PHY2011 Lecture Notes - Lecture 22: Somatic Nervous System, Somatosensory System, Grey Matter
20 Jun 2018
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Week 8 L3 (T5L2) -Processing somatic sensations in the CNS (No L2-
Anzac Day)
Three concepts to understand CNS processing
o1. Even in the same sensory system, different types of information are segregated
from each other all the way from the receptor to the cortex (everything is kept
separate)
o2. Information flow is ordered between each level of a sensory pathway (number of
stops)
o3. Responses of neurons at progressively higher levels of the pathway become more
complex (new information added at each stop)
Information flow segregation at the spinal cord
oSensory information enters spine from the back (dorsal) side
oDiscriminatory somatic senses go straight up
Enters grey matter, moves up through white matter (myelinated axon)
oNon-discriminatory somatic senses cross over, then go up
Sensory nerve branches out; synapse; new neuron; crosses; goes into white
matter; goes up
oLeft side of spinal cord:
Fine touch and proprioception on left side of body (discriminatory)
Pain and temperature detection on right side of body (non-discriminatory)
Information flow pathways to the thalamus
oDiscriminative: same axon travels up, reaches cuneate/gracile nucleus and swaps to
a new neuron to the opposite side of the brain
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Document Summary
Week 8 l3 (t5l2) -processing somatic sensations in the cns (no l2- Three concepts to understand cns processing: 1. Even in the same sensory system, different types of information are segregated from each other all the way from the receptor to the cortex (everything is kept separate: 2. Information flow is ordered between each level of a sensory pathway (number of stops: 3. Responses of neurons at progressively higher levels of the pathway become more complex (new information added at each stop) Information flow segregation at the spinal cord: sensory information enters spine from the back (dorsal) side, discriminatory somatic senses go straight up. Enters grey matter, moves up through white matter (myelinated axon: non-discriminatory somatic senses cross over, then go up. Sensory nerve branches out; synapse; new neuron; crosses; goes into white matter; goes up: left side of spinal cord: Fine touch and proprioception on left side of body (discriminatory)
