physiology Flashcards
1
Q
what triggers contraction of cardiac muscle cells
A
action potentials
2
Q
what are the 2 types of cardiac muscle cells
A
- contractile cells
- autorhythmic cells
3
Q
are the cardiac cells stable
A
no they express spontaneous pacemaker activity
4
Q
what does it mean by pacemaker activity
A
their membrane potential slowly depolarises until threshold is reached
5
Q
what is it called when cell membrane is drifting to threshold
A
pacemaker potential
6
Q
what ion movements cause pacemaker potential
A
- increased inward Na+ current
- decreased K+ current
- increased Ca+ current
7
Q
what is it called when cell becomes less negative
A
depolarisation
8
Q
what is it called when cell becomes more negative
A
hyperpolarisation
9
Q
what is inward Na+ called
A
funny current
10
Q
what calcium channels open during pacemaker potential
A
T tubules
11
Q
what does T stand for
A
transient
12
Q
what happens once threshold is reached
A
- L type calcium channels open
2. K+ channels open (efflux)
13
Q
where is SA node located
A
in right atrial wall near the opening of the SVC
14
Q
where is AV node located
A
base of right atrium near septum
15
Q
what does bundle of His split into
A
right and left branches
16
Q
what heart cells have the fastest rate of action potential initiation
A
SA node cells
17
Q
how is the action potential spread
A
via gap junctions
18
Q
what is the SA node known as
A
pacemaker of the heart
19
Q
what is the next fastest cells
A
AV node
20
Q
what drives the heart if the atrial cells fail
A
Purkinje fibres
21
Q
what is it called when atria and ventricles are contracting at different rates
A
complete heart block
22
Q
what is ectopic focus
A
when one of the slower cells goes faster initiating a premature action potential
23
Q
what does complete ventricular filling require
A
that atrial contraction precede ventricular contraction
24
Q
what state are the AV valves in during cardiac relaxation
A
open
25
how does the remaining 20% of blood fill the ventricles
during atrial contraction
26
do the cardiac chambers contract simultaneously or individually
simultaneously
27
what is fibrillation
when the cardiac muscle fibres contract uncoordinately
28
what does ventricular fibrillation cause
death
29
what is the interatrial pathway
from SA node in right atrium to left atrium
30
what is the internodal pathway
SA node to AV node
31
what is special about the AV node
only point of contact between atria and ventricles
32
does the AV node have fast or slow conduction potential
slow
33
why is the slow AV node conduction beneficial
ensures time for complete ventricular filling
34
what does the membrane potential reverse to in phase 0
-90mv to +20mv
35
what causes the upstroke in cardiac action potential
Na+ influx
36
what causes phase 1
K+ efflux (partial)
37
what is unique about a cardiac action potential
plateau phase
38
what causes plateau phase
Ca+ influx through L-channels
39
what causes falling phase in action potential
- inactivation of Ca+ channels
| - activation of K+ channels
40
what does calcium entry trigger
the opening of nearby ryanodine calcium release channels in adjacent lateral sacs in sarcoplasmic reticulum
= calcium induced calcium release
41
where is calcium stored
in sarcoplasmic reticulum
42
what is the role of calcium in cytosol
bind with the troponin-tropomyosin complex and pull it aside so that cross bridge can bind
43
what does an increase in calcium concentration cause
prolonged plateau phase
44
how does verapamil work
blocks the L-type calcium channels, reducing the force of contraction
45
what does a refractory period ensure
that a second action potential cannot be triggered
46
what are the Na+ channels like during the refractory period
inactivated
47
where does ECG lead I go
from right arm to left arm
48
where does ECG lead II go
right arm to left leg
49
where does ECG lead III go
left arm to left leg
50
what are the waves of an ECG
- p
- QRS
- T
51
what does p wave represent
atrial depolarisation
52
what does QRS complex represent
ventricular depolarisation
53
what does T wave represent
ventricular repolarisation
54
what does PR segment represent
AV nodal delay
55
what does ST segment represent
systole
| - ventricles contracting and emptying
56
what does TP segment represent
diastole
| - ventricles relax and filling
