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Physiology Exam 1 > Lecture 7: Cardiac Muscle Tissue > Flashcards

Lecture 7: Cardiac Muscle Tissue Flashcards

1
Q

the blood flow path through the heart

A 
vena cave
right atrium
tricuspid valve
right ventricle
pulmonary valve
pulmonary artery
lungs
pulmonary vein
left atrium
mitral valve
left ventricle
aortic valve 
aorta
body
vena cava
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2
Q

cardiac muscle tissue characteristics

A 
striated
mononucleated
central nuclei
syncytium
intercalated discs
cells can be branched
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3
Q

define ‘syncytium’

A

the ability of the heart to act as one giant cell, the AP can rapidly spread so that all cells contract as one

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4
Q

depolarization values of the heart

A

-85 —-> +20mV

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5
Q

how long does the plateau last?

A

0.2 seconds

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6
Q

special requirements for cardiac AP

A
  1. self-generated
  2. prolonged
  3. propagated
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7
Q

what does it mean for the AP to be propagated?

A

to spread from cell to cell (syncytium)

in proper sequence and rate

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8
Q

cardia AP pathway

A 
generated in SA node
atria contract
AV node
purkinje fibers
ventricles contract
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9
Q

automaticity of the heart

A

some tissues gradually depolarize during phase 4

eventually reaching threshold

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10
Q

automaticity of the heart: tissues affected

A

SA and AV nodes

but SA reaches threshold first

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11
Q

the SA node is known as the heart’s ?

A

pacemaker

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12
Q

what determines rhythmicity of heart cells?

A

depolarization rates

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13
Q

what causes gradual depolarization during phase 4?

A

special Na channels which open after phase 3

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14
Q

compare skeletal and cardiac muscle fibers: t-tubules, cisternae, and SR

A

t-tubules are found along Z-lines
1 cisternae per t = diad
SR is less extensive

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15
Q

2 types of cardiac AP

A

fast and slow

determined by location in the heart

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16
Q

fast AP

A

heart chambers and purkinje fibers
rapid conduction and contraction
amplitude = 100mV

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17
Q

was is significant about the purkinje fibers?

A

are conductive only

never contract

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18
Q

slow AP

A 
SA and AV nodes
slow conduction
no contraction
automatic depolarization
amplitude = 60mV
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19
Q

phase 4

A

resting potential

slow depolarization of nodes

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20
Q

phase 0

A

rapid depolarization

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21
Q

phase 1

A

initial incomplete repolarization
peak
beginning of plateau

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22
Q

phase 2

A

plateau

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23
Q

phase 3

A

repolarization

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24
Q

fast AP factors

A

large cell diameter
high amplitude
rapid onset of AP
resting potential -90mV

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25
Q

slow AP factors

A

small diameter
low amplitude
slow depolarization rate due to Ca
resting potential -60mV

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26
Q

ventricular fiber AP

A

caused by opening of fast Na channels and slow Ca/Na channels

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27
Q

calcium sources in cardiac AP

A

from SR

From extracellular matrix

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28
Q

ions responsible for plateau

A

large concentration of K and Ca inside cell

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29
Q

SA node threshold

A

-40mV

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30
Q

channels at resting potential

A

slow Na/Ca channels open
K+ channels open
fast Na channels closed

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31
Q

resting potential for ventricles

A

-85/-90

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32
Q

during resting potential

A

slow leak of Na into cells
membrane becomes more positive
SA threshold at -40

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33
Q

phase 4 ions

A

slow Na influx

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34
Q

phase 0 ions

A

Ca influx

35
Q

phase 3 ions

A

K efflux

36
Q

SA node AP generate the ____ rhythm

A

sinus rhythm

37
Q

ectopic rhythm

A

an action potential that originates anywhere besides the SA node

bad — heart will not sequence correctly

38
Q

does skeletal or cardiac muscle cells have finer control over Ca concentrations and contractility?

A

cardiac

39
Q

Ca pathway in a cardiac muscle cell

A 
AP travels across sarcolemma
t-tubules conduct AP
DHP receptors allow extra Ca into cytosol
increasing intra Ca triggers ryanodine
Ca from SR into cytosol
Ca threshold reached
Ca binds to troponin
contraction
40
Q

Ca transportation during relaxation

A

SERCA into SR

sarcolemma channels allow Ca into extra matrix

41
Q

SERCA in cardiac muscle

A

primary transport to move Ca

Phospholambian helps

42
Q

Phospholambian

A

integral protein within the SR

when phosphorylated this protein can stop the SR from preventing the SERCA pump

43
Q

moving Ca back into the extracellular matrix

A

secondary transport via Ca/Na channels (antiporter)

[Na] outside cell is maintained via Na/K exchange channels

44
Q

when looking at graphs of heart pressures and volumes, compare the left and right sides

A

volumes are the same

but the right side of the heart goes to the lungs which are fragile so pressure is lower

45
Q

____ of blood flows from atria to ventricles before the atria even contract. atrial contraction moves the _____ blood.

A

80%

contraction moves the remaining 20% of blood

46
Q

isovolumic contraction occurs when….?

