Skeletal Muscle

Question 1

What innervates skeletal muscle?

Answer 1

motor neurons in the ventral horn of the spinal cord

-they disperse to provide innervation to multiple muscles, but each fiber is only innervated by 1 neuron

Question 2

Motor Unit

Answer 2

Motor neuron + muscle fibers that it innervates

Question 3

Small Motor Neuron Body

Answer 3

• innervate few muscle fibers
• relatively small cross-sectional diameters
• “slow” motor unit (b/c mechanical characteristics)

Question 4

Large Motor Neuron Body

Answer 4

• innervate large # of muscle fibers
• large cross-sectional diameters
• “fast” motor unit (b/c mechanical characteristics)

Question 5

What happens when action reaches nerve terminal?

Answer 5

• ACh is released from synaptic vesicles in to the synaptic cleft from Ca2+ channels
• nicotinic channels are targets for ACh (ion channels)

Question 6

How is ACh removed from motor end plate?

Answer 6

-acetylcolenesterase

Question 7

T-tubules

Answer 7

bring musclee cell membrane close to sarcoplasmic reticulum

Question 8

Sacrcoplasmic Reticulum

Answer 8

endoplasmic reticulum that stores Ca2+ at high conc. in cell

Question 9

Triad

Answer 9

1) T-tubule
2) SR
3) intervening structure

Question 10

Depolarization of T-tubule membrane does?

Answer 10

confermation change of dihydropyrodine receptor

• activated Ca2+ channel (riadanine receptor)
• passive eflux of Ca that increase Ca conc.
• then channel close, and active transport puts Ca back in SR
• Ca2+ acts as secondary messanger for action potential causing intracellular space to have Ca in response to action potential

Question 11

Sarcomeres

Answer 11

striations of light and dark bands (under polarized light), myofibril proteins

Question 12

I band

Answer 12

has Z line, light bands, think filamentous proteins

Question 13

Unit from 1 Z line to the next?

Answer 13

sarcomere

Question 14

A band

Answer 14

dark bands, thick filamentous proteins

Question 15

Sliding filament theory?

Answer 15

force is generated as thin and thick filaments slide over one another

Question 16

Thick filaments

Answer 16

myosin

Question 16

Thick filaments

Answer 16

myosin

Question 17

Thin filaments

Answer 17

actin
troponins (C, T, I)
tropomyosins

Question 17

Thin filaments

Answer 17

actin
troponins (C, T, I)
tropomyosins

Question 18

Actin monomers

Answer 18

form fibrous helical chains, high affinity binding side for myosin heads

Question 18

Actin monomers

Answer 18

form fibrous helical chains, high affinity binding side for myosin heads

Question 19

Myosin

Answer 19

large protein with filamentous tail and globular head (2 light chains per head)

Question 19

Myosin

Answer 19

large protein with filamentous tail and globular head (2 light chains per head)

Question 20

Tropomyosins

Answer 20

fibrous proteins that extend on the length of the thin filament
-can cover myosin binding sites

Question 20

Tropomyosins

Answer 20

fibrous proteins that extend on the length of the thin filament
-can cover myosin binding sites

Question 21

Troponins

Answer 21

form ternary complex of C, I, and T (binding complex)

Question 21

Troponins

Answer 21

form ternary complex of C, I, and T (binding complex)

Question 22

Tropomosin at Rest

Answer 22

prevents actin and myosin interaction

Question 22

Tropomosin at Rest

Answer 22

prevents actin and myosin interaction

Question 23

Tropomosin Action Potential

Answer 23

Ca+2 moves tropomosin and lets actin and myosin bind

Question 23

Tropomosin Action Potential

Answer 23

Ca+2 moves tropomosin and lets actin and myosin bind

Question 24

What happens when actin and myosin bind?

Answer 24

conformational change, pulls thick filament toward Z-line
Power stroke (pulls Z-lines toward each other)
-muscle fiber contraction

Question 24

What happens when actin and myosin bind?

Answer 24

conformational change, pulls thick filament toward Z-line
Power stroke (pulls Z-lines toward each other)
-muscle fiber contraction