Skeletal Muscle (Lecture 6)

Question 1

the important functions of skeletal muscle

Answer 1

locomotion, postural support, and heat production

Question 2

3 layers of skeletal muscle (in order)

Answer 2

epimysium, perimysium, endomysium

Question 3

epimysium

Answer 3

surrounds the entire muscle

Question 4

perimysium

Answer 4

surrounds bundles of muscle fibers (fascicles)

Question 5

endomysium

Answer 5

surrounds individual muscle fibers

Question 6

satellite cells

Answer 6

play a role in muscle growth/repair, protein synthesis, and adaptions to strength training (hypertrophy)

Question 7

the basic function unit of skeletal muscle

Answer 7

sarcomere

Question 8

the part of the sarcomere that provides structural support to proteins to anchor them in place

Answer 8

M line

Question 9

the part of the sarcomere that stabilizes and anchors actin

Answer 9

Z line

Question 10

thick filaments of skeletal muscle

Answer 10

myosin

Question 11

thin filaments of skeletal muscle

Answer 11

actin

Question 12

myofibrils

Answer 12

contain contractile proteins (rod-like structures) actin and myosin

Question 13

terminal cisternae

Answer 13

enlarged portion of SR that acts like a “middle-man”

Question 14

sarcoplasmic reticulum (SR)

Answer 14

storage sites for calcium (Ca2+) that is responsible for coupling of excitation to contraction of muscle fibers

Question 15

transverse tubules (T-tubules)

Answer 15

extend from the sarcolemma to SR to allow nerve impulses to be transmitted rapidly to individual fibers (throughout the cell)

signals release of Ca2+ from SR (excitation-contraction coupling)

Question 16

triad

Answer 16

association of a T-tubule and 2 adjacent terminal cisternae

Question 17

neuromuscular junction (NMJ)

Answer 17

the connecting point between the a-motor neuron and muscle fiber

Question 18

motor unit

Answer 18

motor neuron and all fibers it innervates

Question 19

motor end-plate

Answer 19

region/pocket formed around the motor neuron by sarcolemma

Question 20

synaptic/neuromuscular cleft

Answer 20

short gap between neuron and muscle fiber

Question 21

neurotransmitter in the NMJ

Answer 21

acetylcholine (Ach)

Question 22

acetylcholine

Answer 22

neurotransmitter that is released from motor neurons, diffused through synaptic cleft, binds to receipts on motor end-plate, and causes end-plate potential (EPP)

Question 23

end-plate potential (EPP)

Answer 23

depolarization of muscle fiber and signal to being the contractile process

Question 24

excitation-contraction (E-C) coupling

Answer 24

depolarization of motor end-plate (excitation) coupled to muscular contraction

Question 25

sliding filament model

Answer 25

muscle shortening from the movement of actin filament over myosin filament, causing formation of cross-bridges between actin and myosin filaments

Question 26

power stroke

Answer 26

series of structural changes in the actin-myosin cross-bridge driven by hydrolysis of ATP

Question 27

troponin and tropomyosin

Answer 27

proteins that regulate the interaction between actin and myosin (via Ca2+ binding)

Question 28

the action of troponin/tropomyosin tropomyosin rest to exercise (contraction)

Answer 28

-Ca2+ released from SR
-Ca2+ binds to troponin
-tropomyosin moves away
-exposing the site for actin-myosin interaction
-cross-bridge is formed (contraction)

Question 29

muscle fatigue

Answer 29

decline in muscle power output, force generation and shortening velocity

power = force x shortening velocity

Question 30

causes of muscle fatigue in short duration, high intensity exercise (~60 seconds)

Answer 30

accumulation of H+, ADP, Pi, and free radicals (reduces cross bridges)

Question 31

causes of muscle fatigue in long duration, low intensity exercise (2-4 hours)

Answer 31

muscle factors including accumulation of free radicals, electrolyte imbalance, and glycogen depletion

Question 32

muscle fiber types

Answer 32

• slow, oxidative, type I
• fast, glycolytic, type II

Question 33

biochemical properties of muscle fibers

Answer 33

• oxidative capacity
• myosin ATPase isoform type
• amount of contractile protein in fiber

Question 34

contractile properties of muscle fibers

Answer 34

• maximal force production
• speed of contraction
• maximal power output
• muscle fiber efficiency