5.5.12 Factors Affecting Heart Rate Flashcards
1
Q
What does myogenic mean?
A
- No external stimuli needed to initiate contraction
- Cardiac muscle in heart as an example
2
Q
What is the autonomic nervous system?
A
- Medulla split into 2 parts
- Acceleratory centre (causes heartrate to speed up)
- Inhibitory centre (causes heartrate to slow down)
- Connected to sinoatrial node by nerves
- Self controlling
3
Q
How does the acceleratory centre work?
A
- Acceleratory centre activated
- Impulses sent to SAN along sympathetic neurones
- Noradrenaline secreted at synapse within SAN
- Causes SAN to increase frequency of electrical waves it produces to initiate heartbeat
- Increased heartrate
4
Q
How does the inhibitory centre work?
A
- Activated
- Impulses sent along parasympathetic neurones to SAN
- Acetylcholine secreted at synapse with SAN
- Reduces frequency of electrical waves it produces initiating heartbeat
- Reduces elevated heartrate to resting rate
5
Q
How are the acceleratory and inhibitory centres triggered for activation?
A
- CO2 concentration increase of blood
- Fall in blood pressure from dilating muscle arterioles
- Chemoreceptors and pressure receptors in aorta
- When change is detected, nerve impulses released and sent to acceleratory and inhibitory centers which are the coordinators
- Low frequency impulses activate inhibitory centre to slow heartrate
- High frequency impulses activate acceleratory centre to speed up heartrate
5
Q
What hormones increase heartrate?
A
- Adrenaline and noradrenaline
- Thyroxine
