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MB1: Cardio > Physiology > Flashcards

Physiology Flashcards

1
Q

What is autorhymicity

A

electrical signals generated by the heart, capable of beating in the absence of external stimuli

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2
Q

where does heart excitation occur

A

SAN

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3
Q

if the heart is controlled by SAN it is said to be in ____

A

sinus rhythm

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4
Q

what is pacemaker potential

A

slow depolarisation occurring due to decrease in potassium efflux and constant sodium influx and transient calcium influx from T type calcium channels

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5
Q

what type of calcium channel causes rapid depolarisation of pacemaker cells?

A

L-type channels

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6
Q

what causes repolarisation of pacemaker cells

A

inactivation of L-type calcium channels and activating potassium channels

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7
Q

how do impulses from SAN reach AVN

A

gap junctions

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8
Q

where do electrical impulses travel from AVN

A

bundle of his, dividing into purkinje fibres

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9
Q

where is the AVN located

A

base of right atrium

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10
Q

why are impulses delayed in AVN

A

to allow atrial systole to precede ventricular systole

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11
Q

what is phase 0 of cardiac muscle

A

depolarisation by fast Na influx from -90 to +20mV

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12
Q

What is phase 1 cardiac muscle

A

closure of Na channels and transient potassium efflux

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13
Q

what is phase 2 cardiac muscle

A

calcium influx (L-type). plateau phase for few hundred milliseconds

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14
Q

what is phase 3 cardiac muscle

A

repolarisation by calcium channel closure and potassium efflux

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15
Q

what is phase 4 cardiac muscle

A

resting potential

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16
Q

true/false - vagal done is dominant in resting conditions

A

true

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17
Q

ACh acts on M_ receptors

A

2

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18
Q

where may atropine be used and what does it do

A

extreme bradycardia

competitive antagonist of ACh

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19
Q

ACh has a ____ chronotropic effect

A

negative

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20
Q

sympathetic nerves supply

A

SAN, AVN, myocardium

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21
Q

noradrenaline acts on

A

Beta 1 adrenoceptors

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22
Q

noradrenaline causes a ____ chronotropic effect

A

positive

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23
Q

Lead I ECG has electrodes on?

A

Left and right arm and earth on right leg

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24
Q

Lead II ECG has electrodes on?

A

right arm and left leg with ground on right leg

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25
Q

Lead III ECG has electrodes on?

A

left arm and left leg with ground on right leg

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26
Q

true/false- cardiac muscle has nervous innervation

A

false - they are electrically coupled by gap junctions

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27
Q

cardiac muscle contains ____ which contains the contractile proteins ____ and ____

A

myofibril

actin and myosin

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28
Q

how does calcium aid muscle contraction

A

causes a conformational change in troponin and tropomyosin to expose actin binding site to myosin binding site

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29
Q

What do T tubules of the sarcoplasmic reticulum carry?

A

action potentials

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30
Q

when calcium enters a cardiac myocyte it binds to channels on the SR. what does it cause

A

calcium induced calcium release

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31
Q

what si the refractory period

A

period following an action potential where it isn’t possible to have another

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32
Q

why is the refractory period good for the heart

A

prevents generation of tetanic contraction

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33
Q

what is stroke volume

A

volume of blood ejected by the ventricle per minute

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34
Q

SV=?

A

EDV-ESV

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35
Q

what does starlings law state

A

the more the ventricle is filled with blood in diastole, the greater the volume ejected during systole

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36
Q

why does cardiac muscle stretch cause better contraction

A

calcium binds to troponin better so more myosin heads bind to actin for stronger contraction

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37
Q

does starlings law support ventricular matching of stroke volume

A

yes it does

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38
Q

what is afterload

A

resistance into where the heart is pumping

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39
Q

afterload prevents a full SV ejection. how else can the heart pump more blood out?

A

increases EDV so force of contraction is increased

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40
Q

noradrenaline causes a ____ inotropic effect

A

positive

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41
Q

noradrenaline causes increased cardiac contractility. what does this do to the frank starling curve?

A

left shift and slightly upwards

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42
Q

true/false - the parasympathetic system has innervatioon all over the heart

A

false - only over the atria

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43
Q

what is cardiac output

A

volume of blood pumped by each ventricle per minute

CO=SV x HR

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44
Q

what is cardiac cycle

A

events occurring from one heartbeat to next

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45
Q

how long does diastole usually last

A

around 0.5s at 75 bpm

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46
Q

how long does systole usually last

A

around 0.3s at 75 bpm

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47
Q

during passive filling do the atria or ventricles have a higher pressure?

