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9 Cards in this Set
- Front
- Back
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Define Automaticity |
The ability of cardiac pacemaker cells to spontaneously depolarise and generate their own action potential - This is due to the 'leak' of ions that slowly bring the membrane to threshold |
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Define Excitability |
The ability of (all) cardiac cells to respond to (be excited by) an action potential |
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Define Conductivity |
The ability of (all) cardiac cells to conduct an action potential |
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Define Contractility |
The ability of cardiac myocytes to contract |
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What is the absolute refractory period |
The period from when a membrane reaches threshold potential and depolarises, to when it repolarises past threshold potential - During this time the membrane is absolutely unresponsive to stimuli (you can't bring it to threshold potential if it's already past it) |
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What is the relative refractory period |
The period from when a membrane repolarises past threshold potential, to when it returns to resting potential - During this time, the membrane is responsive only to strong stimuli |
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What is an ectopic beat |
A beat originating from somewhere other than the pacemaker for the underlying rhythm |
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What is a premature ectopic and what causes it? |
An ectopic beat occurring early in the cardiac cycle, normally caused by 'irritability' of the cardiac cells |
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What is an escape ectopic and what causes it? |
An ectopic beat occurring late in the cardiac cycle, normally as part of the 'escape' failsafe mechanism when the pacemaker does not fire |
