Lecture 6 Cardiac Muscle Tissue

Question 1

Syncytium

Answer 1

Network of cells that are branched

Question 2

Action potential in a ventricular fiber

Answer 2

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

Question 3

Skeletal Muscle Fibers T Tubule System

Answer 3

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

Question 4

Cardiac Muscle Fibers T Tubule System

Answer 4

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

Question 5

Phonocardiogram

Answer 5

Lub dub heart beat

Question 6

Systole

Answer 6

Ventricular contraction, lub proceeds this

Question 7

Diastole

Answer 7

Ventricular relaxation, dud proceeds this

Question 8

P

Answer 8

Atrial depolarization

Question 9

QRS

Answer 9

Ventricular depolarization

Question 10

T

Answer 10

Ventricular repolarization

Question 11

Atrial repolarization

Answer 11

Is hidden in QRS, just can’t see it

Question 12

Isovolumic contraction

Answer 12

Pressure changes but volume stays the same

Question 13

Atria as primer pumps

Answer 13

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

Question 14

Ventricular Systole

Answer 14

AV valves are closed during systole

Question 15

End of ventricular systole

Answer 15

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

Question 16

Chordae tendineae

Answer 16

Anchors valves down, tendinous cords

Question 17

First third of diastole

Answer 17

Rapid filling

Question 18

Middle third of diastole

Answer 18

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

Question 19

Last third of diastole

Answer 19

Atria contract to push last 20% of blood into ventricles

Question 20

Isometric (isovolumic) contraction

Answer 20

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

Question 21

Period of rapid ejection

Answer 21

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

Question 22

Period of slow ejection

Answer 22

Remaining 30% of blood is ejected from the ventricles

Occurs during the last two-thirds of ejection

Question 23

Blood in proximal aorta

Answer 23

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

Question 24

Negative value is

Answer 24

Dicrotic notch

Question 25

Blood in distal aorta and arteries

Answer 25

Velocity is greater in systole than diastole | Forward flow is continuous because of elastance of vessel walls during diastole

Question 26

Forces altering flow

Answer 26

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

Question 27

Microvessels of each tissue

Answer 27

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

Question 28

ANS

Answer 28

Fight or flight

Question 29

Action Potential Plateau

Answer 29

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

Question 30

SERCA

Answer 30

Sarcoplasmic reticulum calcium ATPase

Question 31

Frank-Starling Law

Answer 31

The more it is stretched, the stronger the contracton

Question 32

EDV

Answer 32

End diastolic volume | 110-120mL

Question 33

SV

Answer 33

Stroke volume | 70mL

Question 34

ESV

Answer 34

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

Question 35

Ejection Fraction

Answer 35

SV/EDV = 70/110 = 64%

Question 36

Stroke volume output can be increased to more than double by

Answer 36

Increasing EDV - more blood flowing in | Decreasing ESV - decreasing the end systolic volume