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Physiology > Cardiac Muscle; The Heart As A Pump And Function Of The Heart Valves > Flashcards

Cardiac Muscle; The Heart As A Pump And Function Of The Heart Valves Flashcards

0
Q

Atrial and ventricular types of muscle contract like skeletal muscle but…

A

With a longer duration

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1
Q

What are the 3 types of cardiac muscles?

A
  1. Atrial
  2. Ventricular
  3. Specialized excitatory and conductive muscle fibers
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3
Q

Describe the specialized excitatory and conductive muscle fibers.

A
  1. Contract feebly
  2. With few contractile fibers
  3. With automatic rhythmical discharge via the action potential
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4
Q

(Blood transfer)

Right heart : 1 :: left heart : 2

A
  1. Blood to lungs

2. Blood to peripheral organs

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5
Q

It is a weak primer pump for the ventricle

A

Atrium

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6
Q

Ventricles propels blood through (circulation type):

  1. Right ventricle
  2. Left ventricle
A
  1. Pulmonary circulation

2. Peripheral circulation

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7
Q

Similarities of cardiac muscles with skeletal muscles:

A
  1. Striated
  2. With typical myofibrils (actin + myosin)*
  • almost identical
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8
Q

At each intercalated disc the cell membranes fuse which form a permeable communicating junction that allow rapid diffusion of ions called:

A

Gap junctions

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9
Q

The heart is composed of 2 syncytiums:

A
  1. Atrial syncytium

2. Ventricular syncytium

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10
Q

Intracellular potential rises from a very negative value, (1), between beats to a slightly positive value, (2), during each beat.

A
  1. -85 millivolts

2. +20 millivolts

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11
Q

After the initial spike, the membrane remains 1, exhibiting a plateau followed at the end of the plateau by abrupt 2.

A
  1. Depolarization

2. Repolarization

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12
Q

Its presence causes ventricular contraction to last as much as 15 times as long in cardiac muscle as in skeletal muscle:

A

Plateau in the action potential

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13
Q

Action potential of skeletal muscle is caused by sudden opening of large numbers of (1) that allow tremendous numbers of sodium ions to enter the skeletal fiber from the (2).

A
  1. Fast sodium channels

2. Extracellular fluid

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14
Q

Channels that remain open for only a few thousandths of a second and then abruptly close:

A

Fast channels

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15
Q

At the closure of fast channels, (1) occurs, and the action potential is over within another thousandth of a second or so.

A

Repolarization

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16
Q

In cardiac muscle, the action potential is caused by opening of two types of channels:

A
  1. Fast sodium channels
  2. Slow calcium-sodium channels*

Remain open for several tenths of a second thus large quantity of calcium and sodium ions flows through and maintains a prolonged depolarization

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17
Q

Where calcium ions are derived for:

  1. Cardiac muscle contractile process
  2. Skeletal muscle contractile process
A
  1. Calcium ions that enter during plateau phase

2. Intracellular sarcoplasmic reticulum

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18
Q

Immediately after the onset of the action potential, the permeability of the cardiac muscle membrane for potassium ions…

A

Decreases about fivefold

*This does not happen in skeletal muscle.

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19
Q

Decreased potassium permeability may result from…

A

The excess calcium influx

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20
Q

Decreased potassium permeability decreases (1) during the action potential plateau and thereby prevents (2).

A
  1. Outflow of positively charged ions

2. early return of action potential voltage to its resting level

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21
Q

Are dark areas crossing the cardiac muscle fibers and are actually cell membranes that separate individual cardiac muscle cells.

A

Intercalated discs

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22
Q

Refractory period of the heart is the interval of time during which…

A

A normal cardiac impulse cannot re-excite an already excited area

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23
Q

What is relative refractory period?

A

Period during which the muscle is more difficult to excite but can still be excited by a very strong excitatory signal.

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24
Q

The refractory period of atrial muscle is (shorter / longer) than that for the ventricles.

A

Shorter

0.15 sec : atria :: 0.25-0.30 sec : ventricles

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25
Q

Refers to the mechanism by which the action potential causes the myofibrils of muscle to contract.

A

Excitation-contraction coupling

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26
Q

When an action potential passes over the cardiac muscle membrane, the action potential spreads to the (interior / exterior) of the cardiac muscle fiber along the membranes of the transverse (T) tubules.

A

Interior

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27
Q

The T tubule action potential act on the membranes of the (1) to cause release of calcium ions into the (2) from the (3).

A
  1. Longitudinal sarcoplasmic tubules
  2. Muscle sarcoplasm
  3. Sarcoplasmic reticulum
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28
Q

Catalyze the chemical reaction s that promote sliding of the actin and myosin filaments – produces muscle contraction.

A

Diffusion of calcium ions into the myofibrils

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29
Q

True or false…

The mechanism of excitation-contraction coupling for cardiac muscle is the same as that for skeletal muscle.

A

False

There are similarities but the cardiac muscle has a second effect that is different.

