SMT 1 again

Question 1

our skeletal muscles are composed of ?

Answer 1

bundles of fascicles

Question 2

each fascicle is composed of linearly aligned ?

Answer 2

muscle fibers (myofiber)

Question 3

T or F: Muscle fiber is a single, multi-mucleated, elongated cell

Answer 3

true

Question 4

each muscle fibre is composed of many ?

Answer 4

myofibril

Question 5

myofibrils have many ?

Answer 5

sacromere

Question 6

what is a sacromere?

Answer 6

structural units of myofibrils that facilitate contraction and relaxation

Question 7

what is the epimysium

Answer 7

the connective tissue sheath surrounding the whole muscle and extending from the tendons

Question 8

what is the sheath surrounding each fascicle?

Answer 8

perimysium

Question 9

what is the sheath that surround each individual muscle fiber?

Answer 9

endomysium

Question 10

what is the cell membrane of the muscle cell?

Answer 10

sarcolemma

Question 11

each myofibril composed of many ?

Answer 11

myofilaments

Question 12

what are the contractile proteins of the muscle?

Answer 12

actin and myosin

Question 13

what are the regulatory proteins of the muscle?

Answer 13

tropomyosin and troponin

Question 14

sacromeres consist of interdigitating myofilaments called

Answer 14

thin filaments and thick filaments

Question 15

thin filaments are made of ?

Answer 15

actin

Question 16

thick filaments are made of?

Answer 16

myosin

Question 17

the striated appearance of skeletal muscle is due to ?

Answer 17

the overlapping of thick and thin filaments

Question 18

each sarcomere is bound by the ?

Answer 18

Z-disk

Question 19

thin filament attaches to the

Answer 19

Z-disk

Question 20

at the center of the sarcomere is the ?

Answer 20

M-line

Question 21

thick filaments lie between the

Answer 21

thin filaments

Question 22

what are light bands (I bands)

Answer 22

regions of thin filaments that do not overlap with thick filaments

Question 23

what is at the center of the light bands?

Answer 23

the Z-disk

Question 24

what are dark bands (A bands)

Answer 24

the region where the thick and thin filaments do overlap

Question 25

during muscle contraction, the I band ?, while the A band ?

Answer 25

- shortens - does not change in length

Question 26

what is the monomer of Actin?

Answer 26

G-actin

Question 27

what is the polymer of actin?

Answer 27

F-actin

Question 28

thin filaments are composed of 2 strands of ?

Answer 28

F-actin

Question 29

each G-actin monomer has a?

Answer 29

binding site for myosin

Question 30

what is the major constituent of the thin filament?

Answer 30

F-actin

Question 31

what is the thick filament composed of?

Answer 31

myosin

Question 32

myosin head region, has 3 important biochemical features:

Answer 32

- ATPase activity - actin-binding region - ATP binding region

Question 33

what is the regulatory protein that associates with actin?

Answer 33

tropomyosin

Question 34

what are the 3 subunits of troponin?

Answer 34

- troponin C - troponin T - troponin I

Question 35

which troponin binds to calcium?

Answer 35

troponin C

Question 36

which troponin binds to tropomyosin

Answer 36

troponin T

Question 37

which tropinin binds to actin and inhibits contraction

Answer 37

troponin I

Question 38

how do cross-bridge formation occur

Answer 38

when calcium binds to tropinin C, the troponin complex undergoes a conformational change and troponin T "pulls" tropomyosin and troponin I off of the myosin-binding site of G-actin subunits

Question 39

what is the plasma membrane of the muscle fiber called?

Answer 39

sarcolemma

Question 40

the sarcolemma contains invaginations called?

Answer 40

transverse tubules (aka T-tubules)

Question 41

what allows the action potential to be carried deep into the muscle fiber?

Answer 41

transverse tubules

Question 42

what is the sarcoplasmic reticulum

Answer 42

a specialized endoplasmic reticulum containing high concentrations of calcium

Question 43

what are the terminal cisternae of the sarcoplasmic reticulum

Answer 43

specialized regions that associate with the T-tubules

Question 44

what is the junction between T-tubules and sarcoplasmic reticulum cisterna called?

Answer 44

muscle triad

Question 45

a motor nerve axon contacts each muscle fiber near the middle of the fiber, foriming a synapse called the ?

Answer 45

neuromuscular junction

Question 46

what is the region of the sarcolemma in closest contact with the presynaptic nerve terminal called?

Answer 46

motor end plate

Question 47

what does the motor nerve terminal release?

Answer 47

acetylcholine

Question 48

what bind to the nicotinic receptor on the sarcolemma?

Answer 48

acetylcholine

Question 49

what happens when the acetylcholine binds to the nicotinic receptor?

Answer 49

it activates voltage-gated sodium channels

Question 50

what happens when voltage-gated sodium channels are activated?

Answer 50

triggering an action potential that propagates along the sarcolemma

Question 51

the action potential propagates along the surface of the skeletal muscle fiber and penetrate deeper into the muscle fiber via what?

Answer 51

T-tubules

Question 52

what is the purpose of T-tubule

Answer 52

to "bring" the action potential deep within the very large muscle fibres

Question 53

action potential propage along the T-tubules and activate what? in the sarcolemma

Answer 53

L-type Ca2+ channels

Question 54

activation of the L-type Ca2+ channels also triggers mechanical activation of what? on the surface of the SR terminal cisterna within the cell

Answer 54

Ryanodine receptors (RYR) which release calcium into the cytosol of the muscle fiber

Question 55

opening of L-type Ca2+ channels and RYR allows what?

Answer 55

Ca2+ to flow down its concentration gradient into the cytosol of the muscle fiber

Question 56

what happens to the calcium released by L-tyoe Ca2+ channels and RYR?

Answer 56

it bins to troponin C subunit to expose the binding sites for myosin

Question 57

T or F: most of the calcium that activates the skeletal muscle sarcomere is from the SR, NOT the extracellular fluid

Answer 57

true

Question 58

what is a motor unit?

Answer 58

all the muscle fibers innervated by a single nerve fiber

Question 59

what is a tetany?

Answer 59

development of force (tension) in a muscle fiber due to many action potentials

Question 60

what is fused tetany?

Answer 60

maximal force development in the muscle fibres of a motor unit