Blood Vessels and Hemodynamics for Exam 3 Flashcards
(86 cards)
1
Q
what is blood flow?
A
the volume of blood that flows through a tissue in a given period of time (mL/min)
2
Q
what does cardiac output represent?
A
total blood flow relative to the heart
3
Q
how does cardiac output become distributed into circulatory routes that serve various tissues? (2)
A
- pressure differences
- resistance to blood flow
4
Q
how does pressure relate to blood flow?
A
blood flows down a pressure gradient; the greater the pressure difference the greater the blood flow
5
Q
how does resistance relate to blood flow?
A
the higher the resistance, the smaller the blood flow
6
Q
what is blood pressure generated by?
A
the contraction of ventricles causing hydrostatic pressure to be exerted by blood on walls of vessels
7
Q
what 3 things determine blood pressure?
A
- cardiac output
- blood volume
- vascular resistance
8
Q
where is blood pressure highest?
A
at the aorta and large systemic arteries
9
Q
in a resting young adult, give blood pressure during systole and diastole
A
about 110 mmHg in systole
about 70 mmHg in diastole
10
Q
when does blood pressure fall naturally?
A
pressure falls progressively as distance from left ventricle increases
11
Q
sum up blood flow due to pressure changes in 5 points
A
- flows down a pressure gradient
- due to the force of heart contraction
- highest at the heart (the driving pressure) and decreases over distance
- also related to compliance or distensibiltiy of vessels
- decreases 90% from aorta to vena cava
12
Q
describe blood pressure in the venous system
A
much much lower, close to 0 when reenter the heart
13
Q
what is blood flow directly propotional to? what is it iversely proportional to?
A
- blood flow is directly proportional to the difference in blood pressure between two points in the circulation (flows down a pressure gradient)
- blood flow is inversely proportional to resistance (more resistance less blood flow)
14
Q
what is the rate of blood flow equal to?
A
the pressure difference divided by the resistance
15
Q
is resistance or pressure chhane more important in regulating local blood pressure?
A
resistance is more important than pressure changes in influencing local blood pressure
16
Q
what is mean arterial pressure (MAP)?
A
average blood pressure in arteries; approx 1/3 between diastolic and systolic pressures
17
Q
how is MAP calculated?
A
MAP = diastolic BP + 1/3 (systolic BP-diastolic BP)
18
Q
how can cardiac output be calculated when given MAP and R?
A
CO = MAP/R
19
Q
describe what happens to blood pressure when a decrease in blood volume is greater than 10%
A
blood pressure drops
20
Q
if blood volume increases, what will likely happen to blood pressure?
A
blood pressure will likely also increase
21
Q
what is vascular resistance?
A
opposition to blood flow caused by friction between blood and walls of blood vessels
22
Q
what does the friction between blood and walls of vessels depend on? (3)
A
- size of lumen
- blood viscosity
- total blood vessel length
23
Q
describe how lumen size relates to resistance to blood flow
A
the smaller the lumen the greater the resistance to blood flow
24
Q
how is resistance related to diameter of blood vessel lumen?
A
resistance is inversely proportional to the fourth power of the diameter (d) of blood vessels lumen
25
aknowing that resistance is inversely proportional to the fourth power of the diameter of the blood vessel lumen, if the diameter of a blood vessel decreases by 1/2, how much does resistance to blood flow increase?
increases 16 times (1/2^4)
26
what are moment-to-moment fluctuations in blood flow through tissue due to? give what happens when arterioles dilate or constrict
due to vasoconstriction/vasodilation of tissue's arterioles
1. when arterioles dilate, resistance decreases
2. when arterioles constrict, resistance increases
27
what does blood viscosity depend on? (2)
1. blood viscosity depends on the ratios of RBCs to plasma volume
2. also depends on concentration of proteins in plasma, to a smaller extent than RBC ratio
28
how does blood viscosity relate to vascular resistance?
the higher the blood viscosity, the higher the resistance
29
what increases blood viscosity (2)? what is the result on blood pressure?
dehydration or polycythemia; both increase viscosity and therefore increase blood pressure
30
what decreases blood viscosity (2)? what is the effect on blood pressure?
anemia or hemorrhage both decrease blood viscosity and therefore decrease blood pressure
31
what does it mean when blood is more viscous?
has more cells in the fluid
32
describe how total blood vessel length relates to vascualr resistance
resistance to blood flow through a vessel is directly proportional to the length of the vessel, so that longer the blood vessel the greater the resistance
33
why do obese people often have hypertension?
additional blood cells in adipose tissue increase total blood vessel length, increasing vascular resistance and therefore increasing blood pressure
34
how many miles of additional blood vessels develop for each extra pound of fat?