A

volume stays the same
pressure builds from ventricle contraction

first 0.02 seconds the aortic valve does not open

blood has no where to go

47
Q

first third of diastole

A

rapid filling of ventricles

48
Q

second third of diastole

A

small amount of blood flows into ventricles representing the blood that is constantly flowing into the atria

49
Q

final third of diastole

A

atria contract

pushing final 20% of blood into ventricles

50
Q

period of rapid ejection

A 
1/3 of systole
left ventricle pressure 80mmHg
right ventricle 8
semilunar valves open
70% of blood is ejected
51
Q

final two thirds of systole

A

30% of blood is ejected from ventricles

52
Q

frank-starling law

A

the greater the heart muscle is stretched, the greater the contractile force, that greater the volume of blood that can be moved

53
Q

EDV

A

end diastolic volume —- amount of blood in ventricles after diastole (filling)
rest = 120mL

54
Q

ESV

A

end systolic volume —- amount of blood left in ventricles after contraction
rest = 40-50mL normal

55
Q

SV

A

stroke volume = how much blood does the ventricle actually pump out

SV = EDV - ESV
rest = ~70mL
56
Q

effective ejection fraction

A

SV/EDV

at rest ==== 70/120 ~ 64%

57
Q

how can SV be increased?

A

increase EDV

decrease ESV

58
Q

40 cm/sec

A

mean velocity of blood coming from ventricle to aorta
120 is systole
(-) in diastole

59
Q

proximal aorta velocity in diastole

A

negative values

because initial backflow of blood is what causes semilunar valves to close

60
Q

blood flow in proximal vs distal aorta

A

proximal – flow is phasic

distal – flow is constantly forward

61
Q

what allows blood to constantly flow forward in distal aorta, arteries and tributaries?

A

elastance of vessels walls

62
Q

what controls blood flow to tissues?

A

tissues themselves

ANS stimulation

63
Q

CO

A

cardiac output
measured in L/Minute

at rest = 5L/min

64
Q

blood flow to tissues

A

controlled by tissue itself depending upon it’s current need, will act directly upon near vessels with their needs

Microvessels also help monitor needs

65
Q

sympathetic blood flow stimulation

A

results in an CO increase

66
Q

parasympathetic blood flow stimulation

A

results in a CO decrease

67
Q

ANS stimulations can indirectly influence blood flow, how?

A

changing heart rate

changing contractile strength of heart

68
Q

active tissues….

A

require 20x to 30x more blood flow than at rest

69
Q

cardiac output cannot exceed _____ times resting amount

A

4-7x resting amount

70
Q

what helps to keep CO at a constant rate?

A

ANS stim

tissues

71
Q

if EDV = 120
ESV = 50
ejection fraction = ?

A

60%

72
Q

P wave

A

atria contraction

73
Q

QRS complex

A

ventricle contraction

74
Q

T wave

A

repolarization of ventricles

75
Q

P-Q interval

A

0.16 seconds

delay of signal from initial origin to onset of ventricular contraction

76
Q

the AV nodes receives signal from SA node ___ seconds after origin.

A

0.3 seconds

77
Q

signal is delayed in the AV node for ____ seconds. due to ?

A

0.9 seconds

small cell size
low amplitude
slow depolarization rate

78
Q

a final delay of ___ seconds occurs in the _______.

A

0.4 seconds in the penetrating bundles

79
Q

amount of time between SA signal origination and ventricular contraction?

A

0.16 seconds

80
Q

excess K in extracellular fluid would have what effect on heart activity?

A

heart walls become dilated

81
Q

prior to ventricular isovolumic contraction, there is a slight but marked elevation in atrial pressure. what is responsible for this elevated pressure?

A

atrial contraction

82
Q

resting potential of -85mV is characteristic of which phase in the cardiac AP?

A

phase 4

83
Q

conductance of which ions is responsible for phase 0?

A

Ca and Na

Physiology Exam 1 (6 decks)

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