trigeminal system Flashcards
what is included in trigeminal perception
touch Proprioception temp pain chemesthesis (common chemical sense) Stereognosis Flavor
what is stereognosis
3D ability to sense in the mouth
what can be sensed via stereognosis
size
texture
viscosity
hardness
what makes up flavor(mouth feel)
taste olfaction (special senses) texture temp chemesthesis (trigeminal)
3 major visions of the trigeminal
Ophthalmic
Maxillary
Mandibular
what does the opthalmic trigeminal do
sensory only
what does the maxillary trigeminal do
sensory only
what does the mandibular trigeminal do
sensory and motor
parts of the spinal trigeminal nucleus
oralis interpolaris caudalis (medullary dorsal horn)
where is the spinal trigeminal nucleus located
in the medulla
what is the trigeminal motor nucleus and the priniciple (main/chief) sensory nucleus located
pons
where is the mesencephalic nucleus located
Midbrain
do all cell bodies that work in the trigeminal system find themselves in the trigeminal gnaglion
no, some cell bodies in the mesencephalic nucleus to project to the motor nucleus
cell bodies found in the mesencephalic nucleus that project to the trigeminal motor nucleus give rise to what
Monosynaptic motor reflexes
where does the trigeminal ganglion terminites
- priniciple sensory nucleus
- spinal trigeminal nucleus (oralis, interpolaris, caudalis)
projections of the trigeminal nerve must past through what to get to the primary sensory cortex
pass through the ventral posterior medial nucleus of thalamus
does the trigeminal project conra or ipsilateral to its primary somatic sensory cotex
contralateral side
what does the fact that the trigeminal nerves projectioning to the primary somatic sensory cortex mean
that you need to sense and be aware of this stuff
how does the face and hand look based on there somatotpic representation
both very large representations
ranking of fibers based on size
A-beta: large
A-delta: medium
C: small
speed ranking of fibers
A-beat: fast
A-delta: medium
C: slow
threshold ranking of fibers
A-beta: low
A-delta: medium
C: high
rolls of A belta fibers
no pain
touch
proprioceptive
Muscle I and II
rolls of A-delta fibers
sharp pain touch temp chemesthesis Muscle III
roll of C fibers
Dull and burning pain temp chemesthesis Touch? Muslce IV
RA I mechanoreceptors
Small sharp bordered receptive field ( good locationing)
Fast, with no static responce adaptation (changes quickly)
RA II mechanoreceptors
Large, obscure borded receptive field (wide borders)
Fast, with no static response adaptation (changes quickly)
SA I mechanoreceptors
Small sharp bordered receptive fields ( good locationing)
Slow, static responding adaptation (changes slowly)
SA II mechanoreceptors
Large obscure bordered receptive fields (wide borders)
Slow static responding adapatation (Changes slowly)
mechanoreceptor for meissner corpuslce
RAI
roll of meissner corpuscle
Spatial discrimination
mechanoreceptor for merkel disk
SA I
roll of merkel disk
Pressure
Mechanoreceptor for Pacinian corpuscle
RA II
roll of pacinian corpuscle
Vibration
Mechanoreceptor for Ruddini ending
SA II
roll of Ruffini ending
Skin stretch
what makes up a Pacinian Corpuscle
composed of myelinated fiber (A beta) surrounded by lamellae)
roll of the lamellae of Pacinian Corpuscles
provides a cushion to applied stimulus
upon release, decompression imparts a 2nd (off) response to nerve ending
what makes up the lamellae of Pacinian corpuscle
cells and collagen fibers separated by fluid
what are the mechanisms of mechanotransduction
ENaC (epithelial Na+ Channels)
TRP channels (transient receptor potentials)
Piezo1 and Piezo 2
how many transmembrane domains are in ENaC
6 transmembtrane domains
how many transmembrane domains are in TRP channels
6 transmembrane domains
how many transmembrane domains are in piezo1 and piezo2
36
what does stretch or mechanical contact do to mechanoreceptors
opens cation channels
steps of merkel cell activation
- Piezo2 found in merkel cells
- pressure on piezo2 leads to depolarization
- Voltage gated Ca++ channels open
- neurotransmitter release (glutamate)
- Postsynaptic response leading to action potentials
what rule is merkel cell activation an exception of
exception to the rule regarding somatosesnory transduction taking place on primary afferent rather than specialized sensory (since it is special sensory cell)
what factors influence mechanorecepotrs
- size of fiber and degree of myelination
- location of receptor (deep vs superficial)
- structure of ending (degree of encapsulation
- transduction (piezo1 and piezo2, ENacS, TRP channels)
what happens to the response time if piezo2 on both the merkel cell and the afferent
leads to a slow response
what is a threshold stimuuls
stimulus intensity detected on 50% of trials
what does a doctor use to measure touch discrimination
Semmes - weinstein monofilamens (Von Frey Hairs)
is the lateral part of face or the midline have better two point discrimination
the midline (lips)
what is microneurography
Recording from human nerves
Maps receptive fields
Determine neuron properties
what does the infraorbital branch off
Maxillary N (Div 2)
