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Kin 426 > 1: Overview of Circulation > Flashcards

1: Overview of Circulation Flashcards

1
Q

What constitutes the principal coordinating and integrating systems of the body

A

the circulatory, endocrine, and nervous system

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2
Q

nervous system

A

primarily concerned with communication

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3
Q

endocrine glands

A

primarily concerned with regulation of certain body functions

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4
Q

primary role of circulatory system

A

serves to transport and distribute essential substances to the tissues and to remove metabolic by-products (like CO2)

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5
Q

what else does the circulatory system share in

A

homeostatic mechanisms as regulation of body temperature, humoral communication throughout the body, and adjustments of O2 and nutrient supply in different physiologic states

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6
Q

what is O2 delivered for

A

generate ATP for muscle contraction

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7
Q

what happens if you perturb amount O2

A

perturb amount of ATP
will rely on other energy pathways for contraction but won’t be aerobic pathways so not long term

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8
Q

the heart consists of

A

two pumps in series

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9
Q

the heart consists of two pumps in series:

A

the right ventricle to propel blood through the lungs for exhange of O2 and CO2 and the left ventricle to propel blood to all other tissues of the body

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10
Q

right ventricle to propel blood through lungs for exchange of O2 and CO2

A

pulmonary circulation

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11
Q

left ventricle to propel blood to all other tissues of the body

A

systemic circulation

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12
Q

cardiac output

A

total flow of blood out of the left ventricle

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13
Q

what is the rhythmic contraction of the heart

A

intrinsic property of the heart whose sino-atrial node generates actions potentials spontaneously

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14
Q

how many phases of an action potential

A

5

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15
Q

How are these action potentials propogated

A

in an orderly manner through the organ to trigger contraction and to produce the currents detected in the electrocardiogram

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16
Q

what does the heart have

A

automaticity
generates its own electrical impulse that starts in the SA node

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17
Q

SA node

A

bundle of cells in right atrium that are very leaky
generate electrical impulse

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18
Q

what is atrial fibrillation

A

when the cells from SA node migrate and are not in one place anymore

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19
Q

what does the heart need compared to skeletal muscle

A
  • both do not need to be innervated
  • but skeletal needs external stimuli cardiac does not
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20
Q

Phase 0

A

upstroke

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21
Q

phase 0: upstroke

A

a suprathreshold stimulus rapidly depolarizes the membrane by activating the fast Na+ channels

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22
Q

Phase 1

A

early partial repolarization

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23
Q

phase 2

A

plateau

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24
Q

phase 3

A

final repolarization

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25
Q

phase 4

A

resting potential

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26
Q

phase 1: early partial repolarization

A

achieved by the efflux of K+ through channels that conduct transient outward current, Ito

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27
Q

Phase 2: plateau

A

achieved by a balance between the influx of Ca++ through Ca++ channels and the efflux of K+ through several types of K+ channels

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28
Q

what is the plateau phase

A

a steady state

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29
Q

when is the plateau less apparent

A

in slow responding cardiac fibers (SA node)

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30
Q

phase 3: final repolarization

A

initiated when the efflux of K+ exceeds the influx of Ca++
The resulting partial repolarization rapidly increases the K+ conductance and rapidly restores full repolarization

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31
Q

what is phase 3 on the graph

A

large downstroke

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32
Q

phase 4: resting potential

A

the transmembrane potential of the fully repolarized cell is determined mainly by the conductance of the cell membrane to K+ (resetting of cell membrane status in order to prepare for next)

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33
Q

depolarizing

A

one ion is exchanged for another and exchange of ions generates voltage

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34
Q

Two types of cardiac fibers

A

fast response (more typical AP) and slow response (seen in SA node AP)

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35
Q

what can be infused into the heart to stop it

A

K+
alot can put you in permanent phase 4 and heart must be flushed to get out

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36
Q

why is phase 0 in slow response AP sloped

A

SA node very leaky

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37
Q

what is depolarization on the graphs

A

upstroke (phase 0)

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38
Q

resting potential of slow fiber is

A

less negative

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39
Q

the upstroke (phase 0) of AP of slow fibers is

A

less steep and the amplitude of the AP is smaller

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40
Q

what drives the amplitude of the AP

A

Ca++

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41
Q

what is absent in the slow fiber AP

A

phase 1

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42
Q

what does the relative refractory period do for slow fiber APs

A

extends well into phase 4 after fiber has fully depolarized

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43
Q

what gets closer as heart rate gets closer

A

depolarizations (why HR can only get so high)

