Download Cardiovasular Questions - Seattle Central College

Cardiovascular Questions
Due 2-28
1. Beginning at the superior vena cava, trace the path of blood on its journey through the heart, lungs,
body tissues and back to the vena cava, naming all the chambers and vessels it passes through on its
journey (you can omit the peripheral vessels, concentrating only on those that exit or enter the heart
directly). (4)
Vena cava - Right atria - Right ventricle - pulmonary trunk - Pulmonary artery - Lung capillary beds Pulmonary Veins - Left atria - Left ventricle - Aorta - Arteries - Arterioles - Tissue capillary beds - Veinules Veins - Vena cava
2. Why are there three major waves of the ECG? What events correspond to each of them? (4)
Each wave represents a change in membrane potential across the heart. The P wave appears first, and is due
to the propagation of an action potential, which was initiated by the sinoatrial node, across the atria to the
atrioventricular node; it precedes a gentle atrial systole. The QRS complex appears second, and is produced
by the rapid propagation of the action potential from the AV node, down the purkinje fibers and throughout
the myocardium; it precedes strong ventricular systole. The T wave comes last, and is produced by the
repolarization of the ventricles; this immediately precedes ventricular diastole.
3. What events are responsible for the first and second heart sounds? (2)
The closing of the AV valves and the closing of the Semilunar valves
4. What is the Starling law? What property of heart muscle is responsible for it? (2)
Starlings law states that the amount of ventricular stretch during diastole is directly proportional the the
volume of blood that will be ejected during the subsequent systole; OR "more in = more out"
5. Increasing the plasma (interstitial / inter-cellular) Ca2+ concentration increases the strength of
contraction of cardiac muscle but not of skeletal muscle. Why is there a difference? (2)
The opening of Ca2+ channels on the plasma membrane of myocardial cells is a part of action potential
propagation through cardiac muscle. If the extracellular Ca2+ levels are increased, more Ca2+ will enter the
cell when those channels open. Therefore more troponin will bind Ca2+ ions, so more active sites on actin
filaments will be exposed, more myosin filaments will bind, and a stronger contraction will result.
6. List 3 factors that determine the Resistance of a single vessel? (3)
Viscosity, turbulence, and diameter.
7. The diameter of a capillary is smaller than that of an arteriole, yet collectively the capillaries have
lower resistance than the arterioles. Explain how this is possible. (2)
While much smaller than arteries and arterioles, the capillaries collectively provide far more area for the
same volume of blood to pass through. This increased area results in a tremendous blood pressure drop in
the capillaries. Since Flow is directly proportional to pressure, the resistance to flow in the capillaries is
smaller than in the arterioles.
8. What effect would a decrease in venous compliance have on the volume of blood in the veins? On
the venous pressure? On the venous return? On the total peripheral resistance? What effect would
arteriole dilation have on the total peripheral resistance? On venous return? (3)
Decreased venous compliance would reduce the volume of blood in the veins; increase venous pressure;
decreases venous return; and increase the peripheral resistance. Arteriole dilation would decrease
peripheral resistance and increase venous return.
9. Give two examples of how heart rate and/or blood pressure are controlled: what kinds of receptors are
involved, what stimuli are they responding to, where are they located, and what part of the CNS
receives the afferent sensory information? (4)
Chemoreceptors located in the carotid sinus and the aortic arch, respond to lowered O2 levels or increased
CO2 and blood pH levels. These sensors stimulate the cardiovascular centers in the medulla oblongata
(brainstem) and increase cardiac output and vasomotor tone. Baroreceptors, located in the carotid artery
and the aortic arch, respond to mechanical deformation (stretch). When BP drops, for example, these
receptors stimulate the cardioregulatory center in the MO which increases sympathetic stimulation of the SA
nodes of the heart and reduces parasympathetic stimulation of the myocardium; this increases cardiac
output. It also stimulates vasoconstriction of the arteries and arterioles, which increases BP.
10. Why must arteries be very thick and elastic? Why can veins afford to be thinner and less elastic? (2)
Arteries must handle a large volume of blood delivered at high pressure. Therefore they must be built to
withstand high pressure expand, and regain their original shape. Veins do not deal with high pressure so
they can be thinner and do not need to stretch as much.