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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
what is Reynolds number | high Reynolds number = high turbulence
(velocity of flow x radius of vessel ) / viscosity also abnormal vessel wall increases turbulence
26
what is a thixotropic fluid
flow affects viscosity
27
what is la place's law
tension = distending pressure x radius t=pr
28
what is flow autoregulation
response to change in arterial pressure increased pressure, arterioles constrict to reduce flow and vice versa
29
what factor causes vasoconstriction
endothelin 1 released from endothelial cells
30
what hormones act as vasodilators
adrenaline atrial naturetic peptide also NO releasing nervers
31
what local factors cause vasodilation
adenosine NO bradykinin
32
what local factors cause vasoconstriction
endothelin 1
33
what hormones cause vasoconstriction
adrenaline angiotensin 2 vasopressin
34
what is the difference between bulk flow and diffusion
bulk flow is distribution of extracellular fluid | diffusion is net movement of nutrients, O2 and metabolic end products
35
what generates oncotic pressure
plasma proteins, mainly albumin
36
what is the approximate pressure of the venous system
3-18 mmHg 60% total blood volume
37
what controls venous return
sympathetic innervation muscle pumps inspiratory movements blood volume
38
what nerve are aortic baroreceptors connected to
vagus
39
what nerve are carotid body chemoreceptors and sinus connected to
herrings nerve and glossopharyngeal (ninth cranial)
40
what is the primary purpose of the baroreceptors
controls minute to minute variations of arterial pulse
41
what do cardiopulmonary baroreceptors sense
central blood volume
42
what is the Bainbridge reflex
sympathetic mediated response to increased blood in the atria increases HR and contractility
43
where are BP signals integrated
the MCVC centre or vasomotor centre
44
what is found in the sensory area
input from baroreceptors
45
what is found in the lateral portion
efferent sympathetic nerves
46
what is found in the medial portion
efferent parasympathetic nerves (vagal)
47
what is the predominant tone in the blood vessels
sympathetic vasoconstriction veins: decreased capacitance, increased venous return, stroke volume and CO
48
what happens in the CNS ischaemic response
peripheral vasoconstriction sympathetic stimulation of the heart increased systemic arterial pressure
49
how is blood pressure in organs decreased if blood pressure rises too high
myogenic (vascular depolarisation of smooth muscle) metabolic theory local factors washed out
50
where is ADH released from
posterior pituitary atrial baroreceptors normally inhibit its release
51
where is the integration centre for blood osmolality
hypothalamus
52
where is renin released from
kidney juxtaglomerular cells
53
what is renin converted to
angiotensin
54
what does angiotensin do
vasoconstriction and salt and water retention
55
what does atrial naturetic peptide do
opposes effects of RAAS | counteract volume overload
56
what is class 1 shock
10-15 % blood loss
57
what is class 4 shock
40%
58
what are the immediate responses to hypovolaemia
increased HR and total peripheral resistance
59
what are the later responses to hypovolaemia
``` arteriolar constriction fluid reabsorption decreased renal blood flow thirst water retention ```
60
describe priming of the cvs before exercise
decrease parasympathetic tone increase CO and TPR release ADH reset baroreceptors
61
how is arterial blood pressure maintained
reducing blood flow to non essential organs | increase CO
62
what is the biggest difference between static and dynamic exercise
static- large increase in TPR due to contraction of muscles so large increase in MABP dynamic - small or no change
63
what is the fick principle
uptake of a substance is dependant on the arterio venous concentration difference and the blood flow
64
cardiac output =
rate of O2 consumption / arteriovenous O2 difference
65
decreased alveolar O2 causes what
decreased local blood flow blood doesn't go to poorly ventilated areas
66
how is coronary blood flow controlled
local metabolism | sympathetic stimulation
67
what receptor does adrenaline bind to in skeletal muscles
beta 2- causes vasodilation
68
what does catch 22 stand for
``` cardiac abnormalities abnormal facies thymic aplasia cleft palate hypothyroidism ``` aka digeorge syndrome due to partial deletion of chromosome 22
69
what is allelic heterogeneity
different mutations at the same locus can lead to the same phenotype
70
locus heterogeneity
mutations at different loci can cause the same phenotype defects in different genes can cause the same phenotype
71
what is penetrance
the proportion of individual with a mutation that express the phenotype
72
Compound heterozygosity
2 recessive alleles for the same gene that are different causing disease
73
Cascade testing
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
how does diabetes affect the cvs
metabolic disorders incl hyperglycaemia increased oxidative stress leading to accelerated vascular damage hypertension
75
how does COPD affect the CVS
pulmonary hypertension, cor pulmonale
76
how does amyloidosis affect the cvs
leads to heart failure - amyloid deposits in the heart | also nephrotic system
77
how does RA affect the heart
``` pericarditis cardiomyopathy vasculitis arrhythmia atherosclerosis due to chronic inflammation ```
78
how does thyroid dysfunction affect the heart
heart failure
79
what drugs can affect the heart
anti cancer immunosuppressive diabetogenic anti inflammatory
80
describe a methodical approach to ecg analysis
``` identify and standardise rate and rhythm p wave pr interval qrs qt st t cardiac axis other interpretation ```
81
what does 1cm equal on an ecg
1 mv
82
how do you calculate rate on an ecg
300/ large squares
83
describe a sinus rhythm
normal p waves normal qrs p wave followed by qrs regular rhythm

MD3001 (33 decks)

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