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44
Q

What needs to happen to cause AP

A

charge must exceed threshold

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45
Q

absolute refractory period

A

cannot start a new cardiac contraction (heart is already in somewhat depolarized state)

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46
Q

relative refractory period

A

may or may not be able to get a new depolarization

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47
Q

how is unidirectional flow in heart achieved

A

by arrangement of valves
heart valves keep it flowing in one direction

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48
Q

is cardiac output continuous

A

no it is intermittent

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49
Q

even though CO is intermittent, how is continuous flow achieved to periphery

A

distention of the aorta and its branches during ventricular contraction (systole) and elastic recoil of the walls of the large arteries that propel blood forward during ventricular relaxation (diastole)

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50
Q

what does the distension of aorta and its branches absorb

A

energy to recoil and push blood forward

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51
Q

why is the recoil of the walls of the large arteries important

A

to keep moving blood forward during relaxation and minimizes DBP

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52
Q

when aorta stretches what happens

A

will have stored energy and then recoils back
aorta is like a second pump for LV

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53
Q

Where does blood move rapidly through

A

aorta and its arterial branches

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54
Q

what happens to the arterial branches as they become more distal

A

become narrower and their walls become thinner and change histologically toward periphery

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55
Q

what is aorta

A

predominantly elastic structure

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56
Q

from aorta what happens histologically to peripheral arteries

A

become more muscular until the muscular layer predominates at the arterioles

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57
Q

what are arterioles referred to as

A

stop cock

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58
Q

what do arterioles do

A

determine direction of flow and are source of peripheral resistance

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59
Q

What do all vessels have

A

endothelial cells

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60
Q

as age why do arteries get stiff

A

less elastin and more fibrous tissue

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61
Q

composition of aorta

A

lots of elastic tissue
little smooth muscle
lots of fibrous tissue
diameter 25mm
wall thickness 2mm

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62
Q

what does fibrous tissue do

A

gives structure and keeps from tearing

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63
Q

composition of artery

A

little less elastic tissue than aorta
more smooth muscle than aorta
less fibrous tissue
diameter 4mm
wall thickness 1mm

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64
Q

composition of vein

A

less elastic tissue
little smooth muscle
little fibrous tissue (same as artery)
diameter 5mm
wall thickness 0.5mm

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65
Q

composition of vena cava

A

little more springy then vein
little more smooth muscle than vein
lots of fibrous tissue
diameter 30mm
wall thickness 1.5mm

66
Q

composition of arteriole

A

less elastic
lots of smooth muscle
little fibrous tissue
diameter 30um
wall thickness 6um

67
Q

composition of terminal arteriole

A

little elastin
most smooth muscle
little fibrous tissue
diameter 10um
wall thickness 2um

68
Q

composition of capillary

A

only endothelial cells
diameter 8 um
wall thickness 0.5um

69
Q

composition of venule

A

tiny amount of fibrous tissue
diameter 20um
wall thickness 1um

70
Q

whats on end of arterioles

A

capillaries

71
Q

what can go through capillaries

A

only single cells
O2 diffusion happens

72
Q

what do BP meds do at level of arteriole

A

lower BP by relaxing smooth muscle

73
Q

what does venous side of capillary work into

A

up until veins

74
Q

when arterioles contract what does it still cause (high BP)

A

massive resistance to LV
pressure will go back to LV and LV will have to work harder
LV will eventually hypertrophy

75
Q

in large arteries, frictional resistance is

A

relatively small, and mean pressure throughout the system of large arteries is only slightly less than in the aorta (drops as father away)

76
Q

what do small arteries and arterioles serve to do

A

regulate flow to individual tissues by varying their resistance to flow (to tissues that need it)

77
Q

what do the small arteries offer

A

moderate resistance to blood flow

78
Q

what do the arterioles offer

A

maximal level of resistance

79
Q

what are arterioles also referred to as

A

stopcocks of the vascular system

80
Q

where is the pressure drop most significant and the greatest

A

in the small arteries and in the arterioles

81
Q

where does pressure gradually drop from

A

from aorta to distal

82
Q

what does adjustments in the degree of contraction of the circular muscle of these small vessels permit

A

regulation of tissue blood flow and aid in the control of arterial blood pressure

83
Q

where is largest drop in pressure

A

arterioles

84
Q

where is pressure generated and where is it maintained

A

generated by LV and maintained by arterioles

85
Q

more force produced

A

means greater pressure

86
Q

in addition to sharp reduction in pressure across arterioles, what else changes

A

change from pulsatile to steady flow as pressure continues to decline from the arterial to the venous end of the capillaries

