The Motor Pathways The motor pathways are concerned

The Motor Pathways 运动传导路

The motor pathways are concerned with motor function, include pyramidal system 锥体系 extrapyramidal system 锥体外系 upper motor neuron （一） Pyramidal System 锥体系 It concerned with voluntary movement 随意运动of the skeletal m. and is composed of two orders of neurons: upper motor neuron 上运动神经元 lower motor neuron 下运动神经元 lower motor neuron effector

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

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

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

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

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

Corticonuclear tract facial nucleus hypoglossal nucleus and inferior part of facial nucleus receive only the fibers from the contralateral corticonucleal tract. 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 核上瘫; The paralysis caused by the injury of the lower motor neuron is called the infranuclear paralysis 核下瘫

supranuclear paralysis of facial n. 面神经核上瘫 ---- the paralysis of facial m. in opposite side below the pelpebral fissure 对侧睑裂以下 面肌瘫痪 infranuclear paralysis of facial n. 面神经核下瘫 ---- the paralysis of facial m. of same side 同侧面肌瘫

supranuclear paralysis of hypoglossal n. 舌下神经核上瘫 ----when tongue extend, the apex of tongue inclined to the opposite side infranuclear paralysis of hypoglossal n. 舌下神经 核下瘫 ----when tongue extend, the apex of tongue inclined to the same side

Effects of Upper and Lower Motor Neuron Damage UMN damage ( supranuclear paralysis ) LMN damage ( infranuclear paralysis ) Paralysis Spastic 痉挛性（硬瘫） Flaccid 软瘫 Muscle tone 肌张力 Increased↑ Decreased↓ tendon reflexes 腱反射 Increased↑ Decreased ↓ Pathological reflexes病理反射 Positive (＋) Negatively (－) Amyotrophy 肌萎缩 No present Distinctly 明显

（二） Extrapyramidal System 锥体外系 1. composision：the extrapyramidal System include the 2. following structures Cerebral cortex、corpus striatum 纹状体、dorsal thalamus、subthalamus、red necleus、substantia nigra、pontine neuclei脑桥核、vestibular neuclei、 cerebelum、 reticular formation and the fibers connection among them.

1、The corticoneosstriated bodydorsothalamus –cortex circuit 皮质—新纹状体—丘脑—皮 质环路 对皮质运动区有反馈调节作用 2、The neostriated body-subsantia nigra circuit 新纹状体—黑质环路 多巴胺能通路，损伤可致震颤 麻痹

1. Injury of the internal capsule

1. Injury of the spinal cord