Week 9 and 10 HEART fixed Worksheet

Week 9 and 10 HEART fixed Worksheet - Action Potential at...

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Action Potential at SA Node 
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Ca ion influx   brings it up to -40mV (threshhold)   Autonomic Tone Affecting heart Rate  Dual innervation  - sympathetic and parasympathetic  In healthy, resting individuals,  parasympathetic effects dominate  –  Acetylcholine  is released If parasympathetic activity increases, the heart rate declines  If sympathetic activity increases, the heart rate increases  Autonomic Tone Affecting Heart Rate –  Effects on SA Node  The sympathetic and parasympathetic divisions  alter heart rate by changing the ionic  permeabilities of cells in the conducting system  Acetylcholine  (released by parasympathetic)  opens chemically gated K+ channels  (positive ions leak out) - this  slows the rate of spontaneous depolarization  and  extends the duration of repolarization so the heart rate slows  Norepinephrine (sympathetic) opens sodium-calcium channels;  this  influx of  positively charged ions increases the rate of depolarization  and shortens the period of  repolarization so the  SA node reaches threshold faster and you get a quicker  heartbeat   Action Potential in Cardiac Muscle  See pg. 701  Rapid depolarization - from sodium (Na + ) influx   Plateau - from  Ca +  ion entry   Repolarization - from  K +  ion loss   Skeletal vs. Cardiac Muscle  Action Potentials  Skeletal muscle - Action potential and contraction are much shorter duration than cardiac 
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This note was uploaded on 02/11/2010 for the course AHS 132 taught by Professor Klinger during the Spring '09 term at Nassau CC.

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Week 9 and 10 HEART fixed Worksheet - Action Potential at...

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