Regulation of Heart Rate Flashcards
How does the sympathetic nervous system affect the heart?
Releases noradrenaline acting in beta-1 receptors on SAN; increases heart rate and slope of the pacemaker potential. Contractility increases
How does the parasympathetic nervous system affect regulation of heart rate?
Vagus nerve releases acetylcholine acting on muscarinic receptors on SAN; hyperpolarises cells and decreases slope of pacemaker potential and decreases heart rate
What does Starling’s law tell us?
The energy of contraction is proportional to the initial length of the cardiac muscle fibre.
What is the main determinant of preload?
End diastolic volume
What does afterload refer to?
The load against which the muscle tries to contract
What is the determinant of afterload?
Arterial pressure against which the blood is ejected which depends on the total peripheral resistance.
What effect does the PNS have on stroke volume?
Little effect
What can cause increased venous return?
Venoconstriction and skeletal/respiratory pumps, (maintains preload)
