Cardiovascular Flashcards
1
Q
Hemodynamics
A
blood flow through blood vessels
2
Q
hydrostatic pressure
A
pressure exerted by a fluid
3
Q
F=ΔP/R
A
F = flow
ΔP = pressure difference between two fixed points
R = resistance to flow
4
Q
flow
A
high to low pressure
ΔP > R
5
Q
no pressure difference
A
= no flow
6
Q
pressure gradient
A
creates flow
differences in pressure move blood
7
Q
pressure
A
created from contraction of heart chambers
blood exerts pressure on the walls of blood vessels and heart chambers
8
Q
resistance to blood flow
A
viscosity
length of blood vessel
diameter of vessel
9
Q
viscosity
A
friction between molecules of a flowing fluid
increased red blood cells
10
Q
length and diameter of blood vessel
A
determines amount of contact between moving blood and stationary wall of vessel
11
Q
Poiseuille’s equation
A
only used with laminar blood flow
R = 8ηl / πr^4
12
Q
laminar flow
A
fluid particles follow smooth paths in layers - each layer moves smoothly past adjacent layers with no mixing
13
Q
functions of cardiovascular system
A
- deliver O2 and nutrients, remove waste products of metabolism
- fast chemical signaling to cells by circulating hormones or neurotransmitters
- thermoregulation
- mediation of inflammatory and host defense responses
14
Q
components of the cv system
A
heart (pump)
blood vessels (pipes)
blood (fluid)
15
Q
arterioles
A
small branching vessels with high resistance
16
Q
capillaries
A
transport blood between arterioles and venules
exchange of materials
17
Q
arteries
A
move blood away from the heart
18
Q
veins
A
move blood towards the heart
19
Q
closed circulatory system
A
blood is always in blood vessels or the heart
allows body to generate greater pressures
20
Q
atria
A
two
thin walled
low pressure chambers
receive blood returning to the heart
21
Q
apex
A
bottom of heart (left of midline)
21
Q
ventricles
A
two
forward propulsion of blood
22
Q
base
A
top of heart
where blood vessels enter
23
Q
interatrial septum
A
separates left and right atria
24
interventricular septum
separates left and right ventricles
25
septa
dual pump
allows right and left sides to function independently
26
pulmonary circulation
blood leaves the right heart by the pulmonary trunk and is carried to the gas exchange surfaces of the lungs
poorly oxyg. blood enters lungs → O2 diffuses from alveoli to blood → oxyg. blood leaves lungs + returns to left heart
27
systemic circulation
blood leaves the left heart via the aorta → carried to body
oxyg. blood enters tissues → O2 diffuses from blood to tissues → poorly oxyg. blood leaves tissues + returns to right heart via vena cavae
28
series flow
blood must pass through the pulmonary and systemic circuits in sequence
29
parallel flow
within systemic circuit - most organs
each organ is supplied by a different artery = independent regulation of flow to different organs
30
pericardium
fibrous sac surrounding the heart and roots of vessels
has 3 layers
31
functions of pericardium
- stabilization of heart in thoracic cavity
- protection of heart from mechanical trauma, infection
- secretes pericardial fluid to reduce friction
- limits overfilling of the chambers, prevents sudden distension
32
fibrous pericardium
outside layer
33
serous pericardium
produces the fluid that fills pericardial cavity
- parietal
- visceral
34
parietal pericardium
attached to fibrous pericardium
35
visceral pericardium
epicardium
layer closest to heart
36
pericardial fluid
in the cavity
decreases friction
37
pericarditis
inflammation of pericardium
decreases ventricular filling
38
cardiac tamponade
compression of heart chambers due to excessive accumulation of pericardial fluid
decreases ventricular filling
39
ventricular walls
left ventricle wall is thicker than right ventricle (thicker myocardium)
left develops higher pressures than right
40
heart wall
epicardium
myocardium
endocardium
all four chambers
41
epicardium
visceral pericardium
covers outer surface of heart
42
myocardium
muscular wall
myocytes, blood vessels, nerves
43
endocardium
endothelium covering inner surfaces of heart and heart valves
continuous with endothelium of blood vessels
44
myocytes
cardiac muscle cells
branched (y shaped) and joined longitudinally
striated
one nucleus per cell, many mitochondria
45
intercalated disk
interdigitated region of attachment (where myocytes join)
desmosomes and gap junctions
46
gap junctions
spread action potentials across the atria or ventricles
47
valves
thin flaps of flexible endothelium-covered fibrous tissue attached at the base to the valve rings
made of collagen
leaflets/cusps
48
valve rings
dense fibrous connective tissue
