Control of heart beat-yr 12

Control of heart beat-yr 12 - The Heart Control of the...

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The Heart Control of the Heart Beat
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The Heart Beat The heart is made up of cardiac muscle. Cardiac muscle is myogenic , which means it naturally contracts and relaxes. Therefore, it receives no impulse from a nerve to make it contract.
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The Heart Beat The cardiac cycle is initiated by a small patch of muscle called the Sinoatrial node (SAN) or pacemaker . This node sets the rhythm for all the other cardiac muscle. Pacemaker cells have an inbuilt rhythm that is faster than the other cells in the heart.
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The Heart Beat The SA node sends out an excitation wave of electrical activity over the atrial walls. The cardiac muscle responds to this wave by contracting at the same speed as the SAN . This results in both atria contracting simultaneously.
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There is a delay between atrial contraction and ventricular contraction. Fibres between the two chambers that do not conduct the excitation phase cause this delay. Therefore, the wave is conducted through a
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This note was uploaded on 11/23/2011 for the course BIO 100 taught by Professor Robinson during the Fall '08 term at BYU.

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Control of heart beat-yr 12 - The Heart Control of the...

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