Chapter 15: Blood Flow and the Control of Blood Pressure Flashcards
1
Q
closed system
A
circulatory system
2
Q
force exerted by blood
A
pressure
3
Q
which direction does flow occur?
A
from high pressure to low pressure
4
Q
Blood flow to the organs and blood pressure are regulated by ……?
A
- intrinsic controls
- extrinsic controls
5
Q
flow =
A
=ΔP/R
=cardiac output (CO)
6
Q
ΔP =
A
mean arterial pressure (MAP)
7
Q
R=
A
total peripheral resistance (TPR)
8
Q
CO=
A
MAP/TPR
9
Q
- take blood away from the heart
- Elastic walls and thick layers of vascular smooth muscles
- act as a pressure reservoir
A
arteries
10
Q
- take blood back to the heart
- thin walls of vascular smooth muscles
- act as volume reservoir
- valves allow unidirectional blood flow (present in peripheral veins)
A
veins
11
Q
site of variable resistance
A
arterioles
12
Q
exchange between the blood and cells
A
capillaries
13
Q
serve as an expandable volume reservoir
A
systemic veins
14
Q
functions as an independent pump
A
each side of the heart
15
Q
a pressure reservoir that maintains blood flow during ventricular relaxation
A
elastic systemic arteries
16
Q
facilitates exchange
A
Absence of vascular smooth muscle and elastic tissue reinforcement in capillaries
17
Q
what do capillaries have that help with exchange?
A
one cell-thick layer of endothelial cells on basal lamina
18
Q
Contract and relax in response to local factors
A
precapillary sphincters
19
Q
- Intermediate between arterioles and capillaries
- Function as shunts to bypass capillaries
A
Metarterioles
20
Q
what happens when precapillary sphincters are relaxed?
A
blood flows through all capillaries in the bed
21
Q
what happens if precapillary sphincters constrict?
A
blood flow bypasses capillaries completely and flows through metarterioles
22
Q
- Storage site for pressure
- Thick, elastic arterial walls
- Low compliance
- Expand as blood enters arteries during systole
- Recoil during diastole
A
arteries as a pressure reservoir
23
Q
is the ease with which a hollow vessel expands
A
compliance
24
Q
- in arteries
- Small increase in blood volume causes a large increase in pressure (balloon requires greater effort to inflate)
A
low compliance
25
Large increase in blood volume is required to produce a large increase in pressure (balloon expands easily)
high compliance
26
pushes blood into elastic arteries, causing them to stretch
ventricular contraction
27
what are the steps of ventricular contraction?
1. ventricle contracts
2. semilunar valve opens; blood ejected from ventricles flows into the arteries
3. aorta and arteries expand and store pressure in elastic walls
28
how can blood pressure be measured?
- pressure cuff and sphygmomanometer
| - uncompressed artery
29
- Compressed artery
- Turbulent flow produces -Korotkoff sound
- Pressure at first Korotkoff sound = systolic blood pressure
pressure cuff and sphygmomanometer
30
- flow, no sound
| - Pressure when sound disappears = diastolic blood pressure
uncompressed artery
31
when can the first Korotkoff sounds be heard?
- created by pulsatile blood flow through the compressed artery
- cuff pressure between 80 and 120 mmHG
32
when is the blood flow silent?
- artery no longer compressed
| - cuff pressure <80 mmHg
33
what is the measured BP shown as?
systolic pressure/diastolic pressure
-example 120/80
34
SP-DP=
pulse pressure
35
= diastolic P + 1/3(systolic P – diastolic P)
mean arterial pressure (MAP)
36
aortic pressure is closer to the minimum pressure twice as long
weighted mean
37
determines the mean arterial pressure
cardiac output and peripheral resistance
38
mean arterial pressure is directly proportional to.....?
cardiac output x resistance of arterioles
39
what are some factors that affect mean arterial pressure?
- blood volume
- effectiveness of the heart as a pump (cardiac output)
- resistance of the system to blood flow
- relative distribution of blood between arterial and venous blood vessels
40
- resistant vessels
- part of microcirculation
- connect arteries to capillaries or metarterioles
- Contain rings of smooth muscle to regulate radius and, therefore, resistance
arterioles
41
- provide greatest resistance to blood flow
- greater than 60% of TPR
- resistance is regulated
- largest pressure drop in vasculature
arterioles
42
alter the contractile state of arteriolar smooth muscle
intrinsic and extrinsic control mechanisms
43
- include local metabolites
| - controlling blood flow to individual capillary beds
intrinsic controls
44
- control both ANS and hormones
| - regulating mean arterial pressure
extrinsic controls
45
causes vasoconstriction
contraction of smooth muscle (arterioles)
46
causes vasodilation
relaxation of smooth muscle (arterioles)
47
what is regulation of blood flow to organs based on?
based on need
48
how is blood flow to organs regulated?
