Skeletal Muscle Flashcards
What innervates skeletal muscle?
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
Motor Unit
Motor neuron + muscle fibers that it innervates
Small Motor Neuron Body
- innervate few muscle fibers
- relatively small cross-sectional diameters
- “slow” motor unit (b/c mechanical characteristics)
Large Motor Neuron Body
- innervate large # of muscle fibers
- large cross-sectional diameters
- “fast” motor unit (b/c mechanical characteristics)
What happens when action reaches nerve terminal?
- ACh is released from synaptic vesicles in to the synaptic cleft from Ca2+ channels
- nicotinic channels are targets for ACh (ion channels)
How is ACh removed from motor end plate?
-acetylcolenesterase
T-tubules
bring musclee cell membrane close to sarcoplasmic reticulum
Sacrcoplasmic Reticulum
endoplasmic reticulum that stores Ca2+ at high conc. in cell
Triad
1) T-tubule
2) SR
3) intervening structure
Depolarization of T-tubule membrane does?
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
Sarcomeres
striations of light and dark bands (under polarized light), myofibril proteins
I band
has Z line, light bands, think filamentous proteins
Unit from 1 Z line to the next?
sarcomere
A band
dark bands, thick filamentous proteins
Sliding filament theory?
force is generated as thin and thick filaments slide over one another
Thick filaments
myosin
Thick filaments
myosin
Thin filaments
actin
troponins (C, T, I)
tropomyosins
Thin filaments
actin
troponins (C, T, I)
tropomyosins
Actin monomers
form fibrous helical chains, high affinity binding side for myosin heads
Actin monomers
form fibrous helical chains, high affinity binding side for myosin heads
Myosin
large protein with filamentous tail and globular head (2 light chains per head)
Myosin
large protein with filamentous tail and globular head (2 light chains per head)
Tropomyosins
fibrous proteins that extend on the length of the thin filament
-can cover myosin binding sites
Tropomyosins
fibrous proteins that extend on the length of the thin filament
-can cover myosin binding sites
Troponins
form ternary complex of C, I, and T (binding complex)
Troponins
form ternary complex of C, I, and T (binding complex)
Tropomosin at Rest
prevents actin and myosin interaction
Tropomosin at Rest
prevents actin and myosin interaction
Tropomosin Action Potential
Ca+2 moves tropomosin and lets actin and myosin bind
Tropomosin Action Potential
Ca+2 moves tropomosin and lets actin and myosin bind
What happens when actin and myosin bind?
conformational change, pulls thick filament toward Z-line Power stroke (pulls Z-lines toward each other) -muscle fiber contraction
What happens when actin and myosin bind?
conformational change, pulls thick filament toward Z-line Power stroke (pulls Z-lines toward each other) -muscle fiber contraction
