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Physiology I > Cardiac muscle (exam 1) > Flashcards

Cardiac muscle (exam 1) Flashcards

1
Q

Which of the following represents the first thing that happens after Ach binds to the ligand-gated channels on the Sarcolemma

A

An end-plate potential is created on the muscle fiber (local potential)

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2
Q

The resting potential of -85mV is a characteristic of what phase of the fast cardiac AP

A

Stage 4

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3
Q

name the characteristics of cardiac muscle

A

Sarcomeric arrangement (striated), mono nucleated, central nuclei, syncytium, intercalated discs, cells may branch

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4
Q

Are cardiac mono nucleated or multinucleated

A

Mononucleated

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5
Q

Where is the nuclei of cardiac muscle

A

Centrally located

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6
Q

what is the average AP in ventricular AP

A

105mV

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7
Q

What is the range of AP in ventricular cardiac muscles

A

-85-+20mV

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8
Q

How long does the Ventricular fiber remain deploarized

A

about 0.2 seconds

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9
Q

What are purkinje fibers derived from

A

Modified cardiac muscle cells

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10
Q

Where are the T-Tubules in skeletal muscle fibers located

A

At the ends of the thick filaments, where the A and I filaments meet

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11
Q

Where are the T-Tubules in Cardiac Muscle fibers located

A

Found along the z-line

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12
Q

How many T-tubules are there per Sarcromere in skeletal muscle cells

A

2

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13
Q

How many T-Tubules are there per sarcromere in cardiac muscles

A

1

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14
Q

in what type of muscle are triads formed and what composes them

A

Triads are formed in skeletal muscles, composed of two T-tubules and one SR

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15
Q

In what type of muscle are diads formed and what composes them

A

Cardiac muscle, One T-Tubule and one SR

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16
Q

Is the SR more extensive in skeletal muscle or cardiac muscle

A

The SR is more extensive in Skeletal muscle

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17
Q

What is a syncytium

A

a single cell or cytoplasmic mass containing several nuclei, formed by the fusion of cells or by division of nuclei

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18
Q

What types of muscle cells form a syncytium

A

Cardiac muscle cells

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19
Q

Where are fast cardiac muscle cells found

A

Atria, ventricles, and conduction system and Purkinje fibers (which are non-contractile)

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20
Q

Where are slow cardiac muscle cells found

A

SA and AV nodes

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21
Q

What do Purkinje fibers not have in common with other fast AP muscle cells

A

Purkinje fibers are not contractile while the Atria and ventricles are

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22
Q

What is the amplitude of the fast AP cardiac tissue

A

about 100mV

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23
Q

What is the amplitude of the slow AP cardiac tissue

A

Low amplitude (60mV)

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24
Q

What leads to the automatic depolarization of the slow cardiac tissue

A

They possess leak ion channels

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25
Q

Do slow cardiac muscle cells depolarize automatically

A

Yes

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26
Q

What is the resting potential phase of fast action cardiac muscles

A

Phase 4

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27
Q

What is the rapid depolarization phase of fast action potential

A

Phase 0

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28
Q

What is the initial, incomplete repolarization phase of fast AP cardiac muscles

A

Phase 1

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29
Q

What is the plateau phase of fast acting cardiac muscles

A

Phase 2

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30
Q

What is the Repolarization phase of fast cardiac muscles

A

Phase 3

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31
Q

What ions are responsible for the fast action potentials of cardiac muscle cells

A

Potassium, sodium, and calcium conductance

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32
Q

What factors increase the rate of conduction velocity of cardiac muscles

A

Greater AP amplitude, more rapid rate of rise of phase 0, larger cell diameter

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33
Q

An increase in cell diameter would have what effect on the conduction velocity of cardiac muscle

A

It would increase the speed of velocity

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34
Q

Slow cardiac muscle AP does not have fast sodium ion gates

A

True

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35
Q

The upstroke of action potential is due to what ion in slow cardiac muscles

A

Calcium

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36
Q

What is the resting phase of slow cardiac muscle

A

-60mV

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37
Q

Do slow cardiac cells have a smaller or larger amplitude than that for fast action cardiac cells

A

Smaller

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38
Q

At what phase do the SA and AV nodal tissue spontaneously depolarize

A

Phase 4 (resting phase)

