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Unformatted text preview: BIO 188 November 20, 2009 BIO 188 November 20, 2009 • Today: how does a heart work 1. pacemaker and contractile cells 2. action potential in pacemaker cells 3. action potential and contraction in contractile cells 4. conducting system of the heart 5. cardiac output? What a re pacemaker cells? • 99% of cardiac cells are ≈ contractile contractile muscle cells 1. excitable cell if depolarized to threshold, they contract and fire AP 2. mechanical pumping cells • 1% of cardiac cells do ≈ not not contract 1. these a re pacemakers cells pacemakers cells 2. their job is electrical and they have rhythm their job is electrical and they have rhythm What do pacemaker cells do if they don’t contract?..… ..autorhythmic ..autorhythmic 3. most important pacemaker cells in sinoatrial (SA) node They spontaneously and rhythmic generate action potentials that spread through…. generate action potentials that spread through…. Complete.. Complete.. How does this work? • Pacemaker cells rhythmically and spontaneously initiate action potentials that spread Pacemaker cells rhythmically and spontaneously initiate action potentials that spread through heart through heart 1. as APs spread from pacemaker cells to contractile cells, contractile cells are depolarized - this triggers contraction 2. heart muscle cells are depolarized by each other, so they don’t need motor neurons • But, you ask, how do the action potentials spread from heart cell to heart cell?...
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This note was uploaded on 02/02/2010 for the course BIO 188 taught by Professor Capco during the Spring '08 term at ASU.
- Spring '08