Motor System (1)

Motor signals typically begin in an upper motor neuron in the thalamus.

• True

• False

motor unit consist of

• Motor neuron

• ­nerve fibers that innervate skeletal muscle fibers

• ­Muscle fibers it innervates

• receptor field

Alpha motor neuron

• innervates intrafusal skeletal muscle

• will cause skeletal muscle to contract

• consist of 2 subtype (alpha1 and alpha2)

• adjust the sensitivity of muscle spindles

Name this receptor

• muscle spindle

• golgi tendon organ

• free nerve ending

• pacinian corpuscles

sensory fibers related to muscle spindles

• group 1a

• group 1b

• group II

Function of this structure

• sense tendon tension or rate of change of tension

• maintain muscle length

• detect muscle length or rate of change of length

Structure X

• consist of II afferent fibers

• involved in inverse stretch reflex

• is regulated by descending tract

Upper motor neuron

• has cell bodies in spinal cord

• track is from cns to posterior horn cells

• terminates peripherally as myoneural junction

Lower motor neuron lesion includes

• hypertonia

• rigidity

• extonsor plantar response

• muscle wasting

Upper motor neuron lesion includes

• hypotonia

• hypereflexia

• fasciculation

• positive Babinski test