Heart Physiology

These flashcards cover key concepts and functions related to heart physiology, including muscle contraction, pacemaker activity, cardiac output, and the cardiac cycle.

What process occurs during isovolumic contraction?

The ventricles contract with no change in volume as pressure rises.

What is the role of calcium ions in cardiac muscle contraction?

Calcium ions bind to troponin which initiates contraction.

What is the function of intercalated discs in cardiac muscle?

They connect cardiac myocytes and facilitate the spread of action potentials.

Which node is known as the natural pacemaker of the heart?

The SA (sinoatrial) node.

What is the difference between stroke volume (SV) and cardiac output (CO)?

SV is the amount of blood pumped out per beat, while CO is the volume of blood pumped per minute.

What does the Frank-Starling Law of the Heart state?

Stroke volume is proportional to the end diastolic volume.

What happens during atrial systole?

Atrial contraction forces additional blood into relaxed ventricles.

How do ectopic pacemakers affect the heart?

They can disrupt the timing of atrial and ventricular contractions, leading to arrhythmias.

What are the two factors affecting cardiac output?

Stroke volume (SV) and heart rate (HR).

What triggers the 'lubb' and 'dubb' heart sounds?

Lubb is caused by AV valve closure; Dubb is caused by semilunar valve closure.

What effect do hormones like epinephrine have on the heart?

They increase heart rate and contractility.

What is the result of increased venous return on the heart?

It increases the end diastolic volume and thus enhances preload.

What is an autonomic reflex that affects heart rate when blood pressure increases?

The barostatic reflex decreases heart rate.

In cardiac muscle, what happens during the phases of cardiac cycle such as ventricular diastole?

All chambers relax, and ventricles fill with blood.

What is the significance of the absolute refractory period in cardiac muscle?

It prevents the heart from undergoing tetany, ensuring proper rhythmic contractions.