Chapter 10 The Blood Vessels and Blood Pressure

Question 1

Patterns and Physics of Blood Flow

• ________ that replenish nutrient supplies and remove metabolic wastes from the blood receive a greater percentage of the cardiac output (CO) than is warranted by their metabolic needs.
• These reconditioning organs can better tolerate reductions in ________ than can organs that receive blood solely for meeting their metabolic needs.

The reconditioning organs are the ________, ________, and ________/

Answer 1

Patterns and Physics of Blood Flow

• Reconditioning organs that replenish nutrient supplies and remove metabolic wastes from the blood receive a greater percentage of the cardiac output (CO) than is warranted by their metabolic needs.
• These reconditioning organs can better tolerate reductions in blood supply than can organs that receive blood solely for meeting their metabolic needs.

The reconditioning organs are the digestive organs, kidneys, and skin

Question 2

Patterns and Physics of Blood Flow

• The _____ is especially vulnerable to reductions in its blood supply. Therefore, maintaining adequate ow to this vulnerable organ is a high priority in circulatory function.

Answer 2

Patterns and Physics of Blood Flow

• The brain is especially vulnerable to reductions in its blood supply. Therefore, maintaining adequate ow to this vulnerable organ is a high priority in circulatory function.

Question 3

Patterns and Physics of Blood Flow

• Blood flows in a closed loop between the _____ and the _____.
• The _____ transport blood from the heart throughout the body.
• The _____ regulate the amount of blood that flows through each organ.
• The _____ are the actual site where materials are exchanged between blood and surrounding tissue cells.
• The _____ return blood from the tissue level back to the heart.

Answer 3

Patterns and Physics of Blood Flow

• Blood flows in a closed loop between the heart and the organs.
• The arteries transport blood from the heart throughout the body.
• The arterioles regulate the amount of blood that flows through each organ.
• The capillaries are the actual site where materials are exchanged between blood and surrounding tissue cells.
  ​
• The veins return blood from the tissue level back to the heart.

Question 4

Patterns and Physics of Blood Flow

• The flow rate of blood through a vessel (in volume per unit of time) is directly proportional to the _________ and inversely proportional to the _______ (F=∆P/R).
• The pressure gradient (∆P) is the _____ in _____ between the beginning and end of a vessel.
• The pressure imparted to the blood by __________ establishes the higher pressure at the beginning of a vessel.
• The lower pressure at the end is the result of _________ as flowing blood rubs against the __________.

Answer 4

Patterns and Physics of Blood Flow

• The flow rate of blood through a vessel (in volume per unit of time) is directly proportional to the pressure gradient and inversely proportional to the resistance (F=∆P/R).
• The pressure gradient (∆P) is the difference in pressure between the beginning and end of a vessel.
• The pressure imparted to the blood by cardiac contraction establishes the higher pressure at the beginning of a vessel.
• The lower pressure at the end is the result of frictional losses as flowing blood rubs against the vessel wall.

Question 5

Patterns and Physics of Blood Flow

• Resistance (R), the hindrance to blood flow through a vessel, is influenced most by the vessel’s _____.
• Resistance is inversely proportional to the____________________, so small changes in radius profoundly influence flow.
• As the radius _____, resistance _____ and flow _____, and vice versa.

*

Answer 5

Patterns and Physics of Blood Flow

• Resistance (R), the hindrance to blood flow through a vessel, is influenced most by the vessel’s radius.
• Resistance is inversely proportional to the fourth power of the radius (R= 1/r⁴), so small changes in radius profoundly influence flow.
• As the radius increases, resistance decreases and flow increases, and vice versa.

Question 6

Arteries

• Arteries are large-radius, low-resistance passageways from the heart to the organs.
• They also serve as a ______________.
• Because of their _______, owing to their abundant _______ fibers, arteries expand to accommodate the extra volume of blood pumped into them by cardiac contraction and then recoil to continue driving the blood forward when the heart is relaxing.

*

Answer 6

Arteries

• Arteries are large-radius, low-resistance passageways from the heart to the organs.
• They also serve as a pressure reservoir.
• Because of their elasticity, owing to their abundant elastin fibers, arteries expand to accommodate the extra volume of blood pumped into them by cardiac contraction and then recoil to continue driving the blood forward when the heart is relaxing.

Question 7

Arteries

• Systolic pressure (average 120 mm Hg) is the peak pressure exerted by the ________ against the vessel walls during cardiac systole.
• Diastolic pressure (average 80 mm Hg) is the minimum pressure in the arteries when blood is ________into the vessels downstream during cardiac diastole.
• When blood pressure is 120/80, ________ (the difference between systolic and diastolic pressures) is 40 mm Hg.
• The average driving pressure throughout the cardiac cycle is the mean arterial pressure (MAP), which can be estimated using the following equation:

MAP = (________ )+ (1/3)*(________.)

