_____ _______ _______: collection of alpha motor neuron innervating 1 muscle.
Motor Neuron Pool
_____ _____ _____: ( effects presynaptic AP) causes EPSP's in muscle fibers (endplate potential) and triggers AP in muscle. Results in muscle twitch. Twitch summation causes increased tension in muscle fibers and smooth contraction.
Vary Firing Rate of motor neurons
_______ _______: high frequency with barrage of AP's resulting in postsynaptic responses.
Recruiting of additional synergistic motor units results in extra _____ on a muscle.
Muscle recruitment goes from ____ to ______.
smallest to largest. why finger control is possible when muscle under small and light load than with larger load (size principle)
_____ _____: slow to contract; can sustain contraction long time; found in antigravity muscles of leg.
_____ _____: fast to contract; rapid fatigue; escape muscles (jump, run, human arm)
True or False: each type of motor units coexist in a given musle but motor units contains only single type.
_____ motor units: rapid fatiguing white fibers; larger axons= faster axons; occasional high frequency bursts of AP's.
Fast motor units
_______ motor units: slow fatiguing red fibers; smaller axons= slower axons; steady low threshold.
True or False: Muscle fiber type cannot be changed.
False: put slow axons on fast muscles results in changed to slow muscles and fiber type changed
________ ______ Contraction: AP's in presynaptic membrane release Ach from pre- into cleft. This activates nicotinic Ach receptors on post-synaptic membrane (EPSP's). Causes AP in muscle fiber and triggers Ca2+ release from organelle and contraction of fiber.
_______: within muscle fibers; cylindrical, contract due to AP going down sarcolemma and surrounded by Sarcoplasmic Reticulum which Ca2+.
AP enters sarcoplasmic reticulum by tunnel: _____ _____
_______: voltage sensitive cluster of 4 Ca2+ channels linked to calcium release channel in SR
____ lines: myofibril divided into segments by disks.
_______: Z lines and myofibril in between.
_____ _____: anchored to Z line.
______ _____: between thin filaments.
______ ______: thin filaments slide along thick filaments bringing Z lines closer= shortens sarcomere= Sliding Filament Model
Sliding filament model: occurs due to interaction between ____ and ____.
actin and myosin
Myosin can't bind to actin as actin sites are covered by _____.
_____ ______: stretch receptor; special skeletal muscle fibers in fibrous capsule in parallel with muscle fibers. Middle is " swollen".
Muscle Spindle (1a sensory axons wrap around muclse fibers of spindles)
____sensory axons: larges and fastest, enter SC via dorsal root adn form synapses on interneurons and alpha motor neurons of ventral horn.
_____ ______ reflex: increase synapse separates sensory input from motor neuron output.
Myotatic Reflex (Stretch Reflex)
_______ _______: weight on a muscle causes muscle spindle to stretch which depolarizes 1a endings and depolarizes alpha motor neurons. This increases AP in motor neurons and muscle contracts.
Myotatic Reflex (Stretch Reflex)
_______ Fibers: great number of fibers outside of spindle (muscle bulk) innervated by alpha motor neurons.
_______ Fibers: modified skeletal fibers in muscle spindle; innervated by gamma motor neurons
_____ Loop: gamma motor neuron--> intrafusal muscle fiber--> 1a afferent--> alpha motor neuron--> extrafusal muscle fiber--> repeat
____ _____ ____: proprioception, monitors force of contraction; located at junction on muscle and tendon; innervated by 1b afferents in series with muscle fibers.
Golgi Tendon Organ
_____ _____ _____: some inhibitory to alpha motor neurons that innervate same muscle. protects muscle from overload and regulates muscle tension in optimal range.
Reverse Myotatic Reflex
____ _____: respond to change in angle, direction, and velocity of movement of joint.
______ ______: myotatic reflex involves contraction of flexors and also relaxation of antagonist.
______: descending control destroyed
_____ _____: withdraw limb from pain
__ ___ ___: activates extensors and inhibits flexors of opposite limb
crossed extensor reflex
_____ of _____: maintians muscle bulk, helps support circulatory function, assist in activities of daily living, may assist with postural control