nervous System
Topic
159
Cardiovascular physiology
17646
What is the mechanism through which raised levels of circulating adrenaline increase the heart rate?
a