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NEURO > Touch and Mechanoreception > Flashcards

Touch and Mechanoreception Flashcards

1
Q

Define exteroception

A

Exteroception refers to information detected from stimuli coming into contact with the body.

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2
Q

Where can exteroceptors be found?

A

Skin and Mucosa

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3
Q

List the 4 types of exteroceptors.

A
  1. Mechanoreceptors
  2. Thermoreceptors
  3. Chemoreceptors
  4. Nociceptors
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4
Q

Define proprioception

A

Proprioception refers to information detected that leads to an awareness of position.

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5
Q

Give 4 examples of proprioceptors

A
  1. Muscle spindles (masseter)
  2. Golgi tendon organs
  3. Joint receptors (TMJ)
  4. Inner ear
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6
Q

Name an example that is both an exteroceptor and proprioceptor

A

PDLM (Periodontal ligament mechanoreceptors)

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7
Q

What type of receptors are mechanoreceptors and what do they detect?

A

Exteroceptors;

Displacement

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8
Q

What is interoception?

A

Interoception refers to sensation from receptors in internal organs (e.g. GI tract, bladder)

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9
Q

Mechanoreception VS Touch

A

Mechanoreception refers to the detection of mechanical stimuli.
whereas
Touch is a sensory experience and therefore the CNS is involved.

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10
Q

Define Mechanoreception

A

Mechanoreception refers to the detection of mechanical stimuli which are applied externally (i.e. to the skin or oral mucous membrane)

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11
Q

What triggers/stimulates mechanoreceptors?

A

Mechanical distortion:

  • pressure
  • tension
  • vibration
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12
Q

List the locations where mechanoreceptors are found (x6)

A
  1. Hairy skin
  2. Non-hairy skin
  3. Mucous membranes
  4. Periodontal Ligament
  5. Internal tissues (e.g. joints, muscles)
  6. Ear (sound) - cochlear hair cells
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13
Q

Define transduction

A

Transduction is the process of transforming energy from a stimulus (e.g. pressure) into coded action potentials.

Physical stimulus excites a mechanoreceptor and creates a receptor potential, which is converted into action potentials which propagate to the central nervous system via transduction.

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14
Q

What is the relation of transduction to mechanoreceptors?

A

Physical stimulus excites a mechanoreceptor and creates a receptor potential, which is converted into action potentials which propagate to the CNS via transduction.

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15
Q

Give 4 effects of the stimulation of mechanoreceptors

A
  1. Sensation of touch
  2. Reflex effects e.g. salivation or jaw reflexes
  3. Effect on other sensory modalities e.g. gate control theory involved in pain
  4. Gag reflex
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16
Q

Name an area where the sensation of touch is very well developed and an area where it is less well developed

A

well developed: Fingertips

less developed: Elbow / Back

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17
Q

Threshold forces on the lips and oral mucosa VS on the teeth

A

lips and oral mucosa: 10mg

teeth: 500mg

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18
Q

What does the two point threshold of discrimination measure?

A

It measures the density of mechanoreceptive nerves in a given area of the body.

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19
Q

List an area where the two point discrimination is low and an area where the discrimination threshold is high

A

Low: Finger tips / Orofacial regions (1-2mm)
High: Skin of the back (40-50mm)

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20
Q

What type of nerve fibres are mechanoreceptors associated with?

A

A-beta fibres

myelinated with fast conduction velocities

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21
Q

How can mechanoreceptors be classified physiologically?

A
  1. Rapidly adapting

2. Slowly adapting

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22
Q

What are Meissner corpuscle associated with?

Where are they located?

A

RA I receptors; non-hairy / glabrous skin

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23
Q

What are RA I receptors associated with?

A

Meissner corpuscle

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24
Q

Where are RA I receptors present in?

A

Glabrous (Non-hairy) skin,

Lying close to the surface of the epithelium in the basement membrane

25
Q

Which receptors have a small receptive field?

A

RA I and SA I receptors

26
Q

What is the size of RA I receptive field?

A

Small

27
Q

What are RA I receptors stimulated by?

