Action Potentials and Cardiac Conduction System

Flashcards to aid in understanding action potentials and the cardiac conduction system.

What initiates the action potential in the heart?

The sinoatrial (SA) node initiates the action potential in the heart.

What channels open during depolarization in the pacemaker cells?

Slow voltage gated sodium channels open during depolarization in pacemaker cells.

What is the effect of norepinephrine on heart rate?

Norepinephrine speeds up heart rate by shortening the time for depolarization and repolarization.

What neurotransmitter slows down the heart rate?

Acetylcholine slows down the rate of spontaneous discharge, leading to a slower heart rate.

What is the resting membrane potential of myocardial cells?

The resting membrane potential of myocardial cells is approximately -90 millivolts.

What is the role of the AV node in the cardiac conduction system?

The AV node provides a brief pause to ensure the atria have fully contracted before the ventricles contract.

What is a refractory period in cardiac action potentials?

A refractory period is a time during which no stimulus can cause depolarization, preventing erratic electrical discharges.

What are Purkinje fibers?

Purkinje fibers are specialized fibers that carry action potentials deep into the ventricular myocardium, ensuring coordinated contraction.

What happens during the plateau phase of the action potential in myocardial cells?

During the plateau phase, slow voltage gated calcium channels open, prolonging depolarization and creating a refractory period.

Describe the flow of blood from the right atrium to the lungs.

Oxygen-poor blood enters the right atrium from the superior and inferior vena cava, flows through the tricuspid valve into the right ventricle, and is then pumped through the pulmonary valve into the pulmonary trunk for gas exchange in the lungs.