BIO2A03-2011-L12-template

BIO2A03-2011-L12-template - Biology 2A03 Lecture 12...

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1 Biology 2A03 Lecture 12 Circulation VI
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2 Heart affected by changes in rates of AP generated by pacemaker Regulation of heart rate (hr) Pacemakers get direct input by autonomic nervous system SNS NE Acts on SA and AV nodes via β 1 adrenergic receptors to increase hr PSNS ACh Acts on SA and AV nodes via M 2 muscarinic receptors to decrease hr Vegus nerve Cardiac nerve (acetylcholine) Predominant factor in setting resting heart rate of 70 bpm (rate without any inputs = 100bpm) SNS and PSNS have opposite effects NOTE : SNS has more connections to myocardium (more effects on force than PSNS)
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3 Hormones (e.g. epinephrine) can affect heart rate Increases hr via same mechanisms as SNS Temperature: directly alters the intrinsic rate of the SA node Changes hr by 15bpm / ˚ C, e.g. 1 deg fever hr is ~85 bpm Regulation of heart rate (hr)-cont…. Molecular Mechanism (neuro- and hormonal): Receptor binding alters ion movements and changes rate of spontaneous AP e.g. Norepi (or Epi) binding to a G-coupled receptor alters Na + and Ca + movement into pacemaker cell (for faster depolarization) Fig 14-23A Shorter time btw AP = faster hr Fig 14-24
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4 Sequence of electrical events that triggers a heartbeat 1 AP initialed in SA node AV node pathway Spreads through atrial muscle 2 Transmission slows down at the AV node by ~0.15sec 3 AP transmitted through the AV node to the Bundle of His
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This note was uploaded on 04/12/2011 for the course BIOL 2A03 taught by Professor Mccelland&dej during the Winter '11 term at McMaster University.

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BIO2A03-2011-L12-template - Biology 2A03 Lecture 12...

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