M+O 4 - mechanoreception Flashcards
What is mechanoreception?
detection of mechanical stimuli
What is adequate stimulus for mechanoreceptors?
mechanical distortion
- pressure
- vibration
- tension
What is exteroception?
give information about things coming into contact with the body
What is proprioception?
awareness of position
What is touch?
the sensory experience when mechanoreceptors are excited - involves central nervous system
Where can you find oro-facial mechanoreceptors?
- mucosa (and skin)
- periodontal ligament
- muscles
- joints
What do mechanoreceptors in the mucosa and skin tell us?
- food texture etc
- important for mastication
What do mechanoreceptors in the PDL tell us?
- forces on teeth
What do mechanoreceptors in the muscles tell us?
muscle length (muscle spindles)
What do mechanoreceptors in the joints tell us?
joint position and movement
What is the effect of stimulation of mechanoreceptors?
- 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
What are classifications of mechanoreceptors?
- physiological classification:
- adaption properties
- receptive field size
- anatomical classification
What does it mean if a mechanoreceptors is rapidly adapting?
adapts to force, gives information about something changing
What does it mean if a mechanoreceptors is slow adapting?
doesn’t adapt, carries on firing the whole time force is being applied
What are the 4 classes of mechanoreceptors?
- RA I
- RA II
- SA I
- SA II
What mechanoreceptor class has a small receptive field and rapid adaptation?
RA I
What mechanoreceptor class has a large receptive field and rapid adaptation?
RA II
What mechanoreceptor class has a small receptive field and slow adaptation?
SA I
What mechanoreceptor class has a large receptive field and slow adaptation?
SA II
What is an example of an RA I mechanoreceptor?
meissner’s corpuscle
What is an example of an RA II mechanoreceptor?
pacinian corpuscle
What is an example of an SA I mechanoreceptor?
merkel cells
What is an example of an SA II mechanoreceptor?
ruffini ending
What kind of nerve endings/mechanoreceptors are in the PDL?
ruffini (SA II)
Why is it easy to localise PDLM activation to a specific tooth?
no branched axons between adjacent teeth PDLs (unlike pulpal pain - axon supplying multiple teeth)
What provides PDLMs with adequate stimulus?
- tension in the PDL due to pressure applied to tooth
- tooth move around a fulcrum
- tension causing nerves to be activated
What does the amount of PDLM activity depend on?
- direction of applied force
- magnitude of force
- adaptation properties
- threshold of the receptors
- position of receptors in PDL
PDLMs are very sensitive, what forces can they be activated by?
<0.1N
What is the adaptation and threshold of PDLMs like apically?
- slowly adapting
- low threshold
What is the adaptation and threshold of PDLMs like cervically?
- rapidly adapting
- high threshold
Why do the receptors have different properties apically and cervically?
- linked to position relative to fulcrum
How much tooth movement is enough to activate PDL mechanoreceptors and cause a reflex/response pathway?
8.5 um (microns)
What are the 4 stages of a sensory pathway?
- mechanoreception
- transduction of stimulus
- propagation along primary afferent nerve - processing at first synapse
- trigeminal nucleus
- processing in thalamus
- conscious perception
- somatosensory cortex
What are the primary afferent cell bodies of the trigeminal pathways?
- V ganglion
- mesencephalic nucleus (PDL)
Where do trigeminal pathways synapse?
- mainly in main sensory nucleus
- project to spinal V nuclei as well
Where do trigeminal pathways project to?
sensory cortex via thalamus
What does surround inhibition do?
“sharpens” touch perception - gets rid of blurs at the edges
Where does surround inhibition occur?
during processing at the first synapse - pre-synaptic inhibition
