【基础医学】神经传导路

Nervous Pathway . The Sensory (Ascending) Pathways ) The deep sensory (or the proprioceptive) pathways1.The conscious deep sensory pathways1).The deep sensory and fine touch pathways of trunk and limbsThe first neurons: spinal ganglionThe second neurons: gracile and cuneate nucleiThe first neurons: ventroposterior lateral nucleusDecussation of medial lemniscusLesion : hemiplegia Receptors muscles tendon periosteum and jointSpinal nerve（ peripheral processes）Spinal gangliaThe first neuronsDorsal roots(medial bundle)(Central processes : fasciculus cuneatus and gracilis)Gracile and cuneate nuclei The second neuronsthalamocortical tractRunning through the posterior limb of the internal capsuleCortex of the cerebrumDecussation of medial lemniscusThe third neuronsVentroposterior lateral nucleusMedial lemniscus, through the medulla oblongata pons and midbrain2.The unconscious deep sensory pathwayReceptors muscles tendon periosteum and jointSpinal nerve（ peripheral processes）Spinal gangliaThe first neuronsDorsal roots(Central processes)Thoracic nucleus of C8-C12 and lateral part of lamina - of lumbosacral enlargement The second neuronsThe anterior and posterior spinocerebellar tractsBy way of the superior and inferior cerebellar pedunclesCortex of the cerebellum ) The superficial sensory pathways1.The superficial sensory pathway of trunk and limbs1).The pathway concerned with pain and thermal sensationsThe first neurons: spinal ganglionThe second neurons: nucleus propriusThe first neurons: ventroposterior lateral nucleusCross through the anterior white commissure Receptors Cutaneous exteroceptor of the trunk and limbsSpinal nerve（ peripheral processes）Spinal gangliaThe first neuronsDorsal roots(lateral bundle)(Central processes : dorsolateral fasciculus)Nucleus proprius The second neuronsthalamocortical tractRunning through the posterior limb of the internal capsuleCortex of the cerebrumCross through the anterior white commissure and form the lateral spinothalamic The third neuronsVentroposterior lateral nucleusRun upward within one or two segments2).The rude tactile and pressure sensation pathwayThe route is almost same as the pain and thermal pathway except for a little difference. .The superficial sensory pathway of head and faceReceptor skinmucosaPeripheral processesTrigeminal ganglionThe first neuronsCentral processes enter the ponsSpinal nucleus of trigeminal nerve（ pain and thermal）、 pontine nucleus of trigeminal nerve（ tactile and pressure）The second neurons trigeminal lemniscusVentroposterior medial nucleusThe third neuronsThalamocortical tractPosterior limb of the internal capsule Inferior part of the postcentral gyrus ) The visual pathways1.Visual pathwaysReceptor Rod and cone cellsBipolar cells The first neuronsGanglionic cellsThe second neuronsOptic nerve, optic chiasma ,optic tractPartial decussatuion of the fibers from the nasal halves of the retinaLateral geniculate bodyThe third neuronsOptic radiationPosterior limb of the internal capsuleBoth back of the calcarine sulcus2. Pupillary reflexes(the direct pupillary light reflex and indirect pupillary light reflex)Retina Optic nerveOptic chiasmaBilateral optic tractBrachium of superior colliculus Pretectal areaAccessory nucleus of oculomotor nerveOculomotor nerveCliary ganglionPostganglionic fibersSphincter of the iris ) Acoustic pathwayReceptorCorti organ Cochlear ganglionThe first neuronCochlear nerve through the niternal acoustic meatusCochlear nucleiThe second neuronsTrapezoid bodyLateral lemniscusMedial geniculate bodyThe third neuronsAcoustic radiation Transverse temporal gyri . The Motor (Descending) PathwaysThe motor pathways include pyramidal and extrapyramidal systems.Upper motor neuronsLower motor neurons ) The pyrmidal system1.The corticospinal tract： arising from the giant pyramidal cells and certain other smaller cells of the superior and middle parts of the precentral gyrus and anterior part of the paracental lobule. course the posterior limb of internal capsule,intermediate 3/5 of the crus cerebri,the basilar part of the pons. form the pyramidal decussation (70-90%) and continues as the lateral corticospinal tractin opposite side. uncrossed fibers form the anterior corticospinal tract.2.The corticonuclear tract： arising from the inferior part of the precentral gyrus . course through the genu of internal capsule and the brain stem. gives rise to the collaterals to the bilateral oculomotor , trochlear , trigeminal motor , ambiguus , accessory nuclei and superior part of the facial nucleus , and to the contralateral hypoglossal nucleus and the inferior part of the facial nucleus.Supranuclear paralysis (spastic paralysis or hard paralysis)Infranuclear paralysis (flaccid paralysis or soft paralysis)This patient with right facial nerve paralysis cannot close the right eye. On smiling, the right side of his face is immobile. He is unable to wrnkle the forehead.This patient with right facial nerve paralysis cannot close the right eye. On smiling, the right side of his face is immobile with a flattened nasolabial fold ) The extrapyramidal systemIt is a common name for the descending pathways except the pyramidal system.Main functions : 1. Regulate the tonicity of the muscles.2. Coordinate the muscular activities .3. Maintain the normal body posture and produce habitual and rhythmic movements.1. The cortico-neostriated body-dorsothalamus-cortex circuitCortical cellsCaudate nucleus and putamenGlobus pallidus