M+O 4 - mechanoreception

Question 1

What is mechanoreception?

Answer 1

detection of mechanical stimuli

Question 2

What is adequate stimulus for mechanoreceptors?

Answer 2

mechanical distortion
- pressure
- vibration
- tension

Question 3

What is exteroception?

Answer 3

give information about things coming into contact with the body

Question 4

What is proprioception?

Answer 4

awareness of position

Question 5

What is touch?

Answer 5

the sensory experience when mechanoreceptors are excited - involves central nervous system

Question 6

Where can you find oro-facial mechanoreceptors?

Answer 6

• mucosa (and skin)
• periodontal ligament
• muscles
• joints

Question 7

What do mechanoreceptors in the mucosa and skin tell us?

Answer 7

• food texture etc
• important for mastication

Question 8

What do mechanoreceptors in the PDL tell us?

Answer 8

• forces on teeth

Question 9

What do mechanoreceptors in the muscles tell us?

Answer 9

muscle length (muscle spindles)

Question 10

What do mechanoreceptors in the joints tell us?

Answer 10

joint position and movement

Question 11

What is the effect of stimulation of mechanoreceptors?

Answer 11

• sensation of touch
• reflexes e.g. jaw muscle reflexes, salivary reflexes
• interact/modulate other sensory modalities:
  
  • the effect of rubbing a painful area - gate control

Question 12

What are classifications of mechanoreceptors?

Answer 12

• physiological classification:
  
  • adaption properties
  • receptive field size
• anatomical classification

Question 13

What does it mean if a mechanoreceptors is rapidly adapting?

Answer 13

adapts to force, gives information about something changing

Question 14

What does it mean if a mechanoreceptors is slow adapting?

Answer 14

doesn’t adapt, carries on firing the whole time force is being applied

Question 15

What are the 4 classes of mechanoreceptors?

Answer 15

• RA I
• RA II
• SA I
• SA II

Question 16

What mechanoreceptor class has a small receptive field and rapid adaptation?

Answer 16

RA I

Question 17

What mechanoreceptor class has a large receptive field and rapid adaptation?

Answer 17

RA II

Question 18

What mechanoreceptor class has a small receptive field and slow adaptation?

Answer 18

SA I

Question 19

What mechanoreceptor class has a large receptive field and slow adaptation?

Answer 19

SA II

Question 20

What is an example of an RA I mechanoreceptor?

Answer 20

meissner’s corpuscle

Question 21

What is an example of an RA II mechanoreceptor?

Answer 21

pacinian corpuscle

Question 22

What is an example of an SA I mechanoreceptor?

Answer 22

merkel cells

Question 23

What is an example of an SA II mechanoreceptor?

Answer 23

ruffini ending

Question 24

What kind of nerve endings/mechanoreceptors are in the PDL?

Answer 24

ruffini (SA II)

Question 25

Why is it easy to localise PDLM activation to a specific tooth?

Answer 25

no branched axons between adjacent teeth PDLs (unlike pulpal pain - axon supplying multiple teeth)

Question 26

What provides PDLMs with adequate stimulus?

Answer 26

- tension in the PDL due to pressure applied to tooth - tooth move around a fulcrum - tension causing nerves to be activated

Question 27

What does the amount of PDLM activity depend on?

Answer 27

- direction of applied force - magnitude of force - adaptation properties - threshold of the receptors - position of receptors in PDL

Question 28

PDLMs are very sensitive, what forces can they be activated by?

Answer 28

<0.1N

Question 29

What is the adaptation and threshold of PDLMs like apically?

Answer 29

- slowly adapting - low threshold

Question 30

What is the adaptation and threshold of PDLMs like cervically?

Answer 30

- rapidly adapting - high threshold

Question 31

Why do the receptors have different properties apically and cervically?

Answer 31

- linked to position relative to fulcrum

Question 32

How much tooth movement is enough to activate PDL mechanoreceptors and cause a reflex/response pathway?

Answer 32

8.5 um (microns)

Question 33

What are the 4 stages of a sensory pathway?

Answer 33

1. mechanoreception - transduction of stimulus - propagation along primary afferent nerve 2. processing at first synapse - trigeminal nucleus 3. processing in thalamus 4. conscious perception - somatosensory cortex

Question 34

What are the primary afferent cell bodies of the trigeminal pathways?

Answer 34

- V ganglion - mesencephalic nucleus (PDL)

Question 35

Where do trigeminal pathways synapse?

Answer 35

- mainly in main sensory nucleus - project to spinal V nuclei as well

Question 36

Where do trigeminal pathways project to?

Answer 36

sensory cortex via thalamus

Question 37

What does surround inhibition do?

Answer 37

“sharpens” touch perception - gets rid of blurs at the edges

Question 38

Where does surround inhibition occur?

Answer 38

during processing at the first synapse - pre-synaptic inhibition