Central somatosensory pathways Flashcards Preview

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Flashcards in Central somatosensory pathways Deck (34):
1

Are the dorsal columns grey matter or white matter?

White matter

2

What sort of information travels in the dorsal columns?

Ascending sensory information from the tactile receptors

3

How are the dorsal columns organised?

Segregated into topographic regions

4

How many neurons are involved in the tactile mechanoreceptive pathway?

Three neurons

5

Where does decussation occur in the tactile mechanoreceptive pathway?

Caudal medulla

6

Where does information from the tactile mechanoreceptive pathway travel to in the brain?

Somatosensory cortex

7

How far up does the first axon in the tactile mechanoreceptor pathway travel?

To medulla

Then meets next neuron

8

What are the dorsal column nuclei called?

Gracile nucleus and Cuneate nucleus

9

What areas of the body do the gracile and cuneate nuclei transmit information about? 

Gracile: lower limb

Cuneate: thoracic and cervical regions

10

What are the internal arcuate fibres?

Internal arcuate fibers are the axons of neurons within the gracile and cuneate nuclei of the medulla oblongata.

These fibres cross from one side of the medulla to the other to form the medial lemniscus.

11

Where are the gracile and cuneate nuclei located?

Medulla 

12

What happens to the axons in the tactile mechanoreceptor pathway once they leave the dorsal column nuclei?

Enter medial lemniscus

Twisting: dorsal goes to ventral

'Bundle of fibres that form a ribbon'

13

What happens to the axons in the tactile mechanoreceptor pathway when they leave the medial lemniscus? 

More twisting > orgnaising topography for somatosensory cortex

Go to thalamus > terminate in ventral posterolateral nucleus

14

Where in the thalamus do axons in the tactile mechanoreceptor pathway terminate?

Ventral posterolateral nucleus

15

Where does the ventral posterolateral nucleus project to?

Cerebral cortex (somatosensory cortex)

16

Describe the tactile mechanoreceptive pathway?

A image thumb
17

Where in the brain do proprioceptive pathways project to?

Cerebellum

18

Give a basic description of the tactile mechanoreceptor pathway?

A image thumb
19

Which part of the tactile mechanoreceptor pathway is ipsilateral?

Primary sensory neuron (first neuron in chain)

20

How many somatic sensory cortices are there? What are they called?

S1: Primary somatic sensory cortex

S2: Secondary somatic sensory cortex

21

How many subregions are there in S1? What are they called?

4: Areas 1, 2, 3a and 3b

22

Describe the locations of the subregions in S1?

A image thumb
23

Where does S2 receive most of its input from?

S1

24

How do we know that there are two somatic sensory cortices (ie. S1 and S2)?

Body is represented twice in the cortex (repeated in miniature form in S2)

25

Describe the representation of the body surfaces within the somatic sensory cortices?

Topographic organisation 

A image thumb
26

What determines the size of a body part's represenation on the somatic sensory cortex?

The amount of sensory information coming from that body part

27

How many maps of the body are represented in the somatic sensory cortices on each side of the brain?

6 on each side; 1 from each region of S1, and 2 from S2

28

Describe the arrangement of slowly adapting and rapidly adapting receptors in the somatic sensory cortex?

A image thumb
29

Why do four maps exist in S1?

May each receive information about different aspects of sense; segregation of information 

eg. Area 1 receives information about texture

30

Which subregion of S1 receives the greatest amount of thalamic input?

Area 3b

31

Describe the concept of somatosensory plasticity?

Changes in somatosensory cortex can occur after changes in use 

eg. after amputation

32

Describe how the somatosensory cortical representation of the digits changes after differential stimulation of digits 2 and 3?

Territories of digits 2 and 3 in the cortex expand 

A image thumb
33

Where does somatosensory plasticity occur?

Unknown

34

Describe the problem with nerve regeneration after injury in the PNS?

Nerves can regrow, but often regrow to the wrong place 

Central plasticity doesn't change to match > perception in the wrong place