somatosensory part 2

Question 1

what is glabrous skin

Answer 1

palms of hands, lips and soles of feet

Question 2

what types of cutaneous receptors are on glabrous skin

Answer 2

Merkel cells (ABeta SAI-LTMR)
Ruffini ending (ABera SAII-LTMR)
Meissner corpuscle (ABeta RAI-LTMR)
Pacinians corpuscle (ABeta RAII-LTMR)

Question 3

what types of cutaneous receptors are on hair skin

Answer 3

Abeta RA-LTMR
Adelta-LTMR
C-LTMR
circumferential lanceolate endings
free nerve endings (HTMR)

Question 4

SA and RA =

Answer 4

slowly adapting and rapidly adapting

Question 5

LTMR and HTMR =

Answer 5

low and high threshold mechanoreceptor

Question 6

Abeta, Adelta and C refer to

Answer 6

classes of nerve fibres

Question 7

high threshold means…

Answer 7

it required a strong stimulus compared to low threshold

Question 8

how does the sensory receptors and spinal cord connect

Answer 8

nerve travels from the skin along the limb and reaches the spinal cord through the dorsal root
they enter the spinal cord at the dorsal horn of the grey matter

Question 9

what is the dorsal root ganglion

Answer 9

a swelling when the cell bodies of these nerve fibres are found

Question 10

Abeta nerve fibres

Answer 10

myelinated
larges diameter
fastest conduction velocity

Question 11

Adelta nerve fibres

Answer 11

myelinated

Question 12

C fibres

Answer 12

unmyelinated
smallest diameter
slowest conduction velocity

Question 13

RA fibres

Answer 13

the nerve fibre fires when the stimulus is applied and when it is removed, theres no response during the maintained phase of the stimulus

Question 14

SA fibres

Answer 14

higher rate of firing near the beginning of the stimulus bit the firing is maintained throughout the time the stimulus is being maintained

Question 15

RA only respond during the onset and offset of a stimulus
SA fire throughout the duration
so RA highlight…

Answer 15

what is changing

Question 16

which of the glabrous receptors are deep in the dermis

Answer 16

Ruffini ending and pacinians corpuscle

Question 17

which of the glabrous receptors are between the dermis and the epidermis

Answer 17

merkel cells and meissner corpuscle

Question 18

free nerve endings are not specialised, they are HTMR and they are nociceptor fibres that respond to…

Answer 18

pain (something sharp for example)

Question 19

hairy skin:
longest hairs =

Answer 19

guard

Question 20

smallest hairs =

Answer 20

zigzag

Question 21

middle length

Answer 21

auchene

Question 22

what receptor is present at the top of the guard hair follicle

Answer 22

merkel cells

Question 23

longitudinal receptor types are LTMR.
how are they arrange

Answer 23

around the hair so which ever direction the hair is bent it will push against some parts of these receptors are trigger action potentials in these nerve fibres

Question 24

Merkel receptor (SA1)

Answer 24

the nerve fibres branch at their terminals and associate with merkel cells which embed into the lower layer of the epidermis

Question 25

Ruffini corpuscle (SA2)

Answer 25

consists of a collagen capsule with an axon that enters the capsule
the best stimulus for these is being stretched along this axis

Question 26

meissner corpuscle RA1

Answer 26

collagen fibres that spiral around to form the corpuscle and the axon also coils around the layers of collagen
anchored into the base of the epidermis so as the epidermis moves it tugs on the meissner corpuscle

Question 27

pacinian corpuscle (RA2)

Answer 27

found deep in the dermis
axon through the core and then around it

Question 28

thermoreceptors

Answer 28

free nerve endings
warm and cold spots
max sensitivity: cold 25-30, warm 40-43
cold receptors are highly sensitive to temperature changes

Question 29

what type of receptors are cold thermoreceptors

Answer 29

small myelinated ADeltas fibres

Question 30

what type of receptors are warm thermoreceptors

Answer 30

unmyelinated C fibres

Question 31

nociceptors

Answer 31

fibres terminate as free nerve endings
mechanoreceptors (responds to a prick, squeeze etc)
Adelta fibres - first pain
mechano - thermal: sensitive to painfully hot or cold temperatures
C fibres - second pain (throbbing pain after injury)

Question 32

defining cutaneous receptive fields using micro-neurography

Answer 32

electrode pushed in through the skin to reach a nerve
can record individual AP from a single nerve fibre and therefore from THE single receptor
then you use a probe to map out on the surface of the hand the area of skin which activates that particular nerve fibre
that region of the skin is known as the receptive field of that fibre and that receptor

Question 33

SA1 (merkel) and RA1 (meissner) receptive fields

Answer 33

the receptive fields are quite small and increase in density at the finger tops

Question 34

SA2 (ruffini) and RA2 (pacinian) receptive fields

Answer 34

have larger receptive fields

Question 35

what is spatial resolution

Answer 35

ability to recognise two points of stimuli (two point discrimination)

Question 36

at the finger tips there is higher spatial resolution which correlates with an increase in density of…

Answer 36

RA1 and SA1 receptors

Question 37

which receptor type shows the highest spatial resolution

Answer 37

SA1 (merkel)
its responsible for detecting fine details of texture etc

Question 38

RA nerve fibres

Answer 38

respond best to a stimulus that is changing as they respond to onset and offset of stimulus
RA2 (pacinian) has a low threshold (low pressure will cause a response) and is most sensitive at 300Hz