490 Chapter 14
14.6 Blood Pressure 475
A. Baroreceptors in the aortic arch and carotid sinuses affect the
cardiac rate and the total peripheral resistance via the
sympathetic nervous system.
- The baroreceptor reflex causes pressure to be
maintained when an upright posture is assumed. This
reflex can cause a lowered pressure when the carotid
sinuses are massaged. - Other mechanisms that affect blood volume help to
regulate blood pressure.
B. Blood pressure is commonly measured indirectly by
auscultation of the brachial artery when a pressure cuff
is inflated and deflated. - The first sound of Korotkoff, caused by turbulent flow
of blood through a constriction in the artery, occurs
when the cuff pressure equals the systolic pressure. - The last sound of Korotkoff is heard when the cuff
pressure equals the diastolic blood pressure.
C. The mean arterial pressure represents the driving force for
blood flow through the arterial system.
14.7 Hypertension, Shock, and Congestive Heart
Failure 482
A. Hypertension, or high blood pressure, is classified as either
primary or secondary.
1. Primary hypertension, also called essential
hypertension, may result from the interaction of
numerous mechanisms that raise the blood volume,
cardiac output, and/or peripheral resistance.
2. Secondary hypertension is the direct result of known
specific diseases.
B. Circulatory shock occurs when delivery of oxygen to the
organs of the body is inadequate.
1. In hypovolemic shock, low blood volume causes low
blood pressure that may progress to an irreversible state.
2. The fall in blood volume and pressure stimulates
various reflexes that produce a rise in cardiac rate, a
shift of fluid from the tissues into the vascular system, a
decrease in urine volume, and vasoconstriction.
C. Congestive heart failure occurs when the cardiac output is
insufficient to supply the blood flow required by the body.
The term congestive is used to describe the increased venous
volume and pressure that result.Test Your Knowledge
- According to the Frank-Starling law of the heart, the strength
of ventricular contraction is
a. directly proportional to the end-diastolic volume.
b. inversely proportional to the end-diastolic volume.
c. independent of the end-diastolic volume. - In the absence of compensations, the stroke volume will
decrease when
a. blood volume increases.
b. venous return increases.
c. contractility increases.
d. arterial blood pressure increases. - Which of these statements about tissue fluid is false?
a. It contains the same glucose and salt concentration as
plasma.
b. It contains a lower protein concentration than plasma.
c. Its colloid osmotic pressure is greater than that of plasma.
d. Its hydrostatic pressure is lower than that of plasma.- Edema may be caused by
a. high blood pressure.
b. decreased plasma protein concentration.
c. leakage of plasma protein into the interstitial fluid.
d. blockage of lymphatic vessels.
e. all of these.- Both ADH and aldosterone act to
a. increase urine volume.
b. increase blood volume.REVIEW ACTIVITIES
c. increase total peripheral resistance.
d. produce all of these effects.- The greatest resistance to blood flow occurs in
a. large arteries. c. arterioles.
b. medium-size arteries. d. capillaries. - If a vessel were to dilate to twice its previous radius, and if
pressure remained constant, blood flow through this vessel
would
a. increase by a factor of 16.
b. increase by a factor of 4.
c. increase by a factor of 2.
d. decrease by a factor of 2. - The sounds of Korotkoff are produced by
a. closing of the semilunar valves.
b. closing of the AV valves.
c. the turbulent flow of blood through an artery.
d. elastic recoil of the aorta. - Vasodilation in the heart and skeletal muscles during
exercise is primarily due to the effects of
a. alpha-adrenergic stimulation.
b. beta-adrenergic stimulation.
c. cholinergic stimulation.
d. products released by the exercising muscle cells. - Blood flow in the coronary circulation
a. increases during systole.
b. increases during diastole.
c. remains constant throughout the cardiac cycle.