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BS22001 Human Physiology and Pharmacology > Cardiac Action Potential > Flashcards

Cardiac Action Potential Flashcards

1
Q

specialise types of cardiac cell

A

contractile cells and autorhythmic cells are the two types specialised types of cardiac cell

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2
Q

what is pacemaker potential

A

autorhythmic cell membrane slow drift threshold is called pacemaker potential

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3
Q

how are autorhythmic cells initate action potential

A

autorhythmic cells cyclically initiate Action potential which then spread through the heart to trigger contraction without any nervous stimulation

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4
Q

the four specific site

A

the four specific site are Sinoatrial node , atrioventricular node , bundle of His , Purkinje fibres

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5
Q

SA node

A

SA Node is the pacemaker of the heart

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6
Q

AV node

A

AV causes a delay that allows depolarisation

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7
Q

Bundle of His

A

bundle of his transmits the impulse to the left and right bundle branches and into the ventricles

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8
Q

Purkinje Fibres

A

Purkinje fibres play role in electrical conduction and propagation of impulse to the ventricular muscle

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9
Q

only conducting pathway

A

AV node forms the only conducting pathway between the atrial muscle and Bundle of His and hence the ventricles

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10
Q

what is the latent power

A

AV node cells have well developed latent powers of rhythmicity and can take over pacemaking if impulses from the SA node fail to reach them

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11
Q

membrane potential

A

Slow depolarisation towards threshold, reaches potential action potentail in which pacemaker potential is fires causing stimulation of the contractile cells allowing heart rate

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12
Q

permability of the membrane channels

A

Increase when membrane channels open
Decrease when membrane channels close

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13
Q

Pacemaker potential

A

the two stages of pacemaker potential is specific sodium gated voltage channels and funny channels close
end of pacemaker potential action potential is initiated

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14
Q

Action potential in a cardiac contractile cell

A

transient potassium channels open and then slow I type long lasting channels open

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15
Q

what is refractory peroid

A

transient potassium channels open and then slow I type long lasting channels open

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16
Q

recording

A

No wave is recorded for SA nodal depolarisation

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17
Q

ECG seperate

A

Normal ECG no seperate wave for atrial repolarisation is visible. the electrical activity associated with atrial repoalrisation occurs simultaneously with ventricular depolarisation is masked by the QRS complex

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18
Q

p wave

A

the p wave is smaller than the QRS complex because the atria have much smaller muscle mass than the ventricles

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19
Q

what is cardiac output

A

Cardiac output is the volume of blood pumped by each ventricle per minute
CO = HR X SV

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20
Q

what is stroke volume

A

Stroke volume is the volume of blood ejected per contraction
SV = EDV - ESV

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21
Q

what is CO controlled

A

CO is controlled according to physiological requirements via control of HR and SV

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22
Q

strength of cardiac muscle contraction

A

Strength of cardiac muscle contraction by
varying the initial length of the cardiac muscle fibres which in turn depends upon EDV
Varying the extent of sympathetic stimulation

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23
Q

intrinsic control of SV depends on what

A

Intrinsic control of SV depends on the direct correlation between EDV and SV

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24
Q

what does intrinsic control depend on

A

Intrinsic control depends on the length-tension relationship of cardiac muscle, which is similar to that of skeletal muscle

25
Q
A

increased EDV the more the heart is stretched
the more the heart is stretched the longer the initial cardiac fibre length before contraction

26
Q
A

the increased length results in a greater force on the subsequent cardiac contraction and thus in a stroke volume

27
Q

what is Frank Starling Law

A

the intrinsic relationship between EDV and SV is known as the Frank Starling law of the heart

28
Q

summary of frank starling

A

Frank Starling law is the heart normally pumps out during systole the volume of blood returned to it during diastole, increased venous return results in increased stoke volume

29
Q

the advantages of SV is

A

equalising output between the left and right sides of the heart
when a larger CO is required - during exercise venous return is increased through action of sympathetic NS. the resulting increase EDV automatically increases SV
exercise also increases HR so these two factors act together to increase CO so more blood can be delivered to the excising skeletal muscle

30
Q

cellular basis of the franks starling mechanism

A

the frank starling mechanism
greater initial length increases the sensitivity of contractile proteins in the myofibrils to Ca2+
increased initial fibre length may also increase Ca2+ release from the SR

