Cardio Physiology Flashcards
1
Q
define autorhythmicity
A
the heart generates its own electrical impulse in the absence of external stimuli
2
Q
define sinus rhythm
A
heart whose pace its controlled by the sa node
3
Q
which cells exhibit spontaneous pacemaker potential
A
sa node cells
4
Q
function of gap junctions
A
cell to cell current flow for spread of depolarisation from sa to av node
5
Q
what takes the membrane to the ap threshold
A
pacemaker potential
6
Q
what ion movement happens in the pacemaker potential
A
decreased k+ efflux, slow na+ influx
7
Q
what ion movement represents the repolarisation phase of the sa node action potential
A
k+ efflux
8
Q
what ion movement represents the depolarisation phase of the sa node action potential
A
ca influx though L type ca channels
9
Q
in the ventricular action potential what does phase 4 represent
A
the resting membrane potential
10
Q
in the ventricular action potential what does phase 3 represent
A
K+ efflux, repolarisation
11
Q
in the ventricular action potential what does phase 0 represent
A
depolarisation, fast na+ influx
12
Q
in the ventricular action potential what does phase 1 represent
A
slow k+ influx
13
Q
in the ventricular action potential what does phase 2 represent
A
ca+ influx through L type ca channels
14
Q
in the ventricular action potential what does the plateau phase represent
A
phase 2, ca+ influx through L type ca channels
15
Q
from the sa node where does excitation next spread
A
av node
16
Q
from the av node where does excitation next spread
A
bundle of his
17
Q
from the bundle of his where does excitation next spread
A
L & R branches
18
Q
from the L & R branches where does excitation next spread
A
purkinje fibres
19
Q
what allows rapid spread of excitation through the ventricles
A
the bundle of his & the purkinje fibres
20
Q
what is vagal tone
A
parasympathetic stimulation (<hr>
21
Q
what does vagal tone bring the intrinsic HR down from? and to what?
A
100bpm to 70bpm on average
22
Q
how does the vagus nerve supply the heart
A
parasympathetic to AV & SA node, increases AV node delay
23
Q
what is the parasympathetic supply to the heart
A
cn x
24
Q
through what receptor does the parasympathetic system supply the heart
A
m2
25
through what neurotransmitter does the parasympathetic system supply the heart
acetylcholine
26
mechanism of atropine
inhibits aceytlcholine
27
what is a -ve chronotropic effect
decreases hr
28
where is the sympathetic supply to the heart
sa node, av node, myocardium
29
effect of sympathetic supply to the heart
positive inotropic & positive chronotropic
30
through what receptor does the sympathetic system supply the heart
beta 1
31
contractile unit of the heart
myofibril
32
resistance in gap junctions
low
33
actin
thin, light filament
34
myosin
thick, dark filament
35
in the sliding filament theory where is the atp binding site
on myosin heads
36
what ion is required for the sliding filament theory
ca++
37
does the sliding filament theory require energy
yes
38
what is excitation contraction coupling
the action potential switching on ventricular systole
39
what effect does extracellular ca++ have in the excitation contraction coupling
stimulate release from intracellular ca++ from sarcoplasmic reticulum
40
in excitation contraction coupling when does the action potential stop
when ca++ influx stopsq
41
in excitation contraction coupling how is ca++ transported back to the sarcoplasmic reticulum
ca+ATPase
42
what happens during ca++ influx in the plateau phase
diastole
43
what happens in systole (excitation contraction coupling)
ca++ binds to troponin, pulling troponin tropomysin complex to expose cross bridge binding sites
44
clinical benefit of the refractory period
prevents tetanic contractions of the heart
45
stroke volume definition
volume of blood ejected by each ventricle per heart beat
46
what is preload
end diastolic volume
47
frank-starling curve:
increased end diastolic volume, increased stroke volume
48
in cardiac muscle optimal length when stretching/relaxed
stretching
49
what law matches SV in RV & LV
starling's (intrinsic control)
50
afterload definition
force against the lv contracting to eject blood into the systemic circulation
51
