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cardiovascular > physiology > Flashcards

physiology Flashcards

1
Q

what triggers contraction of cardiac muscle cells

A

action potentials

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2
Q

what are the 2 types of cardiac muscle cells

A
  • contractile cells

- autorhythmic cells

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3
Q

are the cardiac cells stable

A

no they express spontaneous pacemaker activity

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4
Q

what does it mean by pacemaker activity

A

their membrane potential slowly depolarises until threshold is reached

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5
Q

what is it called when cell membrane is drifting to threshold

A

pacemaker potential

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6
Q

what ion movements cause pacemaker potential

A
  • increased inward Na+ current
  • decreased K+ current
  • increased Ca+ current
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7
Q

what is it called when cell becomes less negative

A

depolarisation

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8
Q

what is it called when cell becomes more negative

A

hyperpolarisation

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9
Q

what is inward Na+ called

A

funny current

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10
Q

what calcium channels open during pacemaker potential

A

T tubules

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11
Q

what does T stand for

A

transient

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12
Q

what happens once threshold is reached

A
  1. L type calcium channels open

2. K+ channels open (efflux)

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13
Q

where is SA node located

A

in right atrial wall near the opening of the SVC

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14
Q

where is AV node located

A

base of right atrium near septum

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15
Q

what does bundle of His split into

A

right and left branches

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16
Q

what heart cells have the fastest rate of action potential initiation

A

SA node cells

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17
Q

how is the action potential spread

A

via gap junctions

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18
Q

what is the SA node known as

A

pacemaker of the heart

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19
Q

what is the next fastest cells

A

AV node

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20
Q

what drives the heart if the atrial cells fail

A

Purkinje fibres

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21
Q

what is it called when atria and ventricles are contracting at different rates

A

complete heart block

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22
Q

what is ectopic focus

A

when one of the slower cells goes faster initiating a premature action potential

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23
Q

what does complete ventricular filling require

A

that atrial contraction precede ventricular contraction

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24
Q

what state are the AV valves in during cardiac relaxation

A

open

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25
Q

how does the remaining 20% of blood fill the ventricles

A

during atrial contraction

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26
Q

do the cardiac chambers contract simultaneously or individually

A

simultaneously

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27
Q

what is fibrillation

A

when the cardiac muscle fibres contract uncoordinately

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28
Q

what does ventricular fibrillation cause

A

death

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29
Q

what is the interatrial pathway

A

from SA node in right atrium to left atrium

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30
Q

what is the internodal pathway

A

SA node to AV node

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31
Q

what is special about the AV node

A

only point of contact between atria and ventricles

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32
Q

does the AV node have fast or slow conduction potential

A

slow

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33
Q

why is the slow AV node conduction beneficial

A

ensures time for complete ventricular filling

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34
Q

what does the membrane potential reverse to in phase 0

A

-90mv to +20mv

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35
Q

what causes the upstroke in cardiac action potential

A

Na+ influx

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36
Q

what causes phase 1

A

K+ efflux (partial)

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37
Q

what is unique about a cardiac action potential

A

plateau phase

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38
Q

what causes plateau phase

A

Ca+ influx through L-channels

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39
Q

what causes falling phase in action potential

A
  • inactivation of Ca+ channels

- activation of K+ channels

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40
Q

what does calcium entry trigger

A

the opening of nearby ryanodine calcium release channels in adjacent lateral sacs in sarcoplasmic reticulum

= calcium induced calcium release

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41
Q

where is calcium stored

A

in sarcoplasmic reticulum

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42
Q

what is the role of calcium in cytosol

A

bind with the troponin-tropomyosin complex and pull it aside so that cross bridge can bind

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43
Q

what does an increase in calcium concentration cause

A

prolonged plateau phase

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44
Q

how does verapamil work

A

blocks the L-type calcium channels, reducing the force of contraction

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45
Q

what does a refractory period ensure

A

that a second action potential cannot be triggered

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46
Q

what are the Na+ channels like during the refractory period

A

inactivated

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47
Q

where does ECG lead I go

A

from right arm to left arm

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48
Q

where does ECG lead II go

A

right arm to left leg

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49
Q

where does ECG lead III go

A

left arm to left leg

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50
Q

what are the waves of an ECG

A
  • p
  • QRS
  • T
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51
Q

what does p wave represent

A

atrial depolarisation

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52
Q

what does QRS complex represent

A

ventricular depolarisation

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53
Q

what does T wave represent

A

ventricular repolarisation

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54
Q

what does PR segment represent

A

AV nodal delay

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55
Q

what does ST segment represent

A

systole

- ventricles contracting and emptying

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56
Q

what does TP segment represent

A

diastole

- ventricles relax and filling

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57
Q

why is the p wave much smaller than the QRS

A

because atria have much smaller muscle mass than the ventricles so generate less electrical activity

