Heart As A Pump

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Heart As A Pump

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Lecture Note
University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 25 Current Lecture Cardiovascular System  Sympathetic stimulation increases heart rate o o How NTs modulate heart rate o Sympathetic (norepi) increases heart rate by affecting the nodal tissue o Increases the strength of cardiac contraction o Rate determined by the rate of the SA node o Epinephrinebinds to beta adrenergic receptortwo effects: 1. Increases mean open time of the calcium channel which increases calcium current which lowers the threshold and 2. The HCN channel increases its mean open time which increases the inward funny current through the HCN channel which increases rate at which inward current coming in so this causes more depolarization o Red is normal without sympathetic stimulation and blue is with sympathetic stimulation  Parasympathetic Stimulation Slows Heart Rate o o Slows down the heart by… o Acetylcholine binds to muscarinic receptorvia g protein this activates a type of potassium channel called a GIRK channel (G protein activated inwardly rectifying potassium channel) causes an increase in opening of this channel since at hyperpolarized levels it is openthis reduces the slope of the pacemaker potential (less depolarization) less net inward current heart rate slowed down Heart Pump  Slide 1- Electrical Conduction in the heart o

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