BIOL 208 Lecture Notes - Lecture 16: Purkinje Fibers, Sympathetic Nervous System, Stroke Volume
5 Apr 2017
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** within limits, the greater the length of stretched ventricular fibers the stronger the contraction (like a rubber band) More blood that gets in ventricle causes greater stretching and stronger contraction. These forces are dealt with influence of heart rate. As heart wall expands, internal lumen also expands and increases contraction similar to venous return. If venous return increases, causes more blood coming into heart and ventricles, expands heart/ventricles. *** the changing hr is principal mechanism of short term control over both co and therefore bp if co increases, bp increases and allows for heartbeat to increase. Av node, av bundle, av branches, purkinje fibers, Some cardiac cells are not individually innervated - travel through intercalated discs. Most of exogenous factors affecting heart rate also affect stroke volume. Whenever heart rate increase, stroke volume increases. Efferent fibers (effectors): leave brain and influence blood vessels, sympathetic and parasympathetic increases heart rate. Somatic system - only influences striated muscles tachycardia- rapid hr.
