Cardiac Conduction Flashcards
What is the average resting membrane potential of nodal cells?
~ -60mV
What is the average resting membrane potential of contractile cells?
~ -90mV
What causes nodal cells to start becoming less negative?
Leaky Na, sodium channels. Start to leak through and raises membrane potential.
What are the two types of cells within the myocardium?
Nodal Cells (electrical conduction)
Contractile Cells (heart muscle)
At what point do leaky sodium channels trigger T-Calcium channels to open?
When resting membrane potential reaches ~ -50mV, calcium starts flowing into the cell and slowly continues to raise the membrane potential.
At what voltage do L-Calcium channels open and flood the cell to depolarize?
Around ~ -40mV, L-type Calcium floods the cell and depolarizes.
At what voltage do L-Calcium channels close and end depolarization?
Around ~ +40mV
How do nodal cells repolarize back to -40mV?
When L-Calcium channels close at around +40mV, Potassium channels open and K+ starts to leave the cell. Making the membrane potential become less positive.
What are Gap Junctions? What is the role of Gap Junctions in cardiac myocyte contraction?
Protein-lined channels along the Z-Line of sarcomere. Allow the flow of electrical current.
What are intercalated discs? What are their role in cardiac myocyte contraction?
Structures that connect adjacent cardiac myocytes. They support synchronized contraction.
What is the Syncytium within cardiac myocytes?
Anastomising network allowing propagation of contraction
Do ventricles depolarize faster or slower than atria?
Faster, almost a straight line (Steep slope) from resting membrane to Action Potential Peak
Atria depolarization occurs mainly due to ____ influx.
Calcium. Specifically L-Type Calcium
Ventricle depolarization occurs mainly due to ____ influx.
Sodium
