The Somatosensory System Flashcards

1
Q

Define Somatosensory function

A
Ability to interpret bodily sensations
o mechanical
o thermal
o proprioceptive
o nociceptive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the somatosensory system consist of?

A

o Sensory receptors in skin, tissues & joints
o nerve cells & tracts in body & spinal cord
o brain centres that process & modulate sensory information

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

What is referred to as somatosensory modalities?

A
Includes all conscious senses:
o touch
o proprioception
o temperature
o pain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 3 main receptors making up the somatosensory modalites?

A

o Mechanoceptor

o Thermoceptors

o Nociceptors

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

Describe the nerve endings for the 3 main receptors making up the somatosensory modalities?

A

o FREE nerve endings:

  • thermoceptors
  • nociceptors

o ENCLOSED nerve endings
- mechanoceptors

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

Nerve Fibre Classification?

A

FIBRE A:

o Alpha - proprioception (MOTOR)
o Beta - touch, pressure
o Gamma - MOTOR to muscle spindle
o Delta - pain, cold & touvh

FIBRE B:

o POSTganglionic autonomics

FIBRE C:

o Dorsal root - pain, temperature & mechanoception
o Sympathetic - POSTganglionic sympathetic

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

Main SENSORY neurones?

A

o A-beta

o A-delta

o C-fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Properties of the MAIN SENSORY neurones?

A

A-delta & C-fibres heavily invovled in PAIN (noxious)

A-beta heavily involved in TOUCH & PRESSURE (non-noxious)

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

Speed of conduction of the MAIN SENSORY neurones?

A

A-beta = MOST QUICKLY (most abundant)

A-delta = SMALLER but myelinates

C-fibres = SMALLEST & NO myelination

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

Define sensory receptor

A

Transducers

that convert energy from the environment into neuronal APs

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

Fibres associated with thermoreceptors and their properties?

A

A-DELTA & C-FIBRES
(have FREE nerve endings)

Work via. TRP ION CHANNELS

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

Specific TRP channels associated with thermoreceptors and what they’re activated by?

A

Transient Receptor Potential (Ion Channels)

o TRPV1-4 - HEAT activated
o TRPM8 & TRPA1/V1 - COLD activated

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

Thermoreceptors that have sense overlap?

A

TRPV - heat & spice

TRPM8 - cold & menthol

TRPV1 - hear & cold

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

5 example of Mechanoreceptors?

A

o Meissner’s Corpuscles

o Merkel Cells

o Pacinian Corpuscle

o Ruffni Endings

o Hair follicle

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

Meissner’s Corpuscle?

A

Mechanoreceptor

o Fine, discriminate touch
o LOW frequency vibration

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

Merkel Cells?

A

Mechanoreceptor

o Light touch
o Superficial pressure

17
Q

Pacinian Corpuscles?

A

Mechanoreceptor

o Detects deep pressure
o High frequency vibration & tickling

18
Q

Ruffni Endings?

A

Mechanoreceptors

o Continous pressure
OR
o Touch & stretch

19
Q

Fibres associated with mechanoreceptors?

20
Q

Define Stimulus Threshold

A

Described as the weakest stimulus detectable

The point of intensity at which the person can DETECT the PRESENCE of a STIMULUS 50% OF THE TIME (absolute threshold)

21
Q

Define Stimulus Intensity

A

Info. regarding this is conveyed by a variation of:

o Frequencies of APs generated
o Number of seperate receptors activated (recruitment)

22
Q

What does Stimulus Threshold vary with?

A

o Anatomical location

o Inter-individual differences

23
Q

Explain the Neural Adaptation phenomenon

A

If stimulus of CONSTANT STRENGTH is maintained for a period time, the FREQUENCY of APs DIMINISHES

24
Q

Tonic receptors?

A

SLOWLY adapting (e.g. Merkel cells)

o Detect CONTINOUS stimulus strength (continue to transmit impulse to brain as long as stimulus present)

Allows for (to be perceived):
o superficial pressure
o fine touch

25
Phasic receptors?
RAPIDLY adapting (e.g. pacinian receptors) o Detect a CHANGE in stimulus strength (transmit impulse @ start & end of stimulus) It: o sudden pressure excites receptor o transmits signal again when pressure released
26
Define Receptive Field
Region on skin which causes activation of a SINGLE SENSORY NEURONE when activated
27
Difference between SMALL & LARGE Receptive Fields
Small R.F: o allows for detection of fine detail over a SMALL area o precise perception Large R.F: o detects changes over a WIDER area o less precise perception
28
Can Receptive Fields overlap?
YES Recruitment of adjacent field can INCREASE STIMULUS INTENSITY = INCREASE APs
29
Define 2-point Discrimination
MINIMUM DISTANCE at which TWO POINTS are perceived as separate
30
What does 2-point discrimination depend on?
1. Peripheral mechanoreceptors (density of innervation area of receptive fields) 2. Spinal posterior column (convergence of signals) 3. Cortical function (sensory homunculus)
31
Where are the sensory cell bodies for the body & face?
Body: o Dorsal Root Ganglia Face: o Trigeminal Ganglia
32
Define Lateral Inhibition
Activation of one neural unit INHIBITS the activation of other neural units Prevents the OVERLAP of RECEPTIVE FIELDS - enhances sensory perception (discrimination)
33
What mediates lateral inhibition?
Inhibitory INTERNEURONES within the dorsal horn
34
2 main types that the dorsal horn neurone can be divided into?
o Projection neurones - project to brin o Interneurones - remain in SC