Cardiovascular system - Cardiac action potential Flashcards
What muscle makes up the heart?
Cardiac myocytes which contract due to action potentials
Where does the heart begin the process of contracting?
A small group of myocytes called pacemaker cells which initiate action potentials
What part of the heart initiates and controls heart beats?
SA node
What can happen if the SA node is damaged and unable to work as expected?
An escape pacemakers assumes control such as the The AV node or bundle of His
How does the action potential pass throughout the atria?
The myocytes are connected by gap junctions that allow ions to flow through cells and trigger action potentials.
How are action potentials generated?
The cell becomes less negative (depolarised), to the threshold level, due to voltage gated pumps.
When do funny channels open?
When membrane potential drops below the threshold of -40, causing an influx of sodium and further depolarization
What causes depolarisation and how is it represented on a graph?
Sodium channels open, letting Na+ ions flow inside the cell, making membrane potential less negative
What causes repolarisation and how is it represented on a graph?
closing of sodium ion channels and the opening of potassium ion channels out of the cell
What causes hyperpolarisation and how is it represented on a graph?
potassium channels open, letting K+ ions flow out the cell, making membrane potential more negative
What is happening at the pink in pacemaker cells?
Current is below the threshold, so funny channels causing an influx of sodium and further depolarization
What is happening at the yellow in pacemaker cells?
Calcium channels open, calcium ions flow into the cell causing depolatisation
What is happening at the blue in pacemaker cells?
closing of sodium ion channels and the opening of potassium ion channels out of the cell.
What is happening at the light blue?
The resting potential of -90, ions pass into the cell through channels to trigger them to cause depolarisation
What is happening at the green?
Ions from the adjacent cell enter, and bring the voltage up to the threshold, which cause sodium and calcium channels to open, causing a depolarisation
What is happening at the initial blue drop?
The sodium channels close and potassium channels open, so potassium ions leave causing a small decrease called, early repolarizaation
What is happening at the initial yellow drop?
After early repolarisation, the calcium channels which are still open, have calcium ions enter the cell and balance the change causing a slight plateu
What is happening at the blue drop?
Potassium channels open and potassium leaves the cell causing repolarisation
What is happening at the light blue?
The voltage resets back to resting level
