CH 15 reading questions/ study guide
7. Describe the key characteristic of arterioles.
-The walls of arterioles contain several layers of of smooth muscle that contract and relax under the influence of various chemical signals
17. How can low-pressure venous blood in the feet flow uphill against gravity to get back to the heart? (Fig. 15.4)
-Uses VALVES to push it uphill -AKA skeletal muscle pump and respiratory pump
16. What is pulse pressure and how do you calculate it?
-a PULSE or PRESSURE WAVE can be felt -A measure of the strength of the pressure wave is defined as systolic pressure minus diastolic pressure: systolic pressure -diastolic pressure=pulse pressure Ex: 120mmHg-80mmHg=40 mmHg
44. List the types of catecholamine receptors and indicate their affinities for norepinephrine and epinephrine.
-alpha receptors -beta receptors
10. Describe the structure of capillary walls. How does capillary wall structure relate to capillary function? What are pericytes?
-walls consist of a flat layer of endothelium, one cell thick, supported on an acellular matrix called the basal lamina (basement membrane) -walls facilitate to exchange materials
30. Write the mathematical expression for the relationship between radius (r) and resistance (R).
According to Poiseuille's Law, resistance to blood flow (R) is directly proportional to the length of the tubing through which the fluid flows (L) and to the viscosity (n) of the fluid, and inversely proportional to the 4th power of the tubing radius (r):*Note, normally the length of the systemic circulation and the blood's viscosity are relatively constant. That leaves only the radius of the blood vessels as the primary resistance to blood flow:R @ 1/r^4
36. What are the goals of autonomic reflex control of arteriolar resistance?
2) Sympathetic reflexes mediated by the CNS maintain mean arterial pressure and govern blood distribution for certain homeostatic needs, such as temp reg
37. What are the goals of hormonal control of arteriolar resistance?
3) Hormones--particularly those that reg salt and water excretion by the kidneys influence BP by acting directly on the arterioles and by altering autonomic reflex control
21. Explain a blood pressure of 100/70.
-100 is systole, highest pressure-70 is diastole, lowest pressure-This is a normal range since recommended is below 120/80
5. Describe the physical characteristics of the aorta and major arteries. (Fig. 15.2)
-Characterized by walls that are both stiff and springy-Arteries have a thich smooth muscle layer and large amounts of elastic and fibrous tissue
71. How is net fluid flow determined? Compare net fluid flow at the arterial end of a capillary with net fluid flow at the venous end. (Fig. 15.18)
-Determined by the difference btw the hydrostatic pressure Ph and the colloid osmotic pressure-positive value for net pressure indicates net filtration; a negative value indicates net absorptionThere is net filtration at the arterial end and net absorption at the venous end
20. Explain how a sphygmomanometer and Korotkoff sounds can be used to estimate arterial pressure of the radial artery. (Fig. 15.7)
-Estimate arterial BP in the radial artery of the arm using a sphygmomanometer-The cuff is inflated until it exerts a pressure higher than the systolic pressure driving arterial blood, when cuff pressure exceeds arterial pressure, blood flow into the lower arm stops-Pressure on the cuff s gradually released and when cuff pressure falls below systolic arterial BP, blood begins to flow again.As blood squeezes through the still compressed artery, a thumping noise, KORTKOFF SOUND, can be heard with each press wave. KOROTKOFF SOUNDS are caused by the turbulent flow of blood through the compression Once the cuff pressure no longer compresses the artery, flow smooths out and the sounds disappearThe pressure at which a KORTKOFF sounds is first heard represents the highest pressure, systolic pressure; the point at which the sounds disappear is the lowest pressure, diastole pressure-Suggested BP is BELOW 120/80
29. Name two ways the cardiovascular system tries to compensate for a decrease in blood volume.
-Includes vasoconstriction and increased sympathetic stimulation of the heart to increase cardiac output
22. Write the mathematical expression that relates MAP to cardiac output and resistance.
-Mean arterial pressure (MAP) is proportional to cardiac output (CO) times resistamce (R) of the arterioles:MAP @ CO x RarteriolesEx: if cardiac output increases, the heart pumps more blood into the arteries per unit time...and arterial blood pressure increases p.484
8. How do metarterioles differ from arterioles? What is the function of metarterioles? (Fig. 15.3)
-Only partially surrounded by smooth muscle-Can take one of two paths: if precapillary sphincters are relaxed, blood flowing into a metarteriiole is directed into adjoining cappilary bedsif the precapillary sphincters are all constricted, metarteriole blood bypasses the capillaries and goes directly to the venous circulation
14. Define systolic pressure and diastolic pressure. Provide average aortic systolic and diastolic values (with units). (Fig. 15.6)
Aortic pressure reaches an average high of 120 mmHG during ventricular systole (systolic pressure)-Aortic pressure falls steadily to a low of 80 mmHg during ventricular diastole (diastolic pressure)
25. Explain how the relative distribution of blood between the arterial and venous sides of the circulation can be an important factor in maintaining arterial blood pressure.
