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Physiology > Exam 2 – Cardio Ch 9 > Flashcards

Exam 2 – Cardio Ch 9 Flashcards

1
Q

What is a syncytium?

A

Cardiac cells are so interconnected that when one becomes excited, the action potential rapidly spreads to all of the cardiac cells
Act as one instead of individually

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2
Q

How many syncytiums does the heart have?

A

2

Atrial and ventricular

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3
Q

Where is the fibrous insulator between the atrium and ventricle located?

A

At the base of the heart

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4
Q

Why does the fibrous insulator exist between the atrium and ventricle?

A

This division of muscle of heart into two functional syncytiums allows atria to contract a short time ahead of ventricular contraction, which is important for effectiveness of heart pumping
Don’t want all four chambers contracting at once

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5
Q

KNOW INTERIOR STRUCTURES OF HEART

A

KNOW INTERIOR STRUCTURES OF HEART

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6
Q

What is a primer pump for the ventricle?

A

Atrium

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7
Q

How does the atrium act as a primer pump?

A

Helps move blood into the ventricle

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8
Q

What supplies the main pumping force for the heart?

A

Ventricles

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9
Q

What two pathways do the ventricles pump blood to?

A
  1. Through pulmonary circulation by right ventricle

2. Through systemic circulation by left ventricle

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10
Q

What are the characteristics of cardiac muscles?

A 
Actin and myosin filaments 
Low resistance intercalated discs (1/400 the resistance of cell membrane)
T-tubules for calcium membrane
Striated 
Involuntary
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11
Q

What are the differences between cardiac and skeletal muscle?

A

Cardiac muscle is interdigitating, multi-nucleated that lie among membranes, and has intercalated disks
Calcium is needed for both

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12
Q

What allows for quick movement of calcium in cardiac muscle?

A

T tubules

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13
Q

Is the contraction longer in skeletal or cardiac muscle?

A

Cardiac

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14
Q

What are intercalated discs?

A

Cardiac muscle fibers are made up of many individual cells connected in series and in parallel with one another

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15
Q

What do the gap junctions in cardiac muscle allow?

A

Rapid diffusion of ions

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16
Q

What are the 3 types of cardiac muscle?

A

Atrial
Ventricular
Specialized excitatory and conductive muscle fibers

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17
Q

What is the resting membrane potential of cardiac muscle?

A

-85 to -95 millivolts

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18
Q

What is the action potential of cardiac muscle?

A

+105 millivolts

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19
Q

How long does the plateau last in ventricular muscle?

A

0.2-0.3 seconds

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20
Q

Is the plateau longer in cardiac muscle or skeletal muscle?

A

Cardiac

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21
Q

What does the presence of the plateau allow?

A

Allows ventricular contraction to last as much as 15 times as long in cardiac muscle as in skeletal muscle
IE: longer contractions

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22
Q

In cardiac muscle, what is the action potential caused by?

A

By opening two types of channels

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23
Q

What are the two channels that open and cause an action potential?

A
  1. Same voltage-activated fast Na+ channels as those in skeletal muscle
  2. L-type calcium channels (slow Ca++ channels) or sodium-calcium channels
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24
Q

What are the characteristics of the slow calcium channels?

A

Slower to open
Open longer
Both Ca++ and Na+ ions flow through channels to interior of cardiac muscle fiber

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25
Q

What does the influx of calcium via slow calcium channel maintain?

A

Prolonged period of depolarization, which causes a plateau

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26
Q

What does the calcium that enters during the plateau activate?

A

Muscle contractile process

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27
Q

What is phase 0 of a ventricular muscle action potential?

A

Fast Na+ channels open then slow Ca++ channels

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28
Q

What is phase 1 of a ventricular muscle action potential?

A

K+ channels open

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29
Q

What is phase 2 of a ventricular muscle action potential?

A

Ca++ channels open more

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30
Q

What is phase 3 of a ventricular muscle action potential?

A

K+ channels open more

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31
Q

What is phase 4 of a ventricular muscle action potential?

A

Resting membrane potential

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32
Q

How does the onset of an action potential affect K+ permeability?

A

Drastically decreases K+ permeability

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33
Q

What happens to K+ permeability when the influx of Na+ and Ca++ ceases?

A

Drastically increases K+ permeability

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34
Q

What is the refractory period?

A

Interval of time during which a normal cardiac impulse cannot re-excite an already excited area of cardiac muscle
during this time cardiac muscle cannot be re-excited

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35
Q

How long does the refractory period last in ventricles?