A

atria

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48
Q

what is the aortic pressure at passive filling roughly

A

80mmHg

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49
Q

atrial contraction is seen by what wave on ECG

A

P wave

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50
Q

what happens in isovolumetric ventricular contraction

A

ventricular pressure exceeds atrial pressure to close AV valve to produce S1
sharp pressure rise before opening of aortic valve

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51
Q

when does the aortic/pulmonary valve open

A

when ventricular pressure exceeds arterial pressure

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52
Q

what produces the dicrotic notch

A

vibration from closure of the aortic valve

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53
Q

isovolumetric ventricular relaxation is…

A

fall in ventricular pressure following systole

when below atrial pressure AV valves open

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54
Q

S1 is caused by

A

closure of AV valves

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55
Q

S2 is caused by closure of?

A

Aortic and pulmonary valves

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56
Q

4 points of auscultaton

A

right of sternum 2nd intercostal
left of sternum 2nd intercosal
sternal edge 4th intercostal
5th intercostal mid clavicular line

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57
Q

why does aortic pressure not drop to zero during diastole

A

presence of elastic recoil

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58
Q

the pressure of JVP fluctuates with?

A

pressure change in the right atrium

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59
Q

what is blood pressure

A

hydrostatic pressure exerted by blood on blood vessel walls

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60
Q

how can hypertension be defined

A

clinical blood pressure of >140/90 mmHg or daytime average of >135/85

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61
Q

what is pulse pressure and what is the usual value

A

difference between systolic and diastolic BP, usually 30-50 mmHg

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62
Q

what is the equation for the driving pressure gradient of systemic circulation

A

Pressure gradient = MAP - CVP

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63
Q

What is MAP and how is it calculated?

A

Average arterial blood pressure in a single cardiac cycle

((2 x DBP) + SBP)/3

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64
Q

what is the normal range of MAP

A

70-105 mmHg

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65
Q

what MAP is required to perfuse brain, coronary arteries and kidneys

A

at least 60mmHg

66
Q

what is SVR and what has the most resistance

A

systemic vascular resistance, sum of all resistance in vasculature. arterioles have the most resistance

67
Q

BP postural changes are managed by what reflex

A

baroreceptor reflex

68
Q

aortic baroreceptors signal via____

A

vagus nerve

69
Q

carotid baroreceptors signal via _____

A

glossopharyngeal nerve

70
Q

postural hypotension is caused by?

A

failure of baroreceptor responses to gravitational shifts

71
Q

a positive result of postural hypotension is…

A

drop of systolic bp +/- symptoms by 20 mmHg in 3 mins OR

drop of diastolic bp +symptoms by 10 mmHg

72
Q

can baroreceptors lower chronically high BP

A

no, they reset to a higher BP

73
Q

in the long term control of BP, what happens when plasma volume falls

A

fluid is shifted from interstitial fluid to plasma compartment

74
Q

what two factors affect ECFV

A

water excess/deficit

sodium excess or deficit

75
Q

what does renin do

A

produced in kidneys and converts angiotensinogen to angiotensin I

76
Q

what does angiotensin do?

A

ACE converts angiotensin I to angiotensin II
Systemic vasoconstriction
thirst and ADH release
Aldosterone release

77
Q

what does aldosterone do?

A

increases sodium and water retention in kidneys

78
Q

what stimulates renin production

A

renal artery hypotension
stimulation of renal sympathetic nerves
decreased sodium in renal tubular fluid

79
Q

NPs are released in response to?

A

cardiac distention

80
Q

what do NPs do?

A

cause kidney excretion of salt and water
decrease renin release
vasodilators to reduce SVR

81
Q

two types of NP

A

ANP

BNP

82
Q

where is ANP stored/released

A

response to atrial distention

atrial myocytes

83
Q

what is the conversion for BNP

A

prepro-BNP to pro-BNP to BNP

84
Q

where might serum BNP and pro-BNP be of use?

A

suspected heart failure

85
Q

when is ADH released

A

reduced ECVF or increased ECF osmolality

86
Q

what does ADH do

A

water reabsorption to concentrate urine

small vasoconstriction- important in hypovolaemic shock

87
Q

what vessels acciunt for the majority of SVR

A

arterioles

88
Q

resistance to blood flow is directly proportional to _____ and ______ and inversely proportional to _____ by power 4

A

blood viscosity
blood vessel length
blood vessel radius

89
Q

what is vasomotor tone?

