Week13

they are located in the ventral horn of spinal cord, one alpha motor metro innervates only one type of skeletal muscle fiber, alpha motor neurons can innervated a variable number of skeletal muscle fibers, their axons leave the spinal cord through the ventral roots

have their cell bodies in the ventral horn gray matter, can receive excitatory input from the contralateral motor cortex, receive an input from the vestibular nuclei which involved in posture

consists of a motor nueron and all the muscle fibers it supplies

they monitor the tensions of skeletal muscles, they are proprioceptive sensory receptor, is innervated by affetrent type In sensory nerbe fiber

Renshow cells, interneurons

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the static nuclear bag fiber has type 2 afferents, the intramural fibers are parallel with the extrafusal fibers

the muscle spindles has both sensory and motor components, muscle spindles measure the lingth of skeletal muscle, muscle spindles receive both afferent and efferent nerve fibers

the dynamic nuclear bag receptor contains elastic elements, the muscle spindle density is high in the neck muscles, the muscle spindle density is low in the back muscles

nuclear bag jntrafusal fibers monitor the rate of muscle stretch, nuclear chain fibers produces a steady discharge proportional to the amount of stretch, the rubrospinal tract exerts its major influence in the muscle of the arms, the axons of the lateral corticopinal tract may synapse directly with motor neurons in the spinal cord, Golgi tendon organs respond to the for ce developed by muscles

monosynapticis, is promoted by stimulation of gamma motor eurons, is associated with reciprocal inhibition of antagonist muscles

it is ininitated by passive stretch of the muscle, there is a limited(0.5-1ms) synaptic decay, the muscle spindle is the receptor, is accompanied by reciprocal innervation of antagonistic muscle groups

it is a bisynaptic reflex, it is also called the Golgk tendon reflex, skeletal muscle contraction causes the against muscle to simultaneously lengthen and relax

involuntary spinal reflex, extericeltive reflex

the central dearly is less than 1ms in case of monosynaptic reflex, the knee jerk reflex is an exam0le of a stretch reflex

motor areas of the cortex receive somatosensory input, the pre motor are has direct control of some movements ( i.e. trunk muscles of the body)

substantial nigra, subthalamic nucleus, putamen