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Name the three basic components of a circulatory system

circulatory fluid, a set of interconnecting vessels, and a muscular pump, the heart.


open circulatory systems.

found mainly in insects. Circulatory fluid called hemolymph that bathes body cells. No distinction between blood and interstitial fluid.

Out: One or more tubular hearts pump the hemolymph into an interconnected system of sinuses (open space surrounding the organs).

In: Body wall (muscle) contractions and relaxation of the heart(s) help move hemolymph back.


closed circulatory systems.

found in vertebrates and many invertebrates

Fluid bathing the internal organ (interstitial fluid) is different from the fluid (blood) in the circulatory system.

Heart: drives circulation.

Materials are exchanged between the blood and the interstitial fluid.

Benefit: (a) high pressure (rapid transport), (b) directed flow, (c) regulated distribution.


Compare and contrast single and double circulation.

single circulation (fish)- the blood passes through the heart once in each complete circuit. Blood leaving the heart passes through two capillary beds before returning. CO2/O2 exchange. Blood pressure drops substantially when blood flows through a capillary bed. Swimming helps circulation.

double circulation (mammals and amphibians) - 3 chambered heart in amphibians, 4 chambered heart mammals.

2 atria and 2 ventricles. The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood. Complete segregation of oxygen-rich and oxygen–poor blood in the heart.

There is no mechanism to vary relative blood flow to the lungs and body.

Mammals and birds are endotherms and require more O2 than ectotherms to generate heat through metabolism.

Higher demand for material exchange (O2, CO2, nutrients, wastes) is made by a more efficient transport system: separate and independently powered pulmonary and systemic circuits and by large powerful hearts.


Humans and other vertebrates have a closed circulatory system called the cardiovascular system:

consists of heart, blood vessels, and blood


Three main types of blood vessels

arteries - carry blood from heart to organs and capillaries.

veins - carry blood back to heart from capillaries.

capillaries - microscopic vessels with thin porous walls. The sites of chemical exchange between the blood and interstitial fluid.


Arteries and veins are distinguished by what?

the direction of blood flow, not by O2 or nutrient content.


Describe the cardiac cycle, distinguishing between systole and diastole.

1. atrial and ventricular diastole - during relaxation phase blood returning from the large veins flows into the atria and then into the ventricles through the AV valves.

2. Atrial systole and ventricular diastole - A brief period of atrial contraction then forces all blood remaining in the atria to the ventricles.

3. Ventricular systole and atrial diastole - During the remainder of the cycle, ventricular contraction pumps blood into the large arteries through the semilunar valves.

systole - contraction

diastole - relaxation


Define cardiac output and its relationship with heart rate and stroke volume.

depends on both the heart rate and stroke volume.

Cardiac output = Heart Rate x Stroke Volume

4000-5000 ml = 70 beats/min x 70 ml

Heart rate is the pulse, is the number of beats per minute. Normal heart rate is about 70-80 beats/min

Stroke volume is the amount of blood pumped in a single contraction. Regulated by the sympathetic nervous system (degree of muscle contraction)


Describe how the flow of electrical signals from the pacemaker coordinates heart function

The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which all other cardiac muscle cells contract.

produces electrical impulses that spread rapidly through the heart.

Impulses from the SA node travel to the atrioventricular (AV) node. At the AV node, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract.

The pacemaker is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisions.

The sympathetic division speeds up the pacemaker (norepinephrine). The parasympathetic division slows down the pacemaker (acetylcholine).

The pacemaker is also regulated by hormones (e.g. adrenaline) and temperature (1C increase raises heart rate by about 10 beats/min)


Distinguish between a heart attack (myocardial infarction) and a stroke.

Heart attack occurs when blood flow stops to part of the heart causing damage to the heart muscle (plumbing problem). The coronary arteries are the only source of blood supply to the heart. There is very little redundant blood supply, and thus blockage of these vessels can be critical.

Severe arrhythmia (electricity problem). Cardiac defibrillator can “reboot” the heart.

Common symptom of heart attack: chest pain, or pain travels into the shoulder, arm, back, neck or jaw.

Stroke - death of neurons in the brain, usually resulting from blockage of arteries in the head.



lodging of embolus, a transported clot, that blocks blood vessels.



a fibrinous clot formed in a blood vessel of heart chamber.



hardening of the arteries by fatty deposit (cholesterol & lipids) named plaque

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