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MD3001 > heart physiology > Flashcards

heart physiology Flashcards

1
Q

what receptor does noradrenaline bind to (sympathetic stimulation)

A

beta 1

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2
Q

what effect does noradrenaline have on the heart (to whole heart)

A 
increases cAMP production
increase in SAN phase 1 depolarisation
increase Ca slow channels
increase Na through funny channels
increase chronotropic effect
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3
Q

where does acetylcholine bind

parasympathetic stimulation

A

M2 receptors

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4
Q

what effect does parasympathetic stimulation have (mostly to SAN)

A

reduces rate of phase 1 depolarisation
hyperpolarises membrane potential
increases extent and duration of opening of K+ channels
negative chronotropic effect

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5
Q

what is the intrinsic rate of the SAN

A

90 per min

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6
Q

what is the intrinsic rate of the AVN

A

60 per min

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7
Q

bundle of his intrinsic rate

A

50 per min

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8
Q

what is the formula for the observed signal on an ECG

A

E x Cos theta

smallest angle is largest observed signal

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9
Q

what is the length of the PR interval

A

0.15 - 0.2

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10
Q

what is the length of the QRS complex

A

0.08-1.2

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11
Q

what is the length of the QT interval

A

0.25- 0.35

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12
Q

what channels are opened by the action potential

A

L-type dihydropyridine

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13
Q

what does DHP activation cause

A

release of CA2+ from sarcoplasmic reticulum via ryanodine release channels

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14
Q

what is the absolute refractory period of cardiac muscle

A

245 ms
(skeletal is 1-2 ms)

this means summation is not really possible because of inactivation of Na channels

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15
Q

what percentage of ventricular filling is passive

A

80%

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16
Q

what are the stages of ventricular contraction

A

isovolumic/isometric
period of rapid ejection (1/3)
period of slow ejection(2/3)
isovolumic period of relaxation

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17
Q

what is the approximate pulmonary pressure

A

30 / 12

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18
Q

how are imbalances between the left and right heart adjusted

A

frank starling

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19
Q

what causes vascular resistance to decrease

A

age and vasoconstriction

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20
Q

how do you calculate MABP

A

diastolic + 1/3 pulse pressure

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21
Q

how do you calculate pulse pressure

A

systolic - diastolic

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22
Q

how do you calculate arterial pressure

A

cardiac output x total peripheral resistance

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23
Q

how do you calculate flow (poiseuille eqn)

A

change in pressure / resistance

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24
Q

what factors increase resistance

A

decrease vessel radius (big impact due to power 4)
increased viscosity
increased length of vessel

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25
Q

what is Reynolds number

high Reynolds number = high turbulence

A

(velocity of flow x radius of vessel ) / viscosity

also abnormal vessel wall increases turbulence

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26
Q

what is a thixotropic fluid

A

flow affects viscosity

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27
Q

what is la place’s law

A

tension = distending pressure x radius

t=pr

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28
Q

what is flow autoregulation

A

response to change in arterial pressure

increased pressure, arterioles constrict to reduce flow and vice versa

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29
Q

what factor causes vasoconstriction

A

endothelin 1 released from endothelial cells

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30
Q

what hormones act as vasodilators

A

adrenaline
atrial naturetic peptide

also NO releasing nervers

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31
Q

what local factors cause vasodilation

A

adenosine
NO
bradykinin

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32
Q

what local factors cause vasoconstriction

A

endothelin 1

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33
Q

what hormones cause vasoconstriction

A

adrenaline
angiotensin 2
vasopressin

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34
Q

what is the difference between bulk flow and diffusion

A

bulk flow is distribution of extracellular fluid

diffusion is net movement of nutrients, O2 and metabolic end products

35
Q

what generates oncotic pressure

A

plasma proteins, mainly albumin

36
Q

what is the approximate pressure of the venous system

A

3-18 mmHg

60% total blood volume

37
Q

what controls venous return

A

sympathetic innervation
muscle pumps
inspiratory movements
blood volume

38
Q

what nerve are aortic baroreceptors connected to

A

vagus

39
Q

what nerve are carotid body chemoreceptors and sinus connected to

A

herrings nerve and glossopharyngeal (ninth cranial)

40
Q

what is the primary purpose of the baroreceptors

A

controls minute to minute variations of arterial pulse

41
Q

what do cardiopulmonary baroreceptors sense

A

central blood volume

42
Q

what is the Bainbridge reflex

A

sympathetic mediated response to increased blood in the atria

increases HR and contractility

43
Q

where are BP signals integrated

A

the MCVC centre or vasomotor centre

44
Q

what is found in the sensory area

A

input from baroreceptors

45
Q

what is found in the lateral portion

A

efferent sympathetic nerves

46
Q

what is found in the medial portion

A

efferent parasympathetic nerves (vagal)