what effect does increased afterload have on edv
increased
52
cause of continuous increased afterload
hypertension
53
compensation for hypertension increased afterload
lvh
54
effect of sympathetic system on frank-starling curve
shifts left
55
what effect do b-blockers have on the frank-starling curve
shift right
56
what effect does heart failure have on the frank-starling curve
shifts right
57
what volume of blood is pumped out by each ventricle per minute
5 litres
58
cardiac output definition
blood volume pumped by each ventricle per minute
59
cardiac output formula
co = sv X hr
60
cardiac cycle definition
events occuring from beginning of one heart beat to the beginning of next
61
ventricle 80% full by what
passive filling
62
what causes the av valves to shut
ventricular pressure > atrial pressure
63
what causes the ap valves to open
ventricular pressure > aortic/pulmonary pressure
64
what causes the ap valves to shut
ventricular pressure < aortic/pulmonary pressure
65
causes of third heart sound
lv systolic dysfunction, e.g. LVF, CHF, or mitral regurg or constrictive pericarditis
66
causes of fourth heart sound
hypertension, aortic stenosis, LVH, myocardial ischaemia, HOCM
67
components of jvp
a, c, v
68
what is a in the jvp
atrial contraction
69
what is c in the jvp
tricuspid bulging into the atrium during systole
70
what is v in the jvp
atrial filling
71
what vein is the jvp
external jugular vein
72
what is an ecg
vector graph of voltage V time
73
ecg dipole; what does magnitude represent
mass of cardiac muscle involved
74
ecg dipole; what does direction represent
electrical activity at any instant
75
ecg; what is a lead
measures potential difference between 2 parts of the body
76
ecg; when is maximum deflection
when lead axis parallel to dipole
77
ecg; when is minimum deflection
when lead axis perpendicular to dipole
78
ecg; upward deflection
towards +ve recording electrode
79
ecg; downward deflection
away from +ve recording electrode
80
what plane are the chest leads in
horizontal
81
what plane are the augmented limb leads in
frontal
82
what plane are the standard limb leads in
frontal
83
where is V1 in the standard limb leads
right sternal edge, 4th intercostal
84
where is V2 in the standard limb leads
left sternal edge, 4th intercostal
85
where is V3 in the standard limb leads
halfway between v2 & v4
86
where is V4 in the standard limb leads
5th interocostal, mid-clavicular line
87
where is V5 in the standard limb leads
anterior axillary line, 5th intercostal
88
where is V6 in the standard limb leads
midaxillary line, 5th intercostal
89
which leads detects rhythm distrubances
lead ii
90
where is standard limb lead 1
right arm to left arm
91
where is standard limb lead 2
right arm to left leg
92
where is standard limb lead 3
left arm to left leg
93
what does the p wave represent & duration
atrial depolarisation, 0.08-0.1
94
what does the q wave represent
interventricular septum depolarisation
95
what does the pr interval represent & duration
av node delay, 0.12 - 0.2
96
what does the qrs complex represent & duration
ventricular depolarisation, <0.1 seconds
97
what does the s wave represent
ventricular bases depolarisation
98
what does the t wave represent
ventricular repolarisation
99
at which points on an ecg are the atria/ventricles completely depolarised
isoelectric
100
how to count hr from ecg
300/big squares between QRSs
101
how to count irregular hr from ech
number of QRSs in 30 big squares x 10
102
why are there 12 ecg leads
determine the axis of the heart in the thorax, voltage criteria changes, to see st segment or t wave changes in specific regions of the heart (ischaemia)
103
blood pressure definition
outwards hydrostatic pressure exerted by blood on blood vessel walls
104
what kind of blood flow can't be auscultated
laminar
105
map definition
average arterial bp during 1 cycle
106
map formula (both of them)
2x diastolic + systolic / 3
| and diastolic + 1/3(systolic-diastolic)
107
where is central venous pressure measured
ra / svc
108
tpr definition
sum of resistance of peripheral vasculature in systemic circulation
109
main resistance vessels
arterioles
110
where are the baroreceptors
aortic arch & carotid sinus
111
through what nerves do the baroreceptors send signals to the brain