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39
Q

Name three basic characteristics of fast type contractile myocytes

A

large diameter, high amplitude, rapid onset of AP

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40
Q

name three characteristics of slow type non-contractile myocytes

A

Small diameter, low amplitude, and slow rate of depolarization

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41
Q

Which type of non-contractile myocyte has a small diameter

A

Slow non-contractile

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42
Q

Purkinje fibers would have what size of diameter

A

Very large

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43
Q

Which have a larger diameter fast non-contractile myocytes or fast contractile myocytes

A

Fast non-contractile

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44
Q

describe the characteristics of fast type non-contractile myocytes

A

Very large diameter, very rapid upstroke

45
Q

What causes the AP for Ventricular fibers

A

Fast sodium channels (as in skeletal muscle) and also slow calcium-sodium channels (fast sodium channels are responsible for the initial spike

46
Q

What is responsible for the initial spike of Ventricular fibers

A

Fast sodium channels

47
Q

What is largely responsible for the calcium necessary in cardiac muscles for electro-mechanical coupling

A

Dihydropyridine Receptors (DHP) and ryanodine receptors

48
Q

what are the L-Type voltage-dependent calcium channels in T-Tubles called

A

Dihydropyridine receptors (DHP)

49
Q

what would the diameter size of a ventricular myocyte be

A

Large

50
Q

Calcium influx is directly more affected by DHP receptors in skeletal or cardiac muscle

A

Cardiac

51
Q

What is the absolute refractory period

A

The period when it is impossible to generate another AP

52
Q

What is the relative Refractory period

A

The period when a stronger than normal stimulus can generate an AP

53
Q

What would shorten the refractory period

A

Gates return to their phase 4 stage faster (resting phase)

54
Q

What would lengthen the refractory period

A

Ion channels and gates take longer to get to their phase 4 stage

55
Q

What node depolarizes more rapidly than the others

A

SA node

56
Q

What node is referred to as the pacemaker

A

SA node

57
Q

The rate of depolarization of the heart determines what

A

The rhythmicity

58
Q

what tissues will gradually depolarize during Phase 4 in cardiac muscle

A

SA and AV nodes, as well as the perkinje fibers

59
Q

what happens at the action potential plateau in cardiac muscle

A

Sodium channels close rapidly, but calcium channels open slowly and stay open for a longer period of time
also a delay in the potassium channels opening
the large concentration of both calcium ions and potassium ions is responsible for the plateau

60
Q

Are there fewer calcium-induced calcium release channels in cardiac muscle compared to skeletal muscle

A

Yes, allow for fine control over the sarcoplasmic calcium concentration and contractility

61
Q

Relaxation of Cardiac muscle is a result of what two transporters

A

SERCA and Sodium-calcium exchanger in sarcolemma

62
Q

What is SERCA stimulated by

A

Phosphorylation via an integral SR protein called phospholambian which, when phosphorylated, reduces its ability to inhibit the SERCA pump

63
Q

When does SERCA return calcium to the SR

A

During Diastole

64
Q

When does the Aortic valve close

A

When the pressure of the left ventricle equals pressure in the aorta

65
Q

What are the primer pumps

A

The Atria

66
Q

About what percent of blood flows form the atria to the ventricles before the atria contract

A

80%

67
Q

About percent of blood flow in the ventricles is secondary to atrial contraction

A

20%

68
Q

The AV values are closed during what

A

Ventricular Systole

69
Q

When do the AV valves open

A

At the end of ventricular systole caucus of increased pressure in Atria

70
Q

what third of diastole is the period of rapid filling

A

The first third

71
Q

What is diastasis

A

The middle third of diastole

- a small amount of blood flows into the ventricles representing blood that continues to flow into atria during diastole

72
Q

When might diastasis be lost

A

During periods of increased heart rate

73
Q

What happens in the last third of diastole

A

The atria contract to push last 20% of blood into the ventricles

74
Q

When is the isometric (isovolumic) contraction

A

ventricles contract pressure rises causing the A-V valves to close. Than an additional 0.02 to 0.03 seconds is required for ventricle to build up sufficient pressure to push the semilunar valves open.

