Regulation of Stroke Volume, Heart Rate and Arteriolar Resistance

Question 1

Nervous systems that regulate heart rate?

Answer 1

Autonomic Nervous System: Sympathetic and Parasympathetic.

Question 2

How does the sympathetic nervous system affect the heart rate?

Answer 2

Sympathetic nerves release noradrenaline
Plus there is circulating adrenaline from the adrenal medulla
Both act on B1 receptors on sinoatrial node
Increases slope of pacemaker potential
Increases heart rate = tachycardia

Question 3

How does the parasympathetic nervous system affect the heart rate?

Answer 3

Vagus releases acetylcholinesterase
Acts on muscarinic receptors on sinoatrial node
Hyperpolarises cells and decreases slope of pacemaker potential
Decreases heart rate = bradycardia

Question 4

What is Starling’s Law?

Answer 4

Starling’s law states that the energy of contraction is proportional to the initial length of the cardiac muscle fibre, and thus the preload.