PSL301H1 Lecture Notes - Lecture 9: Sympathetic Nervous System, Stroke Volume, Cardiac Muscle

• School: UTSG
• Department: Physiology
• Course: PSL301H1
• Professor: TBA

Document Summary

Sv = edv (~135 ml) - esv (~65 ml) Ie. the volume of blood pumped by one ventricle in one contraction. ~70 bpm & 70 ml/beat " approximately 5 l/min (normal blood volume is ~5 l) Ie. the amount of blood pumped per ventricle per unit time. Frank-starling law: preload of cardiac muscle cells is the critical factor controlling stroke volume (stretch increases the number of crossbridges and approaches optimal sarcomere length) Slow heart beat & exercise increase venous return to the heart, increasing sv. Blood loss and extremely rapid heartbeat decrease sv. Contractility: increase in contractile strength (independent of stretch and edv) Comes from increased sympathetic stimuli, certain hormones, ca2+ and some drugs. Catecholamines (epinephrine & norepinephrine) modulate cardiac contraction.