site of attachment for the heart valves
49
how valves function
unidirectional flow of blood through heart
open/close passively due to pressure gradients
- forward p.g. opens one-way valve
- backward p.g. closes one-way valve but it cannot open in opposite direction
50
atrioventricular valves
between atria and ventricles
prevent backflow of blood into atria when ventricles contract
AV valve apparatus: cusps, chordae tendineae, and papillary muscles
51
tricuspid valve
right AV valve
three cusps
52
bicuspid valve
mitral valve
left AV valve
two cusps
53
chordae tendineae
tendinous type tissue
extend from edges of each cusp to papillary muscle
54
papillary muscles
cone shaped
contraction causes the chordae tendineae to become taut (tension)
55
function of AV valve apparatus
prevents eversion of the AV valves into the atria during contraction of the ventricles
56
semilunar valves
between ventricle and artery
3 cusps
no apparatus
prevent backflow of blood from arteries into ventricles when ventricles relax
57
pulmonary valve
between right ventricle and pulmonary trunk
58
aortic valve
between left ventricle and aorta
59
cardiac skeleton
fibrous skeleton of the heart; made of dense connective tissue (does not conduct action potentials = electrically inactive)
separates atria and ventricles
point of attachment for valve cusps, myocardium
60
cardiac skeleton attachment
cardiac muscle attaches to cardiac skeleton
dense connective tissue between valve rings
61
coronary circulation
movement of blood through tissues of the heart
62
coronary arteries
originate at aortic sinuses at base of ascending aorta
63
coronary veins
drain into the coronary sinus, which empties into right atrium
64
coronary sinus
collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart
65
cardiac syncytium
set of cells that act together
how myocytes communicate with each other
functional = excitation spreads over both ventricles or both atria
all or none property
2: atrial and ventricular syncytia
66
automaticity
autorhythmicity
cardiac muscle contracts in the absence of outside stimulation as a result of its own generation of action potentials
67
two types of myocytes
contractile cells - 99%
conducting cells - 1%
68
contractile cells
myocardium
mechanical work → pump, propel blood, do not initiate action potentials
69
conducting cells
initiate and conduct the action potentials
have few myofibrils
make up the conducting system
70
components of the conducting system
sinoatrial node
internodal pathways
atrioventricular node
bundle of His
bundle branches
Purkinje fibers
71
SA node
cardiac pacemaker
initiates action potentials = sets heart rate
72
internodal pathways
stimulus is passed to contractile cells of both atria and to AV node
73
AV node
100 msec delay ensures atria depolarize and contract before the ventricles
(slower pacemaker potential)
allows ventricles time to fill with blood before they contract and shut the AV valve
74
Bundle of His
below AV node; together = only electrical connection between atria and ventricles
75
bundle branches
left and right travel along interventricular septum
76
Purkinje fibres
branch from bundle branches
large number; diffuse distribution
fast conduction velocity → left and right ventricular myocytes depolarize and contract at the same time
77
Wolff-Parkinson-White Syndrome
electrical signals bypass AV node and move from the atria to ventricles faster than normal
accessory pathway transmits electrical impulses abnormally from ventricles back to atria
rapid heart rate (tachycardia), arrythmias
78
action potential
initiate contraction in muscle cells
brought on by rapid change in membrane permeability to certain ions
79
fast action potential
depolarization is instantaneous
in atrial and ventricular myocardium (contractile cells)
in Bundle of His, bundle branches, and Purkinje fibers
80
slow action potential
depolarization is a gradual increase
in SA node and AV node (conducting cells)
81
cardiac action potential
phases are due to changes in permeability of cell membrane of myocyte to Na+, K+, and Ca2+ ions
82
K+ gradient at rest
[K+] in > [K+] out
83
Ca2+ gradient at rest
[Ca2+] out > in
84
Na+ gradient at rest
[Na+] out > in
85
pacemaker potential in slow a.p.
phase 1
slow depolarization to threshold due to changes in movement of ions
closing of K+ channels
influx of Na+ through F-type channels
influx of Ca2+ through T-type channels
86
depolarization in slow a.p.
L-type channels open at threshold = influx of Ca2+
slow phase due to slow movement of Ca2+
87
repolarization in slow a.p.
opening of K+ channels and closing of L-type Ca2+ channels
efflux of K+
88
stable resting phase
fast a.p.
