BIOL 4510 Lecture Notes - Nifedipine, Verapamil, Ryanodine Receptor 2
Document Summary
The amount of blood pumped by the heart per minute is given by: Cardiac output (l/min) = co = stroke volume (l/beat) x heart rate (beats/min) = sv*hr. For a typical human, sv ~ 70 mls and hr ~60 beats/min, therefore co ~ 4. 2litres/min. Heart rate (hr) is the major factor determining the cardiac output. Hr can vary by a factor of 3-4 in most people (although the ability to vary hr declines strongly with age). Since the beating in the heart is initiated by the sa node, to understand the regulation of hr we need to understand how the spontaneous firing rate of the sa node is regulated. When there is an increased demand for co, hr increases. This occurs primarily be altering autonomic nerve inputs to the heart. The autonomic nervous system is comprised of two parts: 1) the sympathetic nerve system and 2) the parasympathetic nerve system.