trigeminal perception Flashcards
what is stereognosis
3 dimensionality, size, texture, hardness
what are the 3 branches of the CN V
opthalamic (sensory)
maxillary (sensory)
mandibular (sensory and motor)
sensory input to the trigeminal ganglion can project to what nuclei (and where are they located)
- mesencephalic nucleus (midbrain)
- motor nucleus (pons)
- main sensory nucleus (pons)
- spinal trigeminal nucleus (medulla)
what are the 3 subdivisions/nuclei of the spinal trigeminal nucleus located in the medulla
- oralis
- interpolaris
- caudalis
trigeminal projections to the CNS cross where
(from one of the nuclei in the brainstem) they cross at the VPM of the thalamus and then go to the parietal cortex (primary somatosensory cortex) in the oral/facial region
what are the 3 fiber types of the trigeminal nerve
a-beta, a delta, c-fiber
properties of an a-beta fiber
largest diameter, fastest, low threshold, TOUCH AND PROPRIOCEPTION
properties of an a-delta fiber
high threshold, SHARP PAIN, TOUCH, TEMP, CHEMESTHESIS
properties of a c-fiber
smallest diameter, slowest, highest threshold, DULL & BURNING PAIN, TEMP, CHEMESTHESIS
what are the 2 types of mechanoreceptors
- fast adapting
2. slow adapting
what is a fast adapting mechanoreceptor
no a.p/response during static stimuli. includes RA I and RA II
what is a slow adapting mechanoreceptor
a.p/response during static stimuli. includes SA I and SA II
what is the difference between type I and type II mechanoreceptors
type 1= small, sharp borders
type 2= large (receptive field), obscure borders…located deeper in the tissue
meissner corpuscles are what type of fiber and sense what stimuli
RA I, spacial discrimination
pacinian corpuscles are what type of fiber and sense what stimuli
RA II, vibration
merkel discs are what type of fiber and sense what stimuli
SA I, pressure
ruffini endings are what type of fiber and sense what stimuli
SA II, skin stretch (pain?)
what feature of pacinian corpuscles impart their rapid adapting response
lamellae encapsulation. when the lamellae are removed there is no “off response”
what 3 channels/mechanisms are their for the mechanoreception transduction with a “stretch stimuli”
- ENaC
- TRP channels
- Piezo1 and Piezo2
(cation channels)
what are TRP channels
transient receptor potential channels
what factors influence mechanoreceptor sensing (4)
- size of the fiber and degree of its myelination
- location of receptor (whether its deep or superficial)
- structure of ending of mechanoreceptor (aka the degree of its encapsulation…by lamellae?)
- its method of transduction (what type of channel it uses)
what measures touch discrimination (sensitivity to stimuli)
Von Frey Hairs…calibrated in mg
what measures 2-point discrimination
two-point discrimination tools….calibrated in distance (how far 2 stimuli have to be from each other to distinguish b/w the 2). distances correspond to the separation b/w 2 points of stimulation. females are typically more sensitive.
the smaller the # in 2 point discrimination measurement the….
the more sensitive the area is
infraorbital nerve is a branch of what CNV division
maxillary (sensory only)…innervates the face
what type of mechanoreceptors are in the infraorbital nerve
- SA1 and SA2
2. RA1
what mechanoreceptor type is absent in the infraorbital nerve
RA2/pacinian corpuscles (responsible for vibration)
describe the perioral and facial area sensitivity to vibration
due to the lack of RA2/pacinian corpuscles in this area there is low vibrotactile sensitivity. this is represented by high measurements in the von frey hair index.
the higher the numbers in a von frey hair test, the…
the more intense vibrations need to be to sense the stimuli. the lower the numbers, the more sensitive the area is
the lingual nerve is a branch of which CN V division
mandibular (sensory and motor)…innervates the tongue
describe the sensitivity of the tongue (von frey)
the tip of the tongue is most sensitive (low von frey numbers). this is due to the high density of mechanoreceptors here (SA and RA) and small receptive fields at the tip of the tongue
what kind of nerve endings are found highly in the tongue and palate
unencapsulated ending and coiled endings (KRAUSE END BULBS specifically)
krause end bulbs are similar to what other type of mechanoreceptor
meissner corpuscles (that are found in the hand)…responsible for spatial discrimination. RA 1
what type of mechanoreceptors are found in the tongue
RA and SA mechanoreceptors…but only have 1 kind of ending (krause end bulbs?)
the auriculotemporal nerve is a branch of which division of CN V
mandibular. innervates the TMJ
describe the innervation of the TMJ
specialized pattern of innervation in which all innervation by the auriculotemporal nerve is on the posterior external portion of the capsule
what nerves innervate the TMJ
all mandibular branch…mostly auriculotemporal, but some masseter and posterior deep temporal
what kind of nerve endings are found at the TMJ
free nerve endings (c-fibers)
what kind of mechanoreceptors are found at the TMJ and in what population
Ruffini endings> golgi tendon organs > pacinian corpuscles
what nerves innervate the PDL
maxillary: superior alveolar
mandibular: inferior alveolar
which teeth/PDL are most sensitive
anterior teeth are more sensitive than posterior
what kind of mechanoreceptor endings are in the PDL
- complex ruffini
- simple ruffini
- unmyelinated free nerve endings
where are nerve fibers of the PDL that project to the mesencephalic nucleus located in higher density in the PDL (compared to nerves that project to the trigeminal ganglia)
mesencephalic nucleus fibers are located predominately deeper in the ligament (compared to the trigeminal ganglia nerves that are evenly distributes through the ligament)
the PDL mechanoreceptors are ___ sensitive and ____ sensitive
rate sensitive. the slower the stimulus is applied, the fewer the a.p that occur. the pdl is also directionally sensitive.
describe the directional sensitivity of the pdl
it is a slow adapting response. certain directions of forces are more sensitive than others (labial and distal= most sensitive). different cells in the PDL have different directional sensitivites
what determines the directional sensitivity of the PDL
the location of the ruffini endings (SAII)
is oral tactile ability compromised following dentures
yes.
what consequences do implants and dentures have on patients
have trouble controlling force (where to put it) but do not have trouble generating force/motor fn
how are denture patient’s stereognosis affected
less stereognosis (3D sensitivity) sensitivity.
what is the fn of the PDL
- detect force to teeth
- interdental discrimination
- sterognosis
- jaw reflexes
- salivation (autonomics!)
temp sensitivity in the oral/facial region
sensitivity varies depending on the region. sensitivity varies most for warm stimuli compared to cold (regions of the face are very similar in sensitivity to cold stimuli). tongue tip is most sensitive to warm stimuli.
temperature transduction is mediated by what type of channels
transient receptor potentials …TRP channels. many different subclasses of TRP channels that respond to different ranges of temperature.
what nuclei is responsible for sensing temperature
spinal trigeminal nucleus…interpolaris division. so sensory comes in from the face/oral cavity to the trigeminal ganglion and then projects to the CNS to the ST/interpolaris nucleus in the MEDULLA
