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First Year > Cardiac Physiology-03 > Flashcards

Cardiac Physiology-03 Flashcards

1
Q

myocardium

A

responsible for pumping action, striated involuntary muscle, fibers swirl diagonally around the heart in bundles; the heart wrings blood out of the ventricles

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2
Q

functional syncytium

A

merging cells performing as a unit; those of the heart are joined electrically

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3
Q

myocytes

A

form a functional syncytium; in b/w adjacent cells, cardiac cells have branching patterns (Y shapes, Z shapes)

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4
Q

intercalated discs

A

specialized connections between myocardial cells containing gap junctions and desmosomes

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5
Q

desmosomes

A

help structurally glue adj. myocytes together; so when one contracts the other contracts + are pulling on e/o to transmit force to blood contained within ventricle

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6
Q

gap junctions

A

each half of a gap junction is formed in one cell and the other; functions to allow ions to move freely b/w these cells to electrically connect them

  • when AP is generated within myocyte in apex, AP spreads like propagated wave through each adjacent myocyte up to base of heart
  • wave of contraction occurs from apex to base
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7
Q

SA node

A

back of right atrium, opening for SVC; where pacemaker cells are found constantly depolarizing, stim. resting HR spontaneously, AP spreads as a wave across all myocytes of atrium to spread across L and R atrium

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8
Q

AV node

A

base of RA, pacemaker cells depolarize slower, wave slows down when AP reaches this point; fewer gap junctions, gives time to allow atria to contract and send blood to ventricles before electrically stimulating ventricles

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9
Q

AV bundles (bundle of His)

A

straddles fibrous skeleton, allows an electrical signal to go from atria to ventricles

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10
Q

R and L bundle branches

A

stim. various regions of ventricle to ensure L and R ventricles contract simultaneously

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11
Q

phases of an AP in a ventricular myocyte

A

depolarization, plateau, repolarization, refractory period

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12
Q

depolarization phase

A

AP generated by pacemaker cell makes myocyte reach threshold; opening of voltage-gated sodium channels

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13
Q

plateau phase

A

voltage-gated potassium and calcium channels open (K+ out, Ca2+ in for stim./regulating contraction)

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14
Q

repolarization

A

when Ca2+ channels close and K+ channels stay open, depolarization back to RMP occurs; also assisted by sodium-potassium KTPase

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15
Q

refractory period

A

another cardiac AP cannot be generated; always longer than contraction phase b/c heart needs to relax to allow it to fill up

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16
Q

electrocardiogram

A

a composite record of APs produced by all the heart muscle fibers, detected at the surface of the body, 3 recognizable waves (P, QRS, and T), electrical event precedes mechanical event (takes time for AP to propagate to stim. myocardiocytes to cause them to release CA2+ to contract)

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17
Q

P wave

A

atrial depolarization

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18
Q

PQ segment

A

atrial contraction; slowing of AP conduction at AV node (smaller fibers; less gap junctions)

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19
Q

QRS complex

A

ventricular depolarization (and atrial repolarization); large amplitude due to amount of muscle in ventricles generating larger electrical signal

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20
Q

ST segment

A

systolic contraction continues

21
Q

T wave

A

ventricular repolarization

22
Q

after T wave

A

ventricular diastole (relaxation)

23
Q

cardiac pressure

A

BP produced by contraction of heart; only present on arterial side of system and measured w/ sphygmomanometer

24
Q

dicrotic wave

A

second wave that occurs when aortic valve closes

25
Q

S1 sound

A

AV valve closure; ventricle starts to contract; pressure on AV valves which closes to prevent blood moving from ventricle to atria

26
Q

S2 sound

A

SL valve closure; prevent blood from moving back from the aorta/pulm. trunk

27
Q

isovolumetric contraction

A

as ventricle contracts, no blood moving anywhere in system, all valves closed, ventricles generate pressure against blood sitting in ventricle, contracts when pressure is greater than the aorta

28
Q

isovolumetric relaxation

A

pressure dropping within ventricle, all 4 valves closed, AV valve hasn’t opened on left side until pressure is low enough for it to open

29
Q

end-diastolic volume

A

volume left ventricle achieves at end of the diastolic phase

30
Q

end-systolic volume

A

at the end of the ventricle undergoing systole

31
Q

stroke volume

A

vol. of blood ejected from the LV or RV into the aorta (or pulm. trunk)

32
Q

what is the formula for stroke volume?

A

SV = EDV - ESV

33
Q

cardiac output

A

volume of blood ejected from the LV (or RV) into the aorta/pulm. trunk each min.

34
Q

what is the formula for cardiac output?

A

CO = HR x SV

35
Q

factors regulating stroke volume

A

preload, contractility, afterload

36
Q

preload

A

degree of stretch on the heart before it contracts

37
Q

contractility

A

forcefulness of contraction of individual ventricular muscle fibers; strength of contraction at any given preload and due to changes in cytosystolic calcium lvls (influx from ECF, release from SR)

38
Q

what increases contractility?

A

positive inotropic agents

39
Q

what decreases contractility?

A

negative inotropic agents

40
Q

afterload

A

pressure ventricles must overcome before SL valves open
normal afterload: pressure in aorta approx. 80mmHg, left side of heart needs to generate a lot more pressure before aortic valve opens

41
Q

factors affecting afterload

A

blood pressure and vessel structure

42
Q

heart rate

A

bpm, regulated by pacemaker cells in SA node

43
Q

native (resting) HR

A

75bmp

44
Q

intrinsic HR

A

100bpm

45
Q

factors regulating heart rate

A

autonomic regulation, chemical regulation, age, body temp.

46
Q

CV center (medulla oblongata) input

A

CV center receives input from higher brain regions and from sensory receptors, sends out neural impulses all the time through SNS and PNS (net effect determines if HR goes up or down)

47
Q

SNS effect on heart

A

via adrenergic receptors on myocardium & pacemaker cells

48
Q

parasympathetic effect on heart

A

via cholinergic receptors on pacemaker cells

First Year (18 decks)

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