Microcapillary Structures and Cardiac Cycle Review

These flashcards cover key terms and concepts related to microcapillary structures and the cardiac cycle.

Metarteriole

A vessel that branches from arterioles with smooth muscle (pre-capillary sphincters) and leads into true capillaries.

True Capillaries

The site where exchange of gases and nutrients occurs.

Types of Capillaries

Continuous, fenestrated, sinusoids; continuous type is the most prevalent.

Fenestrated Capillaries

Capillaries found in kidneys (for filtration) and intestines (for reabsorption).

Sinusoids

A type of capillary found in the spleen.

Isovolumetric Contraction

A phase in the cardiac cycle where all valves are closed and the heart muscles contract without changing the volume.

Atrio-Ventricular (AV) Valves

Valves that open during atrial systole or ventricular diastole.

Semilunar Valves

Valves that open during ventricular systole.

Bainbridge Reflex

A reflex that prevents the heart from overfilling.

Positive Chronotropic Agents

Substances like nicotine, thyroid hormone, and epinephrine/norepinephrine that increase heart rate.

Negative Chronotropic Agent

Acetylcholine (Ach), which decreases heart rate.

Aorta

The largest elastic artery, which is the first blood vessel to take blood from the heart.

Arterioles

The smallest arteries, with less than 6 layers of smooth muscle, just before entering capillary beds.

Venule

The smallest vein that exits the capillaries.

Valves in Medium Veins

Medium veins that start having valves to prevent backflow.

Ventricular Ejection

A phase where the AV valves close and the semilunar valves open, allowing the ventricle to contract.

Stroke Volume

The amount of blood ejected from the heart in one contraction, affected by preload, afterload, and ionotropic agents.