UNIT 3: Blood Vessels (Blood Flow) (Mylab and Mastering)

Which of the following is NOT an important source of resistance to blood flow? A. vessel length B. total blood volume C. blood viscosity D. vessel diameter

total blood volume (Total blood volume is not an important source of resistance to blood flow. However, blood volume does have a direct effect on blood pressure.)

Which structural layer of blood vessels is most responsible for maintaining blood pressure? A. tunica intima B. subendothelial C. tunica media D. tunica externa

tunica media

Which of the following is most likely to occur in the arteriovenous shunts present in the blood vessels of the finger tips and toes? A. Warmer temperatures will result in vasoconstriction in the arteriovenous shunts. B. Colder temperatures will result in vasoconstriction in the arteriovenous shunts. C. Exercise will result in vasoconstriction in the arteriovenous shunts. D. Colder temperatures will result in vasodilation in the arteriovenous shunts.

Colder temperatures will result in vasoconstriction in the arteriovenous shunts

Which of the following would NOT result in the dilation of the feeder arterioles and opening of the precapillary sphincters in systemic capillary beds? A. a local increase in pH B. a decrease in local tissue oxygen content C. an increase in local tissue carbon dioxide D. a local increase in histamine

a local increase in pH

Suppose that at a given point along a capillary, the following forces exist: capillary hydrostatic pressure (HPc) = 30 mmHg, interstitial fluid hydrostatic pressure (HPif ) = 0 mmHg. capillary colloid osmotic pressure (OPc) = 25 mmHg, and interstitial fluid colloid osmotic pressure (OPif) = 2 mmHg. The net filtration pressure at this point in the capillary is__________

7mmHg (Net filtration pressure (NFP) is equal to the outward pressures (HPc + OPif) minus the inward pressures (HPif + OPc). Using the values provided in this question, NFP = (30 mmHg + 2 mmHg) - (0 mmHg + 25 mmHg) = 7 mmHg.)

Which of the following statements describes the significance of blood pressure changes as blood reaches the capillary beds? A. Blood pressure drops as it reaches the capillary beds because high pressure would rupture them. B. Blood pressure increases as it reaches the capillary beds because capillaries need a higher blood pressure for filtration activities. C. Blood pressure drops as it reaches the capillary beds because capillaries depend on the lower pressure to prevent fluid exchange between the capillaries and interstitial space. D. Blood pressure does not change as blood flows from arteries into capillaries.

Blood pressure drops as it reaches the capillary beds because high pressure would rupture them. (Low capillary pressures are desirable because capillaries are fragile and high pressures would rupture them. Most capillaries are extremely permeable and thus even the low pressure forces solute-containing fluids out of the bloodstream into the interstitial space.)

True or False: Edema can be caused by an increase in capillary hydrostatic pressure (HPc) or a decrease in capillary colloid osmo

True (Edema is an abnormal increase in the amount of interstitial fluid. Either an increase in outward pressures (driving fluid out of the capillaries) or a decrease in inward pressures could be the cause. The primary outward pressure (promoting filtration) is HPc and the primary inward pressure (promoting reabsorption) is OPc.)

True or False: Osmotic pressure is fairly constant along the entire length of a capillary bed.

True (The abundant plasma proteins in capillary blood (primarily albumin molecules) develop a capillary colloid osmotic pressure (OPc), also called oncotic pressure, of approximately 26 mmHg. The interstitial fluid colloid osmotic pressure (OPif) is substantially lower-from 0.1 to 5 mmHg-because interstitial fluid contains few proteins. Unlike capillary hydrostatic pressure (HPc), OP does not vary significantly from one end of the capillary bed to the other.)

Which of the following is not a capillary transport mechanism that allows for the exchange of nutrients and gases? A. diffusion through the endothelial cell membrane B. movement through intracellular clefts or fenestrations C. transport in pinocytotic vesicles D. bulk flow

bulk flow (Bulk flow results in fluid being forced out of the capillaries through the clefts at the arterial end of the capillary bed, with most of it returning to the bloodstream at the venous end. The driving force is blood hydrostatic pressure.)

Assume a person is experiencing a hemorrhage and the HPc has dropped to 23 mm Hg at the arteriole end of the capillary. Calculate net filtration pressure (NFP) at the arteriole end of the capillary.

-2 mm Hg (The net filtration pressure would now be negative as a result of the blood pressure drop, which would result in little or no fluid moving across capillary walls into the interstitial fluid at the arteriole end. Net filtration pressure (NFP) for the arteriole end of the capillary = (HPc + OPif) − (HPif + OPc) = (23 + 1) − (0 + 26).)