A

0.25-0.30 seconds

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36
Q

How long does the refractory period last in atria?

A

0.15 seconds

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37
Q

What is the absolute refractory period?

A

CANNOT CONTRACT AGAIN

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38
Q

What is the relative refractory period?

A

If you had a big enough charge to charge it, it could potentially contract again
It doesn’t go as high and is not the same shape as a regular charge

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39
Q

Does the refractory period help atria control rate?

A

Atria can be excited faster and before ventricle

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40
Q

What is a very important source of calcium?

A

Ca++ released from T tubules

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41
Q

What does T tubule Ca++ depend on?

A

Extracellular Ca++ concentrations

Plays a role in ability of heart to contract

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42
Q

How are T tubules in cardiac muscle compared to skeletal muscle?

A

T tubules are more extensive and larger

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43
Q

What does the larger T tubule size in cardiac muscle allow for?

A

Allows for calcium to get in and out quickly

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44
Q

What does calcium released from the sarcoplasmic reticulum into the sarcoplasm open?

A

Voltage-dependent Ca++ channels in membrane of T tubules

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45
Q

When is Ca++ released from the sarcoplasmic reticulum?

A

After stimulation of ryanodine receptors

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46
Q

What happens after calcium is released from sarcoplasmic reticulum?

A

Ca++ ions diffuse into myofibrils and catalyze chemical reactions that promote sliding of actin and myosin filaments along one another, which produces muscle contraction

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47
Q

Why does T tubule depend more strongly on extracellular calcium in cardiac muscle?

A

Because sarcoplasm is less well developed and doesn’t store enough Ca++ to provide full contraction

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48
Q

What binds to calcium in the sarcoplasmic reticulum?

A

Mucopolysaccharides

49
Q

What are the components of the cardiac cycle?

A

Systole
Diastole
EKG

50
Q

Define systole

A

Muscle stimulated by action potential and contracting

period of contraction

51
Q

Define diastole

A

Muscle reestablishing Na+/K+/Ca++ gradient and is relaxing

52
Q

What are the components of the EKG?

A

P wave
QRS complex
T wave

53
Q

What is the P wave?

A

Atrial wave

54
Q

What is the QRS wave?

A

Ventricular wave

55
Q

What is the T wave?

A

Ventricular repolarization

56
Q

What is a cardiac cycle?

A

Beginning of one heartbeat to the beginning of the next?

57
Q

What is each cardiac cycle initiated by?

A

Spontaneous generation of an action potential in sinus node

58
Q

LOOK AT CARDIAC CYCLE CHART

A

LOOK AT CARDIAC CYCLE CHART

59
Q

Is atrial pressure usually high?

A

No because it is only going to the lungs

60
Q

Is ventricular pressure usually high?

A

Yes because it has to circulate to the entire body

61
Q

What happens to the cardiac cycle during increased heart rate?

A

Duration of each cardiac cycle decreases

62
Q

What happens when systole and action potential decrease and diastole drastically decreases?

A

Means heart beating at a very fast rate doesn’t remain relaxed long enough to allow complete filling of cardiac chambers before next contraction

63
Q

What are the components of atrial press wave?

A

A wave
C wave
V wave

64
Q

What is the a wave of the atrial press wave?

A

Atrial contraction

65
Q

What is the c wave of the atrial press wave?

A

Ventricular contraction

AV valves bulge

66
Q

What causes the c wave of the atrial press wave?

A

Caused slightly by backflow of blood into atria at onset of ventricular contraction but mainly by AV bulging

67
Q

What is the v wave of the atrial press wave?

A

Flow of blood into atria

towards end of ventricular contraction

68
Q

What happens to pressure when AV is open and blood is entering and filling with blood?

A

Pressure increases

69
Q

What happens to pressure when AV valve closes?

A

Pressure increases more due to valve pushing up into atrium

70
Q

What happens to pressure when blood leaves ventricle?

A

Pressure decreases

71
Q

What is isovolumic relaxation?

A

Diastole

72
Q

What happens during diastole?

A

AV valves open
Rapid inflow of blood
Diastasis
Atrial systole

73
Q

What is diastasis during diastole?

A

Slow flow into ventricle

74
Q

What is atrial systole during diastole?

A

Extra blood in
This just follows P wave
Accounts for 25% of filling
Atria contracts and gives additional thrust to inflow of blood into ventricles

75
Q

What happens as ventricles get full towards end of diastole?

A

Flow slows down

76
Q

What happens if atria is not working?

