lab_5-electrical_and_mechanical_properties_of_the_frog_heart

lab_5-electrical_and_mechanical_properties_of_the_frog_heart...

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Electrical and Mechanical  Properties of the Frog Heart
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Cardiac Muscle Cardiac muscle is  striated, but the  muscle cells are  shorter than skeletal  muscle Cardiac muscle cells  are connected end- to-end by structures  called  intercalated  disks  Intercalated disks contain:  Desmosomes that contain proteins called adherins  that mechanically bind the cells together  Gap junctions that electrically couple the cells 
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Human Heart
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Electrical Activity of Heart Cardiac action  potentials originate  from the sinoatrial (SA)  node SA node fires APs  spontaneously and at  regular intervals of 60- 100 times/min  ( Pacemaker Activity)    AP from SA node will travel through RA to LA  then to the  atrioventricular (AV) node then to the His-Purkinje fiber  system and then it travels to the ventricles   Neural innervation can modulate pacemaker activity but is  not necessary for contraction as it is in skeletal muscle.
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Cardiac Action Potentials Different cells in the heart will have different types  of action potentials Ventricular muscle cells have “Fast Response”  action potentials Pacemaker cells (ex. SA node) have “Slow  Response” action potentials These APs differ in duration, shape, and are  caused by different ion currents   Once the ventricular muscle is electrically  activated it enters an  effective refractory period   (ERP). ERP is equivalent to the absolute refractory  period in nerves, where the ventricles are not able  to be activated There is also a  relative refractory period  where  an action potential can occur
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Ventricular Action Potential Phase 0: Rapid  depolarization due to  influx of Na +  and to a  lesser extent Ca 2+ Phase 1: Rapid  repolarization from  inactivation of Na +   channels Phase 2: Plateau caused      by continued Ca 2+  influx Phase 3: Repolarization  due to K +  efflux and Ca 2+   channel inactivation Phase 4: Resting  membrane potential 
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lab_5-electrical_and_mechanical_properties_of_the_frog_heart...

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