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Occlusion > Mechanoreception > Flashcards

Mechanoreception Flashcards

1
Q

What is mechanoreception?

A
  • detection of mechanical stimuli
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2
Q

what is considered a mechanical stimuli?

A
  • mechanical stimuli is stimulus which is physical, such as pressure, vibration and tension
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3
Q

define Exteroception

A
  • sensations caused by external stimuli such as touch, smell, hearing etc.
  • it gives info about what is coming into contact with the body
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4
Q

define proprioception

A
  • it is the body’s awareness of position of different body parts, conscious or not. e.g. you know if your teeth are about to touch or your jaw are an inch apart
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5
Q

what is the sensory experience when mechanoreceptors are excited?

A
  • touch
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6
Q

Where are the 4 different places we can find oral mechanoreceptors?

A
  1. Mucosa and skin
  2. PDL
  3. Muscles
  4. joint receptors
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7
Q

Why is having mechanoreceptors in mucosa and skin useful?

A
  • allows us to know food texture

- important for mastication

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8
Q

Why is having mechanoreceptors in PDL useful?

A
  • tells us the forces on teeth
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9
Q

What are muscle spindles?

A
  • found in majority of muscle cells

- they are stretch detectors which tell the CNS how much and how fast a muscle is Lengthened or shortened

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10
Q

Why is having mechanoreceptors in muscle spindles and joint receptors useful?

A
  • In muscle spindles, tells us length of muscles so if muscle is stretched too far, the CNS and nearby soft tissues are alert of danger
  • Join receptors tell us about joint position and movement
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11
Q

which of the mechanoreceptors in the list below are exteroception and which are proprioception:

  • mucosa and skin
  • PDL
  • muscle spindles
  • Joint receptors
A
  • muscle spindles

- joint receptors

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12
Q

What is the effect of stimulating mechanoreceptors?

A
  • sensation of touch
  • reflexed e.g. jaw muscle reflexes and salivary reflexes (to release saliva e.g. during chewing)
  • interacts with other sensory modalities e.g. if you have a belly ache and then rub the belly, the effect of rubbing painful area reduced pain through gate control
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13
Q

what is the gate control theory?

A
  • theory that the spinal cord contains a neurological gate which either allows pain signals to be blocked or to continue
  • theory suggests that non-painful input closes the gate to painful input, preventing pain traveling to CNS
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14
Q

what are the two ways we can classify mechanoreceptors?

A
  • physiological classification: adaptation properties and receptive field size
  • anatomical classification
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15
Q

what type of nerve fibers are mechanoreceptors?

A
  • A-beta fibres
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16
Q

what are the properties of A-beta fibers?

A
  • Myelinated fibres: fast conductors
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17
Q

What are the two types of adaptation properties in classifying mechanoreceptors?

A
  • Rapidly adapting (RA)

- slow adapting (SA)

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18
Q

what are rapidly adapting nerves?

A
  • Nerves which only respond when the force changes -> when force is applied, burst of action potentials propagate then if there is no further change in stimulus and it is constant, action potentials stop as they ‘adapt’, sometimes AP burst again slightly when stimulus stops.
19
Q

what are slow adapting nerves?

A
  • Nerves which respond throughout the duration of the stimulus -> when stimulus is applied, action potentials continue until stimulus stops.
20
Q

What is receptive field of a receptor?

A
  • The area.space where a stimulus will affect the receptor
21
Q

What is the different between a small and large receptive field?

A
  • A large receptive field allows for detection of stimuli over a wide area, but can result in less precise detection
  • A small receptive field allows for detection of stimuli over a small area, which results in more precise detection e.g. only respond to touch in a small area
  • some receptors supply small area, some supply large area
22
Q

what do each of these abbreviations mean: RA I, RA II, SA I, SA II?

