Endoneurium - delicate connective tissue around individual axons. In development, small skeletal muscles innervated by different ventral rami fuse to muscles with compound origin. Gamma efferents are the axons. Sensory neuron always active, enters at dorsal root, synapse on motor neurons in gray horn. Collaterals to brain Stretch nuclear bag distorts dendrites , stimulates sensory neuron, high frequency action potentials Compressing nuclear bad reduces action potential frequency Sensory neuron synapses on CNS motor neuron that controls extrafusal fibers of same muscle.
Some muscles work in opposition of each other.
Crossed extensor refelx at same time as flexor reflex Stiffens other leg to support body weight when you pull your foot away. Positive Babinski relfex Positive reflex disappears as descending motor pathways develop. Reappear if higher centers or descending tracts damaged.