Which of the following is NOT a vasoconstrictor? A. Angiotensin II B. Norepinephrine C. Antidiuretic hormone D. Atrial natriuretic peptide

Atrial Natriuretic Peptide (Atrial natriuretic peptide (ANP) decreases peripheral resistance by causing vasodilation)

Which of the following is NOT correct regarding the relationship between pressure, flow, and resistance in the cardiovascular system? A. Blood flow (F) through the entire circulation equals cardiac output (CO). B. Blood flow (F) is inversely proportional to the pressure gradient (ΔP) in the blood vessels C. Resistance (R) is more important than the pressure gradient (ΔP) in influencing blood flow to an individual organ. D. The relationship between resistance (R) and flow (F) is the opposite of the relationship between pressure (ΔP) and flow (F).

Blood flow (F) is inversely proportional to the pressure gradient (ΔP) in the blood vessels. (Blood flow (F) is directly proportional to the difference in blood pressure (ΔP) between two points in the circulation-that is, the blood pressure, or hydrostatic pressure, gradient. Consequently, when ΔP increases, blood flow increases, and when ΔP decreases, blood flow declines. On the other hand, blood flow is inversely proportional to the total peripheral resistance (TPR) in the systemic circulation; if TPR increases, blood flow decreases.)

Select the correct statement about blood flow. A. It is measured in mm Hg. B. It is relatively constant through all body organs. C. It is greatest where resistance is highest. D. Blood flow through the entire vascular system is proportional to cardiac output.

Blood flow through the entire vascular system is proportional to cardiac output.

Which of the following would NOT be a cause of edema in your patient's lower extremities? A. Pregnancy B. Congestive heart failure C. Excess protein in the diet D. Sitting during a long flight

Excess protein in the diet (If a patient's plasma protein, especially albumin, is too low, then his or her osmotic pressure is low. Recall that plasma proteins act as "water magnets," resisting the force of hydrostatic pressure (i.e., blood pressure) that pushes fluid out of the capillaries. Edema can be a consequence of low plasma protein.)

True or False: Osmotic pressure is created by the presence in a fluid of small diffusible molecules that easily move through the capillary wall

False

A muscle that is being regularly contracted during exercise will attract blood flow by dilating arterioles. Which of these factors would contribute to this effect?

Increased Levels of carbon dioxide (Carbon dioxide produced in muscle respiration would be a metabolic mechanism, which would dilate local arterioles and increase blood flow.)

The velocity of blood is slowest in the capillaries and pressure of blood is lowest in the veins. Which of the following is NOT an accurate description of the benefits of slow, low pressure blood in the capillary beds? A. Lower pressure in the capillary bed helps to increase pressure in the venous circulation. B. Lower pressure on the venous end of the capillary bed allows for greater reabsorption of fluid back to the plasma. C. Lower pressure reduces the chance of injury to delicate capillary vessels. D. Slower blood flow through capillaries allows more time for diffusion to take place in the capillary bed.

Lower pressure in the capillary bed helps to increase pressure in the venous circulation.

In local autoregulation of blood flow, usually low oxygen levels cause vasodilation. Which tissue shows the opposite pattern? A. heart B. lungs C. liver D. skeletal muscles

Lungs (The pulmonary circulation is opposite from what is seen in most tissues. Low pulmonary oxygen levels cause local vasoconstriction and high levels promote vasodilation. This allows blood to skip areas of the lungs where mucous from an infection may render some alveoli ineffective.)

Which of the following is a myogenic factor that influences blood flow?

Stretch of vascular smooth muscle (Myogenic control of vascular smooth muscle occurs in response to the stretch of the vessel because of blood pressure fluctuations.)

Which of the choices below explains why the arterioles are known as resistance vessels? A. They contain a large quantity of elastic tissue. B. The contraction and relaxation of the smooth muscle in their walls can change their diameter. C. They distribute blood to various parts of the body. D. Their prime function is the exchange of nutrients and wastes between the blood and tissue cells.

The contraction and relaxation of the smooth muscle in their walls can change their diameter.

Which of the following statements does NOT correctly describe tissue perfusion in the cardiovascular system? A. Perfusion of the kidneys is important for urine formation. B. Accumulation of local metabolites triggering dilation of arterioles is an example of intrinsic control of tissue perfusion. C. The myogenic response is an example of extrinsic control of tissue perfusion. D. Autonomic nervous system regulation of blood pressure is an example of extrinsic control of tissue perfusion.

The myogenic response is an example of extrinsic control of tissue perfusion. (Myogenic control-control of vascular smooth muscle without the influence of hormones or neural signals-is an example of intrinsic regulation. Extrinsic controls act via the nerves and hormones of the nervous and endocrine systems, the two major control systems of the body.)

True or False: An increase in blood viscosity will cause an increase in total peripheral resistance.

True

True or False: The adjustment of blood flow to each tissue in proportion to its requirements at any point in time is termed autoregulation.

True

True or False: Whereas diffusion is more important for solute exchange between plasma and interstitial fluid, bulk flow is more important for regulation of the relative volumes of blood and interstitial fluid.

