cranial nerve 5 Flashcards
Hyperalgesia
- Pain hypersensitivity
- noxious stimulus that evokes pain sensation greater than normal
Allodynia
“differing from normal-pain”
- pain hypersensitivity
- non-noxious stimuli that evokes pain sensation
Inflammatory pain
A) caused by tissue damage
B) produces hypersensitivity at site
C) usually resolved when disease controlled
Neuropathic pain
A) caused by nervous system lesion
B) independent of peripheral pathology
C) pain persists after lesion is healed
Peripheral sensitization-
stimulation of afferent endings
hyperalgesia
repeated stimulation producing “autosensitization”
Sensitizing agents
peripheral sensitization
A) bradykinin
B) norepinephrin
C) prostaglandins
D) seratonin
T/F: peripheral sensitization takes a long time to reverse
FALSE
its quickly reversible
Central sensitization:
intense and prolonged stimulation of nociceptive fibers
Prolonged stimulation of nociceptive fibers can result in:
A) modification of peripheral receptors
modifying peripheral receptors results in what?
central sensitization
A) enhanced receptor sensitivity
B) increased number of receptor sites
where does central sensitization “wind-up” occur?
in the posterior horn/trigeminal spinal nucleus
enhanced activity of C fibers (pain fibers) results in what?
A) increased sensitivity of glutamate receptors
B) suppressed activity of inhibitory interneurons
Migroglia: overview
1) morphology changes with activity- microgliosis
2) microglia are physically active with pre and post synaptic elements
how does the microglia morphology change when they are activated?
Surveillance state= resting state
- small central region and long, narrow processes
enhanced response state= activated state
-enlarged, ameoboid configuration
how long do microglia make synaptic contact? how often does this occur?
make contact for roughly 5 minutes
one contact per hour
Astrocytes- the 2 states and when they occur
a) active state- normal state
b) reactive state- during pain hypersensitivity
Active state of astrocytes
- interact between neuron and vascular supply
- recycle neurotransmitters (mainly glutamate)
how do active state astrocytes recycle glutamate?
glutamate-glutamine shuttle
Reactive state astrocytes
enhance synaptic activity
promote microglia into “enhanced response state”
during acute inflammatory pain, what is the role of astrocytes?
promoting microlglia toward enhanced response state
what is the main promotor factor involved in acute inflammatory pain?
ATP
what do microglia release during acute inflammatory pain?
Release inflammatory cytokines
activate neurons within spinal cord
what region of the spinal cord is activated by inflammatory cytokines? (acute infl pain)
spinal cord dorsal horn / trigeminal spinal nucleus
what occurs when peripheral inflammatory situations resolve?
microglia enhanced response state returns to resting state
what causes chronic neuropathic pain?
long-term change in CNS structure
microglia activity in chronic neuropathic pain
Migroglia remain in enhanced response state
-continue releasing inflammatory cytokines
astrocyte activity in chronic neuropathic pain
continue promoting activation of microglia
a result of positive-feedback from microglia
name the 3 branches of the trigeminal nerve
1) Opthalmic division- V1
2) maxillary division- V2
3) mandibular division- V3
what region does V1 supply?
upper face
*sensory only
what region does V2 supply?
middle face
*sensory only
what region does V3 supply?
lower face
*BOTH sensory and motor
T/F: the borders between skin areas served by CN V show moderate overlap
FALSE
borders between each division are sharp
what type of nerve fiber makes up 2/3rds of the trigeminal nerve?
C fibers
Cell body origin of SVE for the trigeminal nerve
trigeminal motor nucleus
which division of CN V do the SVE fibers travel thru?
mandibular division (V3)
what do the SVE fibers of the trigeminal nerve control? where do they terminate?
VOLUNTARY control of started muscles
terminate on muscles of mastication
where is the trigeminal motor nucleus located?
Dorsolateral pontine tegmentum
the supratrigeminal nucleus is part of what?
reticular formation
what is the supratrigeminal nucleus responsible for?
rhymic actions of the motor neurons
trigeminal motor nucleus fibers exit thru the what?
thru the pons as smaller motor root
CN V, GSA proprioception:
where is the cell body of origin?
where does it project to?
CBO-
A) unipolar cell bodies
B) trigeminal mesencephalic nucleus
project to-
A) trigeminal motor nucleus
B) supratrigeminal nucleus
the trigeminal mesencephalic nucleus:
1) where is its found?
2) what does the nucleus consist of?
