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27 Cards in this Set
- Front
- Back
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What are arrhythmias |
A group of conditions in which the heart beats irregularly, too fast, or too slowly and as a result of abnormal electrical conductivity |
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What is an abnormality if the cardiac rhythm called |
Cardiac arrhythmia |
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What may arrhythmias arise from |
Ischaemia, infarction, fibrosis or drugs |
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What are the two main types of arrythmias |
Irregular bradycardia( heart rate slow) Irregular tachycardia(heart rate is fast) |
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Symptoms of cardiac arrhythmias |
Palpitations, Heart failure symptoms, fatigue, dyspnea(breathing difficulties), dizziness, angina, syncope(fainting), no symptoms at all |
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How do cardiac arrhythmias arise(1) |
Arise from altered formation of impulses or altered conduction of the impulse through the heart |
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What is the altered formation of impulses in cardiac arrhythmias |
Ectopic beats Heart block Reentry phenomenon |
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What is ectopic beats |
Beats arising from fibres or a group of fibres outside the normal pacemaker region(SA node) |
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What is heart block |
Obstruction or block in the electrical conduction system |
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What is reentry phenomenon |
Return of the same impulse into a zone of heart muscle that has recently activated |
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Whats the type of treatment for cardiac arrhythmias |
Pharmacological therapy DC cardioversion Pacemaker therapy Surgical therapy Interventional therapy |
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Definition of excitability |
Ability of a cell membrane to respond to stimuli by producing and conducting action potentials |
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What is refractory period |
Time following excitation during which a second action potential cant be elicited or conducted |
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What is membrane responsiveness |
Relationship between membrane activation voltage and the maximal rate of rise of the action potential |
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What do effective anti arrhythmic drugs do? |
Increase the refractory period or slowing the upstroke of action potentials or both |
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Antiarrhythmic drugs work to control what |
Electrical signals by altering action potential generation or propagation |
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Whats the two important features channels have |
Gating- allows channels to open and close when they are supposed to Ion selectivity- don’t just let any ion go across the membrane |
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What ions are high conc outside cell |
Sodium and calcium |
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What ion is high inside the cell |
Potassium |
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What are balancing anis |
For every positive charge there is a balancing ani |
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How do you get membrane potential |
One side of the membrane needs to gain charge at the expensive of the other |
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How does sodium make an action potential |
Sodium flows down the conc gradient and takes its postive charge with it so builds up a positive charge and the outside has negative charge because the anis Negative charge tries to move Na back to opposite direction because opposites attract |
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What are the two main phases of action potential |
Rising phase (sodium influx stage) Potassium efflux stage (potassium flows out) |
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What happens during the rising phase |
Na channels all start to open because the channels are sensitive to the membrane potential, positive feedback-more and more start to open |
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The positive feedback look for na needs to be terminated how does it do this(1) |
Na channels shut down and not opening, shut down in a process called inactivation Clamps channels down and once in this state they cannot reopen |
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(2) so clamping down na channel will cause what |
Inactivation of sodium channels Inactivation is voltage dependent-takes more force to do this |
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What does potassium channels do |
They open in large numbers and potassium flows out of the axon taking its positive charge with it then forced into negative direction- forces the membrane potential to go even lower that what it is at rest |
