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Physiology I > Lecture 6 Cardiac Muscle Tissue > Flashcards

Lecture 6 Cardiac Muscle Tissue Flashcards

1
Q

Syncytium

A

Network of cells that are branched

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2
Q

Action potential in a ventricular fiber

A

Averages about 105mV
Rises from -85 to +20mV
Remains depolarized for about 0.2 second following initial spike
-exhibits plateau
Sudden repolarization at the end of the plateau

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3
Q

Skeletal Muscle Fibers T Tubule System

A
  1. T tubules are found at the ends of the thick filaments
  2. There are two T tubules per sarcomere
  3. T tubules form triads with the sarcoplasmic reticulum
  4. The sarcoplasmic reticulum is more extensive in skeletal muscle fibers
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4
Q

Cardiac Muscle Fibers T Tubule System

A
  1. T tubules are found along the Z line (ends of sarcomere)
  2. T tubules form diads with the sarcoplasmic reticulum
  3. The sarcoplasmic reticulum is less extensive than in cardiac muscle fibers
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5
Q

Phonocardiogram

A

Lub dub heart beat

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6
Q

Systole

A

Ventricular contraction, lub proceeds this

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7
Q

Diastole

A

Ventricular relaxation, dud proceeds this

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8
Q

P

A

Atrial depolarization

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9
Q

QRS

A

Ventricular depolarization

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10
Q

T

A

Ventricular repolarization

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11
Q

Atrial repolarization

A

Is hidden in QRS, just can’t see it

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12
Q

Isovolumic contraction

A

Pressure changes but volume stays the same

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13
Q

Atria as primer pumps

A

Priming the ventricles
About 80% of blood flows from the atria to the ventricles before the atria contract
Atria can add an additional 20% by contraction

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14
Q

Ventricular Systole

A

AV valves are closed during systole

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15
Q

End of ventricular systole

A

AV valves open at the end of systole because of increased pressures in the atria

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16
Q

Chordae tendineae

A

Anchors valves down, tendinous cords

17
Q

First third of diastole

A

Rapid filling

18
Q

Middle third of diastole

A

Small amount of blood flows into the ventricles representing blood that continues to flow into atria during diastole

19
Q

Last third of diastole

A

Atria contract to push last 20% of blood into ventricles

20
Q

Isometric (isovolumic) contraction

A

Ventricles contract, but semilunar valves do not open for 0.02 to 0.03 seconds

21
Q

Period of rapid ejection

A

Occurs when left ventricular pressure is a little above 80mm Hg and right ventricular pressure is slightly above 8mm Hg
Semilunar valves open
About 70% of the blood is ejected
Occurs during the first third of ejection

22
Q

Period of slow ejection

A

Remaining 30% of blood is ejected from the ventricles

Occurs during the last two-thirds of ejection

23
Q

Blood in proximal aorta

A

Mean velocity = 40 cm/s
Flow is phasic (ebbs and flows)
Velocity ranges from 129 cm/s (systole) to negative value before aortic valves close in diastole

24
Q

Negative value is

A

Dicrotic notch

25
Q

Blood in distal aorta and arteries

A

Velocity is greater in systole than diastole

Forward flow is continuous because of elastance of vessel walls during diastole

26
Q

Forces altering flow

A

The rate of blood flow to each tissue is usually precisely controlled in relation to tissue need
Active tissues may need 20 to 30 times as much blood flow than at rest
Cardiac output cannot exceed 4-7x greater than at rest
Microvessels of each tissue

27
Q

Microvessels of each tissue

A

Monitor tissue needs
Act directly on local blood vessels
Nervous control and hormones

28
Q

ANS

A

Fight or flight

29
Q

Action Potential Plateau

A

In skeletal muscle, the sodium channels close rapidly
In cardiac muscle the sodium channels also close rapidly, but the calcium channels stay open slowly and stay open for a longer period of time
In cardiac muscle there is also a delay in the opening of the potassium channels
The large concentration of both calcium ions and potassium ions is responsible for the plateau

30
Q

SERCA

A

Sarcoplasmic reticulum calcium ATPase

31
Q

Frank-Starling Law

A

The more it is stretched, the stronger the contracton

32
Q

EDV

A

End diastolic volume

110-120mL

33
Q

SV

A

Stroke volume

70mL

34
Q

ESV

A

End systolic volume
40-50mL
Can be as little as 10-20Ml
Amount left over after ventricle contraction, always a little bit of blood left over

35
Q

Ejection Fraction

A

SV/EDV = 70/110 = 64%

36
Q

Stroke volume output can be increased to more than double by

A

Increasing EDV - more blood flowing in

Decreasing ESV - decreasing the end systolic volume

Physiology I (7 decks)

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