57
why is the p wave much smaller than the QRS
because atria have much smaller muscle mass than the ventricles so generate less electrical activity
58
what is tachycardia
rate over 100bpm
59
what is bradycardia
rate less than 60bpm
60
characteristics of atrial flutter
- rapid regular
- rate of 200-380bpm
- atrial rate is high and ventricular is normal
61
characteristics of atrial fibrillation
- rapid, irregular
| - no p waves
62
ventricular fibrillation
- rhythmic abnormalities
- impulses travel in all directions around the ventricles
- death is imminent
63
what is heart block
- atria beat regularly but ventricles occasionally fail
| - there is varying degrees
64
what happens during systole
contraction and emptying
65
what happens during diastole
relaxation and filling
66
how does contraction occur
spread of excitation across the heart
67
what reflects diastole on ECG
TP interval
68
when does the SA node reach threshold
late in ventricular diastole
69
what on the ECG corresponds to spread through atria
p wave
70
what is the pressure of the atria in atrial depolarisation
atrial pressure exceeds ventricular pressure
71
what is the end diastolic volume
maximum amount of blood that the ventricle will contain
72
what does QRS complex represent
ventricular excitation
73
when does AV valve close
when ventricular pressure exceeds atrial pressure
74
when does aortic valve open
as ventricular pressure continues to exceed atrial pressure
| ventricle is closed so no blood can leave or enter
75
when does ventricular ejection occur
when ventricular pressure exceeds atrial pressure
76
how much blood leaves the ventricle during ventricular ejection
50%
77
what does T wave represent
ventricular repolarisation
78
when does aortic pressure close
when ventricular pressure falls below aortic pressure
79
what does closure of aortic valve cause
dicrotic notch
80
when do AV valves open
ventricular pressure falls below atrial pressure
81
when does atrial pressure rise
as incoming blood pools in the atrium
82
what is the first heart sound
lub
83
what is the second heart sound
dub
84
what causes the first heart sound
closure of AV valves
85
what causes the second heart sound
closure of semilunar valves
86
does valves opening cause a sound
no
87
how does blood flow normally
laminar
88
does laminar flow produce a sound
no
89
what kind of blood flow produces a sound
turbulent
90
what is a stenotic valve
stiff, narrowed valve that does not open completely
91
when does turbulence occur
blood flows back through the insufficient valve and collides with blood moving in opposite direction
92
what is the backflow of blood known as
regurgitation
93
what is valvular stenosis and insufficiency caused by
rheumatic fever
94
when does a systolic murmur occur
between first and second heart sound
95
when does diastolic murmur occur
between second and first heart sound
96
what is a stenotic sound
whistling
97
what is cardiac output
volume of blood pumped by each ventricle per minute
98
what determines cardiac output
stroke volume and heart rate
99
what is stroke volume
volume of blood pumped per beat
100
what is average cardiac output
5L
101
what is cardiac output during exercise
30L
102
why is the SA node the pacemaker
because it has the fastest spontaneous rate of depolarisation
103
what happens when SA node reaches a threshold
action potential is generated
104
what is average heart rate
70 beats per minute
105
how does parasympathetic get to heart
vagus nerve
106
what does parasympathetic supply
SA, AV node
107
what does sympathetic supply
SA, AV, myocardium
108
what does the vagus nerve release
acetylcholine
109
what does acetylcholine bind to
muscarinic receptor
110
what is muscarinic receptor coupled to
Gi that reduces adenyl cyclase
111
what does sympathetic activate
B1
112
what does B1 cause
Gs --> adenyl cyclase
113
what does cAMP lead to
phosphorylation
114
what effect does parasympathetic nerve have
decrease heart rate
115
what does parasympathetic do to cAMP
reduce it
116
how does ACh slow heart rate
increase K+ permeability
117
what effect does parasympathetic have on AV nodal delay
increases it, prolonging transmission
118
does parasympathetic stimulation affect contraction
no
119
what does sympathetic stimulation do to the heart
increase the heart rate
120