Arteries are low volume vessels that contain only about 11% of total blood volume at any one time. Veins, in contrast, are high volume vessels that hold about 60% of the circulating blood at any one time.The constriction of veins redistributes blood to the arterial side of circulation and raises mean arterial bp
distribution of blood in CV system affects MAP
Arteries contain about 11% of blood volume Veins contain about 60% of blood volume ↓MAP leads to ↑SNS causing venoconstriction and returns blood volume to the arterial circulation
resistance: which vessels are mostly responsible for TPR? How do they adjust TPR? Arteriolar Resistance is mediated by:
Arterioles contribute more than 60% By changing radius R= 1/r^4 Local control Hormones Sympathetic reflexes
9. What vessels make up the microcirculation?
Arterioles, along with capillaries and small postcapillary vessels called venules
51. Where are the two main receptors for blood pressure located? What is significant about these locations?
Baroreceptors (stretch-sensitive mechanoreceptors are located in the walls of the CAROTID ARTERIES and the AORTA, where they continuously monitor the pressure of blood flowing to the brain and to the body
53. Create a map showing how the baroreceptor reflex would return homeostasis after a stimulus of increased blood pressure.
Baroreceptors increase their firing rate as blood pressure increases, activating the medullary cardiovascular control centerIn response the cardiovascular control center increases parasympathetic activity and decreases sympathetic activity to slow down the heart and dilate arterioles
45. Fight-or-flight: a. vasodilation = epinephrine on _______ receptors (smooth muscle of heart, liver, skeletal muscle arterioles) b. vasoconstriction = epinephrine on _______ receptors (other arterioles)
Beta receptors
cardiac output and peripheral resistance
Blood flow into the aorta is equal to cardiac output , while blood flow out of the arteries is dictated by peripheral resistance
19. What kinds of problems might result when blood pressure is too low? Too high?
Can be indicative of a problem in the cardiovascular system -Too low (hypotension) could lead to dizziness or faintness -Too high (hypertension) may cause weakened areas to rupture and bleed into the tissues
64. For substances that diffuse freely across capillary walls, what factor is most important for determining the rate of diffusion?
Concentration gradient between the plasma and the interstitial fluid
65. How do protein hormones and other essential proteins move out of the blood and into the interstitial fluid? (Fig. 15.16)
Continuous capillaries have leaky junctions (allow for water and other materials to pass through) Fenestrated capillaries have fenestrations of pores (window) far more susceptible to allow movement into or out of capillaries Proteins have to move by transcytosis- they cannot move through by the gap in-between cells
60. Compare the structure and function of continuous and fenestrated capillaries. (Fig. 15.16)
Continuous capillaries-most common; their endothelial cells are joined together with leaky jx; found in muscle, connective tissue, and neural tissueFennestrated capillaries-have large pores that allow high volumes of fluid to pass btw plasma and interstitial fluid; found primarily in the kidney and the intestine
26. If the volume of blood circulating through the system decreases, blood pressure _________ (increases or decreases?).
Decreases
68. What forces regulate capillary bulk flow?
Direction of fluid movement is dictated by hydrostatic and osmotic pressure gradients
59. What determines capillary density in a tissue? Which tissues have the highest capillary density?
Directly related to the metabolic activity of the tissue's cells.Muscles and glands have the highest capillary density.
elasticity in arteries
Elasticity in the arteries allows them to act as a reservoir on a beat-by-beat basis This converts the pulsatile flow from the heart pump into a steady flow through the systemic circulation
28. True or false: If blood volume decreases, the kidneys can increase blood volume by reabsorbing water. Defend your answer.
False--The kidneys CANNOT restore lost fluid. The kidneys can ONLY CONSERVE blood volume and therby prevent further decreases in blood pressure. when blood volume decreases, kidneys decrease fluid excretion. -Only way to restore lost fluid is through drinking or intravenous infusion
62. Explain the relationship between total cross-sectional area and velocity of flow in the circulatory system. Specifically, how does the total cross-sectional area of capillaries compare to that of larger-diameter blood vessels, and what effect does this have on velocity in the different vessels? (Fig. 15.17)
Fastest flow is in the small diameter arterial system; slowest flow is in the capillaries and venules, which collectively have the largest cross-sectional areathe low velocity of flow thru capillaries is a useful characteristic that allows enough time for diffusion to go to equilibrium. p. 497
24. What happens to MAP if peripheral resistance increases?
Flow into arteries is unchanged, but flow out is decreased;Blood again accumulates in the arteries , and the arterial pressure again increases-Most cases of hypertension are believed to be caused by increased peripheral resistance without changes in cardiac output
67. Distinguish between filtration and absorption in capillaries.
Fluid movement into the capillary is called absorption Fluid movement into the interstitium is called filtration
56. What effect will an increase in parasympathetic activity have on heart rate, force of contraction, and arteriolar diameter?
