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ANATOMY OF SKELETAL MUSCLE
___________________________
________
Extrafusal muscle fiber
Myofibril
_____________
__________________
_________
________
CONTROL OF MOVEMENT: STRIATED MUSCLESSKELETAL (STRIATED) MUSCLE:
- each muscle = ____________________________________- each muscle cell = _______________________________________- Myosin: ___________________________________________- Actin: _________________________________________________
Filamentous protein with ross bridgesFilamentous protein where cross bridges of myosin bind
___________
MUSCLE CONTRACTION
Myosincrossbridges
Actinfilaments
Myosinfilament
Actinfilament
Movement ofactin filament
Myosincrossbridge
Movement ofmyosin filament
Heads of cross bridges:1. Attach to active sites on actin filaments2. “Ratchet” forward3. Release4. Repeat- Only occurs in the presence of ________How is calcium released? ___________________________
________From activity at neuromuscularjunction
Watch muscle contraction movie
NEUROMUSCULAR JUNCTIONSynapse between terminal of _________________and a ___________ is called a neuromuscularjunction;
Terminals of alpha motor neurons synapse on_____________- grooves along the surface ofmuscle fibers;
When motor neuron fires, _____________ isliberated from terminals at the endplate anddepolarizes muscle fibers - ________________;
Depolarization of muscle fiber opens _________________________________, producing a largecalcium influx into the fiber;
Calcium triggers the actin-myosin “rowing”action leading to the __________ of muscle fibers;
Calcium is extruded from fiber by “pump”;
Endplate potential ______ cause muscle fiber tofire = contraction or “twitch” of fiber.
How muscle spindles work!- Gamma motor neurons provide the ________
________________________________- without gamma motor neurons, the spindles
would become _________________________________________
- gamma motor neurons function _________________________________ to an appropriatedegree of tension
Muscle spindles
Gamma motor neurons
Spindle “slack” - insensitive to strech Spindle “tight” - ready to respondto strech
Extrafusal muscle
“slack” and unresponsiveto stretch.
to adjust the length of intrafusal muscles
POLYSYNAPTIC REFLEXES:EXAMPLE OF WITHDRAWAL FROM PAIN
- reflexes requiring _________________________- concept of _______________________________
____________________________- ex., biceps vs. triceps of arms
- reciprocal innervation (excitatory vs. inhibitory)- ____________________________________________________________________________excitatory and inhibitory interneurons worktogether to withdraw limb from pain.
CROSSED EXTENSOR REFLEX
Think of this reflex as being ____________ withprevious polysynaptic withdrawal reflex
For example, if flexion reflex triggered in oneleg, ___________________________________
All this happens _________________________;the brain has nothing to do with it.
This serves to:- ______________________________________________________________