BSNC 6000 Module 1 Midterm Review Questions
What are the effects of hypertension on macrocirculation? - Answer--Hypertension causes injury to the endothelial layer of the arteries which leads to plaque formation. Plaque restricts blood flow and can lead to ischemia. Plaque also weakens artery wal...
What are the effects of hypertension on macrocirculation? - Answer--Hypertension
causes injury to the endothelial layer of the arteries which leads to plaque formation.
Plaque restricts blood flow and can lead to ischemia. Plaque also weakens artery walls
thereby increasing the risk of an aneurysm
-Hypertension increases resistance to blood flow to the tissues. As a result, the heart
pumps harder to overcome the resistance. A chronic increase in the work of the heart to
overcome this resistance leads to enlargement of the heart muscle and increases the
risk of heart disease.
What are the effects of hypertension on microcirculation? - Answer-The microcirculation
(smallest arteries, arterioles, capillaries, and venules) is where the exchange of gases,
nutrients, and metabolites between the blood and tissues occurs.
Adequate perfusion via the microcirculation is essential for these exchanges. Prolonged
elevations of blood pressure can cause lasting changes which include remodeling of
small arteries and arterioles and reduction in number and combined length of arterioles
and capillaries.
What are some of the complications of hypertension? - Answer--Stroke
-Blindness
-Blood vessel damage
-Heart failure
-Kidney failure
What is preload? - Answer-Preload refers to the tension generated by the ventricle walls
due to the filling of blood before the ventricles contract. Preload can be estimated by the
end diastolic volume (EDV). The ventricle contracts more forcefully and ejects more
blood (stroke volume), as the amount of blood delivered to it increases (EDV or
preload). This is known as the Frank-Starling mechanism. This relationship between the
force of contraction and preload is based on the arrangement of actin and myosin
filaments when cardiac muscle fibres are stretched due to filling, before the heart
contracts.
What will be the effect of an increase in venous return on preload? - Answer-Venous
return is the main determinant of preload. An increase in venous return increases
preload. Venous return is influenced by the total blood volume, venous pressure
, (increases with sympathetic activity), and skeletal muscle activity (squeezes blood in
deep veins to move blood toward the heart).
What will be the effect of an increase in heart rate on preload? - Answer-An increase in
heart rate decreases preload because the ventricles have less time to fill with blood.
When heart rate increases, the duration of diastole is shortened while systole remains
fairly constant. This will decrease stroke volume; however, the higher heart rate will
maintain cardiac output (except at high heart rates such as with ventricular tachycardia)
If the heart has problems pumping and stroke volume decreases, then more blood will
remain in the heart after systole (end systolic volume or ESV increases). How will an
increase in ESV affect preload? - Answer-The blood returning to the heart (the venous
return) will add to the higher ESV, and preload will increase. According to the Frank-
Starling mechanism, the increase in preload will increase the force of contraction in
order to maintain stroke volume.
Define afterload - Answer-Afterload is the pressure that the ventricles need to generate
to overcome the resistance to the ejection of blood during systole.
Is diastolic blood pressure or systolic blood pressure a better indicator of afterload? -
Answer-Diastolic blood pressure is a better indicator of afterload. This is the pressure in
the systemic or pulmonary arterial circulations while the ventricles are filling. This is the
pressure that must be overcome for blood to be pumped out of the heart, and it
indicates the workload of the heart.
Afterload inversely affects stroke volume. As afterload increases, stroke volume
decreases. What conditions might cause an increase in afterload? - Answer-Afterload
increases if there is an increase in blood pressure (e.g. hypertension), a circulatory
blockage (e.g. pulmonary embolism), an increase in blood volume, or a narrowing of the
aortic or pulmonary valve openings (e.g. aortic stenosis).
What is myocardial contractility? - Answer-Myocardial contractility is the force of muscle
contraction during systole, independent of preload.
What is myocardial contractility influenced by? - Answer--the amounts of contractile
proteins in cardiac muscle fibres;
-the levels of intracellular calcium; and
-the availability of ATP.
How does sympathetic innervation increase myocardial contractility? - Answer-
Sympathetic innervation and the adrenal catecholamines increase intracellular calcium
levels by stimulating the opening of calcium channels (when epinephrine or
norepinephrine bind to beta 1 adrenergic receptors).
How does the thyroid hormone increase contractility? - Answer-Thyroid hormone acts
by stimulating the synthesis of myocardial contractile proteins and adrenergic receptors.
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