chapter14b Cardiovascular Physiology 2

chapter14b Cardiovascular Physiology 2 - Chapter 14b...

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Chapter 14b Cardiovascular Physiology
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Figure 14-15 Action Potentials in Cardiac Autorhythmic Cells Pacemaker potential - no resting -60mV drifts to -40 to action potential Spread through connections to contractile fibers If channels are permeable to both K+ and Na+ Time Time Ca2+ in Ca2+ in K+ out Net Na+ in Lots of Ca2+ channels open Ca2+ channels close, K+ channels open Some Ca2+ channels open, If channels close If channels open K+ channels close If channels open (b) Ion movements during an action and pacemaker potential (c) State of various ion channels Time Threshold Pacemaker potential Action potential 20 0 –20 –40 –60 (a) The pacemaker potential gradually becomes less negative until it reaches threshold, triggering an action potential. Membrane potential (mV)
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Action Potentials in Cardiac Autorhythmic Cells PLAY Interactive Physiology® Animation: Cardiovascular System: Cardiac Action Potential
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Modulation of Heart Rate by the Autonomic Nervous System Figure 14-16 Normal Parasympathetic stimulation Normal Sympathetic stimulation Hyperpolarized Slower depolarization Time (sec) Time (sec) 20 0 –60 0.8 1.6 2.4 0.8 1.6 2.4 (b) (a) Depolarized More rapid depolarization 20 –20 –40 –60 0 Membrane potential (mV)
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Action Potentials Table 14-3
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Electrical Conduction in Myocardial Cells Figure 14-17 Membrane potential of autorhythmic cell Membrane potential of contractile cell Contractile cell Cells of SA node Depolarizations of autorhythmic cells rapidly spread to adjacent contractile cells through gap junctions. Intercalated disk with gap junctions
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Figure 14-18 1 2 3 4 5 5 4 3 2 1 THE CONDUCTING SYSTEM OF THE HEART SA node AV node Purkinje fibers Bundle branches AV bundle AV node Internodal pathways SA node SA node depolarizes. Electrical activity goes rapidly to AV node via internodal pathways. Depolarization spreads more slowly across atria. Conduction slows through AV node. Depolarization moves rapidly through ventricular conducting system to the apex of the heart. Depolarization wave
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This note was uploaded on 01/03/2012 for the course BIO 308 taught by Professor Acbrown during the Spring '10 term at Portland.

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chapter14b Cardiovascular Physiology 2 - Chapter 14b...

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