5400632
Description
Flashcards by Jonathan Cash, updated more than 1 year ago
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Created by Jonathan Cash
over 8 years ago
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| Question | Answer |
| ECG | The sequence of depolarization and repolarization of the heart related to the deflection waves of an ECG tracing. The ECG is a recording of the collective depolarization of parts of the heart. It is not a recording of the depolarization and repolarization of the individual cells which make up the heart. |
| Autonomic Nervous System HR - nerves - Spinal Cord - Effect | Venus nerve (parasympathetic) Medulla -> SA and AV node Sympathetic cardiac nerve Cervical, T1,2,3,4 -> SA and AV node and Ventricular myocardium |
| Pacemaker | Sinus rhythm is determined by the pacemaker cells at the SA and AV node Pacemaker cells are unique because they can spontaneously produce action potentials in rhythm to control the heart beat. They do this because they exhibit a specialised membrane potential- the pacemaker potential. |
| Action Potential - sinoaterial nodal cells | An action potential in the sinoatrial nodal cells is also a brief change in membrane potential – the timing and ionic movements are different. |
| Autonomic innervation of the pacemaker cells - Parasympathetic | - Acetylcholine released by parasympathetic neurone - Acts on muscarinic receptors at the SA node - Increases the potassium ion conductance - Decreases the slope of the pacemaker potential - Reaching threshold is delayed - Slows heart rate |
| Autonomic innervation of the pacemaker cells - Sympathetic | - Norepinephrine released by sympathetic neurone - Acts on β1 receptors at both SA and AV node - Decreases potassium ion conductance - Increases the slope of the pacemaker potential - Sooner to reach threshold - Increases heart rate |
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