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 NeuronsUpper Motor Neurons

lie in the motor area of cerebral cortex,

Connect directly or through interneurons to Connect directly or through interneurons to lower motor neuronslower motor neurons, ,

Lower Motor NeuronsLower Motor Neurons

include cranial motor nuclei and motor neurons in anterior horn of spinal cord.

their axons leave the CNS and extend their axons leave the CNS and extend though peripheral nerves to supply skeletal though peripheral nerves to supply skeletal musclesmuscles

Corticospinal tract

Corticospinal tract

Decussation of pyramid

Lateral corticospinal tract Anterior 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. su

perior 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 c

alled 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 )

Paralysis Spastic Flaccid

Muscle tone Increased↑ Decreased↓

tendon reflexes Increased↑ Decreased ↓

Pathological reflexes Positive ( ＋ ) Negatively ( － )

AmyotrophyNo present Distinctly 明显

（二） Extrapyramidal System

1. composision ： the extrapyramidal System include the

following structures

Cerebral cortex 、 corpus striatum 、 dorsal thalam

us 、 subthalamus 、 red necleus 、 substantia nig

ra 、 pontine neuclei 、 vestibular neuclei 、 cereb

elum 、 reticular formation and the fibers connectio

n 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:

③supranuclear paralysis ： hard paralysis

④infranuclear paralysisflaccid paralysis or soft paralysis

，