Central Processing of somatosensory input Flashcards
What is carried in the dorsal column medial lemniscal pathway?
Discriminatory touch, pressure, vibration, conscious proprioception
What is carried in the spinothalamic tract?
Pain, thermosensationm crude touch, itch, tickle
Where is the decussation of the DCML pathway?
Brainstem
Where is the decussation of the spinothalamic tract?
At all levels of the cord- close to the point of entry via lissauer’s tract
Dorsal columns consist of the _____ _____ ____ and the more lateral _____ _____
Dorsal columns consist of the medial gracile tract and the more lateral cuneate tract
Sensory input to T6 and below (including legs and lower trunk) travels in the ______ ____ whereas input above level T6 travels in the _____ ____
Sensory input to T6 and below (including legs and lower trunk) travels in the gracile tract whereas input above level T6 travels in the cuneate tract
Across the columns there is a somatosensory map of sensory inputs from lateral to medial: _______, ______, ______ and ______
Across the columns there is a somatosensory map of sensory inputs from lateral to medial: cervical, thoracic, lumbar and sacral
Dorsal and ventral spinocerebellar tracts convey unconscious _______ information to the ______: important in motor coordination
Dorsal and ventral spinocerebellar tracts convey unconscious proprioceptive information to the cerebellum: important in motor coordination
1st order neurones of the DCML synapse
Deep in the dorsal horn upon 2nd order neurones (spinal reflexes)
OR
in the dorsal column gracile nucleus or cuneate nucleus
Axons of 2nd order neurones of the dorsal column nuclei cross collectively in the _____ _______ ________ and ascend in the _______ _______ to the ______ ________ _____ nucleus of the ______
Axons of 2nd order neurones of the dorsal column nuclei cross collectively in the great sensory decussation and ascend in the medial lemniscus to the ventral posterior lateral nucleus of the thalamus
3rd order thalamic neurones of the DCML pathway project to the _______ _____________ cortex via the ________ ________ _______
3rd order thalamic neurones of the DCML pathway project to the primary somatosensory cortex via the posterior internal capsule
What is stereognosis?
Ability to recognise an object by feeling it
What are the capabilities of the DCML pathway?
Stereognosis Vibration Detection Fine touch Conscious proprioception Weight discrimination
What produces contrast enhancement?
When information is conveyed from one neurone to the next in a sensory pathway, differences in the activity of adjacent neurones are amplified, producing contrast enhancement
What is lateral inhibition?
When one neurone is active it inhibits the activity of its neighbours via inhibitory interneurons, a process known as lateral inhibition
What is the role of lateral inhibition?
It sharpens stimulus perception and is one mechanism by which information is transformed at the synapses of the DCML pathway
What mediates general somatic information from the anterior head?
Two trigeminothalamic pathways
What are the two trigeminothalamic pathways
1) Central terminals of the trigeminal nerve synapse upon second order neurones in the chief sensory nucleus (general tactile stimuli) and then decussate and project to the ventroposteriomedial nucleus of the thalamus
2) Central terminals of the trigeminal nerve synapse upon second order neurones in the spinal nucleus (pain, temperature information) and then decussate and project to the ventroposteriomedial nucleus of the thalamus
Third order neurones then relay information to the cortex via thalamocortical neurones
Where is the somatosensory cortex located?
Post central gyrus of the parietal cortex- posterior to the central sulcus and adjacent to the posterior parietal cortex
The ____ are the top of the post central gyrus with the _____ at the lower end, but the _______ separates the head from the face
The toes are the top of the post central gyrus with the tongue at the lower end, but the hand separates the head from the face
How many layers are present in the somatosensory cortex?
six cell layers (I-VI) superficial to deep
What happens to the somatotopic map if a finger is amputated?
The area in the brain representing that part will respond to stimulation of the adjacent areas
The posterior parietal cortex receives and integrates information from where?
SI
Visual
Auditory
Subcortical areas- thalamus
What does the posterior parietal cortex (through stroke) can cause bizarre neurological disorders such as ……with sensory skills intact
agnosia
asteriognosia
hemispatial neglect syndrome
