The AP can propagate between adjacent cells in the heart.
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Where is the AP initiated
Sinoatrial node
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What is the fast AP
Stable RP of -80mV. Entry of Na+ (depol), initial repol due to K+ efflux, depol due to entry of Ca2+, repol due to K+. Allows heart to contract and relax at a certain frequency.
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What is the slow AP
Doesnt have a stable resting MP. Slowly depolarises due to Ca2+ entry until threshold is reached whereby the AP can be propagated. Slow repolarisation due to K+ leaving.
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What is the absolute refractory period and why is it important
No further action potentials can occur. Na+ and Ca+ pumped in and K+ pumped out. Allows the heart to fill with blood before next contraction
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What type of contraction is it
Thin-filament regulated
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Difference between contaction compared to skeletal muscle
Has calcium induced calcium release. When T-tubules depolarised the voltage-gated chanels open enabling calcium ions to flood in. These bind to the ryanodine receptors causing additional Ca2+ release.
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How do they relax
CERCA pumps Ca2+ back into SR with some proteins on the membrane which can pump Ca2+ out of the cell.
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Why does cardiac muscles have high resistance to stretch compared to skeltal
Can stretch but still contract with enough force. Titin contibutes.
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Other cards in this set
Card 2
Front
Where is the AP initiated
Back
Sinoatrial node
Card 3
Front
What is the fast AP
Back
Card 4
Front
What is the slow AP
Back
Card 5
Front
What is the absolute refractory period and why is it important
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