A

You tend to get blood clots

Blood is just sitting in a pool and has nothing to do

77
Q

What is isovolumic contraction?

A

Systole

78
Q

What happens during systole?

A

AV valves close
Aortic value opens
Ejection phase
Aortic valve closes

79
Q

What causes the closure of AV valves?

A

Ventricular pressure is greater than atrial pressure

80
Q

What is the ejection phase?

A

Semilunar valves open and blood pours out of ventricles

81
Q

What is the only artery that has deoxygenated blood?

A

Pulmonary artery

82
Q

What is the only vein that has oxygenated blood?

A

Pulmonary vein

83
Q

When does aortic pressure start increasing?

A

During systole after the aortic valve opens

84
Q

When does aortic pressure start decreasing?

A

Toward end of the ejection phase

85
Q

What occurs after the aortic valve closes?

A

Incisura

86
Q

What is an incisura?

A

Notch in heart

87
Q

What causes an incisura?

A

Sudden cessation of back-flow toward left ventricle

Caused by a short period of back-flow of blood immediately before closure of vein

88
Q

Why does aortic pressure decrease slowly during diastole?

A

Because of elasticity of aorta plus blood flow to periphery

89
Q

During the latter part of the ejection phase, how can blood still leave the ventricle if pressure is higher in the aorta?

A

There is a certain amount of forward momentum

90
Q

What is the total energy of blood leaving the ventricle greater than?

A

Greater than the blood in the aorta

91
Q

What is the other name for ejection volume?

A

Stroke volume

92
Q

What is ejection volume?

A

How many mLs were ejected during that cycle

93
Q

What is the ejection fraction in a resting heat with no external influences?

A

60%

94
Q

How do you calculate cardiac output?

A

Heart rate X stroke volume

95
Q

Why do we measure the volumes of the heart? (ie. diastolic and systolic volume)

A

To evaluate how well heart is working

96
Q

LOOK AT EJECTION FRACTION CALCULATIONS

A

LOOK AT EJECTION FRACTION CALCULATIONS

97
Q

What is the valvular function?

A

To prevent back-flow

98
Q

Where are the AV valves preventing backflow at?

A

From ventricle to atria during systole

99
Q

Where are the semilunar valves preventing backflow at?

A

From aorta and pulmonary arteries into ventricles during diastole

100
Q

what are the chordae tendineae attached to?

A

AV valves

101
Q

What are the papillary muscles attached to?

A

Chordae tendineae

102
Q

When do the papillary muscles contract?

A

During systole and help prevent backflow

103
Q

How do the papillary muscles help prevent backflow?

A

Pull vanes of valves inward toward ventricles to prevent bulging too far backward toward atria during ventricular contraction

104
Q

How do the valves open?

A

Passively

105
Q

How does the smaller opening affect velocity in the aortic and pulmonary valves?

A

Velocity through aortic and pulmonary valves exceed that through the AV valves

106
Q

Are there chordae tendineae in semilunar valves?

A

No

107
Q

What is the muscular contraction of the heart?

A

Work

Pressure-volume work

108
Q

What is work output affected by?

A

Preload

Afterload

109
Q

What is preload?

A

End-diastolic pressure or return of blood to heart
tension in cardiac muscle before contraction
ventricular filling

110
Q

What is afterload?

A

Aortic pressure

pressure in artery that ventricle is pumping against

111
Q

What does the Frank-Starling Mechanism state?

A

Within physiological limits, the heart pumps all the blood that comes to it without excessive damming in the veins

112
Q

How does extra stretch on cardiac muscles affect actin and myosin filaments?

A

It causes filaments to interdigitate to a more optimal degree for force generation
Myocytes contract harder

113
Q

How does sympathetic stimulation affect the heart?

A

Increased heart rate and contractability

114
Q

How does the parasympathetic stimulation affect the heart?

A

Decreases heart rate markedly

Decreases cardiac contractility slightly

115
Q

How does fast heart rate affect cardiac output?

A

Decreases cardiac output because there is not enough time for heart to fill during diastole

116
Q

What is another name for fast heart rate?

A

Tachycardia

117
Q

What does excess K+ cause?

A

Decreases contractility

can block conduction of cardiac impulse from atria to ventricle through AV bundle

118
Q

What does excess Ca++ cause?

A

Spastic contraction

prolonged state of contraction

119
Q

What does low Ca++ cause?

A

Cardiac dilation

Not enough contraction

Physiology (70 decks)

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