MCP 29: Muscles I

Question 1

muscle fiber

Answer 1

group of myofibrils covered in sarcolemma

Question 2

t-tubules

Answer 2

deep pits in sarcolemma continuous with the extracellular environment

Question 3

terminal cisternae of the sarcoplasmic reticulum

Answer 3

found next to the t-tubules

Question 4

sarcoplasmic reticulum

Answer 4

high concentration of calcium bound by calsequestrin

Question 5

potassium and t-tubules

Answer 5

limited extracellular space limits K+ ability to clear during repolarization, leading to elevated extracellular K+ and reducing the rate of K+ efflux from the cell, high extracellular K+ means that the RMP of the cell is depolarized.

Question 6

Cl- leak channels and skeletal muscle

Answer 6

help cell repolarize

Question 7

myotonia

Answer 7

skeletal muscle genetic disorder resulting from defect in Cl- leak channels

Question 8

excitation coupling

Answer 8

process by which AP in the skeletal muscle generates a muscular contraction 1.) AP sent along muscle membrane down T-tubules into triad 2) depolarization reaches the voltage sensitive L-type Ca2+ channel and activates it 3.) the L-type channel tickels and activates the ryanodine receptors 4.) Ca2+ released into the sarcoplasm

Question 9

sarcoplasm

Answer 9

cytosol of muscle

Question 10

calsequestrin

Answer 10

keeps Ca2+ levels high SR with help from Ca2+ ATP pump

Question 11

hierarchy of muscle anatomy

Answer 11

muscle-myofibers (cells with many nuclei)-myofibrils (long stretches of sarcomeres arranged in series)-alternating thin and thick filaments that form striations

Question 12

thin filaments

Answer 12

made up of actin, tropomyosin and troponin

Question 13

thick filaments

Answer 13

made of myosin, do no move during muscle contraction, thin filaments slide over it

Question 14

A-band

Answer 14

encompasses the entire length of myosin, stays the same length during contraction

Question 15

I-band

Answer 15

contains only actin, shrinks during contraction

Question 16

H-band

Answer 16

myosin only, shrinks with contraction

Question 17

Z-line

Answer 17

attachment point for actin filament, from Z-line to Z-line is one sarcomere

Question 18

M-line

Answer 18

midpoint of sarcomere, holds myosin filament in place

Question 19

actin

Answer 19

individual global (G) actin units line up to create filamentous (F) actin filaments, two F filaments wrap around each other, tropomyosin found along length of active sights

Question 20

troponin T

Answer 20

attaches troponin complex to tropomyosin

Question 21

troponin I

Answer 21

lock in place tropomyosin to inhibit actin/myosin interaction

Question 22

troponin C

Answer 22

binds Ca2+, causing tropomysoin to move out of the way so actin, myosin interaction can occur, 4 actin binding sites, two high affinity sites occupied all the time, the other two low affinity sites allow sliding when calcium increases

Question 23

myosin

Answer 23

made of two chains of light myosin and 2 heads of heavy myosin, two hinged regions, head has ATP and actin binding sites

Question 24

cross linking

Answer 24

1.) ATP binds to myosin head, cross linking released 2.) ATP hydrolyzed into ADP and Pi, causing myosin head to be perpendicular to actin filaments 3.) Ca2+ binds to troponin C and changes conformation of troponin/tropomyosin complex Myosin can now attach to actin 4.) ADP and Pi released and power stroke occurs. Myosin head moves 45 degrees and moves actin toward M-line. 5.) Ca2+ removed from sarcoplasm by Ca2+ ATPase, insufficient amount of Ca2+ to bind troponin C.

Question 25

how much does the sarcomere shorten during the power stroke?

Answer 25

1 micrometer

Question 26

speed of power stroke

Answer 26

depends on speed of ATPase on the myosin head

Question 27

strength of cycle

Answer 27

depends on number of cross bridges formed, related to amount of calcium

Question 28

rigor mortis

Answer 28

actin and myosin filament remain attached because not APT to allow the release of the two components `

Question 29

sources of fuel for muscle contraction

Answer 29

glycolysis, Krebs cycle and creatine phosphate