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Human physiology > regulation and adaptation of the heart > Flashcards

regulation and adaptation of the heart Flashcards

1
Q

what factors determine the membrane potential?

A

concentration gradients of K, Na,Ca

electrical conductance of the memebrane being regulated by ion channels

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2
Q

what is an electrogenic pump?

A

contributes to the resting membrane potential

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3
Q

what maintains a negative charge inside the cell?

A

na/K pump

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4
Q

how does electrical activity pass through the heart?

A

contractile fibres

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5
Q

how do myocardial cells work?

A

SAN depolarises across all cells

cells dont contract though till they recieve this activity much like a wave

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6
Q

what is the prepotential?

A

tendency for K and Na chennels to open allowing influf of positive ions into cells
causes depolariasation

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7
Q

what affects the prepotential?

A

autonomic nervous system

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8
Q

what is the sloping prepotetial caused by?

A

slowly declining membrane potential is called the pre-potential, the slope detemines the heart rate
it is caused by the Na pacemaker current

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9
Q

describe the steps of the impulse conduction through the heart

A
  1. SA node fires wave of depolarization across atria
  2. stimulus spreads across atria reaching AV node
  3. millisecond delay at AV node before atria contraction begins
  4. impulse travels along septum with th AV bundle and Purkinje fibres into ventricles
  5. impulse distributed by Purkinje fibres and relayed throughout the ventricular myocardium and ventricular contraction begins
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10
Q

how can the ECG be used as a diagnostic tool

A 
electrical axis
heart rate
activation sequencce disorders
drugs
electrolyte imbalance
carditis
pacearker issues
coronary circulation
hypertrophy
arrhythmias
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11
Q

what is sinus tachycardia

A

impulses from SA node at rapid rate

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12
Q

what is an atrial flutter

A

impulses travel in circular route across atria

ventricular response irregular

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13
Q

what is atrial fibrillation

A

impulses have chaotic, random pathways in the atria

ventricles irregular too

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14
Q

what is ventricular fibrilation

A

very serious as output decreased

rapid, wide, irrregular venticular complexes

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15
Q

what is stroke volume dependent on?

A

energy of contractios
atrial pressure
muscles ability

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16
Q

what does cardiac output depend on?

A

affected by activity

changes affected by heart rate and stroke volume

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17
Q

define inotropy

A

strength of contraction

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18
Q

define chronotrophy

A

contraction frequency

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19
Q

define bradycardia

A

decreased heart rate

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20
Q

define tachycardia

A

increased heart rate

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21
Q

define dromotrophy

A

the velocity of signal conduction

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22
Q

define lusitropy

A

myocardial relaxation

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23
Q

define bathmotropy

A

myocardial excitability

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24
Q

what does the sympathetic nerve innervation do?

A

increases heart rate and force of contraction

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25
Q

what does the parasympthtic nerve innervtion do?

A

slows the heart rate down

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26
Q

what happens during sympathetic regulation?

A 
inotropy up
chronotrophy up
dromotrophy up
bathmotrophy up
lusitriophy up
faster, harder
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27
Q

what increases sympathetic innervation

A

exercise
standing up
stress
haemorrhage

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28
Q

what happens to the ejection fraction during sympathetic inervation?

A

increases

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29
Q

what hapens to stroke volume during sympatetic innervation

30
Q

what causes increased luisotrophy during symatheic innervation

A

phosphorylation of actin filaments

31
Q

what mediates sympathetic innervation?

A

B-adrenergic receptors

32
Q

what mediates parasympathetic innervation?

A

M2 muscarinic acetylcholine receptors

33
Q

what happens during parasympathetic innervation?

A

chronotrophy down
inotrophy down
bathotrophy down
dromotrophy down

34
Q

at rest what keeps heart rate suppressed?

A

parasmpathetic

35
Q

what is the anrep effect?

A

increased arterial pressure causes increased contractility of myocardium

36
Q

what is the effect of temperature

A

fever increased heart rate

cooling is used in surgery to slow heart rate

37
Q

what is the frank-starling mechanism?

A

the more the ventricle is filled with blood during diastole, the greater the stroke voume

38
Q

what does increased blood volume cause in the frank-starling mechanism

A

increased stretch of the myocardium equalling and increase force to pump the bloo out

39
Q

when does the law become invalid ( frank-starling)

A

after a certain LVEDP

left ventricular end-diastole pressure

40
Q

what is the calcium tension curve

A

sensitivity of calcium depends on the sarcomere length

41
Q

what does a long sarcomere mean for calcium?

A

myofilaments mroe sensitive to calcium

more Ca can bind to thin filaments as there is less overlsp

42
Q

what does a short saarcomere mean for calcium?

A

more overlap, less sensitive

43
Q

what is Laplaces law?

A

tension on the wall of the heart is product of the pressure times the radium of the chamber
the tension is invertly related to the thickness of the wall

44
Q

equation of laplace’s law

A

internal presssure P = 2Tension / radius

45
Q

as the radius increased what happened? Laplace’s law

A

pressure decreases

46
Q

what is preload?

A

stretch of the cardiac muscles when exposed to diastole conditons

47
Q

what affect preload?

A

venous presssure, rate of venous blood flow, venous tone and volume of circulating blood

48
Q

define afterload?

A

tension produced by the heart in order to eject blood into vessels

49
Q

what affects afterload?

A

blood pressure

50
Q

what affects the venous pressure?

A 
blood volume
gravit/posture
muscle pump
respiratory pump
cardiac output
51
Q

where are baroreceptors found?

A

arotic arch

52
Q

what are baroreeptors?

A

nerve ending in the adventitia of carotid sinus and aortic arch
sense distortions in vessels in blood pressue

53
Q

what do baroreceptors sense?

A

degree of pressure through stretch

54
Q

what is the baroreceptor refex?

A

depression of the heart rate by activating vagus nerve
vasodilation through decreasing sympathetic activity
loweres blood pressure
contraction strength reduced too

55
Q

what can be reduced to lower blood presure?

A

Bp is result of cardiac output and total peripheral resistance so can chnge one of these two

56
Q

natura causes of long term myocardial adaptation

A

exercise

pregnancy

57
Q

what happens when the heart is stressed?

A

undergoes hypertrophy and changes gene expression

58
Q

what is hypertrophy

A

process where the heart changes gene expression in response to new envirnental requirements

59
Q

how does hypertrophy actually occur?

A
  • expression of genes changes

- isoform shifts in cytoskeletal proteins and ECM

60
Q

what is physical hypertrophy?

A

temp increase in heart size due to enlargement of cardiac myocytes as a result of exercise
improves functioning

61
Q

what is pathological hypertrophy?

A

stress leading to change. leads to inability of the heart to deliver blood and oxygen

62
Q

what can pathological hypetrophy lead to?

A

abnormalities in metabolism
more heart stress
heart failure

63
Q

what is heart failure defined as?

A

progressive disrder which damages the heart

weakens the cardiovascular system

64
Q

what does heart failure cause in the body?

A

inadequate blood flow to tissues

blood pressure issues

65
Q

causes of heart failure

A

myocardial infarction
cornary heart disease
valve diease
hyerptension

66
Q

what is dilated cardiomyopathy?

A

los of myocytes being replaced by fibrobasts

heart cannot contract as cell

67
Q

what happens in cardiac hypertrophy on a cellular level?

A

wall thickens
no proliferations
cells get bigger

68
Q

what is the P wave

A

depolaristion of the atria

69
Q

what is the QRS complex

A

depolaristion of the venticles

70
Q

what is the T wave

A

repolarisation of the venticles

Human physiology (21 decks)

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