-by varying resistance
organ blood flow=MAP/organ resistance
49
what is the Vascular smooth muscle response to four factors:
1. metabolic activity
2. changes in blood flow
3. stretch of arteriolar smooth muscle
4. local chemical messengers
50
what do changes associated with increased metabolic activity cause?
vasodilation
51
what do changes associated with decreased metabolic activity cause?
vasoconstriction
52
increased blood flow in response to increased metabolic activity
active hyperemia
53
- O2 is delivered as fast as it is consumed
| - CO2 is removed as fast as it is produced
steady state
54
- O2 is consumed faster than it is delivered
| - CO2 is produced faster than it is removed
increased metabolic rate (active hyperemia)
55
act on arteriolar
| smooth muscle to promote vasodilation
The decreased oxygen concentration and increased
| carbon dioxide concentration
56
promotes increased blood flow, which
increases oxygen delivery to cells and carbon dioxide
removal from cells
vasodilation
57
matches blood flow to increased metabolism
active hyperemia
58
increased blood flow in response to a previous reduction in blood flow
reactive hyperemia
59
- Metabolites increase and oxygen decreases
| - Vasodilation
blockage of blood flow to tissues (reactive hyperemia)
60
- Increased blood flow due to low resistance
| - Metabolites removed, oxygen delivered
occurs when blockage is released (reactive hyperemia)
61
follows a period of decreased blood flow
reactive hyperemia
62
change in vascular resistance in response to stretch of blood vessels in the absence of external factors
myogenic response
63
- Increased pressure in arteriole stretches arteriole wall
- Stretch of vascular smooth muscle induces contraction of vascular smooth muscle—inherent property of smooth muscle
- Vasoconstriction decreases blood flow
- Purpose: keep blood flow constant (autoregulate)
myogenic autoregulation
64
happens because of changes in perfusion pressure
myogenic response
65
depends on total peripheral resistance (TPR)
mean arterial pressure
66
depends on radius of arterioles
total peripheral resistance (TPR)
67
* regulated by extrinsic mechanisms to control mean arterial pressure
- sympathetic activity
- hormones
radius of arterioles
68
- Sympathetic innervation of smooth muscle of arterioles
- Norepinephrine binds to α adrenergic receptors
- Produces vasoconstriction
- Increases TPR
- Increases MAP
Sympathetic control of arteriolar radius
69
controlled by tonic release of norepinephrine
arteriole diameter
70
as signal rate increases.....?
the blood vessels constricts
71
as the signal rate decreases.....?
the blood vessel dilates
72
what hormones are involved in hormone control?
- epinephrine
- vasopressin (ADH)
- angiotensin II
73
released from adrenal medulla
epinephrine
74
- Secreted by posterior pituitary
- Increases water reabsorption by kidneys
- Vasoconstriction
vasopressin (ADH)
75
- Vasoconstriction
| - Increases TPR
angiotensin II
76
how is mean arterial pressure regulated?
- neural control of MAP
| - negative feedback loops
77
baroreceptors
detector for negative feedback loops (of MAP)
78
cardiovascular centers in the brainstem
integration center (of MAP)
79
autonomic nervous system
controllers (of MAP)
80
heart and blood vessels
effectors (of MAP)
81
- pressure receptors
- sometimes called stretch receptors
- Respond to stretching due to pressure changes in arteries
baroreceptors
82
- sinoaortic receptors
- aortic arch
- carotid sinuses
arterial baroreceptors
83
exchange materials across thin capillary walls
plasma and cells
84
related to metabolic activity of cells
capillary density
85
- have the thinnest walls
- Single layer of flattened endothelial cells
- Supported by basal lamina
capillaries
86
what are the kinds of capillaries?
- continuous
| - fenestrated
87
do not have typical capillaries but rather sinusoids
Bone marrow, liver, and spleen
88
occurs by paracellular pathway or endothelial transport
Exchange between plasma and interstitial fluid
89
move by diffusion, depending on lipid solubility and concentration gradient
small dissolved solutes and gases
90
move mostly by vesicular transport
larger solutes and proteins
91
transported by transcytosis
large molecules and selected proteins in most capillaries
92
- most common capillaries
- small gaps between endothelial cells
- allow small water soluble molecules to move through
continuous capillaries
93
- Large gaps between endothelial cells forming pores or fenestrations (windows)
- Allow proteins, and in some cases blood cells, to move through
fenestrated capillaries
94
have leaky junctions
continuous capillaries
95
may fuse to create temporary channels
some vesicles
96
have large pores
fenestrated capillaries
97
Mass movement as a result of hydrostatic or osmotic pressure gradients
bulk flow
98
- fluid movement out of capillaries
- caused by hydrostatic pressure
- net filtration at arterial end
filtration
99
- fluid movement into capillaries
- Net absorption at venous end
- Caused by colloid osmotic pressure (due to proteins)
absorption
100
forces fluid out of the capillary
hydrostatic pressure
101
net pressure=
hydrostatic pressure-colloid osmotic pressure
102
indicates filtration
positive net pressure
103
indicates absorption
negative net pressure
104
pulls fluid into the capillary
colloid osmotic pressure of proteins within the capillary
105
what is the net average of fluid that filters out of the capillaries?
3L/day
106
picked up by the lymph vessels and returned to the circulation
excess of water and solutes that filter out of the capillary
107
- Return fluid and proteins to circulatory system
- Pick up fat absorbed and transferring it to circulatory system
- Serve as filter for pathogens
lymphatic system
108
what are the two main causes of edema?
- Inadequate drainage of lymph
| - Filtration far greater than absorption
109
- Increase in hydrostatic pressure
- Decrease in plasma protein concentration
- Increase in interstitial proteins
Filtration far greater than absorption
