Download Cardiovasular Questions - Seattle Central College

Cardiovascular Questions
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 (use
the general names of peripheral vessels, but specific names of 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. What events produce the first and second heart sounds, respectively?
(2)
The closing of the AV valves and the closing of the Semilunar valves, respectively.
3. Explain the Frank- 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 to the volume
of blood that will be ejected during the subsequent systole; OR "more in = more out"
4. 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. No such channels exist on
skeletal muscle cells
5. List 3 factors that determine the Resistance of a single vessel?
(1)
Viscosity, turbulence, and diameter.
6. 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.
7. 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; increase
venous return; and increase the peripheral resistance. Arteriole dilation would decrease peripheral resistance and
increase venous return.
8. Explain two examples of how heart rate and blood pressure are controlled: Name the type of receptors
involved, the specific stimuli are they responding to, where they located, and what part of the CNS receives
the 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.
9. Why must arterial walls 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. They must also alter the distribution of blood,
so they have lots of smooth muscle to allow for vasoconstriction and reduced compliance. Veins do not deal with
high pressure so they can be thinner and do not need to stretch as much.
10. Explain how the heart conduction system works to produce rapid, coordinated contraction of the
myocardium; Be sure to name the structures involved.
(3)
The SA node in the right atria produces AP’s autorythmically. These propagate passively across the atrial
myocardium via intercalated discs connecting myocardial cells. In response, the atria contract in sync. The AP
arrives at and depolarizes the AV node. The resulting AP is propagated rapidly along the AV bundle to the apex of
the heart, then across the ventricles via Purkinje fibers. The intercalated discs of myocardial cells ensure that the
AP reaches all ventricular myocardial cells simultaneously and coordinated contraction follows.
11. Describe (mechanistically) how increased skeletal muscle activity will affect Preload, End Diastolic Volume
(EDV), End Systolic Volume (ESV) and finally SV.
(4)
Increased skeletal muscle activity in creases venous return which increases preload. Via the Starling law we know
that increased stretch of the myocardium leads to increased EDV and that alone increases SV. ESV also increases
a little due to the increased afterload caused by increased cardiac output.