31
Q

SV is also subject to extrinsic control by

A

sympathetic stimulation and adrenaline
both enchance the heart contractility

32
Q

increase contraciltiy is due to

A

This increased contractility is due to increased Ca2+ entrytriggered by NorAd/Ad

33
Q

plateau phase

A

Increase in inward Ca2+ flux during the plateau phase of the action potential enhances the intracellular calcium store

34
Q

what is required excitation contraction coupling

A

Ca2+ is required for excitation-contraction coupling in cardiac muscle cells

35
Q

increase the rate of relaxation of cardiac muscle cells by

A

increase the rate of relaxation of cardiac muscle cells by stimulating Ca2+ pumps take up Ca2+ from cytoplasm more rapidly - shortening systole

36
Q

frank starling curve to the left

A

Shift of the frank starling curve to the left by sympathetic stimulation - increase in stroke volume at same end diastolic volume

37
Q

what is after load

A

The arterial blood pressure is called the afterload because it is theworkload imposed on the heart after the contraction has begun

38
Q

increase in afterload

A

The heart may be able to compensate for a sustained increase in afterload by enlarging (hypertrophy)

39
Q

measurement of myocardial

A

the simplest measurements of myocardial contractility use analyses of the pressure waveform during the isometric contraction phase

40
Q

strength of cardiac muscle contraction SV

A

varying the initial length of the cardiac muscle fibres which in turn depends upon EDV
Varying the extent of sympathetic stimulation

41
Q

what are the arteries

A

arteries have low resistance conducting blood to the various organs with little loss in pressure
acts as pressure reservoirs for maintaining blood flow between ventricular contraction

42
Q

what is artrioles

A

arterioles are major sites of resistance of blood flow
responsible for the pattern of blood flow distribution
participate in the regulation of arterial blood pressure

43
Q

what is capillaries

A

capillaries - site of exchange between blood and tissue

44
Q

what is veins

A

Veins are low resistance vessels for blood to flow back to the heart , their capacity for blood is adjusted to facilitate flow

45
Q

vascualr system and flow

A

the vascular system blood is always from a region of higher pressure to one of lower pressure
the pressure exerted by a fluid is often termed the hydrostatic pressure

46
Q

flow rate

A

the pressure difference between two points and also the resistance to flow is flow rate

47
Q

what is resistance

A

resistance a measure of how difficult it is for blood to flow between two points at any given pressure difference
a measure of the friction impeding flow

48
Q

what is blood flow

A

Blood Flow through vessels depends upon the pressure gradient and vascular resistance
driving force is the pressure generated by contraction of the heart
Flow = Pressure gradient/resistance of blood vessels

49
Q

what is parabolic distribution

A

parabolic distribution of the speeds of flow across a circular tube shows how flow through arteries work

50
Q

resistance to blood flow depends upon 3 factors

A

viscosity of the blood (n)
vessel length (L)
vessel radius (r) - major role

51
Q

Calculation for flow rate

A

Flow Rate = pi ^ Pr4 / 8 n L

52
Q

Posuille’s law

A

A two fold change in radius will produce a 16 fold change in flow
a slight change in radius brings about a notable change in flow

53
Q

what happens to arterial pressure

A

arterial pressure fluctuates in relation to ventricular systole and diastole

54
Q

what do the arteriolar walls include

A

Arteriolar walls include a thick layer of smoothmuscle that is richly innervated by nerves of thesympathetic nervous system

55
Q

what is smooth muscle is sensitive

A

This smooth muscle is also sensitive to many local chemical changes and certain circulating hormones

56
Q

smooth muscle runs circularly around the arteriole

A

contraction = decreased radius , increase resistance, decrease local blood flow = vasoconstriction
Relaxation = increased radius, decrease resistance = increased local blood flow = vasodilation

57
Q

What is vascualr tone

A

vascular tone is the arteriolar smooth muscle displays a state of partial constriction

58
Q

what are the two factors responsible for vascular tone

A

two factor are responsible for vascular tone is myogenic and sympathetic activity

59
Q

what happens if there is any change in contractility of arteriolar smooth muscle

A

Any change in contractility of arteriolar smooth muscle will substantially change resistance to flow in these vessels

BS22001 Human Physiology and Pharmacology (11 decks)

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