somato-sensory system Flashcards

1
Q

sensory receptors with encapsulated nerve endings

A

meissner (or tactile) corpuscles

pacinian (or lamellated)
corpuscles

ruffini corpuscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

sensory receptors with unencapsulated nerve endings

A

merkel (or tackle) discs

free nerve endings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

‘encapulsated nerve endings’

A

means they can filter out frequencies

to give specific frequencies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

meissner corpuscles location

A

dermal papillae of skin esp hands, palms, eyelids, lips, tongue ec

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

modality of messier corpuscles

A

light touch, texture (movement)
sensitive to 30-50 Hz
rapidly adapting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

pancinian corpuscles location

A

dermis
joint capsules
viscera

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

pancinian corpuscles modality

A
deep pressure
stretch
 tickle 
vibration 
sensity to 150-350 Hz
rapidly adapting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

ruffini corpuscles location

A

dermis
subcutaneous tissue
joint capsules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

ruffini corpuslces modality

A

heaving touch, pressure, skin stretch
joint movements
slowing adapting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

merkel discs location

A

superficial skin (epidermis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

merkel discs modality

A

light touch, texture , edges shapes

slowing adapting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

free nerve ending locations

A

widespread in epithelia and connective tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

free nerve ending modality

A

pain, heat and cold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

hair follicles location

A

widespread in epithelia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

hair follicles modality

A

varied according to type

both rapid and slowly adapting subtypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

different classes of machine receptor response

A

phasic and tonic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

tonic

A

slowing adapting
continue to response as long as the stimulus is present (info about persistence of stimulus)

e.g. ruffini corp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

phasic

A

rapidly adapting five info about changes in the stimulus

e.g. pacinian corp

19
Q

primary afferent axon subtypes are classified according to….

A

conduction velocity

which broadly reflects diameter (faster=longer diameter)

20
Q

axons coming from the skin are designated by

A

letters ( A, B, C)
a= fastest/largest
c=slowest/smallest

A group further broken down by greek character

alpha, beta delta
a= fastest
d=slowest

21
Q

axons coming from muscles designated by …

A

roman numerals

I II III IV

I = largest
IV= smallest
22
Q

pain fibres are ….. than proprioceptors

A

slower

evolutionarily important- ability to stand, feedback has to be very fast

23
Q

how is sensory info organised

A

The cell bodies of sensory neurons are grouped in the Dorsal root ganglion and their projections are organised to different layers of the dorsal horn

24
Q

two main routes that send info from all sensory subtypes to brain

A

1) medial lemniscal tracts

2) spinothalamic tracts

25
Q

medial lemniscal tract

A

carry mechanoreceptive and proropceptive signals to the thalamus

26
Q

spinothalamic tract

A

carries pain and temp signals to the thalamus

27
Q

Typically, sensory information travels through 3 neurons to reach higher centres:

A

First-order neurons detect the stimulus and transmit to spinal cord via Dorsal Root Ganglion

Second-order neurons relay the signal from spinal cord to the thalamus, the “gateway” to the cortex

Third-order carry the signal from the thalamus to the cortex

28
Q

commissural

A

cross the midline to the contralateral side

29
Q

in both medial lemniscal tracts and spin thalamic tracts 2nd order axons do what?

A

cross the midline i.e. are commissural

30
Q

in the medial lemiscal system, 1st order neurones from the upper body…..

A

follow lateral pathway and synapse on 2nd order neurones in the cuneate nucleus (in medulla)

31
Q

in the medial lemiscal system, 1st order neurones from the lower body…. (below vertebra T6)

A

follow the more medial pathway and synapse on neurons in the gracile nucleus

32
Q

the doors column nuclei

A

the cuneate and the gracile nucleus

33
Q

2nd order axons in the medial lemiscal system

A

cross the midline

and the topology is reversed relative to the midline so that lower body axons are more lateral on reaching the thalamus

34
Q

3rd order axons in the medial lemiscal system

A

again reverse the topoglofy so that lower body axons synapse on the more medial cortical neurones

35
Q

medial ness and laternal ness of axons

A
1st ordeR: upper= lateral
                 lower = medial
2nd order: upper= medial
                   lower= lateral
3rd order: upper=lateral
                  lower = medial
36
Q

somatopoic order in the brain is not simply lower vs upper body axons, the maps is very fine which reflects…..

A

the fact that each dorsal root ganglion innervate a specific domain of the body called a dermatone

37
Q

dermatome

A

area of the skin that is mainly supplied by a single spinal nerve

38
Q

dermatomes arise from

A

embryonic somite (which are repeating structures that give rise to the underlying musculature and skeleton)

each DRG is associated with a specific somite and subsequently innervates the tissues surrounding that somite

39
Q

receptive fields

A

an axon splits into multiple endings and extend over a n area

40
Q

fingers receptive fields

A

small (high discrimination)

cortex more dedicated to these areas

41
Q

receptive fields in legs

A

large (low discrimination)

42
Q

receptive field size

A

In these regions, although the number of receptors (nerve endings) may be similar, the number of endings from different neurons per unit area is higher, therefore the amount of derived information is also higher

43
Q

largest receptive fields

A

upper arm, thigh, calf

44
Q

what factor effects the velocity of propagation of the action potential

A

AXONAL DIAMETER

The influx of sodium that occurs during an action potential causes depolarisation of the axon membrane that lies just ahead of it. As this region reaches threshold, voltage-gated sodium channels open and the action potential is propagated along the axon. The influx of positive charge associated with the inward sodium current has two paths that it can take, it can flow down the inside of the axon or it can cross the axonal membrane. The more charge that flows down the inside of the axon the faster the propagation of the action potential. Therefore, axons with a wider diameter provide more opportunity for the current to flow down the centre of the axon, rather than across the membrane, giving large diameter axons a faster conduction velocity.