what are the lips equally sensitive to
finger tips
what kind of receptors are found in the infraorbital nerve
Both SAI and SAII
RAI
No RAII (No pacinian corpuscles)
what does the fact that the face has no pacinian corpuscles lead to
low vibrotactile sensitivity
the lingual nerve branches off what
the mandibular nerve
tongue sensitivity to threshold mg
tip is very sensitive, then fingers (for comparison), the back of the tongue
what type of endings are found a lot in the tongue
unencapsulated ending predominant
what specific types of ending are found in the tongue
Krause end bulbs- something similar in structure to meissner corpuscles (RA1)
free endings
what are Krause end bulbs
coiled ending in the tongue
are all mechanoreceptors in the tongue raapid or slowly redapting
actually both, despite having one type of ending
is the midline or the lateral more sensitive in the face
Midline is the most sensitive
what receptors does the face lack
pacinian corpuscles
what part of the face has the lowest 2 point thresholds
lips
what can be damaged during 3rd molar extractions
Lingual and mental nerves (branch of IA)
is the lingual or the mental nerve more impacted by 3rd molar extaction
mental nerve (Lip)
damge to the mental nerve via 3rd molar leads to
tongue biting and hot fluid burns and lics
NO problem with taste
where are merkel cells found in the oral mucosa
Buccal mucosa, gingiva, and palate
do merkel cells stop dividing
Can proliferate in peripheral tissue
where are merkel cells most likely to be found
in regions with high masticatory load (tissue subjec to mechanical stress)
what type of patients have lots of merkel cells
edentulous patients that use soft tissues for checking
what is found in merkel cells
contain peptides and growth factors that can promote cell divisions
what happens when merkel cells are proliferated in gingival grafts
MCs not innervated and some tissues is anesthetics
are some MErkel cell phenotypes cancerous
yes (merkel cell carcinoma)
the auriculotemporal nerve branches from
Mandibular Nerve
what part of the the TMJ does the messeter nerve innervate
Anterior
Medial
what part of the TMJ does the Auriculotemporal nerve innervate
Medial
Posterior
Latal
Also anterior slightly via the posterior deep temporal nerve
what determines what nerve gets activated in the TMJ
the direction of movement of the TMJ
what type of nerve endings are found in the TMJ
mostly free nerve endings (C-fibers)
then Ruffini, Golgi tendon organs, and then leads Pacinian
microneurography of the TMJ
Not possible
what does the mechanoreceptors for the PDL
superior alveolar (maxillary) Inferior alveolar (mandibular)
what teeth have the more senseitve PDL fibers
the anterior teeth have more sensitive PDLs
what endings are founding in the PDL
Complex Ruffini
Simple Ruffini
Unmyelinated free endings
Are PDL fibers very seneitive
No, need a very thick hair
what parts of the pDL does the Trigeminal ganglia innervate
the middle of the root
what parts of the PDL does the Mesencephalic nucleus innervate
The appex
how are mandibular and maxillary PDL’s different
no real difference in sensitivity
what sides of the tooth are more sensitive
the labial is more than the lingual
the distal is more than the mesial
what happens to the PDL mechanoreceptors as you apply stimuli more slowly
fewer APs so rate sensitive
how does the PDL mechanoreceptors adapt
slowly
do all cells have the same directional sensitivity in the PDL
different cells have different directional sensitivies
what determines sensivity in PDLs
location of Ruffini endings in the PDL
rol of PDL with bite force
helps to control bite force
effect of Dentures and Implants on forces
have trouble controlling force, but have no problem generating force
denture effect on steognosis sensitivity (shape receognition)
less stereognosis sensitivity
PDL Receptor Function
Detect force to teeth Regulate bite force Interdental discrimination stereognosis Jaw reflexes Salivation
Dual Innervation PAttern of PDL
Sensory Pathway
Reflex Pathway
path of the sensory pathways
- TG
- both to the spinal trigeminal N (O) and the Principle trigeminal nucleus
- spinal trigeminal to motor trigeminal then anterior digastric muscle
- bPinciple trigeminal nucleus to VPM
path of the reflex pathway
- to trigeminal mes nucleus
- to both motor and salivatory nucleus
- motor nucleus to anterior digastric
are all oro-facial tissues equally sesnitive to temp
Not equally sensitive with variation for warm and calt
what is the elast sensitve of intra-oral tissues for warm
Buccal mucosa
what are thermal fibers responsive to
responsive to a range of gibers but have a temp to which they respond to the most
what happens with temp change in warm fibers
fire more when temp chagnes from low to high
what happens with temp changes in cold fibers
fire more when temp changes from high to low
what receptors mediate temperature transduction
TRP channels (multiple types)
what temp is the threshold for pain
42 degrees celsius
afferents from the trigeminal ganglion project to what
decending: oralis of the medulla
asscending to the principle(main or chief) sensory nucleus