89
depolarization in fast a.p.
opening of fast voltage-gated Na+ channels at threshold
90
notch
slight repolarization during fast a.p.
due to transient opening of K+ channels → K+ efflux
91
plateau
fast a.p.
Ca2+ enters cell through L-type channels
slow opening of K+ channels → will repolarize cell
shorter in atrial myocardium compared to ventricular
92
repolarization in fast a.p.
opening of K+ channels and closing of Ca2+ channels
93
ECG
graphic recording of electrical events
electrical activity of the heart (from all myocardial cells) detected on skin surface
94
P-wave
spread of depolarization across atria
atria contract 25 msec after start of P-wave
95
QRS-complex
spread of depolarization across ventricles
atria repolarize simultaneously (no wave seen)
96
T-wave
ventricular repolarization
97
normal ECG
p-wave always followed by QRS complex and t-wave
98
partial AV node block
not all of stimulus gets through due to cell damage
every 2nd p-wave is not followed by QRS complex
99
complete AV node block
no synchrony between atrial and ventricular electrical activities
ventricles driven by slower bundle of His
100
excitation-contraction coupling
contraction of cardiac muscle is regulated by Ca2+
101
calcium-dependent calcium release
Ca2+ bind to ryanodine receptors → release of calcium from SR
102
L-type Ca2+ channel
voltage gated
modified DHP receptor
103
refractory period
new action potential cannot be initiated
inactivation of Na+ channels
~250 msec
no response to another stimulus
prevents tetanic contraction
104
tetanic contraction
continuous contraction of muscle ex. lifting heavy object
dangerous in cardiac muscle → ventricles couldn't fill with blood
105
cardiac cycle
single heart beat
two parts:
1. systole
2. diastole
106
systole
ventricular contraction + blood ejection
myocardial blood flow almost ceases
107
diastole
ventricular relaxation + blood filling
myocardial blood flow peaks
108
isovolumetric ventricular contraction
all heart valves closed
blood volume in ventricles remains constant → pressure rises
muscle develops tension but cannot shorten
109
ventricular ejection
pressure in ventricles exceeds that in arteries
semilunar valves open → blood ejected into the artery
muscle fibers of ventricles shorten
110
stroke volume
vol of blood ejected from each ventricle during systole
SV = EDV-ESV
normal: ~70-75 mL
111
isovolumetric ventricular relaxation
all heart valves closed
blood volume remains constant → pressure drops
112
ventricular filling
AV valves open
blood flows into ventricles from atria
passive + atrial kick
113
passive ventricular filling
ventricles receive blood passively; atria are relaxed
70% of ventricle is filled passively
114
atrial kick
atria contract at the end of ventricular filling
115
end-diastolic volume
amount of blood in each ventricle at the end of ventricular diastole
116
end-systolic volume
amount of blood in each ventricle at the end of ventricular systole
117
Lub
first heart sound
closure of AV valves
118
Dub
second heart sound
closure of semilunar valves
119
sympathetic innervation
thoracic spinal nerves → release of NE and E
also from adrenal medulla
beta-adrenergic receptors on atria and ventricles
atria, ventricles, SA node, AV node
120
parasympathetic innervation
vagus nerve
release acetylcholine
muscarinic receptor on atria
atria, SA node, AV node
121
cardiac output
amount of blood pumped by each ventricle in one minute
CO = HR x SV
122
sympathetic effect on heart rate
increase slope of pacemaker potential (faster depolarization)
increase HR
increases F-type and T-type channel permeability
123
parasympathetic effect on HR
decrease slope of pacemaker potential (slower depolarization)
decrease HR
decreases F-type channel permeability
hyperpolarizes cells (increase K+ permeability)
124
factors affecting stroke volume
EDV
contractility of ventricles
afterload
125
preload
tension or load on myocardium before it begins to contract
or
amount of filling of ventricles at the end of diastole (EDV)
126
Frank Starling Mechanism
relationship between EDV and SV
preload (degree of diastolic filling) determines the length of cardiac muscle fiber (sarcomere)
increase filling → increase EDV → increase cardiac fiber length → greater force during contraction + greater SV
127
contractility
strength of contraction at any given EDV
stimulation of ventricle by sympathetic innervation increases contractility due to increased Ca2+ availability
128
ejection fraction
EF = SV/EDV
129
sympathetic effect on contractility
decreases length of cardiac cycle
more rapid contraction and more rapid relaxation (maintain diastole)
130
afterload
tension (arterial pressure) against which the ventricles contract
as afterload increases, SV decreases
increased by any factor that restricts blood flow through arterial system
