somatosensory part 3

Question 1

what are dermatomes

Answer 1

skin areas innervated by pairs of spinal nerves

Question 2

how many different regions are there in the grey matter of the spinal cord

Answer 2

10

Question 3

which sections are in the dorsal horn

Answer 3

laminae (layers) 1 to 6

Question 4

which laminae is known as the intermediate zone

Answer 4

laminae 7

Question 5

which laminae make up the ventral horn

Answer 5

8 - 10

Question 6

different mechanoreceptors terminate in different
layers of the dorsal horn.
which fibres branch and carry information directly up the spinal cord to the medulla (they also project into the dorsal horn and terminate at layers 3 and 4)

Answer 6

the Abeta SA and RA LTMR

Question 7

the C-LTMR and the Adelta-LTMR terminal in…

Answer 7

layer 2 predominantly

Question 8

where do nociceptors and thermoreceptors fibres terminate

Answer 8

layer 2

Question 9

where do the mechanoreceptors terminate

Answer 9

either on interneurons or projection neurons

Question 10

interneurons

Answer 10

form short range connections just within the local regions of the spinal cord

Question 11

projection neurons

Answer 11

contribute to the tract
project out of the spinal cord to the brain (output neurons from the dorsal horn)

Question 12

how many output tracts are there

Answer 12

3

Question 13

what are the 3 tracts

Answer 13

PSDC - post synaptic dorsal column
anterolateral tract
spinocervical tract

Question 14

the anterolateral tract neurons start in what region of the dorsal horn

Answer 14

the superficial regions (layer 1 and 2)

Question 15

where do the anterolateral neurons get their inputs from

Answer 15

nociceptors, thermoreceptors and the smaller mechanoreceptors

Question 16

spinocervical neurons start in what region of the dorsal horn

Answer 16

layer 3 and 4

Question 17

fibres going into the spinocervical tract are from…

Answer 17

hair follicles (not from glabrous skin)

Question 18

Abeta RA and SA LTMR form collaterals that travel straight up to the dorsal column nuclei, as they do so they branch off creating endings in along the length of the cord.

Question 19

interneurons means there can be segmental processing which means…

Answer 19

the input from one receptor might have an impact on the input from another receptor.
E.g interaction between mechanoreceptors and nociceptors (“rubbing something better” stimulates mechanoreceptors and it seems to have an inhibiting effect on the nociceptor input)

Question 20

what are the three somatosensory pathways in the spinal cord that go to the brain

Answer 20

dorsal column lemniscal system
anterolateral system
spinocervical system

Question 21

information coming in to the dorsal horn of the spinal cord can send collaterals into the dorsal column system. does this run up the spinal cord on the same side or opposite side that in information came in

Answer 21

the same side (homolateral)

Question 22

is the spinocervical system homolateral

Answer 22

yes

Question 23

is the anterolateral system homolateral?

Answer 23

no, the output neurons have to cross to reach the tract

Question 24

dorsal column system contains…

Answer 24

fibres from the receptors themselves and the post synaptic dorsal column fibres (from the glabrous skin and the hairy skin)

Question 25

where does the dorsal column system terminal

Answer 25

the dorsal column nuclei in the medulla

Question 26

within the brain the dorsal column fibres cross over through a bundle of fibres called the…

Answer 26

medial lemniscus

Question 27

they then terminate in the thalamus and then go to the…

Answer 27

somatosensory cortex on the opposite side to which the information entered

Question 28

the spinocervical pathway receives its inputs from hair skin and they travel up to reach the…

Answer 28

lateral cervical nucleus

Question 29

neurons from the lateral cervical nucleus project through the medulla and then cross over to reach the thalamus and the somatosensory cortex on other side.

Question 30

what are most of the dorsal column fibres

Answer 30

collaterals of primary fibres
15-20% are secondary fibres (output of neurons in grey matter)

Question 31

each dorsal column is divided in to what two fascicles

Answer 31

gracile fascicle
cuneate fascicle

Question 32

cuneate fascicle carries information from the

Answer 32

forelimbs

Question 33

gracile fascicle carries information from the…

Answer 33

trunk and hind limbs (runs more medially than the cuneate fascicle)

Question 34

what nucleus in the thalamus is concerned with somatosensory information

Answer 34

the venteroposterior lateral nucleus

Question 35

what is decussation

Answer 35

crossing over within the brain

Question 36

the anterolateral pathway consists of what two tracts

Answer 36

the spinothalamic (STT) and spinoreticular (SRT) tracts

Question 37

what laminae do the neurons of these tracts originate from

Answer 37

laminae 1,5 and 7

Question 38

where is input from the nociceptors and thermoreceptors carried

Answer 38

in the lateral STT

Question 39

where is input from mechanoreceptor and simple touch carried

Answer 39

in the anterior STT

Question 40

the dorsal column pathway inputs from receptors in what type of skin

Answer 40

hairy and glabrous

Question 41

in the DCN theres a distorted representation of stimulus emphasising…

Answer 41

boundaries and edges
important for control of hand movement

Question 42

anterolateral system transmits information about…

Answer 42

pain and temperature
also carries information about coarse touch

Question 43

whether the spinocervical system is in primates is questioned
but inputs information from…

Answer 43

hairy skin