HR RATE slowers, for of contraction lessens, and arteriolar diameter increases
15. True or false: The pulse is created by a wave of blood flowing through the arteries. Defend your answer.
Heartbeat that is felt at an artery, caused by the alternate expansion and recoil of an artery with each contraction of the heart.
35. What are the goals of local control of arteriolar resistance?
Influenced by both local and systemic mechanisms:1) local control of arteriolar resistance matches tissue blood flow to the matbolic needs of the tissue
57. What is orthostatic hypotension? Why does blood pressure initially fall when a person stands up after lying flat? (Fig. 15.14)
It is A decrease in blood pressure upon standing p. 495Happens cuz gravity causes blood to pool in the lower extremities
local control
Local control is also achieved by PARACRINE SECRETIONS by the vascular endothelium or by cells in the tissue that is being supplied by the arterioles: ↓O2, ↑CO2, ↑H+, ↑K+ and ↑Nitric Oxide (NO) all cause VASODILATION If metabolic activity of a tissue increases, tissue O2 levels will decrease and CO2 levels will increase causing vasodilation This will be met with an increased in blood flow called ACTIVE HYPEREMIA
peripheral resistance and MAP
MAP is determined by the combined effects of cardiac output and total peripheral resistance: MAP=Q*TPR slide 30
72. Is filtration in capillaries exactly equal to absorption? Explain. (Fig. 15.18)
NoAmount filtered is more than the amount re-absorbed
69. What creates the osmotic pressure gradient between the plasma and the interstitial fluid? What is colloid osmotic pressure (π)?
Osmotic Pressure = pressure exerted by the PROTEINS in the blood plasma or interstitial fluid Colloid osmotic pressure is the same as osmotic pressure
angiotensin II
Primarily involved in regulating ALDOSTERONE which helps maintain Na+ and water balance in the kidney Also causes VASOCONTRICTION
vasopressin (antidiuretic hormone- ADH)
Primary action is on renal tubules to retain water Also causes vasoconstriction
18. Explain mean arterial pressure (MAP). What formula is used to determine MAP?
Represents the driving pressure of the pumping of the heart -Calculate by diastolic pressure + 1/3 of pulse pressure (diastolicP+ 1/3 (systolicP-diastolicP))
systemic blood pressure (SBP and DBP)
Systolic blood pressure (SBP) is the highest pressure generated by the heart during contraction of the left ventricle Diastolic blood pressure (DBP) is the arterial pressure when the left ventricle is relaxing Pulse pressure (PP) is a measure of the strength of the pressure wave PP=SBP-DBP
4. What is muscle tone? What factors can influence it?
The cells maintaining a state of partial contraction
13. Why does blood pressure decrease as blood flows through the circulatory system? (Fig. 15.5)
The decrease in pressure occurs because energy is lost as a result of the resistance to flow offered by the vessels
27. Which two systems of the body are responsible for homeostatic regulation of blood pressure? (Fig. 15.9)
The kidneys and the cardiovascular system
If blood flow through the systemic circulation is 5 L/min, what is blood flow through the pulmonary circulation?
The pulmonary circulation always contains less blood than the systemic circulation. Of approximately 5L blood volume with the heart containing 360mL in diastole (filled, just prior to contraction) the pulmonary circulation holds only 440mL compared to 4200mL in the systemic circulation.
12. What property of artery walls plays a key role in the ability of arteries to sustain the driving pressure created by the heart? (Fig. 15.5)
The walls recoil and propel the blood forward into smaller vessels. MAP. is. the. driving. pressure. and MAP is dictated by the balance between blood flow into and out of the arteries. if blood flow into the arteries is greater than blood flow out of the arteries MAP would increase because blood flow is collecting and swelling up the arteries
48. Blood flow through individual arterioles depends on __________________. (Fig. 15.13)
Their resistance to flow
49. When blood flow decreases through one set of arterioles, where does that blood go?
To arterioles with lower resistance
3. Contraction of vascular smooth muscle causes _____________, or a narrowing of vessel diameter. Relaxation of vascular smooth muscle causes an increase in vessel diameter, or _____________.
Vasoconstriction; vasodilation
11. Compare the walls of veins with those of arteries. (Figs. 15.2, 15.4)
Veins have thinner walls than arteries, with less elastic tissue; as a result they expand easily when they fill with blood
Blood volume and MAP
What if blood volume decreases? MAP decreases Increased sympathetic stimulation to increase CO and TPR Kidney decreases fluid excretion Increased fluid intake The distribution of blood in the CV system also affects MAP Arteries contain about 11% of blood volume Veins contain about 60% of blood volume ↓MAP leads to ↑SNS causing venoconstriction and returns blood volume to the arterial circulation
52. If you are monitoring the electrical activity of the sensory neurons linking these baroreceptors to the cardiovascular control center, would you observe any electrical activity when a person's blood pressure is in the normal range? Are these receptors tonic or phasic?
