muscle relaxation

phase 1 of muscle fiber relaxation

remove the stimulus (acetylcholine), uses acetylcholinesterase to make acetate and choline

acetylcholinesterase

enzyme found in synaptic cleft, breaks down the acetylcholine

phase 2 of muscle fiber relaxation

stop electrical activity along the sarcolemma

phase 3 of muscle fiber relaxation

active reuptake of calcium into sarcoplasmic reticulum

phase 4 of muscle fiber relaxation

troponin and tropomyosin return to original positions on thin myofilament → cover up active sites on actin

intrinsic elastic properties, gravity, contraction of the antagonist muscle

3 things that cause re-lengthening of a muscle

endomysium

connective tissue layer around a muscle fibers, finds satellite cells

perimysium

connective tissue around a fasicle

epimysium

connective tissue layer around a gross muscle

gross muscle

bundle of fasicles

motor unit

a motor neuron and all of the muscle fibers that it innervates

recruitment

steady increase in number of active motor units in a gross muscle

small motor unit

motor neuron that connects to a small number of muscle fibers

large motor unit

motor neuron that connects to a larger number of muscle fibers