87
Q

pulsatile

A

up and down

88
Q

what is pulsatile arterial blood flow caused by

A

phasic cardiac ejection (each contraction has a bolus of blood)

89
Q

what is the pulsatile arterial blood flow damped at and why

A

at capillaries by the combination of distensibility of large arteries and frictional resistance in the arterioles

90
Q

what happens in hyperthyroidism

A

basal metabolism is high and is often associated with arteriolar vasodilation (like theyre exercising)

91
Q

in hyperthyroidism, what does the reduction in arteriolar resistance diminish

A

the dampening effect on the pulsatile arterial pressure and causes pulsatile flow in capillaries

92
Q

how can the pulsatile flow in capillaries be observed in people with hyperthyroidism

A

looking at fingernail beds
cap refill
would be slower and look more pulsatile

93
Q

what arises from each arteriole

A

many capillaries

94
Q

what forms the micro-circulation

A

capillaries

95
Q

what is the total cross sectional area of the capillary bed

A

very large
despite fact cross sectional area of each capillary is less than that of each arteriole

96
Q

what does large cross sectional area of capillaries create

A

lots of diffusion potential for O2 to be off loaded to muscle

97
Q

as a result of large cross sectional area of capillaries compared to arterioles what happens

A

blood flow velocity becomes relatively slow in capillaries from arterioles

98
Q

example of large cross sectional area in rivers

A

decrease in velocity of flow seen at wide regions of river, at narrow it is fast
as go from low to high cross sectional area, flow will slow

99
Q

where is velocity of blood flow very fast

A

when leaving LV

100
Q

what are conditions in the capillaries ideal for

A

the exchange of diffusible substances between blood and tissue

101
Q

why are conditions ideal for exchange in capillaries

A

because capillaries are short tubes whose walls are only one cell thick and because flow is very slow

102
Q

what do patients with heart failure often have

A

very high arterial venous oxygen content difference (AVO2 diff) at peak exercise
higher than healthy individuals

103
Q

why do patients with heart failure have very high AVO2 diff

A

velocity from ventricle is already slow and at capillary bed it is even slower
allowing for more time for O2 to diffuse

104
Q

AVO2 diff

A

difference in O2 from arterial to venous side

105
Q

on return to heart from capillaries where does blood pass through

A

venules and then through veins of increasing size and then vena cava

106
Q

what changes in veins of increasing size until blood gets to vena cava

A

progressive decrease in pressure

107
Q

as heart is approached, what happens to veins

A

number of veins decreases, the thickness and composition of vein walls change
total cross sectional area of venous channels diminishes and velocity of blood flow increases

108
Q

what are mirror images of each other at each level of vasculature (inversely related)

A

velocity of blood flow and the cross-sectional area

109
Q

where is the biggest drop in pressure

A

happens at distal side of stop cock, after arterioles
pressure goes from high to low

110
Q

what type of system is cardiac system

A

pressurized system
CV system ensure a pressure gradient for movement

111
Q

as move away from aorta what is there a drop in

A

velocity of blood

112
Q

is flow as quick in vena cava as aorta

A

no velocity in aorta is faster

113
Q

what is flow near in capillaries

A

near zero but not zero

114
Q

from aorta to capillaries the total cross sectional area

A

increases about 500 fold

115
Q

the volume of blood in the systemic vascular system is greatest

A

in the veins and small veins (64%)
less muscular, more elastin, more storage

116
Q

of total blood volume how much is in capillaries

A

about 6%

117
Q

of total blood volume how much is in the aorta, arteries and arterioles

A

about 14%

118
Q

blood volume in the pulmonary vascular bed is about equal

A

between the arteries and capillaries (venous vessels display a slightly larger % of pulmonary blood volume)

119
Q

cross sectional area of vanae cavae is

A

larger than aorta

120
Q

where is the velocity of flow slower, aorta or venae cavae

A

venae cavae
cross sectional area larger

121
Q

blood entering right ventricle via right atrium is pumped through pulmonary arterial system at

A

a mean pressure about one seventh that in the systemic arteries

122
Q

where does the blood pass after being pumped from right ventricle to pulmonary arterial system

A

passes through the lung capillaries where CO2 is released and O2 taken up

123
Q

where does the O2 rich blood return via after exiting lung capillaries

A

returns via 4 pulmonary veins to the left atrium and ventricle to complete cycle

124
Q

in normal intact circulation the total volume of blood is

A

constant and an increase in the volume of blood in one area must be accompanied by a decrease in another

