- General somatic efferent(GSE) supply to the face is by facial nerve.Main motor nucleus that carries GSE fibers to the facial muscles is located at lower pons lateral to the abducent nucleus.GSE path way begins from the primary motor cortex ,fibers from motor cortex connected to its cell in thalamus this is upper motor neuron. upper motor nuron fibers goes to opposite side main motor nucleus ,some fibers goes to same side facial nucleus.lower motor neuron is located in lower pons as facial nucleus. fibers from opposite cortex to the nucleus are supplied to the lower quadrant of the contralateral face(that's means opposite cerebral cortex supplies lower quadrant of the facial muscles)upper quadrant of facial muscles receive impulses from both motor cortex as mentioned above.
- so if there is a upper motor neuron lesion contralateral side of the lower quadrant facial muscles get weaken.
- It is a collection of white mater fibers.
- has 2 limbs called anterior and posterior ,2 limbs joined each other by genu
- Anterior limb is related medialy to the head of the caudate nuclues, laterally to the lentiform nuclues(anterior)
- Posterior limb is related medially to the thalamus ,laterally to the lentiform nucleus (posterior)
- Anterior limb contains-frontopontine fibers
- Genu contains-cortico nuclear fibers( efferent fibers for cranial nerve nuclei)
- Posterior limb contains- cortico spinal fibers( Ant 2/3),thalamo cortical fibers
Blood supply of the internal capsule
- From striate arteries derived from anterior choroidal arteries ,anterior cerebral,middle cerebral arteries.
Lesions- Because internal capsule contain cortico spinal tracts in the poterior limb anterior 2/3 if there is a any lesion in that region cause to have contralateral motor weakness in the body except face.
- Likewise if the lesion is in the genu area contralateral lower half of the face will have a muscle weakness (since upper half of the face is supplied by the both cortical ares there is no motor weakness on the upper facial muscles)
Causes for the lesions- Hemorrhage of a striate artery(cerebro vascular accident)
- Thrombosis of a striate artery
- Effect of the lesion to the body varies according to the site of the lesion of internal capsule.