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30
Q

Calcium ions that are released into the sarcoplasm from the cisternae of the sarcoplasmic reticulum, calcium ions also diffuse into the sarcoplasm from the…

A

T tubules themselves during action potential which opens voltage-dependent calcium channels in the membrane of the t tubule.

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31
Q

Calcium entering the cell activates (1) , in the (2) membrane, triggering the release of calcium into the (3).

A
  1. Calcium release channels aka ryanodine receptor channels
  2. Sarcoplasmic reticulum
  3. Sarcoplasm
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32
Q

Calcium ions in the sarcoplasm interact with (1) to initiate cross-bridge formation and (2).

A
  1. Troponin

2. Contraction

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33
Q

Without the calcium from the T tubules, the strength of cardiac muscle contraction would be reduced considerably because (1) and (2).

A
  1. The sarcoplasmic reticulum of cardiac muscle is less well developed than that of skeletal muscle
  2. Does not store enough calcium to provide full contraction
34
Q

Inside the T tubules is a large quantity of (1) that are (2) charged and bind an abundant store of calcium ions.

A
  1. Mucopolysaccharides

2. Electronegatively

35
Q

Strength of cardiac muscle depends on the…

A

Concentration of calcium ions in the extracellular fluids.

36
Q

TRUE or FALSE

A heart placed in a calcium free solution will not stop beating.

A

False, it will quickly stop beating.

because the openings of the T tubules pass directly through the cardiac muscle cell membrane into the extracellular spaces surrounding the cells, allowing the same extracellular fluid that is in the cardiac muscle interstitium to prelocate through the T tubules as well.

37
Q

The quantity of calcium ions in the T tubule system depends to a great extent on the…

A

… Extracellular fluid calcium concentration

38
Q

TRUE or FALSE
The strength of skeletal muscle contraction is largely affected by moderate changes in extracellular fluid calcium concentration.

A

False, they are hardly affected.

…because skeletal muscle contraction is caused by almost entirely by calcium ions released from the sarcoplasmic reticulum inside the skeletal muscle fiber

39
Q

At the end of the plateau of the cardiac action potential,
The (1) of calcium ions to the interior of the muscle fiber is cut off
The calcium ions in the (2) are rapidly pumped back out into both the (3) and (4).

A
  1. Influx
  2. Sarcoplasm
    3&4. Sarcoplasmic reticulum & T tubule-extracellular fluid space
40
Q

Transport of calcium back into the sarcoplasmic reticulum is by a (1) and calcium removed from the cell by a (2). The sodium that enters the cell during this exchange is transported out of the cell by the (3). Results into the ceasing of (4).

A
  1. Calcium-ATPase pump
  2. Sodium-calcium exchanger
  3. Sodium-potassium ATPase pump
  4. Contraction
41
Q

Events that occur from the beginning of one heartbeat to the beginning of the next are called (1) which are generated by spontaneous generation of action potential in the (2).

A
  1. Cardiac cycle

2. Sinus node

42
Q

Cardiac cycle

Period of relaxation : (1) :: period of contraction : (2)

A
  1. Diastole

2. Systole

43
Q

Increase in heart rate leads to (increase / decrease) of cardiac cycle. The duration of the action potential and period of contraction (increase / decrease).

A
  1. Decrease

2. Decrease

44
Q

Heart beating at a (very fast / very slow rate) does not remain (relaxed / contracted) long enough to allow complete filling of the cardiac chambers before the next contraction.

A
  1. Very fast

2. Relaxed

45
Q

Is caused by a spread of depolarization through the atria.

A

P wave

46
Q

Three minor pressure elevations in the atrial pressure curve:

  1. Caused by atrial contraction
  2. Occurs when the ventricles begin to contract
  3. Occurs toward the end of ventricular contraction
A
  1. A wave
  2. C wave
  3. V wave
47
Q

During ventricular systole, large amounts of blood accumulate in the (right & left atria / right & left ventricle) because of the closed (2).

A
  1. R & L atria

2. A-V valves

48
Q

As soon as systole is over and the ventricular pressures (fall / rise) to their diastolic values, the moderately increased pressures in the atria during ventricular (diastole / systole) immediately pushes the A-V valves open and allow blood to flow rapidly into the (atria / ventricles).

A
  1. Fall
  2. Systole
  3. Ventricles
49
Q

Period of rapid filling last for about the (first / middle / last) third of diastole.

A

First

50
Q

During the (first / middle / last) third of diastole, only a small amount of blood normally flows into the ventricles.

A

Middle

51
Q

During the (first / middle / last) third of diastole, the atria contract and give an additional thrust to the inflow of blood into the ventricles.

A

Last

52
Q

Immediately after ventricular contraction begins, the ventricular pressure (rises / falls) abruptly causing the A-V valves to (open / close).

A
  1. Rise

2. Close

53
Q

Period of contraction wherein contraction is occurring in the ventricles, but there is no emptying is called:

A

Isovolumetric contraction

54
Q

In isovolumic or isometric contraction: the tension is (increasing / decreasing) in the muscle but little or no (lengthening / shortening) of the muscle fibers occurring.

