Lecture 20 - Cardiac Muscle Contraction Bio416K Spring 2010

Lecture 20 - Cardiac Muscle Contraction Bio416K Spring 2010...

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Cardiac Muscle (Chapter 14; pp. 481-490)
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Cardiac Muscle Apex of heart
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Cardiac Muscle Myogenic and controlled by neurotransmitters and neurohormones Myofibrils composed of sarcomeres Extensive transverse (T)-tubules - branching Poorly/moderately developed sarcoplasmic reticulum (SR) Ca 2+ signal from SR and extracellular fluid Actin-linked regulatory process Slow speed of contraction Autorhythmic cells with unstable membrane potentials Cells connected by gap junctions – functional syncytium Regenerative – slowly?
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SA Node – Cardiac autorythmic “pacemaker” cells and cardiac contractile cells Nodal fibers
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Action Potentials in Cardiac Autorhythmic Cells (Chapter 14; pp. 481 - 490) T-type Ca 2+ channels open L-type Ca 2+ channels open I f channels open (inward Na + current)
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Action Potential of a Cardiac Muscle Contractile Cell ; Ca 2+ ATPase, Ca 2+
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Unformatted text preview: -Na + antiport Refractory Periods and Summation in Cardiac Muscle Refractory Periods and Summation in Skeletal Muscle Action Potentials in Cardiac Autorhythmic vs. Contractile Cells T-type Ca 2+ channels open 4 1 3 4 + smooth muscle Excitation and Contraction Coupling in Cardiac Muscle Autonomic Innervation of the heart What nerve? Chronotropic heart rate Parasympathetic Sympathetic Inotropic force of contraction Sympathetic Modulation of Heart Rate by Autonomic Nervous System E, NE Beta 1 Adenylate cyclase cAMP cAMP-gated I f open Increases AP rate T-type Ca 2+ channels ACh M2 Adenylate cyclase cAMP Membrane Decrease AP rate hyperpolarization E, NE Beta1 Adenylate cyclase cAMP Protein kinase A Ca 2+ entry Force of contraction ( phosphorylation of Ca 2+ channels) Comparisons of Three Muscle Types...
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Lecture 20 - Cardiac Muscle Contraction Bio416K Spring 2010...

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