cardiac muslce heart pump and contraction ch 9 Flashcards

1
Q

Name the 2 heart pumps and where they pump

A

right pump- pulmonary circulation,

left pump- peripheral circulation

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2
Q

What is Cardiac rhythmicity?

A

sequence of cardiac contractions

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3
Q

name the muslce types in the heart

A

atrial, ventricular, specialized excitatory and conductive fibers

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4
Q

whats special about the atrial and ventricular muslce fibers?

A

they contract longer than skeletal muslce

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5
Q

what are intercalated discs?

A

connections between heart muscle cells. they have gap junctions

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6
Q

What does the AV bundle do?

A

transmits conduction from atrium synctium to ventricular. It allows the atria to contract before the ventricles

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7
Q

Cardiac action potential

A

~105 millivolts, The intracellular potential rises from -85 to +20 mv during each beat. The membrane remains depolarized for about .2 seconds( plateau)

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8
Q

Whats the reason for the plateau in action potential?

A

allows the ventricular contraction to be as much as 15 times longer than skeletal muscle

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9
Q

what allows the cardiac fibers to have a prolonged AP plateau?

A

instead of just sodium channels opening they have calcium-sodium channels ( slow calcium channels) The slow channels maintain the depolarization period which causes the plateau

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10
Q

what else allows the cardiac fibers to have a prolonged AP and plateau?

A

after the onset of the AP the permeability of cardiac fibers for potassium ions decreases about 5 fold which doesnt happen in skeletal muscle. This decreases the outflux of potassium ions which prevents early return.

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11
Q

Conduction speed of Cardiac cells

A

.3-.5 seconds. This is slower than nerve fibers and skeletal fibers

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12
Q

whats a problem with Tachycardia in regards to the atria?

A

the fast heart beat doesnt allow the atria to fill the ventricles quick enough.

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13
Q

P wave

A

depolarization through the atria and followed by atrial contraction. This causes a slight rise in atrial pressure

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14
Q

QRS waves-

A

depolarization of Ventricles and causes the ventricular pressure to begin rising

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15
Q

T wave-

A

repolarizing of the Ventricles and ventricular muslce starts to relax

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16
Q

Atria as primers

A

~80 % of blood flows directly through ventricles even before contraction. The Atria simply act as primers that increase ventricular pumping effectiveness as much as 20%.

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17
Q

A wave-

A

Atrial contraction

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18
Q

C wave

A

ventricles begin to contract and blood backflows into atria

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19
Q

V wave

A

occurs toward the end of ventricular contraction. This is when blood is slowly filling the atria while the AV valves are closed

20
Q

Period of rapid filling of ventricles

A

blood pushes AV valves open and fills the ventricle during the first 1/3 of diastole. Middle 1/3 of diastole involves blood straight from the veins into the ventricles. Last 1/3 of diastole is when the atria contract accounting for an additional 20% of filling

21
Q

isovolumic contraction

A

period between when the AV valves close and the ventrilces contract and push the semilunar valves open.

22
Q

End diastolic volume

A

normal filling of ventricles. about 110-120 ml

23
Q

stroke volume output

A

when ventricles contract and empty to about 70ml

24
Q

end systolic volume

A

remaining volume in each ventricle after contraction. about 40-50 ml.

25
Q

ejection fraction

A

fraction of end diastolic volume that is ejected from the heart( jusually about 60%)

26
Q

in regards to end diastolic and end systolic volume, how can stroke volume increase?

A

increase end diastolic and decrease end systolic volume

27
Q

Semilunar valves functions

A

Pressure from arteries close them rapidly.

28
Q

first heart sound

A

closure of AV valves. Low pitch and long lasting

29
Q

second heart sound

A

aortic and pulmonary valves closing. High pitch and fast

30
Q

stroke work output

A

amount of energy the heart converts to work during each heartbeat

31
Q

minute work output

A

total energy converted in one minute.

32
Q

work output of heart

A

spends energy on moving blood from low to high pressure. Also spends energy speeding blood to its velocity of ejection through the valves

33
Q

the problem with having high systolic pressure

A

it pushes the actin and myosin filaments far apart and they stop working optimally

34
Q

period of filing

A

volume increases as blood is pumped into ventricle

35
Q

period of isovolumic contraction

A

all valves are closed so volume doesnt change but pressure does increase because the ventricles are contracting

36
Q

period of ejection

A

systolic pressure rises even higher because of ventricular contraction . Volume is decreasing because the aortic valve is now open

37
Q

period of isovolumic relaxation

A

aortic valve closes and ventricles fall back to starting point which is about 50 mmHg

38
Q

How the heart gets energy

A

70-90 % is from metabolizing fatty acids. 10-30% from other nutrients like lactate and glucose

39
Q

external work of the heart

A

oxygen consumption and chemical energy expended during contraction

40
Q

potential energy of the heart

A

additional work that could be accomplished by contraction of the ventricle if the ventricle were completly emptied

41
Q

what is the maximum efficency of the normal heart?

A

20-25 % . heart failure can go as low as 5-10%

42
Q

Frank starling mechanism

A

The greater the heart muscle is stretched during filling, the greater the force of contraction it gives

43
Q

sympathetic mechanism on heart

A

cause the heart to double its output

44
Q

parasympathetic mechanism on heart

A

Vagus nerve, Can stop the heart for a couple seonds. Decrease pumping as much as 30% below normal

45
Q

potassium ion effect

A

excess extracellular ions cause the heart to dilate and become flacid which slows the rate. Also block conduction system through AV node

46
Q

Effect of calcium ions

A

spastic contractions!!!