QuestionSBA
QuestionChoice
Ryanodine receptors are found in myocytes, particularly on the membrane of the sarcoplasmic reticulum. They increase intracellular calcium levels which activates the troponin-tropomyosin system to cause heart muscle contraction. They are not involved in pacemaker potentials.
10024413
d
Ryanodine receptors
QuestionChoice
Potassium efflux through voltage-gated potassium channels causes repolarisation of the sino-atrial node, terminating the pacemaker potential before the next potential starts.
10024412
c
K+ channels
QuestionChoice
Voltage-gated calcium channels are activated once the membrane potential reaches the threshold. The firing of the action potential is due to the influx of calcium which causes a faster depolarisation.
10024411
b
Calcium channels
QuestionChoice
IP3 receptors mediate calcium release from the endoplasmic reticulum. They are not involved in pacemaker potentials.
10024414
e
IP3 receptors
QuestionChoice
Pacemaker potentials start with the slow depolarisation of pacemaker cells in the sino-atrial node towards the membrane potential threshold. If (funny current) channels allow sodium influx into cardiomyocytes resulting in this slow depolarisation. Once the membrane reaches the membrane potential threshold, it can fire an action potential.
10024410
a
If channels
Concept
Chapter
2693
3962
Cardiac Action Potential Generation and Conduction
Topic
159
Cardiovascular physiology
17280
The heart can generate electrical activity and contraction without external input.

Which of the following best describes the molecules involved in generating an unstable resting potential in the sino-atrial node which leads to the initiation of pacemaker potentials and determines heart rate?
a