131
factors that restrict blood flow through arterial system
high arterial blood pressure
vascular resistance (arterial constriction)
stenotic valve (can't open completely)
132
endothelium
smooth, single-celled layer of endothelial cells
lines all vasculature
endothelium of vessels is continuous with endocardium of the heart
blood cells do not adhere to - flow smoothly over
133
artery structure
smooth muscle
elastic fibers
connective tissue
134
elastic arteries
ex. aorta
many elastic fibers, few smooth muscle cells
expand and recoil in response to pressure changes
135
muscular arteries
branch from aorta to distribute blood
many smooth muscle cells, few elastic fibers
136
arterioles - structure
smallest arteries
1-2 layers of smooth muscle cells
resistance vessels
137
functions of arterioles
determine relative blood flow to individual organs at mean arterial pressure
determine mean arterial pressure (MAP)
cause drop in MAP as distance from heart increases
138
altering arteriolar diameter
alters resistance and flow
vasodilation: relaxation of arteriolar smooth muscle → increased blood flow to organs
vasoconstriction: contraction of arteriolar smooth muscle → decreases blood flow to organs
139
arteriole intrinsic / basal tone
smooth muscle is partially contracted in absence of external factors
always has low level of activity
140
extrinsic factors alter basal tone
factors external to organ/tissue - affect whole body
whole body needs MAP
nerves and hormones can affect state of contraction of arterial smooth muscle
141
intrinsic factors alter basal tone
local controls
organs/tissues alter their own arteriolar resistances independent of nerves or hormones
142
sympathetic extrinsic control of arterioles
NE → vasoconstriction (a-adrenergic receptors)
increase sympathetic tone = vasoconstriction
decrease sympathetic tone (below basal level) = vasodilation
143
hormonal extrinsic control of arterioles
epinephrine release from adrenal medulla
144
active hyperemia
local control
increased metabolic activity of organ = local chemical changes [decrease O2, increase metabolites → released into interstitial fluid] → vasodilation of arterioles = increased blood flow
no nerves/hormones are involved
145
flow autoregulation
changes in arterial blood pressure alter blood flow to an organ → changes concentration of local chemicals
arterioles change resistance to maintain constant blood flow in presence of pressure change
intrinsic to organ/tissue
146
flow autoregulation: decreased arterial pressure in organ
decrease blood flow to organ
decrease O2, increase metabolites, decrease vessel-wall stretch
arteriolar dilation in organ
restoration of blood flow toward normal
147
flow autoregulation: increased arterial pressure in organ
increase blood flow to organ
increase O2, decrease metabolites, increase vessel-wall stretch
arteriolar constriction in organ
restoration of blood flow toward normal
148
myogenic response
action of myocytes
may mediate flow autoregulation
149
capillaries
smallest blood vessel
one endothelial cell thick
no smooth muscle or elastic tissue
exchange of material between blood and interstitial fluid
150
intercellular clefts
narrow water-filled space at tight junctions between endothelial cells
small water-soluble substances can pass through
151
basement membrane
surrounds endothelial cells of some capillaries
provides support to e. cell
has some connective tissue
152
continuous capillaries
small gap junction between endothelial cells
surrounded by complete basement membrane
least permeable capillary
exchange of water, small solutes, lipid-soluble material
most abundant - found in most tissues
153
fenestrated capillaries
endothelial cells have fenestrae (pores)
[with or without diaphragm]
surrounded by complete basement membrane
rapid exchange of water and small peptides
found in endocrine organs, choroid plexus (brain), GI tract, kidneys → areas where molecules need to cross the capillaries
154
sinusoidal capillaries
most permeable; found in only three specific regions
sinusoids - discontinuous or irregularly shaped (flattened)
large fenestrae in cells; large intercellular clefts between cells
thin or absent basement membrane
free exchange of water and solutes
liver, bone marrow, spleen
155
microcirculation
blood circulation between arterioles and venules
arterioles → metarterioles → capillaries → venules
156
metarteriole
precapillary arterioles
not capillaries → contain smooth muscle cells
connect arterioles to venules
change diameter to regulate flow
157
precapillary sphincter
ring of smooth muscle found at entrance to capillary
can constrict/dilate to alter blood flow into capillary bed
has no innervation
responds to local factors
158
capillary exchange
molecules cross endothelial cells by diffusion
