Functional Organisation of CNS Flashcards
Where does a somatosensory neuron make its first synapse?
all the way up through the dorsal column and synapse at the medulla
What are gracile and cuneate nuclei responsible for?
for somatosensation, gracile nucleus is the location for first synapse from the lower body, whereas cuneate is for the upper body
T/F the primary somatosensory neuron decussate at the medulla
False, primary neuron runs ipsilaterally. It’s the secondary neuron that crosses over
The dorsal column is topographically organised. Neurons from the lower body tend to run more ________ while the upper body neurons, like cervical neurons, run more _________. Therefore, gracile nucleus is _______ to cuneate nucleus
medially (medial for lower body)
laterally (lateral for upper body)
Medial, because it receives lower limb neurons
At the point of decussation, the name given to the neurons crossing over is?
internal arcuate fibres
At the point of decussation at the middle region of spinal cord, where are the fibres of cuneate nucleus in relation to fibres of gracile nucleus?
Gracile is ventral to cuneate
Gracile secondary neurons run laterally to cuneate secondary neurons
Where is the second synapse for somatosensation?
At ventral posterolateral nucelus (VPLN) of the thalamus
Where are the neurons from lower reigion in relation to neurons from upper region at the thalamic region?
neurons from lower limb (gracile) are lateral to neurons from upper region (cuneate)
What is the name of the tract where the secondary neurons run within?
medial lemniscus
after synapsing at the thalamus, the tertiary neurons project to which region of the cortex?
Somatosensory cortex (primary, and some secondary), which is posterior to the central sulcus
What is the topographical organisation of the primary somatosensory cortex? What is the significance of that?
Neurons from gracile (lower limb) are located more medially, and neurons from cuneate are located more laterally.
There is a cross over of topographic organisation in the course of tertiary neuron
What are the sub-divisions of primary somatosensory cortex? How are they organised in relation to the central sulcus?
Area 1, 2, 3a, 3b
from central sulcus - 3a -> 3b -> 1 -> 2
makes no sense whatsoever
What is an evidence suggesting that there is a secondary somatosensory cortex?
the representation of body structures are repeated in S2
How many body maps are there in total for sensory cortex?
4 in primary, 2 in posterior parietal cortex. 6 in total
Are slow adapting and fast adpating neurons segregated ?
Yes, there are islands of slow adapting eurons within each topographical map
Which sub-division of S1 receive most input?
3b
What gives rise to “cognitive touch”?
the integration of information from the four-subdivisions of S1 at S2
Area 1 is more for ________, while area 2 is more for _______
area 1 for texture
area 2 for size/shape
what is the function of posterior parietal cortex
it receives and integrates inputs from visual, auditory and somatosensory, and it’s involved in planning movement and working out where you are spatially
Can you reorganise topographic map?
Yes, in an amputated individual, the unused area will get taken up by the nearby areas of neuron
What is an example of normal physiological cortical reorganisation
during lactation, there is increased somatosensory input from breasts
Do PNS nerve injuries recover?
Yes, but it’s never a complete recovery, because there is a lack of specificity with regrowth. The original function can never be restored
What the CNS plasticity respond to? What is the significance?
CNS plasticity responds to the frequency of use, not the pattern of use
If there is peripheral nerve injury, the CNS cannot reorganise to restore the PNS function
“erroneous peripheral nerve regeneration does not produce compensatory central plasticity”
Where are the reflex patterns generated?
in the spinal cord
During development, the growth of spinal cord is ______ than vertebral column, and it stops at the level of _______ , but beyond that, there are bundles of spinal nerves called _______ which give rise to pairs of spinal nerves for the _______
slower
L1/L2
caudal equina
lower limbs
What colour is white matter on histological sections?
black
What colour is fluid on MRI 1) T1 2) T2
On T1, it is dark
On T2, it is bright
Why is there more white matter towards to the upper spinal region?
there are more fibres closer to the head, because spinal roots fan out at each level
Where in the spinal cord does the nociceptive neurons run?
in the anterolateral column
What are proprio-spinal neurons?
neurons that make connection within the spinal cord
