Control of Heart Rate Flashcards
1
Q
What is the heart rate determined by?
A
Depolarisation of SA node.
2
Q
How is the heart innervated by autonomic nervous system?
A
- increased activity in sympathetic nerves to the heart increases heart rate
- increased activity in parasympathetic nerves to heart decreases heart rate
3
Q
What do the parasympathetic and sympathetic nervous system release?
A
- parasympathetic: ACh
- sympathetic: noradrenaline
4
Q
What effect does parasympathetic stimulation have on the SA node?
A
Decreases heart rate through two effects on pacemaker:
- hyperpolarisation of SA node membrane potential
- decreases the rate of spontaneous depolarisation
ACh increases K+ permeability by slowing the closure of K+ channels.
5
Q
What effect does sympathetic stimulation have on SA node?
A
- speeds up heart rate
- speeds up depolarisation
-
