DOH100 Lecture Notes - Lecture 6: Aortic Stenosis, Atherosclerosis, Catecholamine
Document Summary
Define cardiac output and state its typical values at rest and exercise. Cardiac output (co) - amount in litres ejected by ventricle in 1 minute. Igorous exercise (cid:314) co increases to 22 l/min for untrained male and up to 35 l/min for world class athlete (stroke volume increases) Cardiac reserve - difference between a person"s maximum and resting co. Discuss nervous factors that affect cardiac output (co) Cardioacceleratory center in medulla sends signals via sympathetic cardiac nerves to sa node, a node and myocardium. Secrete norepinephrine, which binds to -adrenergic receptors in the heart (positive chronotropic effect) (cid:313) hr and (cid:313) contractility. Co peaks at hr of 160 to 180 bpm. Cardioinhibitory centre in medulla stimulates vagus nerves. Secretes ach acetylcholine which binds to muscarinic receptors. Background firing rate holds hr to sinus rhythm of 70 to 80 bpm. Severed vagus nerves (intrinsic rate - 100 bpm) Maximum vagal stimulation (cid:315) hr as low as 20 bpm.
