Cardiac Physiology: Excitation and Contraction

How does heart muscle differ from skeletal muscle in terms of stimulation and contraction?

Why is the long absolute refractory period in cardiac muscle important?

What is the primary function of the sinoatrial (SA) node in the heart?

What role does the atrioventricular (AV) node play in the cardiac cycle?

Which of the following accurately describes the sequence of impulse conduction after it leaves the AV node?

What is a key characteristic of autorhythmic cells that distinguishes them from other cardiac cells?

Which ion is primarily responsible for the rising phase of the action potential in autorhythmic cells?

During which phase of the cardiac action potential does rapid depolarization occur?

What ionic movement is primarily associated with Phase 1 (early repolarization) of the cardiac action potential?

What is the primary ionic basis for the plateau phase (Phase 2) of the cardiac action potential?

Which ionic movement is predominantly responsible for the rapid repolarization phase (Phase 3) of the cardiac action potential?

What does the QRS complex on an electrocardiogram (ECG) represent in relation to the cardiac action potential?

What part of the electrocardiogram (ECG) relates to the repolarization phase of the action potential?

What is the typical range for the number of action potentials generated per minute in the heart, under normal conditions?

How does the sympathetic nervous system influence cardiac function?

Which of the following describes the effect of the parasympathetic nervous system on heart function?

What is a key limitation of the nervous system's ability to influence cardiac action potentials?

What is the primary role of calcium channels open as shown in the diagram?

How would the cardiac cycle be affected if the AV node was damaged?

The normal resting membrane potential is around -80mV, but the action potential from the diagram goes significantly higher, up to +40mV. Where does that extra +120mV potential come from?

Heart muscle is stimulated by nerves and is ______ (automaticity).

Heart muscle contracts as a ______, ensuring coordinated pumping action.

Cardiac muscle has a long (250 ms) absolute ______ period, preventing tetanus.

The ______ node generates impulses at approximately 75 times per minute.

The Atrioventricular (AV) node delays the impulse approximately ______ seconds.

Impulses pass from atria to ventricles via the ______ of His.

The Bundle of His splits into two pathways in the interventricular septum called ______.

[Blank] carry the impulse to the heart apex and ventricular walls.

[Blank] cells initiate action potentials in the heart.

The unstable resting potentials in autorhythmic cells are called ______ potentials.

Autorhythmic cells use ______ influx (rather than sodium) for the rising phase of the action potential.

The time course of the intracellular action potential has been superimposed on the ______.

The ______ phase of action potential coincides with the QRS complex on an ECG.

The repolarization phase of the action potential coincides with the ______ wave on an ECG.

The nervous system ______ elicits cardiac action potentials; this can only happen via the SA node.

Heart is ______ by the sympathetic cardioacceleratory centre.

Heart is ______ by the parasympathetic cardioinhibitory centre.

Phase 2 of the cardiac cycle is also known as the ______.

Phase 3, also known as the ______, is identified by the efflux of potassium ions.

Because the vagus nerve is associated with ______ responses, a problem would result with the heart slowing down too much.