Trigeminal Pathways Flashcards
Primary afferents associated with trigeminothalamic pathways extend from cell bodies in the ____ ganglion in 3 divisions: ___, ___, and ____
Trigeminal (semilunar); V1 ophthalmic, V2 maxillary, V3 mandibular
The trigeminal n. attaches to the brainstem as 2 adjacent roots on the ventrolateral aspect of the ______. The two roots include the larger ______ root and the smaller ______ root
Pons; sensory; motor
Each trigeminal division has somatotopic arrangement with rostral-caudal distribution. Fibers representing areas near the center of the face end near the ______, while fibers representing areas toward the back of the head end in the ___________
Obex; upper cervical cord
Trigeminal fibers ending in the cervical cord overlap spinal fibers that represent adjacent areas of skin. Thi leads to characteristic pattern of sensory loss when spinal trigeminal tract is damaged —> onion skin distribution. What is the difference between a more caudal lesion and a more rostral lesion in terms of sensory loss?
The more caudal the lesion, the larger the area around the mouth that is spared from sensory loss
The more rostral the lesion (into brainstem), increased degrees of sensory loss starting at the back of the head and converging on the mouth
4 trigeminal nuclei form a continuous cell column that extends from the ______ junction to the rostral levels of the mesencephalon/midbrain
Spinomedullary
What are the 4 nuclei associated with the trigeminothalamic pathway?
3 sensory:
Main sensory nucleus (msT)
Spinal nucleus
Mesencephalic nucleus (mes)
1 motor:
Trigeminal motor nucleus (mT)
The ______ trigeminal nucleus forms an enlargement in the midpons and is slightly lateral to the motor nucleus
Main sensory
Modality of main sensory nucleus
Termination point of fibers conveying touch and pressure — relays discriminative tactile info from head to ventral posteromedial nucleus (VPM) of thalamus
2 divisions of main sensory trigeminal nucleus and their functions
Dorsomedial division = afferent info from oral cavity
Ventrolateral division = afferent info from V1,V2,V3
The dosomedial division of the main sensory trigeminal nucleus projects to IPSILATERAL VPM via ________________ tract and ascends lateral to periaqueductal gray
Posterior dorsal trigeminothalamic tract (aka dorsal central trigeminal tract)
The ventromedial division of the main sensory nucleus projects to the CONTRALATERAL VPM via ___________ and will be joined by fibers from spinal nucleus of CN V
Trigeminal lemniscus (anterior trigeminothalamic tract)
The ventrolateral division of the main sensory trigeminal nucleus has somatotopic representation of afferents. How does this apply to V1 vs. V2 vs. V3?
V1 = anterior
V2 = sandwiched between
V3 = posterior
The main sensory trigeminal nucleus terminates somatotopically in the VPM. How does this apply to the oral cavity vs. external face?
Oral cavity = medially
External face = laterally
Tertiary axons of the main sensory trigeminal nucleus project from the VPM via posterior limb of _____ _____ to the primary somatosensory cortex.
A moderate amount of secondary neurons project to the _____ ____ of cerebellum via the ____________
Internal capsule
Anterior vermis; superior cerebellar peduncle
The _____ trigeminal nucleus extends caudally (descends) from its level
Spinal
Modality of spinal trigeminal nucleus
Termination point for fibers carrying pain and temperature
Primary afferent fibers associated with the spinal trigeminal nucleus descend as they enter the pons, joining the ________ tract, positioned lateral to the nucleus.
Spinal trigeminal
The spinal trigeminal tract is the descending tract of CN V. This becomes continuous with ______ tract in the upper cervical cord
Both the nucleus and the tract etend caudally to above the ____ cervical segment
Lissaur’s; 3rd
3 regions of the spinal trigeminal nucleus
Pars/subnucleus caudalis
Pars/subnucleus interpolaris
Pars/subnucleus oralis
The pars caudalis region of the spinal trigeminal nucleus is the most caudal part and extends from the spinal cord to the obex. It represents different parts of the ipsilateral _______.
The ____ division is the most posterior, while the _____ division is the most anterior, and the _____ division is in between. This arrangement allows for smooth transition of spinal levels processing cutaneous info originating at the back of the head with brainstem levels processing similar cutaneous info from teh face
Face
Mandibular; ophthalmic; maxillary
Second-order neurons from the caudal nucleus (region of spinal trigeminal nucleus) decussate and ascend in ___________ tract. They terminate in the contralateral ______ of the thalamus.
Tertiary axons extend in posterior limb of internal capsule and proceed to the ________
Anterior trigeminothalamic (trigeminal lemniscus); VPM
Primary somatosensory cortex
The pars/subnucleus interpolaris region of the spinal trigeminal nucleus is the middle region, located in the rostral medulla and extending to the level of the obex. Where does it receive info from in comparison with the pars oralis?
Pars interpolaris receives info from peripheral region of face
Pars oralis receives tactile info from central region of face
The pars oralis region of the spinal trigeminal nucleus is the most rostral part, extending from the ______ nucleus to the pontomedullary junction
Main sensory
Both the pars oralis and interpolaris are heavily involved in functions homologous to somatic functions of the SC. They project fibers to the cerebellum through the __________ ; as well as carry tactile info and project to the contralateral ______
Inferior cerebellar peduncle; VPM
