28.1 - Functional morphology and physiological characteristics of the conduction system of the heart. Automaticity. Cardiac Rhythm. Conduction abnormalities.

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Last updated 12:01 PM on 5/15/26
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9 Terms

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section

cells of heart

natural pacemaker

5 elements of heart

conduction system

automaticity

automatic and cardiac rhythm

cause of increased heart rate

cause of decrease in heart rate

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cells of heart

made of cardiomyocytes- do not require such a stimulus as they have leaking Na+ and k+ ion channels that allow for the entry and exit of Na+ and K+ ions. This allows for constant AP generation.

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natural pacemaker

  • Sinoatrial node is the hearts natural pacemaker - pacemaker cellls

  • it generates its own action potential

  • causes the positive increase in voltage across the membrane.

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5 elements of heart

  1. SAN- in wall of the right atria—60-90 impulses

  2. AVN-base of the right atrium- 40-60 impulses

  3. Bundle of His- 30-40 impulses

  4. Tawara fibres

  5. Purkinje fibres- 20-40 impulses- spreads up to the ventricles

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conduction system

  • conduction system:The heart has a special system that sends electrical signals to make it beat

  • It includes: SA node (sinus node), AV node, Bundle of His, and Purkinje fibers.

  • Automaticity means some heart cells (like in the SA node) can start signals on their own — without brain signals.

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automaticity

Automaticity means some heart cells (like in the SA node) can start signals on their own — without brain signals.

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automatic and cardiac rhythm

  • Sinoatrial node is the hearts natural pacemaker

  • generates its own action potential

  • causes the positive increase in voltage across the membrane. the pacemaker potential therefore controls the rate of the heart.

    • Normal cardiac rhythtm- 60-90bpm at rest

    • Tachycardia- increased HR >100 bpm

    • Bradycardia- decrease HR. <60bpm

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cause of increased heart rate

  • High temperature

  • Sympathetic stimulation

  • By hormones, T3/T4, circulation of catecholamines (adrenaline)

  • Increased Ca2

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cause of decrease in heart rate

  • cardiac conduction disease- disruption of electrical impulses to the heart