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motor neurons of anterior grey horn of spinal cord to innervate skeletal muscle

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Lower motor neurons

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Motor neurons of anterior grey horn of spinal cord to innervate skeletal muscle

Lower motor neurons

Neurons of cortex and other supraspinal centres send their axons to LMN for higher cortical control

Upper motor neurons

Cerebellum receives information about every movement from

Corticopontocerebellar pathway

Pyramidal tracts: end on

Anterior horn ( motor) neuron cells of spinal cord

Origin from motor cortex Descend through corona radiata then Decussate at Junction of medulla & spinal cord 75% of fibres cross to opposite side Terminate in anterior horn cells 25% uncrossed fibres Cross later in spinal cord and descend to cervical and upper thoracic segments

Corticospinal or Pyramidal tracts

Corticospinal or Pyramidal tracts lesion cause

Loss of voluntary skilled movements on opposite side

Originate in Red nucleus in MB in superior colliculus level Cross to opposite side in MB Terminate in anterior horn of SC • Facilitate activity of Flexor muscles &Inhibits extensor

Rubrospinal tracts

Originate in neurons in Superior colliculus cross to opposite side in MB Terminate in upper cervical segments of SC Coordinates visual – body movements: turning head to source of visual stimuli +coordinating extraocular muscle movement

Tectospinal Tracts

Originate in Vestibular nuclei in medulla & pons Lateral division Ends on anterior horn of same side Facilitate activity of extensor muscles Medial division give longitudinal fasciculus for control and balance of head and eye movements

Vestibulospinal tracts

Originate in Reticular formation in medulla and pons Influence voluntary and reflex motor activity Mainly proximal limb muscles and axial muscles , can control sympathetic and parasympathetic outflow & cardiorespiratory centres

Reticulospinal tracts

Flaccid paralysis ,Atrophy of muscles ,Muscle fasciculations & Loss of reflexe

Lower Motor Neuron lesions

Loss of fine, voluntary skilled movements in opposite side Babinski’s sign +ve Absent of superficial abdominal cremasteric reflex

Lesion of the pyramidal tracts

Spasticity or hyper tonicity , Rigidity ,Severe paralysis ,Clasp knife reaction

UMN (extra pyramidal) lesion