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58
Q

what is tachycardia

A

rate over 100bpm

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59
Q

what is bradycardia

A

rate less than 60bpm

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60
Q

characteristics of atrial flutter

A
  • rapid regular
  • rate of 200-380bpm
  • atrial rate is high and ventricular is normal
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61
Q

characteristics of atrial fibrillation

A
  • rapid, irregular

- no p waves

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62
Q

ventricular fibrillation

A
  • rhythmic abnormalities
  • impulses travel in all directions around the ventricles
  • death is imminent
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63
Q

what is heart block

A
  • atria beat regularly but ventricles occasionally fail

- there is varying degrees

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64
Q

what happens during systole

A

contraction and emptying

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65
Q

what happens during diastole

A

relaxation and filling

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66
Q

how does contraction occur

A

spread of excitation across the heart

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67
Q

what reflects diastole on ECG

A

TP interval

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68
Q

when does the SA node reach threshold

A

late in ventricular diastole

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69
Q

what on the ECG corresponds to spread through atria

A

p wave

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70
Q

what is the pressure of the atria in atrial depolarisation

A

atrial pressure exceeds ventricular pressure

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71
Q

what is the end diastolic volume

A

maximum amount of blood that the ventricle will contain

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72
Q

what does QRS complex represent

A

ventricular excitation

73
Q

when does AV valve close

A

when ventricular pressure exceeds atrial pressure

74
Q

when does aortic valve open

A

as ventricular pressure continues to exceed atrial pressure

ventricle is closed so no blood can leave or enter

75
Q

when does ventricular ejection occur

A

when ventricular pressure exceeds atrial pressure

76
Q

how much blood leaves the ventricle during ventricular ejection

A

50%

77
Q

what does T wave represent

A

ventricular repolarisation

78
Q

when does aortic pressure close

A

when ventricular pressure falls below aortic pressure

79
Q

what does closure of aortic valve cause

A

dicrotic notch

80
Q

when do AV valves open

A

ventricular pressure falls below atrial pressure

81
Q

when does atrial pressure rise

A

as incoming blood pools in the atrium

82
Q

what is the first heart sound

A

lub

83
Q

what is the second heart sound

A

dub

84
Q

what causes the first heart sound

A

closure of AV valves

85
Q

what causes the second heart sound

A

closure of semilunar valves

86
Q

does valves opening cause a sound

A

no

87
Q

how does blood flow normally

A

laminar

88
Q

does laminar flow produce a sound

A

no

89
Q

what kind of blood flow produces a sound

A

turbulent

90
Q

what is a stenotic valve

A

stiff, narrowed valve that does not open completely

91
Q

when does turbulence occur

A

blood flows back through the insufficient valve and collides with blood moving in opposite direction

92
Q

what is the backflow of blood known as

A

regurgitation

93
Q

what is valvular stenosis and insufficiency caused by

A

rheumatic fever

94
Q

when does a systolic murmur occur

A

between first and second heart sound

95
Q

when does diastolic murmur occur

A

between second and first heart sound

96
Q

what is a stenotic sound

A

whistling

97
Q

what is cardiac output

A

volume of blood pumped by each ventricle per minute

98
Q

what determines cardiac output

A

stroke volume and heart rate

99
Q

what is stroke volume

A

volume of blood pumped per beat

100
Q

what is average cardiac output

A

5L

101
Q

what is cardiac output during exercise

A

30L

102
Q

why is the SA node the pacemaker

A

because it has the fastest spontaneous rate of depolarisation

103
Q

what happens when SA node reaches a threshold

A

action potential is generated

104
Q

what is average heart rate

A

70 beats per minute

105
Q

how does parasympathetic get to heart

A

vagus nerve

106
Q

what does parasympathetic supply

A

SA, AV node

107
Q

what does sympathetic supply

A

SA, AV, myocardium

108
Q

what does the vagus nerve release

A

acetylcholine

109
Q

what does acetylcholine bind to

A

muscarinic receptor

110
Q

what is muscarinic receptor coupled to

A

Gi that reduces adenyl cyclase

111
Q

what does sympathetic activate

A

B1

112
Q

what does B1 cause

A

Gs –> adenyl cyclase

113
Q

what does cAMP lead to

A

phosphorylation

114
Q

what effect does parasympathetic nerve have

A

decrease heart rate

115
Q

what does parasympathetic do to cAMP

A

reduce it

116
Q

how does ACh slow heart rate

A

increase K+ permeability

117
Q

what effect does parasympathetic have on AV nodal delay

A

increases it, prolonging transmission

118
Q

does parasympathetic stimulation affect contraction

A

no

119
Q

what does sympathetic stimulation do to the heart

A

increase the heart rate

120
Q

how can rate of depolarisation increase

A

as a result of the greater inward movement of sodium and calcium

121
Q

what does sympathetic stimulation do to the AV node

A

reduces AV nodal delay

122
Q

does sympathetic stimulation affect force of contraction

A

yes

123
Q

what dominates under resting conditions

A

parasympathetic discharge

124
Q

how does parasympathetic dominate

A

acetylcholine suppresses sympathetic activity by inhibiting the release of norepinephrine from sympathetic endings

