Central Somatosensory Pathways Flashcards
Where do somatosensory pathways ascend in the spinal cord?
the dorsal columns
How are the dorsal columns organised?
the fibres from neurons lower in the body travel closer to the midline and fibres from areas higher up travel laterally
How many neurons make up the somatosensory pathway from the skin to the somatosensory cortex?
3
Where does the somatosensory pathway decussate?
in the caudal medulla
Where is the first synaptic connection in the somatosensory pathway?
In the medulla - between the mechanoreceptor axon and dorsal column nuclei (gracile and cuneate nucleus)
What is the difference between the gracile and cuneate nuclei?
The gracile nucleus recieves input from the lower limbs and the cuneate nucleus recieves input from the upper limbs
How do the axons of the dorsal column nuclei decussate?
via the arcuate fibres
What is the medial lemniscus?
The fibres from the dorsal column nuclei to the thalamus - they wind around so that the medial structures become lateral and the lateral structures become medial
Where do the dorsal column nuclei synapse?
at the ventral posterolateral nucleus in the thalamus
How are the neurons in the ventral posterolateral nucleus in the thalamus organised?
Neurons from lower limbs are lateral and neurons from the upper limbs are medial
Where do the neurons of the ventral posterolateral nucleus in the thalams synapse?
at the somatosensory cortex
How is the primary somatosensory cortex organised?
areas of the body that are next to each other occupy adjacent areas of the cortex - lower limb structures are more medial and upper limb structures are more lateral
Which areas of the body have the largest areas of cortex?
those most involved in touch e.g. hands, lips
How many seperate maps of the body are there in the somatosensory cortex?
4 - 3 in the primary somatosensory cortex and 1 in the secondary somatosensory cortex
