Cardiovascular System (Chapters 13 and 14)
I. Before you begin, make sure you have mastered the following topics:
A. Physiology of skeletal muscle excitation/contraction coupling and contraction:
depolarization, repolarization, role of calcium, role of actin/myosin, refractory period
B. There is a good review of heart anatomy on Interactive Physiology
C. Heart: tissue features (fig. 13.9)
1. Has characteristics in common with skeletal muscle: branching fibers with similar
actin and myosin arrangement – striated appearance and similar contraction
mechanism (different excitation mechanism)
2. Has some characteristics in common with (single-unit) smooth muscle – cells
connected by gap junctions and by desmosomes – at intercalated disks (fig.
13.9b)
D. Heart: chambers (fig. 13.1)
1. hollow, muscular pumps side by side — left pump and right pump. Each side
pumps about 3000 gallons per day.
2. Upper chambers = atria; singular = atrium; separated by interatrial septum
3. Lower chambers = ventricles; separated by interventricular septum
E. Heart: valves (figs. 13.7, 13.8)
1. Atrioventricular (AV) valves — lie between the atria and ventricles; prevent
backflow into atria when ventricles contract.
a) Right AV valve has three flaps — tricuspid valve.
b) Left AV valve has two flaps — bicuspid or mitral valve.
2. Semilunar valves — between the ventricles and the arteries; prevent backflow into
ventricles when heart relaxes; both valves have three flaps
a) Pulmonary semilunar valve
b) Aortic semilunar valve
F. Great vessels of the heart (fig. 13.1)
1. Veins returning blood to right atrium
a) Superior vena cava — from upper portion of body.
b) Inferior vena cava — from lower body
c) Coronary sinus — from wall of heart
2. Artery from from right ventricle: Pulmonary trunk, which divides into:
a) Right pulmonary artery (to right lung)
b) Left pulmonary artery (to left lung)
3. Veins returning blood to left atrium: four pulmonary veins (two right and two left)
4. Artery from left ventricle: aorta, which passes blood to all parts of the body,
except the lungs
G. Blood flow to heart muscle wall: blood flow is from left ventricle through ascending
aorta and then coronary arteries to myocardial capillaries and then back to coronary
sinus and then the right atrium. (fig. 13.4)
H. The electrical conduction system of the heart (fig. 13.10)
1. Sinoatrial node
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2. Atrioventricular node
3. Atrioventricular bundle (Bundle of His)
4. Right and left bundle branches
5. Purkinje fibers
I. Path of blood through the heart and body (fig. 13.2, 13.3)
1. Systemic circuit: from left ventricle of heart to other body organs (except lungs)
and tissues and back to heart (right atrium)
2. Pulmonary circuit: from right ventricle of heart to lungs and back to heart (left
atrium)
J. Vessels involved
1. Arteries – take blood away from the heart; also called efferent vessels
a) large, muscular walls
b) under relatively high pressure
c) blood in arteries may be oxygenated (systemic circuit; aorta) or not
(pulmonary circuit; pulmonary trunk)
2. Arterioles – smaller arteries
3. Capillaries – smallest diameter; gas and nutrient exchange here
4. Venules – larger vessels
5. Veins – carry blood back toward the heart; also called afferent vessels
a) tend to have larger diameter
b) walls not as muscular
c) lower pressure than arteries
d) most have valves
e) blood in veins may be oxygenated (pulmonary circuit; pulmonary veins)
or not (systemic circuit; superior and inferior vena cavae)
II. Overall physiological ‘design’ of the cardiovascular system – pressure, flow, and
resistance
A. The ultimate function of the cardiovascular system is to ensure adequate blood flow
through capillaries.
B. All gas and nutrient exchange happens at capillaries
1. All cells in the body are within a few centimeters of at least one of the capillaries
2. Capillaries (systemic) bring: nutrients & O2
3. Capillaries (systemic) pick up: wastes & CO2
C. Oxygen and nutrients generally move from the capillaries into the interstitial fluid of the
tissue by diffusion (a little is also pushed out with water by filtration, because the
system is under pressure).
D. Waste products generally move from the interstitial fluid back into the blood by
diffusion and mediated transport .