Answer 7

Arteries

• Systolic pressure (average 120 mm Hg) is the peak pressure exerted by the ejected blood against the vessel walls during cardiac systole.
• Diastolic pressure (average 80 mm Hg) is the minimum pressure in the arteries when blood is draining off into the vessels downstream during cardiac diastole.
• When blood pressure is 120/80, pulse pressure (the difference between systolic and diastolic pressures) is 40 mm Hg.
• The average driving pressure throughout the cardiac cycle is the mean arterial pressure (MAP), which can be estimated using the following equation:

MAP = (diastolic pressure )+ (1/3)*(pulse pressure.)

Question 8

Arterioles

• Arterioles are the major ______ vessels.
• Their high resistance produces a large drop in ______ between the ar- teries and ______.
• This decline enhances blood flow by contributing to the pressure differential between the ______ and organs.

*

Answer 8

Arterioles

• Arterioles are the major resistance vessels.
• Their high resistance produces a large drop in mean pressure between the ar- teries and capillaries.
• This decline enhances blood flow by contributing to the pressure differential between the heart and organs.

Question 9

Arterioles

• Arterioles have a thick layer of __________, variable contraction of which alters arteriolar caliber and resistance.
• Tone, a baseline of __________, is maintained in arterioles at all times.
• Arteriolar vasodilation (expansion of arteriolar caliber above tone level) __________ resistance and __________ blood flow through the vessel, whereas vasoconstriction (narrowing of the vessel) __________ resistance and __________ flow.
• Arteriolar caliber is subject to both__________ controls and __________ controls.

Answer 9

Arterioles

• Arterioles have a thick layer of circular smooth muscle, variable contraction of which alters arteriolar caliber and resistance.
• Tone, a baseline of contractile activity, is maintained in arterioles at all times.
• Arteriolar vasodilation (expansion of arteriolar caliber above tone level) decreases resistance and increases blood flow through the vessel, whereas vasoconstriction (narrowing of the vessel) increases resistance and decreases flow.
• Arteriolar caliber is subject to both local (intrinsic) controls and extrinsic controls.

Question 10

Arterioles

• Local controls primarily involve local chemical changes associated with changes in the level of ____________in an organ, such as local changes in O₂, which cause the release of vasoactive______from the______ cells in the vicinity.
• Examples include ______ nitric oxide and ______ endothelin.
• These vasoactive mediators act on the underlying ____________ to bring about an appropriate change in the caliber of the arterioles supplying the organ.​
• By adjusting the resistance to blood flow, the local control mechanism matches an organ’s blood flow to its momentary ______ needs

Answer 10

Arterioles

• Local controls primarily involve local chemical changes associated with changes in the level of metabolic activity in an organ, such as local changes in O₂, which cause the release of vasoactive paracrines from the endothelial cells in the vicinity.
• Examples include vasodilating nitric oxide and vasoconstricting endothelin.
• These vasoactive mediators act on the underlying arteriolar smooth muscle to bring about an appropriate change in the caliber of the arterioles supplying the organ.
  ​
• By adjusting the resistance to blood flow, the local control mechanism matches an organ’s blood flow to its momentary metabolic needs

Question 11

Arterioles

• Other local influences on arterioles include
  
  1. ____________
  2. ____________
  3. ____________
  4. ____________

Answer 11

Arterioles

• Other local influences include
  
  1. histamine release (important in in ammatory and allergic reactions);
  2. myogenic response to stretch (important in autoregulation, which keeps tissue blood flow fairly constant despite changes in mean arterial driving pressure);
  3. chemical response to shear stress (which resists changes in the force exerted parallel to the vessel surface by flowing blood); and
  4. local application of heat or cold (important therapeutically).

Question 12

Arterioles

• Local control factors can adjust arteriolar caliber ______ in different organs.
• Such adjustments are important in variably distributing ____________.

Answer 12

Arterioles

• Local control factors can adjust arteriolar caliber independently in different organs. “
• Such adjustments are important in variably distributing cardiac output.

