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Flashcards in heart physiology Deck (83)
1

what receptor does noradrenaline bind to (sympathetic stimulation)

beta 1

2

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

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

3

where does acetylcholine bind
(parasympathetic stimulation)

M2 receptors

4

what effect does parasympathetic stimulation have (mostly to SAN)

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

5

what is the intrinsic rate of the SAN

90 per min

6

what is the intrinsic rate of the AVN

60 per min

7

bundle of his intrinsic rate

50 per min

8

what is the formula for the observed signal on an ECG

E x Cos theta

(smallest angle is largest observed signal )

9

what is the length of the PR interval

0.15 - 0.2

10

what is the length of the QRS complex

0.08-1.2

11

what is the length of the QT interval

0.25- 0.35

12

what channels are opened by the action potential

L-type dihydropyridine

13

what does DHP activation cause

release of CA2+ from sarcoplasmic reticulum via ryanodine release channels

14

what is the absolute refractory period of cardiac muscle

245 ms
(skeletal is 1-2 ms)

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

15

what percentage of ventricular filling is passive

80%

16

what are the stages of ventricular contraction

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

17

what is the approximate pulmonary pressure

30 / 12

18

how are imbalances between the left and right heart adjusted

frank starling

19

what causes vascular resistance to decrease

age and vasoconstriction

20

how do you calculate MABP

diastolic + 1/3 pulse pressure

21

how do you calculate pulse pressure

systolic - diastolic

22

how do you calculate arterial pressure

cardiac output x total peripheral resistance

23

how do you calculate flow (poiseuille eqn)

change in pressure / resistance

24

what factors increase resistance

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

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