Cardiovascular Physiology and Heart Function

Caulerpa taxifolia

An example of early multicellularity with simple circulation.

Average distance between a cell and a capillary

About 20-200 microns.

Diffusion principle

Explains why blood must move by bulk flow over long distances; diffusion is too slow over distances greater than a few microns.

Heart development fusion

The two parallel heart tubes fuse to form a single lumen during embryogenesis.

Oval window (foramen ovale) purpose

To allow blood to bypass the nonfunctional fetal lungs.

Diad in cardiac muscle cells

A single T-tubule associated with one sarcoplasmic reticulum (SR) cisterna.

Cardiac muscle action potential plateau phase channels

L-type calcium channels.

Atrioventricular (AV) valves

Prevent backward flow between atria and ventricles.

SA node failure

The AV node takes over pacemaking (~50 bpm).

Specialized conducting fibers

Purkinje fibers found beneath the endocardium.

Ventricles during systole

They contract and eject blood into the arteries.

Fibrous skeleton of the heart

It electrically insulates the atria from the ventricles.

Most permeable capillary type

Fenestrated capillary.

Lymphedema

Swelling due to lymphatic blockage.

Nitric oxide (NO) effect on blood vessels

It causes vasodilation by relaxing smooth muscle.

Blood vessels influencing vascular resistance

Arterioles.

Preload

The degree of stretch of the ventricular myocardium before contraction.

Afterload

The pressure the heart must overcome to eject blood during systole.

Sympathetic effects neurotransmitter

Noradrenaline (norepinephrine).

Poiseuille's Law relationship

Flow is proportional to the fourth power of the vessel radius.

Vasoconstriction receptor type

Alpha-1 adrenergic receptor.

Heart rate change during inspiration

Heart rate increases slightly (respiratory sinus arrhythmia).

Ejection fraction

The percentage of blood pumped out of the ventricles with each heartbeat.

Antidiuretic hormone (ADH)

Increases water reabsorption and causes vasoconstriction to raise blood pressure.