159
diffusion
movement of substance down its concentration gradient
exchange of nutrients, metabolic products
160
lipid soluble diffusion
movement through endothelial cells
161
lipid insoluble diffusion
movement through water-filled channels: intercellular clefts, fenestrae, fused vesicle channels
162
transcytosis
use of vesicles to cross endothelial cells
endocytic and exocytic vesicles form a water-filled channel across the cell
163
bulk flow
movement of protein-free plasma across capillary wall
164
filtration
bulk flow from capillary to interstitial fluid
165
reabsorption
bulk flow from interstitial fluid to capillary
166
pressures that drive bulk flow
hydrostatic pressures (capillary + interstitial fluid)
colloid osmotic pressures (blood + interstitial fluid)
167
capillary hydrostatic pressure
pressure exerted on inside of capillary walls by blood
favours movement out of capillary (filtration)
168
interstitial fluid hydrostatic pressure
pressure exerted on outside of capillary walls by ISF
favours movement into capillary (reabsorption)
negligible
169
blood colloid osmotic pressure
osmotic pressure due to non-permeating plasma proteins inside the capillaries
favours fluid movement into the capillaries (absorption)
170
interstitial fluid colloid osmotic pressure
small amount of plasma proteins may leak out of capillaries into interstitial space
favours fluid movement out of capillaries (filtration)
negligible
171
net exchange pressure
(Pc + πIF) - (PIF + πC)
starling forces
172
transition point
between filtration and reabsorption
lies closer to venous end of capillary = more filtration than absorption
173
venous system
~60% of blood volume
large networks in liver, bone marrow, and skin
174
veins
high capacitance vessels → store large volumes of blood
highly distensible at low pressures and have little elastic recoil
reservoir of blood
175
venous valves
prevent backflow of blood to capillaries
compartmentalize blood
176
varicose veins
vein walls weaken + stretch → valves don't function properly
blood pools and vessels distend
177
mechanisms for venous return
1. smooth muscle in veins
2. skeletal muscle pump
3. respiratory pump
178
smooth muscle in veins
innervated by sympathetic neurons
stimulation → constriction of smooth muscle
179
skeletal muscle pump
compresses veins
venous pressure increases → forces more blood back to heart
180
respiratory pump
inspiration = change in pressure of thoracic cavity → increase venous return
181
venous return + Frank starling law
increased venous return results in increased stroke volume through the Frank Starling mechanism
182
compliance
ability of blood vessels to distend and increase volume with increasing transmural pressure
= change in vol / change in pressure
way to maintain blood flow during diastole
183
transmural pressure
pressure across wall of blood vessel
stretches blood vessel
184
elastic recoil
when valve closes, recoil pushes blood forward
large arteries function as pressure reservoirs
185
systolic pressure
maximum blood pressure during ventricular systole
186
diastolic pressure
minimum blood pressure at end of ventricular diastole
187
arterial blood pressure
systolic/diastolic pressure = 120/80 mmHg
(left ventricle)
188
pulse pressure
difference between systolic and diastolic
189
hypertension
chronically increased arterial blood pressure
190
hypotension
abnormally low blood pressure
191
mean arterial pressure
MAP = diastolic pressure + (pulse pressure/3)
pressure driving blood into tissues
192
pulse pressure
decreases as distance from heart increases
disappears at arterioles
smooth flow at capillaries
193
total peripheral resistance
determined by total arteriolar resistance
194
short term regulation of MAP
occurs within seconds to hours of blood pressure change
baroreceptor reflexes adjust CO and TPR by ANS
195
long term regulation of MAP
adjust blood volume by altering salt and water reabsorption
restore normal salt + water balance through mechanisms that regulate urine output and thirst
196
arterial baroreceptors
pressure sensors
found in carotid sinus and aortic arch
respond to mean arterial pressure and pulse pressure
respond to changes in pressure when walls of vessel stretch/relax
- degree of stretching is directly proportional to pressure
197
baroreceptor action potential frequency
rate of discharge is proportional to mean arterial pressure
198
increase in MAP
increases rate of firing of baroreceptors
*receptors adapt to sustained changes in arterial pressure
199
medullary cardiovascular center
medulla oblongata - brain stem
receives input from baroreceptors
200
MCC reflex
input from baroreceptors →
alters vagal stimulation (para.) to heart and symp. innervation to heart, arterioles, and veins to correct blood pressure