A

Low intensity forces (low threshold)

28
Q

Where are RA II receptors found?

A

Non-hairy / glabrous skin, lying deep in the dermis

29
Q

What is the size of RA II receptive field?

A

Ill defined and large receptive field

30
Q

Which receptor is associated with Pacinian corpuscle

A

RA II

31
Q

Describe the anatomy of Pacinian corpuscle

A

Single central nerve terminal surrounded by layers of lamellae

32
Q

Name 4 oral tissues where RA I receptors would be found

A

Oral mucosa, Vermilion border, Mucosa of the lip, Hard palate

33
Q

State an oral tissue where pacinian corpuscle could be found in

A

Lamina propria of the incisive papilla area

34
Q

Which receptor are Merkel cell neurite complexes associated with?

A

SA I receptor

35
Q

Where would SA I receptors be found?

A

Both hairy and glabrous skin, lying close to the surface of the dermis

36
Q

What type of forces are SA I receptors stimulated by?

A

Low intensity forces (Low threshold)

37
Q

Are the receptive fields of SA I receptors small / large?

A

Small

38
Q

Name 3 places where SA I receptors can be found in oral tissues

A

Mucous membranes of:

  • tongue
  • lips
  • cheek
39
Q

Where are SA II receptors located?

A

SA II are located in hairy and glabrous skin, lying deep to the dermis

40
Q

Are the receptive fields of SA II receptors small/large?

A

Large

41
Q

Where can SA II receptors be found in oral tissue?

A

Periodontal Ligament

42
Q

Which receptor is associated with Ruffini endings?

A

SA II

43
Q

Function of SA nerve fibres

A

Sends information about ongoing stimulation

44
Q

Function of RA nerve fibres

A

Sends information related to changing stimulus

45
Q

What does the amount of activity in the neurones depend on? (x5)

A
  1. Direction in which the force is applied to the tooth
  2. Size of force applied to the tooth
  3. Adaptation properties of the receptors (RA vs SA)
  4. Threshold of the receptors (refers to the point at which a force stimulates a spike in neuronal activity)
  5. Position in the PDL with respect to the fulcrum position - All neurones are found below the fulcrum, with the rapidly adapting (high threshold) neurones found nearer to the fulcrum and the slowly adapting (low threshold) neurones nearer to the apex of the tooth
46
Q

Are the rapidly adapting neurones found nearer to the fulcrum of the tooth or nearer to the apex of the tooth?

A

Nearer to the fulcrum of the tooth

47
Q

Are the slowly adapting neurones found nearer to the fulcrum of the tooth or nearer to the apex of the tooth?

A

Nearer to the apex of the tooth

48
Q

What are the 2 roles played by PDLMs? (periodontal ligament mechanoreceptors)

A
  1. Exteroceptive role in sensation - detection of very small stimuli in the mouth (e.g. fine foils)
  2. Proprioceptive - affects jaw muscle activity by acting on jaw closing muscles
49
Q

Where are the cell bodies of axons of PDL mechanoreceptors located?

A

within the trigeminal ganglion in the PNS, some are in the trigeminal mesencephalic nucleus in the CNS

50
Q

Describe lateral inhibition

A

Mechanoreceptor activity influences activity in other mechanoreceptor neurones by presynaptic inhibition, sharpening touch perception.

51
Q

What are dermatomes?

A

A dermatome is the area of skin innervated by the dorsal roots of a single spinal segment.

52
Q

First synapse of the trigeminal touch pathway

A

Trigeminal Main Sensory Nucleus (evidence: loss of touch sensation following damage to the MSN)

53
Q

Name 2 superficial receptors (epidermis)

A

Meissners

Merkels

54
Q

Name 2 deep receptors (dermis)

A

Pacinian

Ruffini

55
Q

Name 2 slowly adapting receptors

A

Merkels

Ruffini

56
Q

Name 2 rapidly adapting receptors

A

pacinian

Meissner

57
Q

Where are Merkel cells found

A

Hair follicles

58
Q

Where are Meissner cells found

A

Non-hairy skin

NEURO (3 decks)

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