how can rate of depolarisation increase
as a result of the greater inward movement of sodium and calcium
121
what does sympathetic stimulation do to the AV node
reduces AV nodal delay
122
does sympathetic stimulation affect force of contraction
yes
123
what dominates under resting conditions
parasympathetic discharge
124
how does parasympathetic dominate
acetylcholine suppresses sympathetic activity by inhibiting the release of norepinephrine from sympathetic endings
125
what secretes epinephrine
adrenal medulla
126
how does epinephrine affect heart rate
increases it
127
what is stroke volume
the volume of blood pumped out by each ventricle per beat
128
what controls stroke volume
- intrinsic
| - extrinsic
129
what is intrinsic control of stroke volume
venous return
130
what is extrinsic control of stroke volume
sympathetic discharge
131
what determines EDV
venous return
132
what is the main determinant of cardiac muscle fibre length
the degree of diastolic filling
133
what does the frank starling law connect
EDV and stroke volume
134
what is frank starling law
increased venous return results in increased stroke volume
135
what is filling known as
pre-load
136
what does increased contractility result from
increased calcium influx triggered by epinephrine
137
how does sympathetic stimulation affect Frank Starling law
shifts it to the left
138
what is the ejection fraction
ratio of stroke volume to end diastolic volume
139
does sympathetic stimulation affect venous return
yes increases it
140
what does sympathetic stimulation do to veins
constricts the veins
| this squeezes more blood forward from the veins to the heart increasing EDV
141
calculating cardiac output
= HR x SV
142
what is afterload
arterial blood pressure
| = the workload imposed on the heart after the contraction has begun
143
what is heart failure
the inability of the cardiac output to keep pace with the body's demand for supplies
144
what happens to Frank Starling law in heart failure
shifts downwards and to the right
145
what has more consequences right sided or left sided heart failure
left sided
146
what does backward failure of the left side lead to
pulmonary oedema
147
how does left sided heart failure affect kidneys
they retain more salt and water in the body
148
what is diastolic failure
ventricles do not fill normally
149
do cardiac muscle cells contain mitochondria
yes an abundance
150
does the heart get O2 via diffusion
no muscle walls are too thick
151
how does the heart muscle receive blood
via the coronary circulation
152
where do coronary arteries branch from
aorta
153
where do coronary veins empty
into the right atrium
154
when does heart receive most of its blood
during diastole
155
what does adenosine cause
vasodilation of coronary vessels
156
what is atherosclerosis characterised by
plaques forming beneath the vessel lining within arterial walls
157
what does atherosclerosis start with
injury to the blood vessel wall
158
what accumulates beneath the endothelium
LDL
159
what happens to LDL
becomes oxidised
160
what ingests OXLDL
macrophages
161
what do macrophages full of OXLDL look like under a microscope
foamy
162
what to the macrophages with OXLDL form
fatty streak
163
what does OXLDL inhibit
the release of NO
164
what are fibroblasts
scar-forming cells
165
what precipitates in the plaque in the later stages
calcium
166
what does atherosclerosis in the brain cause
stroke
167
when do the symptoms of angina occur
during increased O2 demands
168
what does nitroglycerin bring about
coronary vasodilatation as it is converted to NO
169
what happens when a platelet contacts collagen
they stick to the site and help promote the formation of a blood clot
170
when does heart attack occur
when a coronary vessel is completely plugged
171
what is collateral circulation
when small terminal branches from adjacent blood vessels nourish the same area
172
what are the sources of cholesterol
- dietary intake (egg, red meats, butter)
| - manufacture of cholesterol by cells (liver)
173
is lipid soluble in water
no
174
how are lipids transported
bound to lipoprotein
175
examples of lipoproteins
HDL
LDL
VLDL
176
is LDL good or bad
bad
177
is HDL good or bad
good
178
what does HDL do
remove cholesterol from cells and transports it to the liver for elimination from the body