1) found in the rostral pons and mesencephalon
2) consists of unipolar cells of neural crest origin
Jaw jerk reflex- GSAp component
- neuromuscular spindles- V3
- trigeminal mesencephalic nucleus
- trigeminal motor nucleus
Jaw jerk reflex- SVE component
- trigeminal motor nucleus
- muscles of mastication- V3
jaw jerk reflex: upper an lower motor neuron lesions:
LMNL- attenuates reflex
UMNL- accentuate reflex
CN V: GSAe (General Somatic Afferent Exteroceptive Sensation)
Skin of face
Oronasal mucous membranes
Teeth
Dura mater
what are the 3 divisions of the trigeminal spinal nucleus?
1) pars oralis
2) pars interpolaris
3) pars caudalis
GSAe of trigeminal spinal nucleus
- Pain (slow and fast pain)
- Crude Touch
- Temperature
which cranial nerves give fibers to the trigeminal spinal nucleus
CN 5, 7, 9, 10
70-80% of tooth pulp fibers are what type?
A-delta and C fibers
which fibers make up 10-30& of tooth pulp fibers?
A-beta fibers
tooth pulp fibers project to which nuclei
- Trigeminal principal sensory nucleus (Main projection)
- trigeminal spinal nucleus
- upper cervical spinal cord
which trigeminal spinal nucleus division receives most of the tooth pulp fibers?
pars oralis
pars oralis receives input from what
intraoral and perioral structures
divisions of pars interpolaris
A) interpolaris proper
B) caudalis-interpolaris transition zone
the interpolaris proper activates what reflex
trigemino-autonomic reflex
the caudalis-interpolaris transition zone:
A) not somatotopically organized
B) responds to pain stimuli from CN 5
C) may help with pain supression
pars caudalis- what is the MPH
medullary posterior horn
the laminar structure of the pars caudalis is similar to what?
to the spinal cord posterior horn
what feature of the pars caudalis gives us the “onion peel” organization?
somatotopic organization
inverted representation of the face
the substantial gelatinosa of the pars caudalis contain what
-excitatory and inhibitory neurons
what substance is released from rap he spinal tract fibers onto the pars caudalis?
(in the substantia gelatinosa)
serotonin
the pars caudalis receives afferents from what
cranial nerves 7, 9, 10
the pars caudalis is the target of what type of nerve fibers
A) a-delta and c fibers (pain)
B) fibers from TMJ
estrogen receptors are found where?
Trigeminal spinal nucleus Parabrachial nucleus Periaqueductal gray
Hypothalamus
high estrogen levels and stress increase activity in
_________________ in
response to pain
trigeminal spinal nucleus caudalis laminae
GABA normally dampens pain-induced activity in the what?
trigeminal spinal nucleus caudalis
GABAergic activity is suppressed by high ________ levels
estrogen
Trigeminocardiac reflex: caused by a stimulation of what?
A) eye and periocular structures B) nasal mucosa C) face (diving reflex) D) needle into CN 5 E) TMJ surgery
trigeminocardiac reflex can result in:
- bradycardia (increase vagal tone)
- apnea
- arterial hypotension
- gastric hypermobility
trigeminal neuralgia: what divisions are effected?
A) V3- 70% of cases
B) V1 - less than 5% of cases
what procedure can help stop trigeminal neuralgia?
microvascular decompression
trigeminal principal sensory nucleus is homologous with what?
posterior column nuclei
- Two point discrimination
- Vibratory sense
what are the 2 ascending trigeminal pathways?
A) The ventral trigeminothalamic tract
B) The dorsal trigeminothalamic tract
which ascending trigeminal pathway projects contralaterally? bilaterally?
Contralaterally- ventral
bilaterally- dorsal
where are the cortical representation from cranial nerve 5?
Parietal lobe
- Postcentral gyrus - Brodmann’s Areas 1, 2 & 3
The Simple Story:
Trigeminal mesencephalic nucleus
Homologous with proprioceptive component of posterior
column - medial lemniscal system
the simple story: trigeminal principal sensory nucleus
Homologous with discriminative touch component of posterior column - medial lemniscal system
The Simple Story: Trigeminal spinal nucleus
Homologous with pain, crude touch, and temperature
sensation carried by anterolateral system
Jaw reflexes:
Input from:
Jaw muscles (proprioception) Tactile infomation (food in mouth) Pain information
output of the jaw reflexes
to muscles of mastication
jaw closing reflex: caused by _______
food in contact with oral membranes
jaw opening reflex is caused by what?
- Periodontal afferents activated by dental occlusion
- Pain afferents from mucosal membranes
Corneal reflex: caused by what?
stimulation of cornea (trigeminal nerve)
Corneal reflex: trigeminal nerve projects to what?
- Trigeminal pricipal nucleus -Trigeminal spinal nucleus
- Relays bilaterally to facial nucleus
the _____ is responsible for closing the eye during the corneal reflex
facial nerve
the corneal reflex is considered a ____ reflex
direct and consensual