True

Which of the following is the most significant source of blood flow resistance? A. blood vessel diameter B. blood viscosity C. blood vessels type D. total blood vessel length

blood vessel diameter

Reduction in the concentration of albumin in blood plasma would alter capillary exchange by ________.

decreasing colloid osmotic pressure and edema will occur

Which of the following would decrease total peripheral resistance to blood flow? A. vasoconstriction B. atherosclerosis C. increasing blood vessel length D. decreasing the hematocrit

decreasing the hematocrit (Decreasing the hematocrit (fraction of whole blood consisting of blood cells) would lead to decreased blood viscosity, and thus would decrease resistance.)

Blood flow is ________ proportional to the difference in blood pressure. Blood flow is ________ proportional to the total peripheral resistance.

directly, inversely

Which of the following intrinsic mechanisms (autoregulation) for controlling arteriolar smooth muscle diameter promotes vasoconstriction? A. nitrous oxide B. prostaglandins C. histamine D. endothelins

endothelins

Arteriolar blood pressure increases in response to all but which of the following? A. falling blood volume B. increasing stroke volume C. increasing heart rate D. rising blood volume E. all of these

falling blood volume

Which of the choices below reflects the balance (or imbalance) between the direction and amount of fluid that flows across the capillary walls? A. plasma and formed element concentration B. hydrostatic pressure only C. hydrostatic and osmotic pressure D. blood volume and viscosity

hydrostatic and osmotic pressure

In general, it is expected that ________. A. osmotic pressure will be lower in the arteriole end of the capillary bed compared to the venous end B. hydrostatic pressure will remain constant throughout the capillary bed C. hydrostatic pressure will drop as blood moves away from the arteriole end of the capillary bed D. hydrostatic pressure will rise as blood moves away from the arteriole end of the capillary bed

hydrostatic pressure will drop as blood moves away from the arteriole end of the capillary bed

Blood flow to the skin ________.

increases when environmental temperature rises

Cerebral blood flow is regulated by ________.

intrinsic autoregulatory mechanisms

Brain blood flow autoregulation ________.

is abolished when abnormally high CO2 levels persist

Which of the following organs would experience decreased blood flow during exercise? A. kidneys B. brain C. skin D. skeletal muscles

kidneys (The kidneys and the GI tract (i.e., the stomach and intestines) would experience a decrease in blood flow during exercise. Blood flow would be diverted away from these organs to the exercising muscles, heart, and skin.)

Where in the body would you find low oxygen levels causing vasoconstriction and high levels causing vasodilation?

lungs

What pressure is responsible for reabsorption and for pulling fluids into the venous end of capillaries?

osmotic pressure in capillary (OPc) (Osmotic pressure is based on the concentration of dissolved materials that attract water across a membrane. The osmotic pressure in a capillary (OP) is the force drawing fluid into the blood at the venous end.)

Which of the following is an INCORRECT statement regarding pressure conditions in a capillary as blood moves through it from the arteriole end to the venous end? A. blood hydrostatic pressure (HPc) drops B. net filtration pressure drops interstitial C. hydrostatic pressure does not play a significant role in capillary pressures D. osmotic pressure in the capillary (OPc) drops

osmotic pressure in the capillary (OPc) drops (Osmotic pressure remains fairly constant as blood moves from the arteriole to the venous end of the capillary.)

In general, it is expected that ________. A. osmotic pressure will be lower in the arteriole end of the capillary bed compared to the venous end B. osmotic pressure will be higher in the arteriole end of the capillary bed compared to the venous end C. osmotic pressure will remain relatively consistent throughout the capillary bed D. hydrostatic pressure will remain constant throughout the capillary bed

osmotic pressure will remain relatively consistent throughout the capillary bed

Which of the following CANNOT diffuse across a capillary wall to or from the surrounding interstitial fluid? A. proteins B. lipid-soluble substances C. monosaccharides and amino acids D. oxygen and carbon dioxide

protiens (Large molecules, such as proteins, are actively transported in pinocytotic vesicles. They are too large to pass through the intercellular clefts or fenestrations, which is how smaller water-soluble molecules cross the capillary wall.)

The influence of blood vessel diameter on total peripheral resistance is________

significant because resistance is inversely proportional to the fourth power of the vessel radius

The velocity of blood flow is ________.

slowest in the capillaries because the total cross-sectional area is the greatest

Which of the following would not normally be a direct cause of edema? A. hypoproteinemia in a person with liver disease B. increased leakage of plasma proteins across capillary walls into the interstitial space C. tachycardia D. reduced ability to drain interstitial fluid into lymphatic vessels

tachycardia (Edema is an abnormal accumulation of fluid in the interstitial space. It results not from rapid heart rate, but from an increase in outward pressures promoting the movement of fluid out of the capillaries, or from a decrease in pressures drawing fluid back into the venous end of capillary beds.)