Question 13

Arterioles

• Extrinsic control is accomplished primarily by _______ and to a lesser extent by _______ influence over arteriolar smooth muscle.
• Extrinsic controls are important in determining total peripheral resistance (TPR), the total resistance offered by all______________, most of which is due to ______________.
• TPR in turn plays a key role in maintaining MAP
  
  • MAP = (_______) * (TPR).
• Arterioles are richly supplied with _______ nerve fibers, whose increased activity produces generalized _______ and a subsequent _______ in TPR, thus increasing MAP.
• Decreased _______ activity produces generalized arteriolar vasodilation, which _______ MAP.
• These _______ controlled adjustments of arteriolar caliber help maintain the appropriate pressure head for driving blood forward to the tissues.
• Most arterioles are not supplied by _______ nerves.
• Hormones that extrinsically influence arteriolar radius are _______, epinephrine, _______, and _______, all of which cause generalized arteriolar _______.

Answer 13

Arterioles

• Extrinsic control is accomplished primarily by sympathetic and to a lesser extent by hormonal influence over arteriolar smooth muscle.
• Extrinsic controls are important in determining total peripheral resistance (TPR), the total resistance offered by all systemic vessels, most of which is due to arteriolar resistance.
• TPR in turn plays a key role in maintaining
  
  • MAP: MAP = (CO) * (TPR).
• Arterioles are richly supplied with sympathetic nerve fibers, whose increased activity produces generalized vasoconstriction and a subsequent increase in TPR, thus increasing MAP.
• Decreased sympathetic activity produces generalized arteriolar vasodilation, which lowers MAP.
• These extrinsically controlled adjustments of arteriolar caliber help maintain the appropriate pressure head for driving blood forward to the tissues.
• Most arterioles are not supplied by parasympathetic nerves.
• Hormones that extrinsically influence arteriolar radius are norepinephrine, epinephrine, vasopressin, and angiotensin II, all of which cause generalized arteriolar vasoconstriction.

Question 14

Capillaries

• The thin-walled, small-radius, extensively branched capillaries are ideally suited to serve as sites of _____ between the blood and _______________.
• Anatomically, the _________ for exchange is maximized and _________ is minimized in the capillaries.
• Furthermore because of their large total cross-sectional area, the _____ of blood flow through capillaries (in distance per unit of time) is relatively slow, providing adequate time for _____ to take place.

Answer 14

Capillaries

• The thin-walled, small-radius, extensively branched capillaries are ideally suited to serve as sites of exchange between the blood and surrounding tissue cells.
• Anatomically, the surface area for exchange is maximized and diffusion distance is minimized in the capillaries.
• Furthermore because of their large total cross-sectional area, the velocity of blood flow through capillaries (in distance per unit of time) is relatively slow, providing adequate time for exchanges to take place.

Question 15

Capillaries

• Two types of passive exchanges—______ and ______— take place across capillary walls.

Answer 15

Capillaries

• Two types of passive exchanges—diffusion and bulk flow— take place across capillary walls.

Question 16

Capillaries

• Individual solutes are exchanged primarily by ______ down concentration gradients.
• Lipid-soluble substances pass directly through the single layer of ____________ lining a capillary, whereas water-soluble substances pass through water-filled pores between the ____________.
• Plasma proteins generally____________.

Answer 16

Capillaries

• Individual solutes are exchanged primarily by diffusion down concentration gradients.
• Lipid-soluble substances pass directly through the single layer of endothelial cells lining a capillary, whereas water-soluble substances pass through water-filled pores between the endothelial cells.
  ​
• Plasma proteins generally do not escape.

Question 17

Capillaries

• Imbalances in physical pressures acting across capillary walls are responsible for __________ of fluid through the pores.
  1. Fluid is forced out of the first portion of the capillary (_____), where outward pressures (mainly ____________________) exceed inward pressures (mainly ____________________ ).
  2. Fluid is returned to the capillary (_____) along its last half, when outward pressures fall below inward pressures. The reason for the shift in balance down the capillary’s length is the continuous decline in _____while _____ remains constant.
• Bulk flow is responsible for the distribution of the ECF between _____ and __________.

Answer 17

Capillaries

• Imbalances in physical pressures acting across capillary walls are responsible for bulk flow of fluid through the pores.
  1. Fluid is forced out of the first portion of the capillary (ultrafiltration), where outward pressures (mainly capillary blood pressure; [P_C] ) exceed inward pressures (mainly plasma-colloid osmotic pressure [π_P] ).
  2. Fluid is returned to the capillary (reabsorption) along its last half, when outward pressures fall below inward pressures. The reason for the shift in balance down the capillary’s length is the continuous decline in P_C while π_P remains constant.
• Bulk flow is responsible for the distribution of the ECF between plasma and interstitial fluid.

Question 18

Capillaries

• Normally, slightly more fluid is ______ than is ______. The extra fluid, any leaked ______, and ______ in the tissue are picked up as lymph by the lymphatic system.
• Bacteria are destroyed as lymph passes through ____________ on the way to being returned to the ____________.

