PH - WEEK 8 - Cardiac Physiology Review Flashcards

Flashcards for reviewing cardiac myocyte types, action potentials, conduction system, and factors influencing heart rate.

What are the two types of cardiac myocytes involved in the heart's function?

Contractile cardiomyocytes and autorhythmic (pacemaker) cells.

What is the primary role of contractile cardiomyocytes in the heart?

They are responsible for the contraction of cardiac chambers, necessary for blood propulsion.

What is the primary role of autorhythmic cells (pacemaker cells) in the heart?

They generate and conduct action potentials spontaneously and rhythmically, regulating the rhythm of the heart.

How do pacemaker cells generate action potentials?

Pacemaker cells have special ion channels, such as funny Na+ channels and T-type Ca2+ channels, which lead to spontaneous depolarization.

What is the pacemaker potential?

The gradual depolarization of pacemaker cells due to slow influx of Na+ ions, followed by rapid Ca2+ influx at threshold, and repolarization via K+ efflux.

How does the SA node influence the heart's rhythm?

The SA node is the primary pacemaker, generating approximately 100 action potentials per minute, which sets the heart rate (60-100 bpm).

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

The AV node receives excitation from the atria, depolarizes slowly to delay conduction, allowing for optimal ventricular filling.

How does the electrical signal travel from the SA node to the ventricles?

The signal travels from the SA node through the internodal pathway to the AV node, then to the AV bundle, bundle branches, and Purkinje fibers, leading to coordinated ventricular contraction.

What is the function of Purkinje fibers in the conduction system?

Purkinje fibers transmit excitation quickly from the apex of the heart to the atria, ensuring rapid ventricular activation.

How do conduction velocities vary within the cardiac conduction system?

Conduction velocities are faster in cells with larger diameters and more gap junctions.

What happens if the SA node is compromised?

The AV node can take over as a backup pacemaker, though it fires at a slower rate, which may require an artificial pacemaker.

What is the role of an artificial pacemaker?

It is implanted to deliver electrical impulses to the heart to ensure coordinated contractions and relaxations when the natural pacemaker is not functioning properly.

How does the autonomic nervous system affect heart rate?

The sympathetic nervous system increases heart rate via norepinephrine, while the parasympathetic system decreases heart rate.

How do hormones like epinephrine affect heart rate?

Epinephrine increases heart rate by stimulating the SA node.

How can electrolyte imbalances influence cardiac function?

Electrolyte imbalances, such as abnormal potassium or calcium levels, can affect the generation and conduction of action potentials, impacting heart function.