Sensory Cortex and Somatosensory Pathways

Question 1

Where does sensory info terinate

Answer 1

Primary somatosensory cortex

This info is then passed back to the sensory association areas for interpretation (in parietal)

Question 2

Sensory hommoculus from outside to in

Answer 2

Mouth, face, hands, arm, neck, truck, hip, legs, genitals

Question 3

What is the 3 neuron pathway

Answer 3

It is the pathway through which sensory information from periphery reaches the cerebral cortex
1st order neuron
-cell body in DRG
-peripheral n.
2nd order neuron
-Cell body in SC/brainstem
-may or may not cross at SC level
-terminates in VP nucleus thalamus
3rd order neuron
-Cell body in thalamus
-terminates in primary somatosensory cortex

Question 4

Modalities of Spinothalamic tract

Answer 4

Pain
Temperature
Light touch

Question 5

Where does spinothalamic tract cross

Answer 5

at the level of spinal cord (hence 2nd order neuron crosses to contralateral side once it synapses with 1st order neuron)

Question 6

Path of spinothalamic tract

Answer 6

sensory receptor - peripheral n. - spinal cord - divides into 2- DRG - synapses with other n - medulla - brain stem - thalamus

Question 7

Modalities of Dorsal Column system

Answer 7

Discriminitice touch
Pressure
Vibration
Proprioception

Question 8

Is dorsal column system a crossed tract?

Answer 8

not crossed tract–> does cross later on in the SC, just not at the level

Question 9

What does the fasciculus gracilis and cuneatus carry from dorsal column system?

Answer 9

Fasciculus gracilis–> LL and Lower trunk

Fasciculus cuneatus–> UL and upper trunk,neck

Question 10

Where is the cell body of 2nd order neuron of Dorsal column system

Answer 10

in nucleus gracilis or cuneatus

Question 11

Where does the Dorsal column system cross (descussate)

Answer 11

crosses via internal arcuate fibres in medulla

ascends as the medial lemniscus from there to 3rd order neuron

Question 12

What is lateral inhibition in Dorsal column system

Answer 12

a physiological mechanism to sharpen input
when neighbouring cells inhibit one another to cause contrast enhancement as the difference in activity between neighbouring cells is amplified
hence the stronger input leans forward

Importance of lateral inhibition is that it block the lateral spread of excitatory signals and therefore increases the degree of contrast perceived in the cerebral cortex

Question 13

what is the white matter tract called that ascends from the medulla to the thalamus?

Answer 13

medial leminscus

Question 14

where in does lateral inhibition occur

Answer 14

Primarily in thalamus and cortex

Question 15

Where does the DCS terminate in thalamus

Answer 15

VP of thalamus

Question 16

Modalities of Spinocerebellar tract

Answer 16

unconscious proprioception and cutaneous information for the coordination of movement

Question 17

Why is it spinocerebellar tract subsconscious

Answer 17

never reaches the cerebellar cortex, goes straight to cerebellum

Question 18

Name the structures of the pathway in ventral spinocerebellar tract

Answer 18

DRG, dorsal horn, anterior white commisure, lateral funiculus, superior cerebellar pudencle to cerebellum

Question 19

Name the structures of the pathway in dorsal spinocerebellar tract

Answer 19

DRG, nucleus dorsalis of thoracic and upper lumbar SC, dorsolateral funiculus, medulla, inferior cerebellar peduncle cerebellum

Question 20

Where does the ventral spinocerebellar tract decussate

Answer 20

anterior white commissure and cerebellum

Question 21

Does ventral spinocerebellar tract terminate ipsilaterally or contralaterally

Answer 21

ipsilateral to the side it entered from, because it decussates at level of spinal cord, and crosses again before entering cerebellum