Cardiac Anatomy & Physiology Flashcards

Which ion rapidly entering a cardiac cell initiates the action potential upstroke (Phase 0)?

Answer: Sodium (Na+)

Phase 0 of the cardiac action potential is caused by rapid influx of sodium ions through fast Na+ channels, causing rapid depolarization.

What does the PR interval on an ECG measure?

Answer: Time from atrial depolarization to the start of ventricular depolarization

The PR interval measures the conduction time from the start of atrial depolarization through the AV node to the onset of ventricular depolarization.

Which structure forms the apex of the heart?

Answer: Left ventricle

The apex of the heart is formed by the left ventricle and points downward and to the left, typically at the 5th intercostal space.

What is cardiac output defined as?

Answer: Heart rate multiplied by stroke volume

Cardiac output equals heart rate multiplied by stroke volume and represents the volume of blood the heart pumps per minute.

The right coronary artery most commonly supplies which structure that controls heart rate?

Answer: SA node

In approximately 60% of people, the SA node is supplied by the SA nodal artery, which arises from the right coronary artery.

Which term describes the heart's ability to generate its own electrical impulses without external stimulation?

Answer: Automaticity

Automaticity is the property of cardiac pacemaker cells to spontaneously depolarize and generate action potentials without external stimulation.

During which phase of the cardiac cycle do the semilunar valves open?

Answer: Ventricular ejection (systole)

The aortic and pulmonic semilunar valves open when ventricular pressure exceeds arterial pressure during the ejection phase of systole.