125
Q

why does an increase in one area need decrease in another

A

for the pressure gradient
anything that leaves is replaced

126
Q

what is the Cardiac output controlled by

A

heart rate
cardiac contractility
venous return (pre-load)
arterial resistance (after load)

127
Q

what is the distribution of the circulating blood to different body organs determined by

A

the output of the left ventricle and by the contractile state of the arterioles (resistance vessels) of these organs

128
Q

the systemic and pulmonary vascular systems are composed of

A

many blood vessels arranged in series and parallel, with respect to blood flow
ie., LV and RV are parallel but function in series

129
Q

total peripheral resistance (TPR)

A

total resistance to blood flow of the systemic blood vessels

130
Q

total pulmonary resistance

A

total resistance of the pulmonary vessels

131
Q

what determines the mean arterial pressure (MAP) in the large arteries

A

total peripheral resistance and cardiac output

132
Q

what is the equation for MAP

A

MAP= TPR x CO

133
Q

why stop an exercise test for low BP

A

BP is good indicant of CO
problem is CO is low

134
Q

what is MAP driven by

A

increase in TPR or increase in CO

135
Q

what is normal for TPR to do during exercise

A

drop during exercise due to they are under control of local vasodilators and blood is redistibuted

136
Q

if MAP does not increase during exercise what can you conclude

A

SV is not increasing enough

137
Q

what is normal for CO to do during exercise

A

increase

138
Q

How can MAP be normal if increase in CO

A

increase then reduction in TPR

139
Q

main function of circulating blood

A

carry O2 and nutrients to various tissues in the body, and remove CO2 and waste products from those tissues

140
Q

what else does blood transport

A

other substances such as hormones, white blood cells, platelets, from their sites of production to sites of action

141
Q

what does blood also aid in

A

the distribution of fluids, solutes, and heat

142
Q

what does blood contribute to

A

homeostasis, the maintenance of a constant internal environment

143
Q

what is a fundamental characteristic of the normal operation of the CV system

A

maintenance of a relatively constant mean (average) blood pressure within large arteries

144
Q

difference in MAP (Pa) and the pressure in right atrium (Pra) provides

A

driving force for flow through the resistance (R) of blood vessels of the individual tissues
- down pressure gradient to go from point a to b

145
Q

what creates the pressure gradient difference

A

heart generates the pressure

146
Q

when circulatory system in steady state, total flow of blood from heart CO equals

A

total flow of blood returning to heart

147
Q

what hydraulic equation describes total blood flow from heart CO = total blood returning to heart

A

Pa - Pra = R x CO

148
Q

what kind of pressure is CO

A

constant

149
Q

what maintains the MAP at a relatively constant level

A

CV system, with neural, renal, and endocrine systems despite large variations in CO and peripheral resistance that are required in daily life

150
Q

what is avg MAP

A

average of DBP and SBP
SBP will drive more than DBP

151
Q

why is the MAP maintained at normal level under all circumstances

A

so each individual tissue will be able to obtain the necessary blood flow required to sustain its functions

152
Q

why is maintenance of Pa a critical function of the CV system

A

because blood flow to brain and heart cannot be interrupted for even a few seconds without endangering life

153
Q

what is the pressure a balance of

A

what CO offering to arterioles and what arterioles are doing to contribute to pressure

154
Q

if BP low

A

often something wrong with heart CO

155
Q

If BP high

A

often resistance vessels offering too much resistance

156
Q

CV system is composed of

A

heart, which pumps blood, and blood vessels (arteries, capillaries, veins) that distribute the blood to all organs

157
Q

what are fast response APs characterized by

A

large amplitude, steep upstroke, which is produced by activation of fast Na+ channels

158
Q

slow response APs are characterized by

A

less negative resting potential, a smaller amplitude, less steep upstroke than a fast-response
upstroke produced by activation of Ca++ channels

159
Q

where is the greatest resistance to blood flow and greatest pressure drop in arterial system

A

at level of small arteries and arterioles

160
Q

what is pulsatile pressure progressively damped by

A

elasticity of the arteriolar walls and the functional resistance of the arterioles, so capillary blood flow is essentially non pulsatile

161
Q

velocity of blood flow is inversely related to

A

cross sectional area at any point along the vascular system

162
Q

where is most of blood volume in the systemic vascular bed located

A

in the venous side of the circulation

Kin 426 (4 decks)

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