Motor Neuron Cell Body, Axon, Motor End Plate, Innervated Muscle fibers.
A given number of muscle fibers connected to a motor nerve -- there are small, medium, and large motor units.
Different Motor Units have different performance characteristics -- see later table of motor unit characteristics.
Used to protect the fibers, to connect multiple fibers, to hold together all the fibers, and to attach fibers to bones.
Three distinct connective protective layers of tissue (Endomysium, Perimysium, Epimysium)
Endomysium -- most inner sheath, constitutes the skin of the individual muscle fibers.
Perimysium -- middle sheath that bundles groups of fibers together into Fasciculi (plural) or a Fasciculus (single)
Epimysium -- most outer sheath that bundles all the fasciculi together forming a complete muscle.
Vertical (Depth) Structure: Three levels of structure (fibers, myofibrils, myofilaments)
Muscle is composed of fibers which are composed of myofibrils which are composed of myofilaments (Muscle Magnification & Fiber Magnification).
Myofibrils are made of myofilaments that slide across each other. (Myofibril Magnification)
Actin (small filaments, also known as thin) have the active sites for cross-bridging.
Myosin (large filaments, also know as thick) have the attaching heads
Horizontal (Length) Structure: Sarcomere -- the smallest complete contraction unit of the muscle!!!
a muscle fiber (cell) is made of many sarcomeres connected end to end.
Major Components of muscle
Sarcolemma final thin elastic sheath that contains the individual fibers' contents -- it is the mucle cell's membrane.
Sarcoplasm -- the muscle cell's (fiber) cytoplasm
Sarcoplasmic reticulum -- provides structural support and longitudinal stimulation of fibers
t-tubules (transverse tubules) -- conducting pathways that carries stimulation through the fiber's cross section.
terminal cisternae (lateral sacs) -- location of stored calcium (Ca++) that is actively pumped into and out of the sarcomeres.
"triad" -- Junction where the t-tubules, sarcoplasimic reticulum, and terminal cisternae meet is known as the "triad".