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In insects, bathes internal organs directly, moving through sinuses by contracting of a "heart."


chambers that receive blood


chambers that pump blood out.


carry blood away from the heart to organs


the site of chemical exchange between
blood and interstitial fluid).


return blood to the heart.

single circulation.

A circulatory system consisting of a single pump and circuit, in which blood passes from the sites of gas exchange to the rest of the body before returning to the heart. (fish)

Amphibian double circulation.

A circulation scheme with separate pulmonary and systemic circuits, which ensures vigorous blood flow to all organs. (amphibians)

Mammal/Bird double circulation

Double circulation is similar to that of amphibians except that oxygenated and
deoxygenated blood does not mix due to possession of two ventricles.

Heart cycle

Sequence of events during each heartbeat, lasting about 0.8 second


heart muscle contracts and the chambers pump blood


the ventricles fill with blood.

Atrioventricular valves

Valves between each atrium and ventricle that keep blood from flowing back into the atria

Semilunar valves

Valves located where the aorta leaves the left ventricle and where the pulmonary artery leaves the right ventricle; prevents blood from flowing
back into ventricles.

Heart murmur

A defect in one or more of the valves that allows backflow of blood

Cardiac output

Volume of blood per minute that the left ventricle pumps into the
systemic circuit; depends on heart rate and stroke volume.


Cardiac muscle cells- (self-excitable)

Purkinje fibers

carry impulses throughout the walls of the ventricles.

sinoatrial (SA) node

a specialized region of the heart that controls the rate
of contraction; the pacemaker. Located in the right atrium wall

Heart rate

controlled by hormones, body temperature, and by the opposing actions of
two sets of nerves.


Send signals to the brain that
trigger small blood vessels to relax, increasing their diameter and blood flow. The
brain is also signaled, and heart rate decreases.


Kidneys secrete the enzyme in response to a decreased blood flow in the
kidneys. Converts a protein to angiotensin, a hormone that causes small blood vessels to contract. This in turn causes an increase in blood pressure.

kidney fluid system

Excess pressure in kidney arteries signals that blood pressure has risen too high. The kidneys react by increasing the rate of salt and water excretion,
lowering the amount of fluid pumped by the heart

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