Circulation

The first time ever I held you near
and felt your heart beat close to mine
I thought our joy would fill the world
and would last till the end of time, my Love.
--Peter, Paul and Mary

Campbell and Reece, Chapter 42

In multicellular metazoan, need a vascular system (also in plants)
Circulation : Cardiovascular system
TRANSPARENCY Fig. 42.2
Open circulation Blood = interstitial fluid - hemolymph is term for blood - most molluscs and all arthropods have open circulation
hemocoel is the space where the blood is
- important in insects that gas transport (via air filled trachea) does not rely on circulation being closed
Closed circulation - annelids, cephalopods, echinoderms, vertebrates

Chambers of heart - TRANSPARENCY Fig. 42.3
Fish have 2 chambers (gills and body "wired" in series)
The "circuit" is "in series" - heart -> gills -> body -> back to heart
Amphibia and reptiles have 3 chambers (2 atria, 1 ventricle)
As long as blood does not fully mix, there is some separation of non-oxygenated blood to the pulmonary circulation and of oxygenated blood to the systemic circulation

Birds and mammals have 4 chambers which maintains better separation
TRANSPARENCY Figs. 42.4
note that right is drawn on left as if looking into the chest of a supine subject
pulmonary valve (semilunar) feeds pulmonary arteries
aortic valve (also semilunar) feeds aorta
valves snap shut from arterial back pressure at the end of systole to make second heart sound- "dub"

Here is the circuit: LA - LV - Arteries (aorta, etc.) (blood pressure taken here) - Arterioles (regulate blood flow to muscles, brain, digestion, kidneys and skin) - Capillaries (near, exchange, WBC's) - venules - veins (no pressure, valves)- RA - RV - Pulmonary arteries - Lung capillaries - Pulmonary veins -

TRANSPARENCY (Fig. 42.8) artery is like hose, regulation of arteriole emptying into vascular bed, capillary is one layer of endothelial cells

TRANSPARENCY Fig. 42.10 - blood spreads out as it goes from arteries -> arterioles -> capillaries (top of figure) and hence moves slower (second part of figure). Pressure goes down during movement arteries -> arterioles -> capillaries (bottom). Blood moves slowly and with very little pressure in veins. Movement in veins is mostly passive with a series of valves and where contraction of skeletal muscles assists TRANSPARENCY (Fig. 42.9)

TRANSPARENCY 42.5 Heart, TRANSPARENCY Fig. 42.6 cardiac cycle
superior and inferior vena cava feed right atrium -> ventricle via tricuspid (atrio-ventricular) valve
pulmonary veins feed left atrium -> ventricle via bicuspid (atrioventricular) valve
tricuspid & bicuspid snap shut at start of ventricular contraction to make first heart sound- "lub"
backslosh through valves - - heart murmurs

CO2 and O2 - hemoglobin (later in the respiration lecture)

Diastole (between heart beats), systole is during ventricular contraction, hence terms systolic and diastolic blood pressure.
TRANSPARENCY (Fig. 42.11) close off artery, when it opens (systolic pressure), blood flow is turbulent and noisy, when it is always open (diastolic pressure), blood flow is no longer noisy
Blood pressure is measured in arteries arteries
hypertension 45 million Americans - salt intake is still debated, >140/95 high 140/70 normal
high diastolic is especially bad

Electrical - TRANSPARENCY Fig. 42.7 SA node (or electrical pacemaker) - spread - automatic
sympathetic nervous system speeds it up, parasympathetic nervous system slows it down

Heart attack - atherosclerosis (arteriosclerosis) (cholesterol, saturated fats) - coronary arteries myocardial infarction - coronary thrombosis - ischemia - bypass - fibrillation - CPR (keep brain alive, needs O2) - nitroglycerine - NO
1 million Americans die/yr reducing since 1971
bypass operations, replace coronary artery with vessel from somewhere else in the body, there are 100,000-200,000/yr operations - 30% may be unnecessary
LDL receptors take out cholesterol which otherwise deposits
HDL may lower deposition - excercise good for this

Myocardial cells not regenerate (by mitosis in the adult). This is why heart attack is so damaging. The same is true for the nerves in the central nervous system where similar damage is called stroke.

streptokinase thru catheter dissolve clot
tissue plasmogen activator dissolve vessel clots
catheter with balloon angioplasty

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this page was last updated 1/30/03