A

tonic discharge of noradrenaline by sympathetic nerves on vascular smooth muscle

90
Q

true/false - there is no parasympathetic innervation in vascular smooth muscle

A

false - there is in the penis and clitoris

91
Q

adrenaline binding to alpha receptors causes…

A

vasoconstriction, in skin, gut and kidney

92
Q

adrenaline binding to beta 2 receptors causes

A

vasodilation, in skeletal and cardiac muscles

93
Q

angiotensin II acting on arterioles causes

A

vasoconstriction

94
Q

ADH acting on arterioles causes

A

vasoconstriction

95
Q

what local metabolites cause vasodilation and metabolic hyperaemia

A 
increased local PCO2
increased H concentration (lower pH)
Increased extracellular potassium
increased osmolality of ECF
Adenosine release
96
Q

what chemical agents cause vasodilation

A

histamine
nitric oxide
bradykinin

97
Q

Nitric acid lasts how long and is secreted in response to?

A

a few seconds

calcum release from endothelial stress

98
Q

chemical agents causing vasoconstriction?

A

serotonin
thromboxane A2
leukotrienes
endothelin

99
Q

endothelial produced vasodilators are pro/anti thrombotic, pro/anti inflammatory and pro/anti oxidant

A

anti thrombotic, anti inflammatory and antioxidant

100
Q

endothelial produced vasoconstrictors are pro/anti thrombotic, pro/anti inflammatory and pro/anti oxidant

A

pro thrombotic, pro inflammatory and pro oxidant

101
Q

cold causes vaso___

A

constriction

102
Q

what is sheer stress on arterioles

A

arteriole dilation that causes further dilation to upstream arteries

103
Q

what is the myogenic response

A

regulation of blood flow to brain to maintain blood pressure at constant levels

104
Q

true/false- capillaries contain most of the bodys blood supply

A

false- veins do

105
Q

venomotor tone increases

A

venous return, SV and MAP

106
Q

skeletal muscle pump aids

A

venous return

107
Q

how does the respiratory pump aid venous contraction

A

decrease in intrathoracic pressure and increase in intr-abdominal pressure on inspiration. causes increased pressure gradient for venous return

108
Q

4 ways venous return is increased

A

blood volume
skeletal muscle contraction
respiratory pump
venomotor tone

109
Q

metabolic hyperaemia can overcome vasomotor tone in exercise to cause ____

A

vasodilation

110
Q

an increase in CO increases ____ BP and decreses _____ BP, causing an increase in _____

A

systolic
diastolic
pulse pressure

111
Q

heart rate increase by sympathetic nerves does what to SAN and AVN

A

increases SAN firing rate

decreases AVN delay

112
Q

chronic cardiovascular responses to exercise

A

decreased levels noradrenaline and sympathetic tone
cardiac remodelling
Renin level decrease
less endothelial vasoconstrictors and more vasodilators
lowered arterial stiffening

113
Q

what is shock

A

inadequate tissue perfusion and oxygenation resulting in anaerobic metabolism and accumulation

114
Q

what is hypovolaemic shock

A

loss of blood volume decreasing venous return, EDV, SV, CO, BP and perfusion

115
Q

what is cardiogenic shock

A

hypotension caused by decreased cardiac contractility

decreased contractility lowers SV, CO, BP

116
Q

what is obstructive shock and explain the mechanism within pneumothorax

A

shock due to obstruction
PTX increases intrathoracic pressure and decreases venous return
EDV decreases, SV, CO and BP

117
Q

what is neurogenic shock

A

loss of sympathetic tone causing massive vaso/velodilation and decreased heart rate
Venous return, SVR and HR lost, CO decreased and BP

118
Q

what is vasoactive shock

A

vasoactive mediator release causing massive veno/vasodilation
increased capillary permeability and loss of volume and vasodilation decrese venous return, EDV, SVR, SV, CO, BP

119
Q

how do you treat shock

A 
high flow O2
volume replacement (except cardiogenic, give inotropes)
chest drain tension PTX
adrenaline for anaphylaxis 
vasopressors for septic shock
120
Q

what is hypovolaemic shock caused by?