75
Q

Describe the period of rapid ejection

A

occurs when the left ventricular pressure is a little above 80mm Hg and right ventricular is slightly above 8mm Hg

semilunar valves open

about 70% of blood in ventricle is ejected

occurs during the first 3rd of ejection

76
Q

During what 3rd is the period of rapid ejection

A

the 1st third of ejection

77
Q

What percent of the ventricular blood is ejected during the period of rapid ejection

A

70%

78
Q

What 3rd does the period of slow ejection occur

A

the last 2 thirds of ejection

79
Q

how much blood is ejected during the period of slow ejection

A

30% of blood is ejected from the ventricles

80
Q

Frank-Starling Law

A

The greater the heart muscle is stretched during filling the greater the force of contraction and the greater the quantity of blood pumped into the aorta

  • the stretching of the cardiac muscle brings the actin and myosin filaments to a more nearly optimal degree of overlap of force generation
81
Q

what is the equation for ejection fraction

A

SV/EDV

82
Q

How can stoke volume be increased

A

increasing EDV ( End-diastolic-volume) and decreasing ESV (end-systolic volume)

83
Q

What is stroke volume

A

The difference between EDV and ESV

84
Q

What is the mean velocity of blood in the proximal aorta

A

40cm/s

85
Q

What is the range of velocity in the proximal aorta

A

120 cm/s (during systole) to negative value before aortic valves close in diastole

86
Q

Why is the forward flow of distal aorta and arteries continuous

A

the elastane of vessel walls during diastole

87
Q

The rate of blood flow to each tissue is

A

usually precisely controlled in relation to tissue need

88
Q

Active tissues may need how much more blood flow than ones at rest

A

20 to 30 times more

89
Q

Cardiac output cannot exceed what

A

407 times greater than when at rest

90
Q

What monitors each tissues blood need

A

Microvessels

91
Q

Needs of tissues acts directly on what

A

Local blood vessels

92
Q

_______ and _________ also help control tissue blood flow

A

nervous control and hormones

93
Q

at normal heart rate of 72 beats per minute the systole comprises of about _____

A

0.4 of the entire cardiac cycle

94
Q

what is the pressure in the left ventricle at the start of phase I

A

Phase 1 is the period of filling and the pressure is about 2 to 3 mm Hg. There is about 50 milliliters blood from the en systolic volume

95
Q

How much does the pressure in the left ventricle change by the end of phase I

A

Phase one is the period of filling and the pressure changes from 2-3mm Hg to 5-7 mm Hg. This is due to the increase of blood from 50 milliliters to 120 milliliters

96
Q

What is the pressure in the left ventricle at the beginning of phase II

A

120mm Hg

97
Q

What is happening in Phase II

A

Isovolumic contraction

98
Q

What is the pressure in the left ventricle at the end of phase II

A

80mm Hg

99
Q

What depicted in phase III

A

Period of ejection

100
Q

Why does pressure rise in the ventricle during phase three

A

The ventricle is still contracting

101
Q

What marks the beginning of phase III

A

The aortic valve opens

102
Q

What marks the beginning of Phase IV

A

The aortic valve closes

103
Q

when the heart pumps large quantities of blood what happens to the area of work diagram

A

it becomes much larger. it will extend faster to the right because the ventricle fills with more blood during diastole, it rises much higher because the ventricle contracts with greater pressure, and it usually extends farther to the left because the ventricle contracts to a smaller volume. especially if stimulated by the sympathetic nervous system

104
Q

What is the preload in cardiac contraction

A

Is end diastolic volume and is related to right atrial pressure

105
Q

What is the after load in cardiac contraction

A

the pressure in the aorta leading from the ventricle. or even the resistance to circulation

106
Q

an increase in preload in the left ventricle would cause what

A

Pre-load is directly associated with the end diastolic volume if you increased the EDV then the SV would increase
as would the pressure curve
this would lead to increased blood volume and decreased venous capacity

107
Q

Increased after load would result in what in the left ventricle

A

Increased after load would mean that the aortic valve has an increased pressure this means that the heart is having to work against a higher pressure gradient thus we would have an increased end-systolic volume, thus a smaller SV, and decreased pressure loop

108
Q

What affect would the increase in heart contractility have on the end-styolic volume

A

it would decrease it. and thus increase stroke volume

109
Q

Right atrial pressure and cardiac output increases with what innervation

A

sympathetic

Physiology I (8 decks)

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