Lecture 7 - Cardiac Muscle Tissue

Question 1

Tricuspid valve

Answer 1

“right” side

“ri”

Question 2

Bicuspid

Answer 2

“left” side

Question 3

Venous blood from the Head and upper extremity returns to the heart via:

Answer 3

superior vena cava

Question 4

Venous blood from the trunk and lower extremity returns to the heart via:

Answer 4

inferior vena cava

Question 5

Arteries carry blood:

Answer 5

away from the heart

Question 6

What holds cardiac muscle cells together?

Answer 6

intercalated discs

Question 7

Ventricular fiber action potential voltage?

Answer 7

~105 mV

rises from -85 to +20 mV

Question 8

Requirements of cardiac action potential?

Answer 8

self generating
prolonged to allow “twitch” to become lengthened for contraction to occur
must propagate from myocyte to myocyte

Question 9

Purkinje fibers

Answer 9

conduct but do not contract

Question 10

Fast cardiac action potentials

Answer 10

found in atria, ventricles, and conduction system
rapidly conducting but not contractile in Purk. fibers
rapidly conducting and contractile in A/V fibers
High amplitude (100 mV)

Question 11

Slow cardiac action potentials

Answer 11

Found in SA and AV nodal tissues
conducts slowly
automatically depolarizes during resting phase
low amplitude (60 mv)

Question 12

Phase 4 of fast action potentials

Answer 12

resting potential

Question 13

Phase 0 of fast action potentials

Answer 13

rapid depolarizationi

Question 14

Phase 1 of fast action potentials

Answer 14

Initial, incomplete repolarization

Question 15

Phase 2 of fast action potentials

Answer 15

plateau or slow decline of membrane potential

Question 16

Phase 3 of fast action potentials

Answer 16

repolarization

Question 17

Which is the pacemaker?

Answer 17

SA node

Question 18

What determines the rhythmicity of the cell?

Answer 18

Rate of depolarization (faster depol. faster HR)

Question 19

Special sodium channels in automatic heart tissues open following phase 3 causing

Answer 19

gradual depolarization during phase 4

Question 20

SA node resting membrane potential?

Answer 20

-55 to -60 mV (threshold -40 mV)

Question 21

Ventricular fiber resting potential?

Answer 21

-85 to -90 mV

Question 22

Ca2+ release from sarcoplasmic reticulum via ryanodine receptors caused by DHP conformational change or influx of Ca2++ itself?

Answer 22

influx of Ca2++ itself

through T-tubules (ECF > DHP > ryanodine = Ca2+ release from SR)

Question 23

How is Ca2+ eliminated from cardiac muscle?

Answer 23

Sequestered in SR (via SRCA)
OR
Cotransported to the ECF, exchanged for Na. Then Na pumped out in exchange for K+

Question 24

What is the Frank-Starling law?

Answer 24

Greater the pressure in the ventricles=greater force of contraction & greater quantity of blood in the aorta

Question 25

Veins carry blood:

Answer 25

to the heart

Question 26

Right side of the heart pumps blood to the

Answer 26

Lungs

Question 27

Left side of the heart pumps blood to

Answer 27

everywhere that isn't the lungs

Question 28

T tubules are found at the end of _____ filaments in _____ muscles. However, in _______ muscles, they are found along the ______ line

Answer 28

thick; skeletal | cardiac; Z

Question 29

How to increase venous return?

Answer 29

increase blood volume | decreased venous capacitance

Question 30

How to achieve higher stroke volume?

Answer 30

increase venous return increased contractility (results increased width of pressure loop)

Question 31

effects of increased afterload?

Answer 31

decreased stroke volume/end systolic volume | decreased width of pressure loop

Question 32

increased sympathetic stimulation causes....

Answer 32

increased cardiac output

Question 33

increased parasympathetic stimulation causes...

Answer 33

decreased cardiac output