A

haemorrhage

vomiting, diarrhoea, excess sweating

121
Q

compensatory mechanisms maintain BP up to __% blood loss

A

30%

122
Q

haemorrhagic shock presents as

A

small volume pulse and rapid
cool peripheries
decreased MAP
confusion, lethargy, coma if cerebral blood flow lost

123
Q

what is TLOC

A

real or apparent loss of consciousness with loss of awareness and amnesia
loss of motor control, loss of responsiveness for short duration

124
Q

causes of TLOC

A

TLOC mimic
head trauma
syncope
epileptic seizure

125
Q

what is syncope

A

TLOC due to cerebral hypoperfusion with short duration and spontaneous complete recovery

126
Q

what is reflex syncope

A

neural reflexes cause cardioinhibition and vasodepression to cause systemic hypotension

127
Q

cardioinhibition is by ___ stimulation

A

vagal

128
Q

vasodepression is caused by

A

depression of sympathetic activity to blood vessels

129
Q

what is vasovagal syncope caused by and what is the commonality

A

very common

caused by emotional distress or orthostatic distress

130
Q

symptoms of vasovagal syncope, treatment and main main worry

A

nausea, dizziness, pallor, sweating
leg crossing or horizontal gravity to enhance venous return
injury when falling

131
Q

what is situational syncope and how is it treated

A

syncope in response to a trigger

treat cause if possible and consider cardiac pacing

132
Q

what is carotid sinus syncope, who is it common in and treatment

A

syncope triggered by mechanical manipulation of neck, shaving or tight collar
elderly males
cardiac permanent pacing

133
Q

what is orthostatic syncope and risk factors

A

failure of baroreceptor response to gravitational shifts in blood
age, prolonged bed rest, medicarions, disease, reduced intravascular volume

134
Q

symptoms and diagnosis of orthostatic hypotension

A

lightheadedness, blurred vision, dizziness
in 3 mins:
drop in systolic of 20mmHg +/- symptoms
drop in diastolic of 10mmHg with symptoms

135
Q

first steps for patient with TLOC

A

history
12 lead ECG
full physical exam
orthostatic BP measurement

136
Q

what is cardiac syncope

A

cardiac event causing sudden CO drop, arrythmia, MI, structural disease, PE, aortic dissection

137
Q

features that suggest cardiac syncope

A 
structural abnormality of coronary heart disease 
FHx sudden death young age 
sudden palpitations before syncope 
ECG arrythmia 
syncope when supine or excretion
138
Q

3 special features of coronary circulation

A

high basal blood flow
high capillary density
high oxygen extraction

139
Q

3 ways to intrinsically cause vasodilation of coronary arteries?

A

decreased pCO2
metabolic hyperaemia
adenosine release

140
Q

in which phase of pressure does coronary flow occur

A

diastole

141
Q

when may coronary flow be reduced?

A

tachycardia, diastole would be shortened so blood flow limited

142
Q

when adrenaline binds to B2 receptors does it cause vasodilation or vasoconstriction?

A

vasodilation

143
Q

explain how sympathetic activity on the heart causes a vasodilator effect on coronary arteries

A

coronary arteries directly constricted but increased SV and HR causes metabolic hyperaemia, forcing them open

144
Q

what supplies the brain with blood

A

internal carotids and vertebral arteries

145
Q

what is the circle of willis and why is it good

A

basilar and carotids anastomose to form a circle of arterial blood supply
prevents total loss of cerebral perfusion if supply from one carotid artery is lost

146
Q

the brain autoregulates blood pressure between ___-___ mmHg

A

60-160 mmHg

147
Q

what pressure does blood have to fall under before confusion, brain damage and fainting usually occur

A

50 mmHg

148
Q

hyperventilation causes fainting because….

A

lack of CO2 causes vasoconstriction

149
Q

what is regional hyperaemia

A

blood flow adaptation to active parts of the brain

150
Q

true/false - baroreceptors control blood pressure in the brain

A

false

151
Q

normal ICP range is

A

8-13 mmHg

152
Q

cerebral perfusion pressure =?`

A

CPP = MAP- ICP

153
Q

what does an increase in ICP do to blood flow

A

it decreases it

154
Q

what causes increased ICP

A

trauma, brain tumour

155
Q

what is the blood brain barrier and what is it impermeable to

A

capillaries with tight intracellular junctions to prevent entry of hydrophilic ions to protect the brain from fluctuation of ion levels

156
Q

what does the systemic bronchial circulation supply

A

bronchial tree

157
Q

pulmonary resistance is high/low?

A

low

158
Q

range of pulmonary blood pressure

A

systolic 20-25

diastolic 6-12

159
Q

true/false - hypoxia causes vasoconstriction in pulmonary arterioles

A

true - it is to divert blood from areas of poor ventilation

160
Q

what is stronger in skeletal muscle? metabolic hyperaemia or sympathetic tone

A

metabolic hyperaemia

161
Q

varicose veins causes?

A

pooling of blood in veins in leg due to incompetent valves

162
Q

is there a decrease in blood volume due to varicose veins?

A

no, there is a chronic compensatory increase

MB1: Cardio (17 decks)

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