Cardiac Action Potentials Flashcards
How is an electrochemical gradient established?
Established due to a potassium leak.
What is a potassium leak?
When some of the K+ ions leave the negative side and becomes positive.
How is a potential difference established?
This is when there is MORE NEGATIVE charged molecules inside the cell relative to the outside.
How does depolarisation occur?
When the membrane is MORE permeable : positive charged ions flow into the cell and make the membrane potential MORE positive.
What is the equilibrium potential?
Membrane potential at which FORCES ARE BALANCED and so there is NO net movement.
What is depolarisation?
When membrane potential becomes MORE positive than the resting membrane membrane potential.
What is repolarisation?
When the depolarised membrane potential returns back to the resting membrane potential.
What is the cell a cardiac action potential is seen in?
A ventricular cardiac myocyte.
What is the resting membrane potential for potassium and sodium?
Potassium = -90mV Sodium = +60mV
What is the difference between a cardiac and neuronal action potential?
There is a longer duration for the cardiac action potential compared to the neuronal action potential.
Why is a calcium influx so important?
This allows a contraction to occur.
Explain how the calcium influx can aid contraction.
Calcium binds to troponin (troponin is binded to tropomyosin).
A conformational change occurs and thus, the myosin binding site on actin is exposed.
Myosin BINDS to actin and thus, a myosin - actin crossbridge is formed.
The crossbridges link together and thus, initiates contraction.
What blocks the myosin - actin binding site?
Tropomyosin blocks the binding site.
How does electrical activity spread from cell to cell?
Coupled to muscle cells by INTERCALATED DISCS with gap junctions.
Where do action potentials initiate?
They initiate in the SA node.