Answer 18

Capillaries

• Normally, slightly more fluid is filtered than is reabsorbed. The extra fluid, any leaked proteins, and bacteria in the tissue are picked up as lymph by the lymphatic system.
• Bacteria are destroyed as lymph passes through lymph nodes on the way to being returned to the venous system.

Question 19

Veins

• Veins are large-_____, low-_____ passageways from the organs to the heart.
• In addition, the thin-walled, highly _____ veins, as capacitance vessels, can __________ stretch to store a larger volume of blood and therefore act as a blood __________.
• The capacity of veins to hold blood can change markedly with little change in venous _____.
• At rest, the veins contain more than _____% of the total blood volume.

Answer 19

Veins

• Veins are large-radius, low-resistance passageways from the organs to the heart.
• In addition, the thin-walled, highly distensible veins, as capacitance vessels, can passively stretch to store a larger volume of blood and therefore act as a blood reservoir.
• The capacity of veins to hold blood can change markedly with little change in venous pressure.
• At rest, the veins contain more than 60% of the total blood volume.

Question 20

Veins

• The primary force that produces venous return is the pressure gradient between the ____ and ____ (that is, what remains of the driving pressure imparted to the blood by ____________).

Answer 20

Veins

• The primary force that produces venous return is the pressure gradient between the veins and atrium (that is, what remains of the driving pressure imparted to the blood by cardiac contraction).

Question 21

Veins

• Venous return is enhanced by _______ induced venous vasoconstriction and by external compression of the veins from contraction of surrounding______________ (______________), both of which drive blood out of the veins.
• These actions help counter the effects of _______ on the venous system.

Answer 21

Veins

• Venous return is enhanced by sympathetically induced venous vasoconstriction and by external compression of the veins from contraction of surrounding skeletal muscles (skeletal muscle pump), both of which drive blood out of the veins.
• These actions help counter the effects of gravity on the venous system.

Question 22

Veins

• One-way ___________ ensure that blood is driven toward the heart and kept from flowing back toward the tissues.

Answer 22

Veins

• One-way venous valves ensure that blood is driven toward the heart and kept from flowing back toward the tissues.

Question 23

Veins

• Venous return is also enhanced by the ___________ and the ____________ effect.
• Respiratory activity produces a less- than-atmospheric pressure in the chest cavity, thus establishing an external pressure gradient that encourages flow from the ____________ that are exposed to atmospheric pressure to the ____________ that empty into the ______.
• In addition, slightly negative pressures created within the ______ during ventricular systole and within the ______ during ventricular diastole exert a suctioning effect that further enhances ____________ and facilitates____________.

Answer 23

Veins

• Venous return is also enhanced by the respiratory pump and the cardiac suction effect.
• Respiratory activity produces a less- than-atmospheric pressure in the chest cavity, thus establishing an external pressure gradient that encourages flow from the lower veins that are exposed to atmospheric pressure to the chest veins that empty into the heart.
• In addition, slightly negative pressures created within the atria during ventricular systole and within the ventricles during ventricular diastole exert a suctioning effect that further enhances venous return and facilitates cardiac filling.

Question 24

Blood Pressure

• Regulation of MAP depends on control of its two main determinants, ___ and ___.
• Control of ___, in turn, depends on regulation of HR and SV, whereas ___ is determined primarily by the degree of arteriolar _________.

Answer 24

Blood Pressure

• Regulation of MAP depends on control of its two main determinants, CO and TPR.
• Control of CO, in turn, depends on regulation of HR and SV, whereas TPR is determined primarily by the degree of arteriolar vasoconstriction.

Question 25

Blood Pressure

• Short-term regulation of blood pressure is accomplished mainly by the ______________.
• Carotid sinus and aortic arch baroreceptors continuously monitor _______.
• When they detect a deviation from normal, they signal the __________________, which responds by adjusting autonomic output to the heart and blood vessels to restore blood pressure to normal.

Answer 25

Blood Pressure

• Short-term regulation of blood pressure is accomplished mainly by the baroreceptor reflex.
• Carotid sinus and aortic arch baroreceptors continuously monitor MAP.
• When they detect a deviation from normal, they signal the medullary cardiovascular center, which responds by adjusting autonomic output to the heart and blood vessels to restore blood pressure to normal.

Question 26

Blood Pressure

• Long-term control of blood pressure involves maintaining proper plasma volume through the kidneys’ control of salt and water balance.

Answer 26

Blood Pressure

• Long-term control of blood pressure involves maintaining proper _________ through the kidneys’ control of _____ and __________.