47
Q

what is the predominant tone in the blood vessels

A

sympathetic vasoconstriction

veins: decreased capacitance, increased venous return, stroke volume and CO

48
Q

what happens in the CNS ischaemic response

A

peripheral vasoconstriction
sympathetic stimulation of the heart
increased systemic arterial pressure

49
Q

how is blood pressure in organs decreased if blood pressure rises too high

A

myogenic (vascular depolarisation of smooth muscle)
metabolic theory
local factors washed out

50
Q

where is ADH released from

A

posterior pituitary

atrial baroreceptors normally inhibit its release

51
Q

where is the integration centre for blood osmolality

A

hypothalamus

52
Q

where is renin released from

A

kidney juxtaglomerular cells

53
Q

what is renin converted to

A

angiotensin

54
Q

what does angiotensin do

A

vasoconstriction and salt and water retention

55
Q

what does atrial naturetic peptide do

A

opposes effects of RAAS

counteract volume overload

56
Q

what is class 1 shock

A

10-15 % blood loss

57
Q

what is class 4 shock

A

40%

58
Q

what are the immediate responses to hypovolaemia

A

increased HR and total peripheral resistance

59
Q

what are the later responses to hypovolaemia

A 
arteriolar constriction
fluid reabsorption
decreased renal blood flow
thirst
water retention
60
Q

describe priming of the cvs before exercise

A

decrease parasympathetic tone
increase CO and TPR
release ADH
reset baroreceptors

61
Q

how is arterial blood pressure maintained

A

reducing blood flow to non essential organs

increase CO

62
Q

what is the biggest difference between static and dynamic exercise

A

static- large increase in TPR due to contraction of muscles so large increase in MABP
dynamic - small or no change

63
Q

what is the fick principle

A

uptake of a substance is dependant on the arterio venous concentration difference and the blood flow

64
Q

cardiac output =

A

rate of O2 consumption / arteriovenous O2 difference

65
Q

decreased alveolar O2 causes what

A

decreased local blood flow

blood doesn’t go to poorly ventilated areas

66
Q

how is coronary blood flow controlled

A

local metabolism

sympathetic stimulation

67
Q

what receptor does adrenaline bind to in skeletal muscles

A

beta 2- causes vasodilation

68
Q

what does catch 22 stand for

A 
cardiac abnormalities
abnormal facies
thymic aplasia
cleft palate
hypothyroidism

aka digeorge syndrome due to partial deletion of chromosome 22

69
Q

what is allelic heterogeneity

A

different mutations at the same locus can lead to the same phenotype

70
Q

locus heterogeneity

A

mutations at different loci can cause the same phenotype

defects in different genes can cause the same phenotype

71
Q

what is penetrance

A

the proportion of individual with a mutation that express the phenotype

72
Q

Compound heterozygosity

A

2 recessive alleles for the same gene that are different causing disease

73
Q

Cascade testing

A

is the identification of close relatives of an individual with a disorder to determine whether the relatives are also affected or are carriers of the same disorder. .

74
Q

how does diabetes affect the cvs

A

metabolic disorders incl hyperglycaemia
increased oxidative stress leading to accelerated vascular damage
hypertension

75
Q

how does COPD affect the CVS

A

pulmonary hypertension, cor pulmonale

76
Q

how does amyloidosis affect the cvs

A

leads to heart failure - amyloid deposits in the heart

also nephrotic system

77
Q

how does RA affect the heart

A 
pericarditis
cardiomyopathy
vasculitis
arrhythmia
atherosclerosis
due to chronic inflammation
78
Q

how does thyroid dysfunction affect the heart

A

heart failure

79
Q

what drugs can affect the heart

A

anti cancer
immunosuppressive
diabetogenic
anti inflammatory

80
Q

describe a methodical approach to ecg analysis

A 
identify and standardise
rate and rhythm
p wave
pr interval
qrs 
qt
st 
t 
cardiac axis
other
interpretation
81
Q

what does 1cm equal on an ecg

A

1 mv

82
Q

how do you calculate rate on an ecg

A

300/ large squares

83
Q

describe a sinus rhythm

A

normal p waves
normal qrs
p wave followed by qrs
regular rhythm

MD3001 (33 decks)

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