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
1
Q
What are the 3 types of cardiac muscles?
A
- Atrial
- Ventricular
- Specialized excitatory and conductive muscle fibers
3
Q
Describe the specialized excitatory and conductive muscle fibers.
A
- Contract feebly
- With few contractile fibers
- With automatic rhythmical discharge via the action potential
4
Q
(Blood transfer)
Right heart : 1 :: left heart : 2
A
- Blood to lungs
2. Blood to peripheral organs
5
Q
It is a weak primer pump for the ventricle
A
Atrium
6
Q
Ventricles propels blood through (circulation type):
- Right ventricle
- Left ventricle
A
- Pulmonary circulation
2. Peripheral circulation
7
Q
Similarities of cardiac muscles with skeletal muscles:
A
- Striated
- With typical myofibrils (actin + myosin)*
- almost identical
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
9
Q
The heart is composed of 2 syncytiums:
A
- Atrial syncytium
2. Ventricular syncytium
10
Q
Intracellular potential rises from a very negative value, (1), between beats to a slightly positive value, (2), during each beat.
A
- -85 millivolts
2. +20 millivolts
11
Q
After the initial spike, the membrane remains 1, exhibiting a plateau followed at the end of the plateau by abrupt 2.
A
- Depolarization
2. Repolarization
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
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
- Fast sodium channels
2. Extracellular fluid
14
Q
Channels that remain open for only a few thousandths of a second and then abruptly close:
A
Fast channels
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
16
Q
In cardiac muscle, the action potential is caused by opening of two types of channels:
A
- Fast sodium channels
- 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
17
Q
Where calcium ions are derived for:
- Cardiac muscle contractile process
- Skeletal muscle contractile process
A
- Calcium ions that enter during plateau phase
2. Intracellular sarcoplasmic reticulum
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.
19
Q
Decreased potassium permeability may result from…
A
The excess calcium influx
20
Q
Decreased potassium permeability decreases (1) during the action potential plateau and thereby prevents (2).
A
- Outflow of positively charged ions
2. early return of action potential voltage to its resting level
21
Q
Are dark areas crossing the cardiac muscle fibers and are actually cell membranes that separate individual cardiac muscle cells.
A
Intercalated discs
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
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.
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
25
Refers to the mechanism by which the action potential causes the myofibrils of muscle to contract.
Excitation-contraction coupling
26
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.
Interior
27
The T tubule action potential act on the membranes of the (1) to cause release of calcium ions into the (2) from the (3).
1. Longitudinal sarcoplasmic tubules
2. Muscle sarcoplasm
3. Sarcoplasmic reticulum
28
Catalyze the chemical reaction s that promote sliding of the actin and myosin filaments -- produces muscle contraction.
Diffusion of calcium ions into the myofibrils
29
True or false...
| The mechanism of excitation-contraction coupling for cardiac muscle is the same as that for skeletal muscle.
False
| There are similarities but the cardiac muscle has a second effect that is different.
30
Calcium ions that are released into the sarcoplasm from the cisternae of the sarcoplasmic reticulum, calcium ions also diffuse into the sarcoplasm from the...
T tubules themselves during action potential which opens voltage-dependent calcium channels in the membrane of the t tubule.
31
Calcium entering the cell activates (1) , in the (2) membrane, triggering the release of calcium into the (3).
1. Calcium release channels aka ryanodine receptor channels
2. Sarcoplasmic reticulum
3. Sarcoplasm
32
Calcium ions in the sarcoplasm interact with (1) to initiate cross-bridge formation and (2).
1. Troponin
| 2. Contraction
33
Without the calcium from the T tubules, the strength of cardiac muscle contraction would be reduced considerably because (1) and (2).
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
Inside the T tubules is a large quantity of (1) that are (2) charged and bind an abundant store of calcium ions.
1. Mucopolysaccharides
| 2. Electronegatively
35
Strength of cardiac muscle depends on the...
Concentration of calcium ions in the extracellular fluids.
36
TRUE or FALSE
| A heart placed in a calcium free solution will not stop beating.
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
The quantity of calcium ions in the T tubule system depends to a great extent on the...
... Extracellular fluid calcium concentration
38
TRUE or FALSE
The strength of skeletal muscle contraction is largely affected by moderate changes in extracellular fluid calcium concentration.
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
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).
1. Influx
2. Sarcoplasm
3&4. Sarcoplasmic reticulum & T tubule-extracellular fluid space
40
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).
