regulation of stroke volume and heart rate

Question 1

what does the sympathetic nervous system release in regulation of the heart rate and what receptors do they act on ?

Answer 1

release noradrenaline plus circulating adrenaline from adrenal medulla

both act on B1 receptors on the SA node

Question 2

how does the sympathetic nervous system increase heart rate?

Answer 2

increases the slope of the pacemaker potentials by increasing ion flow through funny sodium channels and calcium channels which decreases cardiac interval and, thus, increases heart rate

Question 3

what is starlings law?

Answer 3

Starling’s Law states - the energy of contraction is proportional to the initial length (preload) of the cardiac muscle fibre