motor cortex - bayanbox.irbayanbox.ir/view/8988788415846394404/motor-cortex.pdf · motor cortex...

Motor Cortex

1. Upper Motor neurons2. Primary Motor area (M1)3. Pre-motor area (PMA)4. Supplementary Motor area (SMA)5. Frontal eye field (area 8)

Cortical Motor System

Primary motor cortex

Execution of movement• Somatopically organized

• Massive descending projections to spinal

cord

• Damage => pronounced weakness in

affected body parts

• Stimulation => simple mov’t in small

muscle groups

Two major descending

pathwaysPyramidal vs. extrapyramidal

Striated muscles

Lower motor neurons

(brain stem and spinal cord)

Brain stem

centers

Motor cortex

Pyramidal

system Extrapyramidal

system

• Pathway for

voluntary movement

• Most fibers originate

in motor cortex (BA

4&6)

• Most fibers cross to

contralateral side at

the medula

• Pathways for postural

control/certain reflex

mov’t

• Originates in brainstem

• Fibers do not cross

• Cortex can influence

this system via inputs to

brain stem

Somatotopy in M1

Motor Cortex Homunculus

• Columnar organization:

• Thumb adduction ● Thumb abduction ■

* Mirror Neurons

Sensory Motor Cortex → Betz Neurons

Direct cortico-spinal synapse

Motor Cortex Symptoms

Upper Motor Neurons Diseases:

• ↑ Pyramid × contra-lateral paralysis

Hypertonocity, Spasticity

• Babinski Sign : Plantar reflex

• ↓ Pyramid × ipsi-lateral paralysis,

Knee jerk reflex absent, passive

movement, clonus (rythmic contraction

of flexor muscles)

• Corticobulbar lesion► contralateral

lower facial muscles paralysis

• Intensive physiotherapy

Frontal Eye Field

Voluntary Eye Movement

• Frontal eye field (caudal area 8)

• Stimulation FEF → eye conjugate deviation to opposite side

• (L) FEF → pontin reticular formation (R) → abducens (R. Lat.Rectus)

• R. abducens → L. oculomotor → (L. Med. Rectus)

Sensory Motor Cortex