Neuromuscular physiology

Question 1

What is the epimysium?

Answer 1

A sheath of fibrous elastic tissue surrounding a muscle

Question 2

What is the perimysium?

Answer 2

the sheath of connective tissue surrounding a bundle of muscle fibers

Question 3

What is the fasciculus (fascicle)?

Answer 3

A small bundle of nerve, muscle or tendon fibers

Question 4

What is the endomysium?

Answer 4

The outermost connective tissue sheath surrounding the entire muscle

Question 5

What is the sarcolemma?

Answer 5

the plasma membrane of the muscle cell and is surrounded by basement membrane and endomysial connective tissue.

Question 6

What is a sarcoplasm?

Answer 6

the cytoplasm of striated muscle cells

Question 7

What is the myofibril?

Answer 7

long contractile fibres, groups of which run parallel to each other on the long axis of the myocytes

Question 8

What is a sarcomere?

Answer 8

the basic contractile unit of muscle fiber.

Question 9

What is the function of the epimysium?

Answer 9

The epimysium surrounds the entire muscle and defines its volume

Question 10

What is the function of the perimysium?

Answer 10

transmitting lateral contractile movements

Question 11

What is the function of the fasciculus (fascicle)?

Answer 11

primary sensory fibers that convey proprioceptive, tactile, and vibratory information from the ipsilateral side of the body

Question 12

What is the function of the endomysium?

Answer 12

separates single muscle fibres from one another

Question 13

What is the function of the sarcolemma?

Answer 13

acts as a barrier between the extracellular and intracellular compartments, defining the individual muscle fiber from its surroundings

Question 14

What is the function of the sarcoplasm?

Answer 14

plays a critical role in muscle contraction as an increase in Ca2+ concentration in the sarcoplasm begins the process of filament sliding

Question 15

What is the function of the myofibril?

Answer 15

to produce muscle contraction and relaxation

Question 16

What is the function of the sarcomere?

Answer 16

muscular contraction

Question 17

What does actin and myosin do within muscle contraction?

Answer 17

bring Z lines closer together

Question 18

What is some terminology associated with the sarcomere?

Answer 18

• myosin filament
• actin filament
• cross-bridge
• power stroke

Question 19

What are the steps of the cross bridge cycle?

Answer 19

1. myosin heads split ATP and become reoriented and energized
2. Myosin heads bind to actin, forming crossbridges
3. Myosin heads rotate toward center of the sarcomere (power stroke)
4. As myosin heads bind ATP, the crossbridges detach from actin

Question 20

What does the rate of ATP hydrolysis depend on?

Answer 20

Myosin heavy chain (MHC) type

Question 21

What is the hydrolysis rate of a Type I MHC?

Answer 21

Slow hydrolysis rate

Question 22

What is the hydrolysis rate of a type IIa MHC?

Answer 22

fast hydrolysis rate

Question 23

What is the hydrolysis rate of a type IIb MHC?

Answer 23

Very fast hydrolysis rate

Question 24

what is the main limitation of the cross-bridge cycle?

Answer 24

the rate of hydrolysis

Question 25

What are type I fibers?

Answer 25

low ATPase activity (at pH 9.4), are slow twitch, have high oxidative and low glycolytic capacity, and are relatively resistant to fatigue

Question 26

What are Type IIa fibers

Answer 26

fast oxidative glycolytic (FOG) fibers, present higher twitch speeds than type I fibers but are less fatigue resistant

Question 27

What are type IIb fibers?

Answer 27

high myosin ATPase activity (pH 9.4), are fast twitch, have low oxidative and high glycolytic capacity, and fatigue rapidly.

Question 28

Explain maximum flexibility in terms of sarcomeres

Answer 28

number of sarcomeres in series

Question 29

Explain maximum strength in terms of sarcomeres

Answer 29

number of sarcomeres in parallel

Question 30

Explain maximum power in terms of sarcomeres

Answer 30

- number of sarcomeres in series - number of sarcomeres in parallel - % MHC IIa

Question 31

What are some terms associated with the motor neuron?

Answer 31

- neuron body - axon - dendrite - myelin sheath - neuromuscular junction

Question 32

What is the motor unit size principle

Answer 32

- motor units are recruited in order from small to large

Question 33

Muscle hypertrophy

Answer 33

- increased muscle fiber and motor unit size - greater resistance force is required to recruit motor units - for some absolute resistance force, fewer motor units are used

Question 34

What is unfused tetanus?

Answer 34

when the muscle fibers do not completely relax before the next stimulus because they are being stimulated at a fast rate

Question 35

what is fused tetanus?

Answer 35

Fused tetanus is when there is no relaxation of the muscle fibers between stimuli and it occurs during a high rate of stimulation

Question 36

What does the Na -K- ATP pump maintain?

Answer 36

ion balance across sarcolemma

Question 37

What does the Na -K- ATP do?

Answer 37

active transport of Na out of and K into muscle fiber do

Question 38

intermuscular coordination

Answer 38

- coordination between muscles/muscle groups - improved activation of synergists - decreased co-contraction of antagonists - associated with neuromotor fitness