cn ix & cn x
112
where is the control centre for regulating map
medulla
113
short term regulation of map
baroreceptor reflex (decreases vagal tone)
114
what causes postural hypotension
failure of baroreceptor reflex
115
how much body fluid does icf make up
2/3
116
what makes up ecf
pv + interstitial fluid volume
117
decreased plasma volume causes
fluid shift from interstitial compartment to plasma compartment
118
where is renin released from
kidneys
119
what is the rate limiting strep in raas
renin secretion
120
where is aldosterone released from
adrenal cortex
121
effect of aldosterone
increases h2o & na retention to increased plasma volume, and cause thirst
122
when is anp released
hypovolaemic state
123
effect of anp
induces h2o & na excretion
124
adh aka
vassopressin
125
where is adh synthesed
hypothalamus
126
where is adh stored
pituitary
127
when is adh secretion stimulated
decreased extracellular fluid volume & increased extracellular fluid osmolarity
128
effect of adh
increases h2o reabsorption, increased plasma volume, concentrates urine
129
which 'system' is activated when you haven't drank enough
adh
130
tpr regulated by changing what
radius of arterioles
131
during rest where is most blood volume
veins
132
blow flow resistance is inversely proportional to what
blood vessel radius to the power of 4
133
blood flow resistance proportional to what
blood viscosity & blood vessel length
134
true/false: no parasympathetic innervation of arterial smooth muscle
false, only penis & clitoris
135
extrinsic tpr control (nerves)
sympathetic discharge
136
increased vasomotor tone causes
vasoconstriction
137
where are alpha receptors located
skin, gut, kidneys, arterioles
138
what does alpha receptor activation cause
vasoconstriction
139
where are beta 2 receptors
cardiac & skeletal muscle arterioles
140
what does beta 2 receptor activation cause
vasodilation
141
extrinsic tpr control; hormones
adrenaline, antiduiretic hormones & angiotensin 2
142
____ control can over ride _____ control of tpr to match blood flow in tissues to metabolic needs
intrinsic, extrinsic
143
which local metabolites cause vasodilation & metabolic hyperaemia
decreased local PO2, increased local PCO2, decreased H+, increased K+
144
which local humoral agents cause vasodilation
histamine, bradykinin, nitric oxide
145
when are local humoral agents released
injury/inflammation
146
function of nitric oxide
regulates blood flow
147
how is nitric oxide produced
by artery's/arterioles endothelium by nitric oxide synthase
148
what activates nitric oxide
increased blood flow
149
which local humoral agents cause vasoconstriction
serotonin, thromboxane AS, leukotrienes, endothelin
150
name causes of endothelial damage
increased BP or cholesterol, diabetes
151
what does shear stress cause
vasodilation
152
effect of increased temp on blood vessels
vasodilation
153
effect of increased map on blood vessels
vasoconstriction
154
define venomotor tone
veins partially constricted at rest due to sympathetic stimulation
155
effect of increased venomotor tone
increased map, increased venous return
156
acute response to exercise
increased HR, SV & CO, decreased blood flow to gut/kidneys, vasodilation to skeletal/cardiac muscle, increased systolic and decreased diastolic blood pressure, decreased tpr
157
chronic response to exercise
decreased blood pressure, increased parasympathetic tone, decreased renin release, vasodilation
158
what kind of metabolism occurs during shock
anaerobic
159
what effect stroke volume
preload, afterload and contractility
160
effect of cardiogenic shock on frank-starling curve
down a lot
161
example of cardiogenic shock
mi
162
examples of obstructive shock
cardiac tamponafe, tension pneumothorax, pe, severe aortic stenosis, increased intrathoracic pressure
163
examples of distributive neurogenic shock
spinal cord, decreased sympathetic drive
164
types of distribute shock
neurogenic and vasoactive
165
examples of vasoactive shock
sepsis, anaphylaxis (increased capillary permeability)
166
management of cardiogenic shock
inotrope
167
management of septic shock
vassopressors (vasoconstrict)
168
haemorrhagic shock presentation
small volume pulse, cool peripheries