Yes, they are Tonically active stretch receptors that fire action potentials continuously
SNS nerves have
a tonic firing activity which helps maintain "myogenic tone" of arterioles which is called "sympathetic or vasomotor tone
Norepinephrine acts on what receptor?
a1-adrenergic receptors on smooth muscle cells to increase tone of vessels
43. Tonic norepinephrine release onto ________ receptors creates myogenic tone. Vasodilation is accomplished by ______________ (increasing or decreasing?) release of norepinephrine.
alpha receptors increasing
61. Which three tissues don't have traditional capillaries? What do they have? Why are these modified vessels necessary?
bone marrow, the liver, the spleen sinusoids they are wider than a capillary
47. At any given moment, the total blood flow through all arterioles of the body = __________________.
cardiac output
55. What effect will an increase in sympathetic activity have on heart rate, force of contraction, and arteriolar diameter?
constriction, of arteries, so arteriole diameter is reduced, speeds up force of contraction, speeds HR
reactive hyperemia
decrease in tissue blood flow due to occlusion, metabolic vasodilators accumulate in ECF, arterioles dilate, but occlusion prevents blood flow, remove occlusion, decrease in resistance creates increase in blood flow, as vasodilators wash away, arterioles constrict and blood flow returns to normal
54. A decrease in blood pressure results in __________________ (increased or decreased?) sympathetic activity and __________________ (increased or decreased?) parasympathetic activity.
decreased sympathetic activity increased parasympathetic activity
during diastole arterial volume...
decreases by elastic recoil of the vessels, this propels the blood into the systemic circulation (shows in slide 23)
6. Blood flow from arteries to arterioles is best described as _____________ (divergent or convergent?).
divergent
46. Why don't all tissues get equal blood flow at all times? At rest, which parts of the body receive most of the cardiac output? (Fig. 15.12)
due to local control-can be due to precapillary sphincters-can change arteriolar resistance-paracrines> O CO2 and NO> gases that changes due to the metabolic levels flow through individual arterioles depends on resistance: Q α 1/R the kidneys receive most of the cardiac output
hormonal influences angiotensin II and vasopressin cause release of:
endothelin from the endothelial cells- also a vasoconstrictor
63. What types of exchange between the plasma and the interstitial fluid can take place at the capillary?
filtration and absorption
23. If blood flow into the arteries increases but there is no change in blood flow out of the arteries, MAP will __________ (increase or decrease?).
increase
active hyperemia (increase in blood flow)
increase in tissue metabolism, increase in release of metabolic vasodilators into ECF, arterioles dilate, decrease in resistance creates increase in blood flow, oxygen and nutrient supply to tissue increases as long as metabolism is increased.
sympathetic vasoconstrictor nerves
innervate arterioles in all systemic organs, these nerves are papamount in controlling TPR and therefore MAP
40. Precapillary sphincters provide ______________ control of blood flow.
local
50. Where in the brain is the main integrating center for the regulation of cardiovascular function?
medulla oblongata
VSM can regulate its own state of configuration by?
myogenic autoregulation (muscle regulates itself) ↑ MAP would increase flow without any compensation stretch in the arteriolar wall signals for vasoconstriction in an attempt to divert blood flow How does this work? Stretch sensitive Ca 2+ slide 36
70. Hydrostatic pressure pushes water ___________ (into or out of?) capillaries. This pressure decreases along the length of the capillary as energy is lost to ______________. (Fig. 15.18)
out of friction
38. When blood pressure in an arteriole increases, myogenic autoregulation causes the arteriole to _______________.
stretch
34. Which vessels are the main site of variable resistance in the systemic circulation? What property of these vessels permits them to change resistance?
tHE ARTERIOLES ARE THE MAIN SITE OF VARIABLE RESISTANCE IN THE SYSTEMIC CIRCULATION AND CONTRIBUTE MORE THAN 60% of the total resistance to flow in the system
Measuring BP
the cuff pressure is > 120 mm Hg so there is no blood flowing or sound of blood flow through the brachial artery distal to the cuff. cuff pressure is decreased to 80-129 mmHg, the korotkoff sounds are created by the pulsatile flow through the compressed artery. blood flow is silent when cuff is below 80mm Kg.
66. Define bulk flow.
the mass movement of fluid between the interstitial space and the plasma
73. Outline the mechanisms underlying the two typical causes of edema.
the normal balance between the flow of fluid out of capillaries and the return of fluid to the vascular space via capillary reabsorption and lymphatic flow is disrupted.
