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Flashcards in Cardiac muscle (exam 1) Deck (109):
1

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

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

2

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

Stage 4

3

name the characteristics of cardiac muscle

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

4

Are cardiac mono nucleated or multinucleated

Mononucleated

5

Where is the nuclei of cardiac muscle

Centrally located

6

what is the average AP in ventricular AP

105mV

7

What is the range of AP in ventricular cardiac muscles

-85-+20mV

8

How long does the Ventricular fiber remain deploarized

about 0.2 seconds

9

What are purkinje fibers derived from

Modified cardiac muscle cells

10

Where are the T-Tubules in skeletal muscle fibers located

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

11

Where are the T-Tubules in Cardiac Muscle fibers located

Found along the z-line

12

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

2

13

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

1

14

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

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

15

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

Cardiac muscle, One T-Tubule and one SR

16

Is the SR more extensive in skeletal muscle or cardiac muscle

The SR is more extensive in Skeletal muscle

17

What is a syncytium

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

18

What types of muscle cells form a syncytium

Cardiac muscle cells

19

Where are fast cardiac muscle cells found

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

20

Where are slow cardiac muscle cells found

SA and AV nodes

21

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

Purkinje fibers are not contractile while the Atria and ventricles are

22

What is the amplitude of the fast AP cardiac tissue

about 100mV

23

What is the amplitude of the slow AP cardiac tissue

Low amplitude (60mV)

24

What leads to the automatic depolarization of the slow cardiac tissue

They possess leak ion channels

25

Do slow cardiac muscle cells depolarize automatically

Yes

26

What is the resting potential phase of fast action cardiac muscles

Phase 4

27

What is the rapid depolarization phase of fast action potential

Phase 0

28

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

Phase 1

29

What is the plateau phase of fast acting cardiac muscles

Phase 2

30

What is the Repolarization phase of fast cardiac muscles

Phase 3

31

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

Potassium, sodium, and calcium conductance

32

What factors increase the rate of conduction velocity of cardiac muscles

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

33

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

It would increase the speed of velocity

34

Slow cardiac muscle AP does not have fast sodium ion gates

True

35

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

Calcium

36

What is the resting phase of slow cardiac muscle

-60mV

37

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

Smaller

38

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

Phase 4 (resting phase)

39

Name three basic characteristics of fast type contractile myocytes

large diameter, high amplitude, rapid onset of AP

40

name three characteristics of slow type non-contractile myocytes

Small diameter, low amplitude, and slow rate of depolarization

41

Which type of non-contractile myocyte has a small diameter

Slow non-contractile

42

Purkinje fibers would have what size of diameter

Very large

43

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

Fast non-contractile

44

describe the characteristics of fast type non-contractile myocytes

Very large diameter, very rapid upstroke

45

What causes the AP for Ventricular fibers

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

46

What is responsible for the initial spike of Ventricular fibers

Fast sodium channels

47

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

Dihydropyridine Receptors (DHP) and ryanodine receptors

48

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

Dihydropyridine receptors (DHP)

49

what would the diameter size of a ventricular myocyte be

Large

50

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

Cardiac

51

What is the absolute refractory period

The period when it is impossible to generate another AP

52

What is the relative Refractory period

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

53

What would shorten the refractory period

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

54

What would lengthen the refractory period

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

55

What node depolarizes more rapidly than the others

SA node

56

What node is referred to as the pacemaker

SA node

57

The rate of depolarization of the heart determines what

The rhythmicity

58

what tissues will gradually depolarize during Phase 4 in cardiac muscle

SA and AV nodes, as well as the perkinje fibers

59

what happens at the action potential plateau in cardiac muscle

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

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

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

61

Relaxation of Cardiac muscle is a result of what two transporters

SERCA and Sodium-calcium exchanger in sarcolemma

62

What is SERCA stimulated by

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

63

When does SERCA return calcium to the SR

During Diastole

64

When does the Aortic valve close

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

65

What are the primer pumps

The Atria

66

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

80%

67

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

20%

68

The AV values are closed during what

Ventricular Systole

69

When do the AV valves open

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

70

what third of diastole is the period of rapid filling

The first third

71

What is diastasis

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

When might diastasis be lost

During periods of increased heart rate

73

What happens in the last third of diastole

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

74

When is the isometric (isovolumic) contraction

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

Describe the period of rapid ejection

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

During what 3rd is the period of rapid ejection

the 1st third of ejection

77

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

70%

78

What 3rd does the period of slow ejection occur

the last 2 thirds of ejection

79

how much blood is ejected during the period of slow ejection

30% of blood is ejected from the ventricles

80

Frank-Starling Law

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

what is the equation for ejection fraction

SV/EDV

82

How can stoke volume be increased

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

83

What is stroke volume

The difference between EDV and ESV

84

What is the mean velocity of blood in the proximal aorta

40cm/s

85

What is the range of velocity in the proximal aorta

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

86

Why is the forward flow of distal aorta and arteries continuous

the elastane of vessel walls during diastole

87

The rate of blood flow to each tissue is

usually precisely controlled in relation to tissue need

88

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

20 to 30 times more

89

Cardiac output cannot exceed what

407 times greater than when at rest

90

What monitors each tissues blood need

Microvessels

91

Needs of tissues acts directly on what

Local blood vessels

92

_______ and _________ also help control tissue blood flow

nervous control and hormones

93

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

0.4 of the entire cardiac cycle

94

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

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

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

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

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

120mm Hg

97

What is happening in Phase II

Isovolumic contraction

98

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

80mm Hg

99

What depicted in phase III

Period of ejection

100

Why does pressure rise in the ventricle during phase three

The ventricle is still contracting

101

What marks the beginning of phase III

The aortic valve opens

102

What marks the beginning of Phase IV

The aortic valve closes

103

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

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

What is the preload in cardiac contraction

Is end diastolic volume and is related to right atrial pressure

105

What is the after load in cardiac contraction

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

106

an increase in preload in the left ventricle would cause what

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

Increased after load would result in what in the left ventricle

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

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

it would decrease it. and thus increase stroke volume

109

Right atrial pressure and cardiac output increases with what innervation

sympathetic