Somatosensory system

Question 1

List the main categories of sensory receptors

Answer 1

Nociceptors- mechanoreceptors and thermoreceptors
Proprioception
Hapsis- touch, pressure temp- Meissner’s Merkel’s Ruffini, Pacinian corpuscles

Question 2

List 4 characteristics of Meissner’s corpuscles

Answer 2

Rapidly adapting
Light touch
Highest sensitivity with lowest threshold
40% abundance

Question 3

List 4 characteristics of Merkel’s receptors

Answer 3

Slow adapting
Light pressure
Discriminative touch
25% abundance

Question 4

List 3 characteristics of Ruffini receptors

Answer 4

Wrapped around collagen- skin stretch
Slowly adapting
20% abundance

Question 5

List 3 characteristics of Pacinian corpuscles

Answer 5

Rapidly adapting
Deep
10-15% abundance
Texture of connective tissue and fluid

Question 6

List two types of proprioceptors and their functions

Answer 6

Golgi tendon organs- compression during muscle contraction

Muscle spindles- rate of change and position

Question 7

List the 3 ascending sensory tracts

Answer 7

Dorsal Column Medial Leminiscus
Spinocerebellar
Anterolateral system

Question 8

List three functions of the DCML pathway and describe it

Answer 8

Tactile touch, vibration, proprioception
receptor activated, Cell body in DRG, 1st order neurone ascends to medulla as fasciculus cuneatus and gracilis, relatively send info to cuneate and gracile nucleus
Decussate at medulla as internal arcuate fibres
(ABOVE PYRAMIDAL DECUSSATION)

2nd order neurone called medial leminiscus, ascends to thalamus
3rd order to cortex

Question 9

List three functions of the anterolateral system and describe it

Answer 9

Pain temperature crude touch
Spinothalamic and spinoreticular tract
2nd order neurones decussate at verterbal level
spinoreticular tract terminates in the brain stem
1st order decussate at vert level- ascend to thalamus as 2nd order, then to cortex as 3rd order

Question 10

List the function of the spinocerebellar tract and describe it

Answer 10

Transmitting signals for unconscious proprioception
no 3rd order neurones
Input to cerebellum is ipsilateral
2 parts- dorsal- dorsalis of clark L3-C8 interneurones at synapse
cuneocerebellar- synapse with cuneate nucleus

1st synapse with 2nd at verterbal level—
cerebellum by inferior cerebellar peduncles

Question 11

Name the function of the thalamus and list the 4 major parts

Answer 11

Sensory info relay station

Medial, lateral, anterior, intermedullary lamina

Question 12

Name the function, input and output of the medial geniculate body

Answer 12

Function: hearing
Input: inferior colliculus
output: auditory cortex

Question 13

Name the function, input and output of the lateral geniculate body

Answer 13

Function: vision
Input: retina
Output: visual cortex

Question 14

Name the function, input and output of the anterior nuclear group

Answer 14

Function: limbic
Input: mammillary bodies
Output: cingulate cortex

Question 15

Name the function, input and output of the medial nuclear group

Answer 15

Function: olfactory and limbic
Input: entorhinal cortex
Output: prefrontal cortex

Question 16

Name the function, and components of the lateral nuclear group

Answer 16

Function: vision and movement
Dorsal- lateral dorsal and lateral posterior LD LP VISION
Ventral- ventral anterior BG, ventral lateral BG and cerebellum, ventral posterior body,- medial and inferior MOVEMENT
VA, VL, VPN- VPL, VPM, VPI

Question 17

Describe the function of the medial geniculate body

Answer 17

Relay hearing info to primary auditory cortex

Question 18

Describe the function of the lateral geniculate body

Answer 18

Relay colour/contrast info to visual cortex

Question 19

Describe the function of the dorsal root ganglion

Answer 19

Contain cell bodies of 1st order neurones

Question 20

Describe the function of the pulvinar

Answer 20

Relay info between visual and visual association cortices

Question 21

Describe the function of the anterior nucleus group

Answer 21

Relay recollective memory info to cingulate gyrus

Question 22

Describe the function of the ventral lateral nuclei

Answer 22

Relay unconscious sensory info to the primary motor cortex

Question 23

Describe the function of the ventral posterior nuclei

Answer 23

Relay sensory info to the primary somatosensory cortex