A
  • rapidly adapting, small receptive field
  • rapidly adapting, large receptive field
  • slow adapting, small receptive field
  • slow adapting, large receptive field
23
Q

What are the four types of mechanoreceptors (anatomical classification)? classify them physiologically

A
  • Meissner’s corpuscle (RA I)
  • pacinian corpuscle (RA II)
  • Merkel cells (SA I)
  • Ruffini ending (SA II)
24
Q

what are the two roles of periodontal ligament mechanoreceptors (PDLMs)? give an example for each

A
  • Exteroceptive role e.g. if we touch teeth, we can feel it

- Proprioceptive role e.g. every time our teeth touch, it tells us pressure applied

25
Q

What types of nerve endings do PDLMs have?

A
  • Ruffini
26
Q

what types of nerves are PDLMs, afferent or efferent?

A
  • afferent- carried nerve impulses from stimulus to CNS
27
Q

what type of axons do the afferent PDLMs have? how many axons per PDL per tooth?

A
  • A-beta axons

- 300 approx.

28
Q

where are the cell bodies of the mechanoreceptor nerves in PDL located?

A
  • Trigeminal (V) ganglion

- Mesencephalic nucleus

29
Q

What are the properties of PDLM?

A
  • No branched axons between teeth, each tooth has its own axons so very easy to localize source
  • Innervation density higher at apex
30
Q

Explain movement of tooth in terms of PDLMs activated and where the tension is. Example, if you push a tooth labially - upper central incisor

A
  • Tooth moves around fulcrum, if you push labially, the mechanoreceptors on palatal side are compressed and the receptors labially are stretched therefore the nerves are more active
31
Q

No receptors activated if you ——- an area of PDL

A

compress

32
Q

Mechanoreceptors in PDL are activated by ——-

A

tension

33
Q

What does the amount of PDLM activity depend on?

A
  • Direction of force applied: whichever side you push, we can feel which direction force has been applied due to the compression of mechanoreceptors in specific part of PDL space
  • Magnitude of force (more force = more activity)
  • adaptation properties
  • threshold of the receptors
  • position of receptors in PDL
34
Q

describe properties of PDL

A
  • respond to tension
  • very sensitive so respond to smallest of stimulus (less than 10 grams)
  • apically: slow adapting, low threshold
  • cervically: rapidly adapting, high threshold
35
Q

Why do PDLMs have different properties apically vs cervically despite being the same receptor?

A
  • linked to position of receptors relative to fulcrum

- smaller stimulus near fulcrum

36
Q

Tooth movement of 8.5 micrometers results in reflex effects in —- muscle

A

masseter

37
Q

Describe the stages of sensory pathway in mechanoreception.

A

stage 1: mechanoreception

  • transduction of stimulus
  • propagation of action potentials along primary afferent nerve

stage 2: processing at first synapse
- Trigeminal nuclei

stage 3: processing in thalumus

stage 4: conscious perception

  • somatosensory cortex
38
Q

Explain what the trigeminal nucleus is and where it is located.

A
  • Trigeminal nuclei are found in the lateral medulla of brainstem
  • It carries info about touch, temperature and pressure from ipsilateral part of face to the contralateral thalumus
39
Q

What is the somatosensory cortex

A
  • part of the brain responsible for processing somatic sensations: touch, proprioception, nociception and temprature.
40
Q

Where are primary afferent cell bodies located?

A
  • trigeminal ganglion

- mesocephalic nucleus (PDL)

41
Q

Where do primary afferent neurons synapse?

A
  • mainly in main sensory nucleus

- may project to spinal trigeminal nuclei too e.g. gate control theory

42
Q

where do afferent neurons project to?

A
  • sensory cortex via thalumus
43
Q

process that occurs at first synapse is called ——

A

surround inhibition

44
Q

what is the purpose of surround inhibition in mechanoreception? how does it work?

A
  • it sharpens touch perception

- it is inhibitory neurons what inhibits pathways was adjacent neurons to the one being stimulated

Occlusion (1 decks)

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