5 miles of blood vessels per pound of fat
35
what is systemic vascular resistance, or SVR?
total peripheral resistance, refers to all vascular resistance offered by systemic blood vessels
36
what kinds of vessels contribute the most to SVR?
the smallest vessels contribute most to systemic vascular resistance
37
what is the major function of arterioles? how do they do this?
the major function of arterioles is to control SVR and therefore blood pressure and blood flow through tissues by changing their diameter; they do this by vasoconstricting/vasodilating, which they can do only slightly and still have a large effect on SVR
38
why do the smallest blood vessels contribute the most to SVR?
they have the smallest lumen and therefore the greatest pressure, so arterioles and capillaries (the smallest vessels) have and contribute the greatest resistance
39
what and where is the main center for SVR?
the vasomotor center in the brain stem, in the medulla oblongata, in part of the cardiovascular center
40
what does the vasomotor center in the medulla oblongata in the CV center of the brain stem do? what is the result?
sends impulses via sympathetic nerves to arterioles throughout the body that results in a moderate state of tonic contraction, or vasomotor tone
41
why does venous return occur?
because of the pressure gradient generated by the controction of the left ventricle
42
what is normally sufficient enough to cause venous retur?
the pressure difference from the venules (16mmHg) to the R atrium (0mmHg)
43
what happens if pressure increases in the right atrium or ventricle? why can this happen and what can it lead to?
venous return will decrease; usually because of a leaky tricuspid valve, will lead to a buildup of blood on the venous side of circulation
44
what happens when you stand up regarding pressure and venous return to the heart?
the pressure pushing blood up the veins in the lower limbs is just enough to overcome the forces of gravity pushing it back down
45
what 2 mechanisms help the heart pump blood from the lower body back to the heart?
1. skeletal muscle pump
2. respiratory pump
46
what is "milking" in terms of the skeletal muscle pump?
muscle contractions that drive venous blood toward the heart
47
describe distal and proximal venous valves when standing at rest
open
48
what happens when you contract the calf muscles in terms of the skeletal muscle pump for venous return to the heart?
contracting the calf muscles pushes blood through open proximal valves while the distal valves close as blood pushes against it
49
what happens when calf muscles relax in terms of the skeletal muscle pump for venous return to the heart?
1. as muscles relax, pressure falls in that section of the vein and the proximal valve closes
2. the distal valve now opens because blood pressure in feet are higher than in the leg
50
summarize the skeletal muscle pump for venous return to the heart
the change in what muscles are squeezing and relaxing control what is happening above and below in terms of blood flow
51
describe the respiratory pump for venous return to the heart
alternating compression and decompression of veins due to inhalation and exhalation
52
what happens in the respiratory pump during inhalation?
1. the diaphragm moves down, causing a decrease in pressure in the thorax cavity and an increase of pressure in the abdominal cavity
2. abdominal veins are compressed so a greater volume of blood moves from the abdominal veins into thoracic veins (which are decompressed) and then into the right atrium
53
what happens in the respiratory pump during exhalation?
pressures reverse from inhalation, so valves in veins prevent backflow of blood from thoracic veins into abdominal veins
54
what is speed of blow flow (in cm/sec) inversely realted to?
speed of blood flow is inversely realted to cross-sectional area
55
where is blood velocity slowest?
where cross-sectional area is greatest
56
describe where blood velocity decreases and increases
blood velocity decreases as it flows from aorta to arteries to arterioles to capillaries and then increases as it flows from capillaries to venules to veins to the heart
57
where is blood flow the slowest?
in capillaries
58
what is cros-sectional area?
the diamete if you cut a vessel open
59
why is blood velocity slowest in capillaries? what does this allow for?
they have the greatest total cross-sectional area; this allows for slowest blood velocity for good nutrient exchange
60
what 4 hormones regulate blood pressure?
