Neurophysiology - trigeminal system Flashcards
What does the trigeminal system provide?
sensory innervation to the face and mucous membrane of the oral cavity
motor innervation to the muscles of mastication
What type of nerve is the trigeminal nerve?
branchiomeric nerve
What is a branchiomeric nerve?
innervates skeletal muscles of branchial arch
Where is the first synapse of the primary afferent neurons?
CNS
Describe the general sensory pathway of the trigeminal nerve?
What do you call a collection of cell bodies in the peripheral nervous system?
Ganglion
What are tracer methods? (anatomical)
HRP, fluorescent dyes, autoradiography
Applying dyes to see where the nerves are synapsing, where is the rain it ends up …
Apart from anatomical studied, how else can you study CNS structures?
Electrophysiological
How do you study the CNS electrophysiologically?
What type of peripheral stimuli excite cells in the nuclei
What part of the CNS is activated in response to stimuli
Intracellular recording
How do you study the CNS neuropathologically?
What happens if one or more nucleus is destroyed by disease (or surgery)
Where is the cell body of the trigeminal primary Afferent neurons?
Trigeminal ganglion
What do you call the second order neuron?
Trigemino -thalamic Tract
What are the 3 main parts of the brain stem?
What are the 3 main components of the trigeminal sensory neculei?
What are the primary Afferent of the main sensory nucleus?
Large diameter
Myelinated Afferent nerve fibers from V1,2,3
What do the primary afferents of the main sensory neuron synapse with? (2)
- Cross the midline, join the ventral trigeminothalmic tract and terminate in ventral posteromedial nucleus (VPM) of the thalamus
- Don’t cross the midline, joint the dorsal trigeminothalmic tract and terminate in VOM of the thalamus
What is the function of the main sensory nucleus?
Processing discriminative tactile
Processing proprioceptive sensation
Where do the spinal trigeminal nucleus extend to?
Both nucleus and tract extend caudally to about the third cervical segment of the spinal cord
What are the 3 parts of the spinal trigeminal nucleus?
What is the function of the spinal trigeminal nucleus?
Processing of pain and temperature information from the face, mouth and nose
What neurons cross the line between PNS and CNS?
Primary Afferent neurones
Where is the 2nd synapse of the general sensory pathway?
Thalamus
Where is the third general sensory synapse?
cerebral cortex
What happens between the 1st and 2nd synapse?
cross the midline
What are 3 different ways to study the CNS?
anatomical
Electrophysiological
Neurological/neuropathological
Where is the first synapse of the trigeminal sensory pathway?
trigeminal sensory nucleus
CNS
What neurone connects the trigeminal sensory nucleus and the thalamus in the trigeminal sensory pathway?
Trigeminal-thalamus tract
Where does the trigeminal-thalamic tract neurone synapse?
In the thalamus
What is the final destination of the trigeminal sensory pathway?
Somatosensory cortex
The second order neuron is called a tract, what is a tract?
a collection of the neuron fibers in the CNS
connects the trigeminal and thalamus = trigemino-thalamic tract
Where is the trigeminal nucleus of the trigeminal nerve located?
pons
What view of the brainstem is shown?
Dorsal
How is the branching organized foe trigeminal sensory nucleus?
not about where they come from but the type of fiber
Describe options A and B of the second order neurons?
A = dorsal trigeminothalmic tract
B = ventral trigeminothalmic tract (cross midline)
Where does A terminate?
Ventral posteromedial nucleus (VPM) of the thalamus
Where does B terminate?
Ventral posteromedial nucleus (VPM) of the thalamus
If someone loses sensation to one side of the face, what is affected?
VTTT
DTTT
Tract effected
What are the subdivision of the spinal trigeminal nucleus?
Where does the V nucleus causal is extend from and to?
Extending from the spinal cord to the obex
V nucleus caudalis
A = trigeminal spinal tract
B = trigeminothalmic tract (TTT)
C ventral posteromedial nucleus in the thalamus
features of the primary afferents of the spinal trigeminal nucleus (V nucleus caudalis)
small and large-diameter fibres
turn caudally and join the spinal trigeminal tract
from V1,2,3
What do the second-order neurones of the spinal trigeminal nucleus (V nucleus caudalis) do? what do they join? Where do they terminate?
cross the midline
join the trigeminothalmic tract (TTT)
terminate in the VPM of the thalamus
What is the function of the V nucleus caudalis?
Processing in pain and temperature information from face, mouth and nose
nociceptive pathway?
pathway of pain in the body
will cause the body harm
Why can a patient find it hard to locate where the pain is in the mouth or point to a different part (not the actual site of pain)?
divergence in nociceptive pathways
convergence in nociceptive pathways
Where do the second-order neurons relay information to? (V nucleus oralis and interporalis)
all cross midline!
some to the condralateral VPM (tactile info)
some to cerebellum
What is the function of the V nucleus oralis and interporalis neurones/fibres?
tactile information
processing of pain and temperature info from the teeth and other intraoral structures (mouth) - more towards centre of the face
reflexes e.g. corneal reflex
What is the onion skin pattern?
arrangements of afferents and their endings in the spinal trigeminal system
What happens if you have damage to the caudalis part of the nucleus?
you lose sensation to the opter part of the face, not the central part
What is the most ventral nerve of trig.?
opthalmic
What is the most dorsal nerve of trig.?
mandibular
Where do parts A-C go in the spinal nucleus?
A = oralis
B = interpolaris
C = caudalis
What nucleus is most superior/rostral?
trigeminal mesencephalic nucleus
In the trigeminal mesencephalic nucleus, is there a synapse between the primary afferents and the second order neurones?
no synapse
What are the cell bodies of the trigeminal mesencephalic nucleus for?
jaw muscle spindles afferents
some mechanoreceptive afferents from PDL
What is unique about the cell bodies of the primary afferents for the jaw muscles and PDL? (mesencephalic nucleus)
they are not in the PNS but the CNS
Where is the parent axon in the mesencephalic nucleus?
V motor root - V3
Where is the first synapse of the mesencephalic nucleus?
V motor nucleus
The trigeminal mesencephalic nucleus pathway does not go to higher cortex, it is a closed loop?
it is a reflex - jaw jerk
non-conscious proprioception
What is the receptor in the jaw jerk reflex?
muscle spindle
In jaw jerk reflex, what does the trigeminal mesencephalic nucleus synapse with?
trigeminal motor nucleus
What are the efferent in the motor root (mandibular)?
muscles of mastication
Is the mesencephalic a motor or sensory root?
motor root
A = sensory root
B = motor root
What happens of there is damage to the trigeminal motor nucleus?
ipsilateral muscle atrophy - muscles of mastication