A
  1. Increasing

2. Shortening

55
Q

When the left ventricular pressure rises slightly above (80 / 20) mmHg, the ventricular pressures push the semilunar valves open.

A

80 mm Hg

56
Q

Percent of blood emptying during:

  1. Period of rapid ejection (1st third)
  2. Period of slow ejection (next two thirds)
A
  1. 70%

2. 30%

57
Q

At the end of (diastole / systole), ventricular relaxation begins suddenly allowing the right and left intraventricular pressure to decrease rapidly.

A

Systole

58
Q

After pushing blood back to the ventricles due to elevated pressure; ventricular muscle continues to relax, even though the ventricular volume does not change giving rise to the:

A

Period of isovolumic or isometric relaxation.

59
Q

End-diastolic volume: (1)
Stroke volume output: (2)
End-systolic volume: (3)
Ejection fraction: (4)

A
  1. About 110-120 ml
  2. About 70 ml
  3. About 40-50 ml
  4. Usually 60% of the end-diastolic volume
60
Q

Prevent backflow of blood from the ventricles to the atria during systole:

A

Atrioventricular valves

61
Q

Prevent backflow from the aorta and pulmonary arteries into the ventricle during diastole:

A

Semilunar valves

62
Q

Mitral and aortic valves close and open passively that is, they (open / close) when a backward pressure gradient pushes blood backward, and they (open / close) when a forward pressure gradient forces blood in the forward direction.

A
  1. Close

2. Open

63
Q

Papillary muscles contract when the ventricular walls (contract / relax) but they don’t help the valves to (open / close). They pull the vanes of the valves inward toward the (atria / ventricles) to prevent bulging.

A
  1. Contract

2. Close

64
Q

If a chorda tendinae becomes ruptured or if one of the papillary muscles become paralyzed, the valves:

A

Bulges far backward during ventricular contraction

65
Q

The aortic and pulmonary artery semilunar valves function quite differently from the A-V valves. High pressures in the arteries at the end of systole cause the (pulmonary / semilunar) valves to snap to the closed position

A

Semilunar

66
Q

Because of the (bigger / smaller) openings,the velocity of blood ejection through the aortic and pulmonary valves is far greater than that through the much (larger / smaller) A-V valves.

A
  1. Smaller

2. Larger

67
Q

The A-V valves are supported by the (1), which is not true for the (2) valves.

A
  1. Chorda tendineae

2. Semilunar

68
Q

When the left ventricle contracts, the ventricular pressure (increases / decreases) rapidly until the aortic valve opens.

A

Increases

69
Q

TRUE or FALSE
Incisura is caused by a short period of backward flow of blood immediately after closure of the valve, followed by a cessation of the backflow.

A

False, its before the closure of the valves.

70
Q

After the aortic valve has closed, the pressure in the aorta decreases slowly throughout (diastole / systole) because the blood stored in the distended elastic arteries flows continually through the peripheral vessels back to the veins.

A

Diastole

71
Q

Is the amount of energy that the heart converts to work during each heartbeat while pumping blood into arteries.

A

Stroke work output of the heart

72
Q

Is the total amount of energy converted to work in 1 minute; is equal to the stroke work output times the heart rate per minute.

A

Minute work output

73
Q

Intrinsic ability of the heart to adapt to increasing volumes of inflowing blood:

A

Frank-Starling mechanism of the heart

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

74
Q

The vagal fibers are distributed mainly to the (atria / ventricles) and not much to the (atria / ventricles), where the power contraction of the heart occurs.

A
  1. Atria

2. Ventricles

75
Q

Excess amount of (1) in the extracellular fluids causes the heart to become dilated and flaccid and also slows the heart rate.

A

Potassium

Large quantities can also block conduction of the cardiac impulse from the atria to the ventricles through the A-V bundle.

76
Q

High potassium concentration in the extracellular fluid decreases the (1) in the cardiac muscle fibers.

A

Resting membrane potentials

High extracellular potassium concentration partially depolarizes the cell membrane, causing the membrane potential to be less negative.

77
Q

Excess of (1) ions causes the heart to go toward spastic contraction.

A

Calcium

Deficiency causes cardiac flacidity.

78
Q

(1) of the heart often is enhanced temporarily by a moderate increase in temperature, as occurs during body exercise.

A

Contractile strength

But prolonged elevation of temperature exhausts the metabolic systems of the heart and eventually causes weakness.

79
Q

TRUE or FALSE
Increasing the arterial pressure in the aorta does not decrease the cardiac output until the mean arterial pressure rises above about the 160 mm.

A

True

80
Q

TRUE or FALSE
During normal function of the heart at normal systolic pressures (20 to 80 mm Hg), the cardiac output is determined almost entirely by the ease of blood flow through the body’s tissues, which in turn controls the venous return of blood to the heart.

A

False, normal systolic arterial pressure is from 80-140 mm Hg.

Physiology (3 decks)

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