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(trigeminal pathway, somatosensory cortex) - Coggle Diagram

- - - - these axons project
        to one of the 3 locations
        (1.mesencephalic nucleus-midbrain
        2.principle sensory nucleus- in pons
        3.spinal nucleus-lower part of medullar & upper spinal cord)
        
        spinal nucleus-recieves info similar to spinothalamic tract
        ie - pain & temperature sensations
        
        mesencephalic nucleus & principle sensory nucleus
        recieve info like that of dorsal column system
        ie
        
        touch
        
        pressure
        
        vibration
        
        proprioception
        
        axons from this 2nd neuron
        decussate
        & ascend to the thalamus
        along the trigeminothalamic tract
        
        in the thalamus,
        each axon synapses with the 3rd neuron
        in it's repective pathway
        
        axons frm the 3rd neuron
        then project frm the thalamus
        to the
        primary somatosensory cortex
        of cerebrum
- - - - is located in the postcentral gyrus
        containing the
        Brodmann's area 3,2,1
        
        area 3
        
        area 3 neurons respond to
        
        light touch
        
        n receive a dense input frm the thalamus
        
        area 1 & 2
        
        area 1 & 2 neurons respond to
        
        deep stimuli such as
        pressure & joint movements
        
        & receive few thalamic fibers
        
        is supplied by afferents frm the
        
        opposite side of the body
        but
        
        from both sides of the face
        
        there is a detailed (somatotropic)
        localization of fibers
        frm various parts of the body
        in the postcentral gyrus
        
        the arrangement of thalamic projection
        is such that body is represented
        upside down with the
        -legs on the top &
        -head at the foot of the gyrus
        
        the extent of it's representation depends on
        -the parts of the body that are
        most densely innervated
        (ie, the no of specialized sensory receptors)
        
        therefore the
        -fingers
        -thumb
        -& lips
        are represented by the largest areas of
        the somatosensory cortex
        
        removal of S1 produces:
        
        deficits in
        -fine touch
        -position
        -& discrimination power
        
        deficits in
        -sensory processing in S2
    - - is located in the
        parietal cortex
        n is mostly buried in the
        superior wall of the sylvian fissure
        (lateral cerebral sulcus)
        
        unlike S1
        
        is supplied by afferents from
        both sides of the body
        
        like S1
        
        it menifests a dermatomal (point-to -point) sequence of representaion.
        
        posterior region
        
        receives afferents frm legs
        
        neurons here can be excited by:
        - touch
        - auditory
        - & nociceptive stimuli
        
        anterior parts
        
        receive afferents frm face
        
        neurons here respond to:
        - touch
        
        the face area of S2 is immediately adjacent to the face area of S1.
        -so the face is represented twice in the somatosensory cortex in areas S1 & S2
        
        removal of S2 produces:
        
        deficits in
        -learning based on tactile discrimination power
        
        S2 removal has no deficits in
        sensory processing of S1