The Motor Pathways SHANDONG UNIVERSITY Liu Zhiyu

（一） Pyramidal System The motor pathways are concerned with motor function, include pyramidal system extrapyramidal system It concerned with voluntary movement of the skeletal m. and is composed of two orders of neurons: upper motor neuron lower motor neuron upper motor neuron lower motor neuron effector

The pyramidal system consists of corticospina tract corticonuclear tract upper motor neuron lower motor neuron effector Upper Motor Neurons Upper Motor Neurons lie in the motor area of cerebral cortex, Connect directly or through interneurons to lower motor neurons, Connect directly or through interneurons to lower motor neurons, Lower Motor Neurons Lower Motor Neurons include cranial motor nuclei and motor neurons in anterior horn of spinal cord. their axons leave the CNS and extend though peripheral nerves to supply skeletal muscles their axons leave the CNS and extend though peripheral nerves to supply skeletal muscles

Corticospinal tract Decussation of pyramid Lateral corticospinal tractAnterior corticospinal tract upper motor neuron Lower motor neuron upper motor neuron is the Giant pyramidal cells (Betz cells) and other pyramidal cells in superior 2/3 of precentral gyrus and ant. part of paracentral lobule

1. Corticospinal Tract Motor neurons of anterior horn Lateral corticospinal tract Anterior corticospinal tract Lower motor neuron is the Motor neurons of anterior horn of spinal cord

2.Corticonuclear Tract Giant pyramidal cells and other pyramidal cells in lower 1/3 of precentral gyrus Genu of internal capsule Brain stem Cranial nerves Cranial motor neuclei upper motor neuron lower motor neuron Skeletal m. of the head,neck and face. Corticonuclear Tract

Bilateral ： nucleus of oculomotor n., nucleus trochlear n., motor nucleus of trigeminal n., nucleus of abducent n. ambiguus nucleus, nucleus of accessory n. superior part of facial nucleus. The Corticonuclear tract send out fibers to end Contralateral: inferior part of facial nucleus hypoglossal nucleus facial nucleus hypoglossal nucleus

Corticonuclear tract hypoglossal nucleus and inferior part of facial nucleus receive only the fibers from the contralateral corticonucleal tract. facial nucleus hypoglossal nucleus

The injury of the unilateral corticonuclear tract can usually cause the paralysis of the contralateral glossal m. and facial m. below the palpebral fissure. The paralysis caused by the injury of the upper motor neuron is called supranuclear paralysis The paralysis caused by the injury of the lower motor neuron is called the infranuclear paralysis

infranuclear paralysis of facial n. supranuclear paralysis of facial n the paralysis of facial m. in opposite side below the pelpebral fissure ---- the paralysis of facial m. of same side

infranuclear paralysis of hypoglossal n when tongue extend, the apex of tongue inclined to the same side supranuclear paralysis of hypoglossal n. ----when tongue extend, the apex of tongue inclined to the opposite side

Effects of Upper and Lower Motor Neuron Damage UMN damage ( supranuclear paralysis ) LMN damage ( infranuclear paralysis ) ParalysisSpasticFlaccid Muscle toneIncreased↑Decreased↓ tendon reflexesIncreased↑Decreased ↓ Pathological reflexes Positive ( ＋ )Negatively ( － ) Amyotrophy No present Distinctly 明显

（二） Extrapyramidal System 1.composision ： the extrapyramidal System include the following structures Cerebral cortex 、 corpus striatum 、 dorsal thalamus 、 subthalamus 、 red necleus 、 substantia nigra 、 pontine neuclei 、 vestibular neuclei 、 cerebelum 、 reticular formation and the fibers connection among them.

（二） Extrapyramidal System 2. character

1 、 The cortico- neosstriated body- dorsothalamus –cortex circuit 2 、 The neostriated body-subsantia nigra circuit

1. Injury of the internal capsule

1. Injury of the spinal cord

3. Upper 、 Lower Motor Neurons ① Upper motor Neurons: ② Lower motor Neurons: ③ supranuclear paralysis ： hard paralysis ④ infranuclear paralysisflaccid paralysis or soft paralysis ，