Sensory and motor pathways Dr. Petra Balogh Semmelweis University 2014

Reorganization of gray matter Closed part of medulla Opened part of medulla Spinal cord Pontomedullary junction pons midbrain

The division of information DORSAL-SENSORY VENTRAL-MOTOR AGAIN!!! SENSORY=AFFERENT MOTOR=EFFERENT

Basic definitions General sensation: Special sensation: Pain Temperature Pressure, vibration Proprioception (information from joints, tendons, muscles) Special sensation: Taste

Sensory pathways Sensory information is induced from the environment (=stimulus) and forwarded to the central nervous system (=spinal cord, brain) through receptors and afferents (=axons of sensory neurons) All the first order neurons of sensory pathways are pseudounipolar cells and the cell body is located in the dorsal root ganglia (spinal cord) or in ganglia of cranial nerves

General organisation of spinal cord Pseudounipolar cell

Division of sensory information Epicritic sensation: fine touch, fine vibration-pressure, proprioception, two point discrimination B) Protopathic sensation: rough touch, rough vibration-pressure pain and temperature

Ascending (sensory) tracts of spinal cord

Epicritic sensory pathways of SC I. Cuneate and gracile fasciculi Carry information about (fine touch, vibration, pressure, two point discrimination, proprioception There are synapting points (medulla and thalamus Vpl nucleus)till the information reaches the cortex From the level of medulla the fibers cross the midline and named as medial lemniscus the fibers project to primary somatosensory area (Brodman 3,1,2) This pathway is considered a CONSCIOUS epicritic one!! General rule: all the tracts going through the thalamus and reaches the cortex is a consciuos tract Medial lemniscus

Epicritic sensory pathways of SC II. Dorsal(posterior) spinocerebellar tract (uncrossed) Ventral (anterior) spinocerebellar tract (crossed-at the level of spinal cord) Terminate in the cerebellar cortex as mossy fibers Both carry information about epicritic sensation but they do not reach the thalamusUNCONSIOUS tracts

Protophatic pathway of SC (anterolateral system) Ventral and lateral spinothalamic tracts (crossed) Ventral spinothalamic tract carries information about rough touch, vibration, pressure Lateral spinothalamic tract carries information about pain and temperature Both terminate in the thalamus VPl nucleus (conscius tract) and the fibers after synapse reach the primary somatosensibility area (Brodman 3,1,2 area) Anterolateral system

Epicritic and protophatic pathway in the head and neck region Afferent information arrives to CNS through branches of trigeminal nerve Into the spinal trigeminal nucleus After synapse via the trigeminal lemniscus the information forwarded to thalamus Vpmcortex (primary somatosensory area, Brodman 3,1,2)

Epicritic and protophatic pathway of head and neck region II. The distribution of trigeminal nerve and its branches: V/1: ophtalmic nerve V/2: maxillary nerve V/3: mandibular nerve

Epicritic and protophatic pathway of head and neck region III.

Taste information (special sensation) In the epithelium of papillae of tonguetaste buds The stimuli(sweet, salty, sour, bitter, water) are forwarded to the CNS through branches of cranial nerves Repeat the innervation of tongue!!!!

Taste pathway I.

Taste pathway II. Primary gustatory area-cortex (Brodman 43) Solitary tract nucleus Peripheral nerves-carrying tasting fibers

Summary of sensory pathways Epicritic, protopathic info via trigeminal lemniscus Head and neck Thalamus Vpm Taste info via solitary tract Sensory cortex Epicritic info via medial lemniscus Spinal cord (trunk and limbs) Thalamus Vpl Protopathic info via spinothalamic tract

Motor pathways (descending tracts)

Motor pathways I. Pyramidal tract =corticospinal tract Anterior corticospianltract (crosses at the level of SC) Lateral corticospinal tract (crosses at the level of medulla=pyramidal decussation) The motor axis of the body Gives the command to the skeletal muscles ‘what to do’

Innervation of skeletal muscles Alpha motor neurons innervate the skeletal muscles of trunk and limbs (neuromuscular junctions-motor end plates)

Motor pathways II. Extrapyramidal system Refine the activity of corticospinanl tract and gives the command ‘how to do’ Maintain a continous muscle tone (mainly in antigravitation muscles=extensors) Synchronize the movements of eyeball and head-neck muscles Reset the sensitivity of muscle spindle!!

The tracts of extrapyramidal system Vestibulospinal tract Reticulospinal tract Reubrospinal tract Olivospinal tract Tectospinal tract

Brodmann Areas: cortical representatives of sensory and motor functions

anatomical localizaton Brodmann areas functions anatomical localizaton 3, 1, 2 primer somatosensory area postcentral gyrus paracentral lobul   secundary somatosensory area dorsalwall of lateral cerebral sulcus 5,7 associative somatosensory area parietal eye centre superior parietal gyrus 17 primer visual area sulcus calcarinus striated area 18 19 secundary visual area tercier visual area parastriate area peristriate area 41, 42 auditory area transversal temporal gyri = Heschl gyrus (22), 40, 39 Wernicke area 22 sensory speech centre memorizing of voices, recognizing of words supramarginal gyrus ( 40) angular gyrus (39) planum temporale ( 22) 45,44 motor speech area of Broca pars opercularis, pars triangularis 43 primary taste area lower part of postcentral gyrus 4, 4s, 6a, 6b primary motor area precentral gyrus paracentral lobule secundary motor area dorsal wall of lateral cerebral sulcus 6aß 8 premotor area frontal eye field anterior to precentral sulcus post part of middle frontal gyrus 9, 10, 11, 12 prefrontal area

Sensory homunculus Picture of the body with proportions of its cortical map

Thank you for the attention!