The somatosensory system lecture 8

Question 1

What are the four segments of the spinal cord from top to bottom?

Answer 1

Cervical, thoracic, lumbar, sacral

Question 2

How many segments of the spinal cord?

Answer 2

31

Question 3

How many segments in cervical segment?

Answer 3

8

Question 4

How many segments in thoracic segment?

Answer 4

12

Question 5

How many segments in the lumbar region?

Answer 5

5

Question 6

How many segments in the sacral region?

Answer 6

5

Question 7

Which laminae are in the dorsal horn?

Answer 7

1-6

Question 8

Which laminae are in the intermediate zone?

Answer 8

7

Question 9

Which laminae are in the ventral horn?

Answer 9

8 and 9

Question 10

Which section of the spinal cord is concerned with somatosensory information?

Answer 10

1-6

Question 11

What is the dorsal column system?

Answer 11

Some fibres come from the periphery and form a collateral which goes directly up the spinal cord to the medulla.

Question 12

Which fibres form collaterals and enter the dorsal column system?

Answer 12

The RA and SA A beta LTMR fibres

Question 13

As well as forming a collateral and entering the dorsal column system, A beta fibres also branch and enter the dorsal horn, which layers do they terminate in?

Answer 13

3 and 4

Question 14

In which layer do A delta and C fibres predominantly terminate in?

Answer 14

2

Question 15

What do we find terminating in the superficial layers of the dorsal horn?

Answer 15

Nociceptors and thermoreceptors

Question 16

What layers do hairy skin receptors terminate in?

Answer 16

3 and 4

Question 17

What are the two types of neurones that these sensory neurones terminate onto?

Answer 17

Projection neurones and interneurons

Question 18

What are the 3 output tracts of the dorsal horn?

Answer 18

The dorsal column, anterolateral and spinocervical

Question 19

Describe the dorsal column system

Answer 19

collaterals from A beta fibres in glabrous skin as well as postsynaptic dorsal column neurones which have cell bodies in layers 3 and 4 and gather info from the sensory neurones terminating here.

Question 20

Describe the anterolateral tract

Answer 20

From superficial layers of dorsal horn, mainly from nociceptors, thermoreceptors and small mechanoreceptors

Question 21

Describe the spinocervical tract

Answer 21

from layers 3 and 4, receives from hairy skin fibres which terminate there.

Question 22

What causes processing at the segmental level in the dorsal horn?

Answer 22

Interneurons projecting onto projection neurones

Question 23

Describe propriospinal neurones

Answer 23

These can span adjacent segments to process information. inputs from one receptor can influence others.

Question 24

Which tracts are homolateral?

Answer 24

Dorsal column and spinocervical

Question 25

Where is the first termination of the dorsal column tract?

Answer 25

Dorsal column nucleus in medulla

Question 26

Where does the DCT cross over?

Answer 26

In the brain in the medial lemniscus- in medulla

Question 27

Where does the DCT terminate?

Answer 27

The thalamus (ventroposterior lateral nucleus)

Question 28

Where does the spinocervical pathway first synapse?

Answer 28

In the LCN

Question 29

Where is LCN?

Answer 29

Cervical region of spinal cord- C1-C3

Question 30

Where does the spinocervical pathway cross over?

Answer 30

after medulla

Question 31

Do they dorsal column tract and spinocervical tract receive inputs from nociceptors and thermoreceptors?

Answer 31

No

Question 32

What is the lateral bundle of the dorsal column tract called?

Answer 32

cuneate fascicle

Question 33

What is the medial bundle of the dorsal column tract called?

Answer 33

Gracile fascicle

Question 34

Where in the thalamus does the somatosensory information terminate?

Answer 34

The ventroposterior lateral nucleus

Question 35

What are the two pathways in the anterolateral tract?

Answer 35

Spinothalamic and spinoreticular

Question 36

What laminae do the anterolateral tract pathways originate from?

Answer 36

Laminae I V and VII (VII from visceral sensations)

Question 37

What signals are carried mainly in the lateral spinothalamic tract?

Answer 37

Nociceptive and thermoreceptors- pain and temperature- fast and slow pain

Question 38

What signals are carried mainly in the anterior spinothalamic tract?

Answer 38

Small diameter nerve fibres- C and A delta from mechanoreceptors- simple touch

Question 39

What is the pathway of the STT?

Answer 39

Crosses over within 2 segments then goes straight to the ventroposterior lateral nucleus of the thalamus

Question 40

What is the pathway of the SRT?

Answer 40

Crosses over within 2 segments, then passes through the reticular formation, then to the intralaminar and posterior nuclei.

Question 41

Which tract is involved in complex active touch?

Answer 41

Dorsal column tract

Question 42

Which specific tract is for fast and slow pain?

Answer 42

Anterolateral tract- Lateral spinothalamic

Question 43

Which specific tract is for simple touch?

Answer 43

Anterolateral tract- anterior spinothalamic tract