1. renin-angiotensin-aldosterone system
2. epinephrine and norepinephrine
3. antidiuretic hormone (ADH)
4. atrial natriuretic peptide hormone (ANH)
61
describe the renin-angiontensin-aldosterone system
1. decreased blood volume of vlood flow to the kidney causes
2. juxtoglomerular cells in the kidney to secrete renin
3. renin and angiotensin-converting enzyme act on susbtrates to produce angiotensin II, which raises blood pressure
62
how does angiotensin II raise blood pressure? (2)
1. is a potent vasocinstrictor, so increases systemic vascular resistance
2. stimulates secretion of aldosterone (from the adrenal cortex) which increases resorption of Na+ ions and water by the kidneys, increasing total blood volume to increase blood pressure
63
what are epinephrine and norepinephrine?
catecholamines that are released from the adrenal mdeulla in response to sympathetic stimulation
64
how do epinephrine and norepinephrine regulate blood pressure?
1. increase cardiac output by increasing the rate and force of heart contraction to increase blood pressure
2. cause vasoconstriction of arterioles and veins in skin and abdominals organs, which helps increase blood flow to muscles during exercise
65
how is antidiuretic hormone produced and released?
produced by the hypothalamus and released from the neurohypophysis in response to dehydration and decreased blood volume
66
what does ADH do? (2)
1. causes vasoconstriction, which increases blood pressure
2. promotes movement of water from kidney tubules into the bloodstream to increase blood volume and decrease urine output
67
what is another name for ADH?
vasopressin
68
what happens to urine when there is a lot of ADH?
urine is very concentrated (fluid is retained in the body and not lost to urine)
69
what inhibits ADH? what does this explain
alcohol inhibits ADH, so this is why you pee so much when you drink!
70
what is the hormone ANP?
atrial natriuretic peptide hormone
71
what is ANP released by?
cells in the atria of the heart
72
what does ANP do?
1. lowers blood pressure by causing vasodilation
2. promotes loss of salt and water in urine to reduce blood volume
73
describe shock (3)
1. failure of the cardiovascular system to deliver enough O2 and nutrients to meet cellular metabolic needs
2. causes inadequate blood flow to tissues
3. which causes cells to switch from aerobic to anaerobic metabolism
74
what is a common (of the many) causes of shock?
trauma
75
what are the 4 different types of shock?
1. hypovolemic
2. cardiogenic
3. vascular
4. obstructive
76
what are 2 common cause of hypovolemic shock?
1. acute hemorrhage, can be internal or external
2. loss of body fluidsthrough excessive sweating, diarrhea, or vomiting
77
describe hypovolemic shock
when body fluid volume falls, venous return to the heart declines, the heart fills less, stroke volume decreases, and cardiac output decreases
78
what is essential with hypovolemic shock?
replacing fluid volume quickly
79
what causes cardiogenic shock? generally, then give 4 conditions that cause this
heart fails to pump adequately;
1. myocardial infarction
2. ischemia
3. heart valve problem
4. arrythmias
80
what causes vascular shock?
decreased systemic vascular resistance due to inappropriate dilation of arterioles or venules
81
give an example of vascular shock
neurogenic shock, is when vasodilation occurs following trauma to the head and leads to malfunction of cardiovascular center in the medulla
82
describe obstructive shock and give a cause
when blood flow through portion of circulation is blocked; due to pulmonary embolism
83
what is the main category under which homeostatis responses to shock fall?
negative feedback systems to return cardiac output and arterial blood pressure to normal
84
describe compensatory mechanisms to prevent shock
can maintain adeqyatre blood flow and blood pressure even with 10% blood loss (of normal volume)
85
give 4 specific homeostatic responses to shock
1. activation of the renin-angiotensin-aldosterone system
2. secretion of ADH
3. activation of sympathetic division of ANS
4. release of local vasodilators
86
give 9 signs and symptoms of shock
1. systolic blood pressure lower than 90 mmHg
2. RHR is rapid (due to sympathetic stimulation) and increased blood levels of epi and norepi
3. pulse is weak and rapid (weak CO and fast HR)
4. skin is cool, pale, and clammy
5. altered mental state
6. urine formation reduced
7. person is thirsty
8. acidosis
9. nausea