125
Q

what secretes epinephrine

A

adrenal medulla

126
Q

how does epinephrine affect heart rate

A

increases it

127
Q

what is stroke volume

A

the volume of blood pumped out by each ventricle per beat

128
Q

what controls stroke volume

A
  • intrinsic

- extrinsic

129
Q

what is intrinsic control of stroke volume

A

venous return

130
Q

what is extrinsic control of stroke volume

A

sympathetic discharge

131
Q

what determines EDV

A

venous return

132
Q

what is the main determinant of cardiac muscle fibre length

A

the degree of diastolic filling

133
Q

what does the frank starling law connect

A

EDV and stroke volume

134
Q

what is frank starling law

A

increased venous return results in increased stroke volume

135
Q

what is filling known as

A

pre-load

136
Q

what does increased contractility result from

A

increased calcium influx triggered by epinephrine

137
Q

how does sympathetic stimulation affect Frank Starling law

A

shifts it to the left

138
Q

what is the ejection fraction

A

ratio of stroke volume to end diastolic volume

139
Q

does sympathetic stimulation affect venous return

A

yes increases it

140
Q

what does sympathetic stimulation do to veins

A

constricts the veins

this squeezes more blood forward from the veins to the heart increasing EDV

141
Q

calculating cardiac output

A

= HR x SV

142
Q

what is afterload

A

arterial blood pressure

= the workload imposed on the heart after the contraction has begun

143
Q

what is heart failure

A

the inability of the cardiac output to keep pace with the body’s demand for supplies

144
Q

what happens to Frank Starling law in heart failure

A

shifts downwards and to the right

145
Q

what has more consequences right sided or left sided heart failure

A

left sided

146
Q

what does backward failure of the left side lead to

A

pulmonary oedema

147
Q

how does left sided heart failure affect kidneys

A

they retain more salt and water in the body

148
Q

what is diastolic failure

A

ventricles do not fill normally

149
Q

do cardiac muscle cells contain mitochondria

A

yes an abundance

150
Q

does the heart get O2 via diffusion

A

no muscle walls are too thick

151
Q

how does the heart muscle receive blood

A

via the coronary circulation

152
Q

where do coronary arteries branch from

A

aorta

153
Q

where do coronary veins empty

A

into the right atrium

154
Q

when does heart receive most of its blood

A

during diastole

155
Q

what does adenosine cause

A

vasodilation of coronary vessels

156
Q

what is atherosclerosis characterised by

A

plaques forming beneath the vessel lining within arterial walls

157
Q

what does atherosclerosis start with

A

injury to the blood vessel wall

158
Q

what accumulates beneath the endothelium

A

LDL

159
Q

what happens to LDL

A

becomes oxidised

160
Q

what ingests OXLDL

A

macrophages

161
Q

what do macrophages full of OXLDL look like under a microscope

A

foamy

162
Q

what to the macrophages with OXLDL form

A

fatty streak

163
Q

what does OXLDL inhibit

A

the release of NO

164
Q

what are fibroblasts

A

scar-forming cells

165
Q

what precipitates in the plaque in the later stages

A

calcium

166
Q

what does atherosclerosis in the brain cause

A

stroke

167
Q

when do the symptoms of angina occur

A

during increased O2 demands

168
Q

what does nitroglycerin bring about

A

coronary vasodilatation as it is converted to NO

169
Q

what happens when a platelet contacts collagen

A

they stick to the site and help promote the formation of a blood clot

170
Q

when does heart attack occur

A

when a coronary vessel is completely plugged

171
Q

what is collateral circulation

A

when small terminal branches from adjacent blood vessels nourish the same area

172
Q

what are the sources of cholesterol

A
  • dietary intake (egg, red meats, butter)

- manufacture of cholesterol by cells (liver)

173
Q

is lipid soluble in water

A

no

174
Q

how are lipids transported

A

bound to lipoprotein

175
Q

examples of lipoproteins

A

HDL
LDL
VLDL

176
Q

is LDL good or bad

A

bad

177
Q

is HDL good or bad

A

good

178
Q

what does HDL do

A

remove cholesterol from cells and transports it to the liver for elimination from the body

cardiovascular (36 decks)

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