Cardiac Muscle Physiology

Flashcards covering key concepts of cardiac muscle physiology, focusing on action potentials, cell types, and contraction mechanisms.

What is the sequence of events in the heart's functioning?

Electrical activity → mechanical activity → blood flow.

What do intercalated disks contain and what are their functions?

Intercalated disks contain desmosomes that transfer force and gap junctions that allow electrical signals to pass rapidly.

What are the two types of cardiac muscle cells?

Autorhythmic (pacemaker) cells and contractile cells.

What is the significance of the plateau phase in a cardiac contractile cell's action potential?

It prevents summation and tetany, allowing the heart to pump effectively.

What are the main ion movements during the action potential in cardiac contractile cells?

Na+ influx during depolarization, Ca2+ influx during plateau, and K+ efflux during repolarization.

How long does the action potential last in cardiac contractile cells compared to skeletal muscle?

250-300 msec in cardiac cells versus 1-2 msec in skeletal muscle.

What role does calcium play in myocardial contraction?

Calcium influx triggers contraction by binding to troponin and exposing myosin binding sites.

What is the normal pacing mechanism of the heart?

The SA node normally paces the heart.

What does an electrocardiogram (ECG) represent?

The electrical events of the heart during different phases of the cardiac cycle.

Why is the refractory period important in cardiac muscle?

It prevents tetanus, allowing the heart to fill and contract properly.

What are the parts of the electrical conduction system of the heart?

SA node, AV node, Bundle of His, Purkinje fibers.

What distinguishes autorhythmic cells from contractile cells?

Autorhythmic cells spontaneously generate action potentials, while contractile cells do not.

What is meant by the term 'cross-bridges' in cardiac muscle contraction?

Cross-bridges refer to the connection formed between myosin and actin filaments during contraction.

How does calcium relaxation occur in cardiac muscle cells?

Calcium is pumped back into the sarcoplasmic reticulum for storage.