1. Calcium-ATPase pump
2. Sodium-calcium exchanger
3. Sodium-potassium ATPase pump
4. Contraction
41
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).
1. Cardiac cycle
| 2. Sinus node
42
Cardiac cycle
| Period of relaxation : (1) :: period of contraction : (2)
1. Diastole
| 2. Systole
43
Increase in heart rate leads to (increase / decrease) of cardiac cycle. The duration of the action potential and period of contraction (increase / decrease).
1. Decrease
| 2. Decrease
44
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.
1. Very fast
| 2. Relaxed
45
Is caused by a spread of depolarization through the atria.
P wave
46
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
1. A wave
2. C wave
3. V wave
47
During ventricular systole, large amounts of blood accumulate in the (right & left atria / right & left ventricle) because of the closed (2).
1. R & L atria
| 2. A-V valves
48
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).
1. Fall
2. Systole
3. Ventricles
49
Period of rapid filling last for about the (first / middle / last) third of diastole.
First
50
During the (first / middle / last) third of diastole, only a small amount of blood normally flows into the ventricles.
Middle
51
During the (first / middle / last) third of diastole, the atria contract and give an additional thrust to the inflow of blood into the ventricles.
Last
52
Immediately after ventricular contraction begins, the ventricular pressure (rises / falls) abruptly causing the A-V valves to (open / close).
1. Rise
| 2. Close
53
Period of contraction wherein contraction is occurring in the ventricles, but there is no emptying is called:
Isovolumetric contraction
54
In isovolumic or isometric contraction: the tension is (increasing / decreasing) in the muscle but little or no (lengthening / shortening) of the muscle fibers occurring.
1. Increasing
| 2. Shortening
55
When the left ventricular pressure rises slightly above (80 / 20) mmHg, the ventricular pressures push the semilunar valves open.
80 mm Hg
56
Percent of blood emptying during:
1. Period of rapid ejection (1st third)
2. Period of slow ejection (next two thirds)
1. 70%
| 2. 30%
57
At the end of (diastole / systole), ventricular relaxation begins suddenly allowing the right and left intraventricular pressure to decrease rapidly.
Systole
58
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:
Period of isovolumic or isometric relaxation.
59
End-diastolic volume: (1)
Stroke volume output: (2)
End-systolic volume: (3)
Ejection fraction: (4)
1. About 110-120 ml
2. About 70 ml
3. About 40-50 ml
4. Usually 60% of the end-diastolic volume
60
Prevent backflow of blood from the ventricles to the atria during systole:
Atrioventricular valves
61
Prevent backflow from the aorta and pulmonary arteries into the ventricle during diastole:
Semilunar valves
62
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.
1. Close
| 2. Open
63
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.
1. Contract
| 2. Close
64
If a chorda tendinae becomes ruptured or if one of the papillary muscles become paralyzed, the valves:
Bulges far backward during ventricular contraction
65
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
Semilunar
66
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.
1. Smaller
| 2. Larger
67
The A-V valves are supported by the (1), which is not true for the (2) valves.
1. Chorda tendineae
| 2. Semilunar
68
When the left ventricle contracts, the ventricular pressure (increases / decreases) rapidly until the aortic valve opens.
Increases
69
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.
False, its before the closure of the valves.
70
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.
Diastole
71
Is the amount of energy that the heart converts to work during each heartbeat while pumping blood into arteries.
Stroke work output of the heart
72
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.
Minute work output
73
Intrinsic ability of the heart to adapt to increasing volumes of inflowing blood:
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
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.
1. Atria
| 2. Ventricles
75
Excess amount of (1) in the extracellular fluids causes the heart to become dilated and flaccid and also slows the heart rate.
Potassium
Large quantities can also block conduction of the cardiac impulse from the atria to the ventricles through the A-V bundle.
76
High potassium concentration in the extracellular fluid decreases the (1) in the cardiac muscle fibers.
Resting membrane potentials
High extracellular potassium concentration partially depolarizes the cell membrane, causing the membrane potential to be less negative.
77
Excess of (1) ions causes the heart to go toward spastic contraction.
Calcium
Deficiency causes cardiac flacidity.
78
(1) of the heart often is enhanced temporarily by a moderate increase in temperature, as occurs during body exercise.
Contractile strength
But prolonged elevation of temperature exhausts the metabolic systems of the heart and eventually causes weakness.
79
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.
True
80
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.
False, normal systolic arterial pressure is from 80-140 mm Hg.
