What are the functions of the sensory nuclei of the trigeminal nerve?
Main sensory nucleus (msT)
- Touch and pressure.
Mesencephalic nucleus (mes)
- Proprioception for chewing.
What are the two divisions of the main sensory nucleus of the trigeminal nerve?
The main sensory nucleus has two divisions:
- Dorsomedial division
- Afferents just from the oral cavity.
- Ventrolateral division
- Afferents from V1, V2, and V3
In the fasciculae gracilis and cuneatus, are the fibers from the upper extremity more lateral or more medial to the fibers from the lower extremity?
Upper extremity fibers are more lateral in the PCML system.
Where do the third order neurons of the PCML system travel?
What important structure do they pass through?
What is the name of the pathway?
The fibers from the ventral posterolateral nucleus runs through the thalamocortical pathway, through the posterior limb of the internal capsule, and to the somatosensory cortex.
What is the specialization of the outer shell and inner core of the nuclei gracilis and cuneatus?
The outer shell of the nuclei gracilis and cuneatus specializes in proprioception.
The inner core specializes in sensation.
What do we call the decussation of the PCML secondary fibers immediately after the synapse of the nucleus gracile/cuneatus?
Internal arcuate fibers.
Where would lesions to the middle cerebral artery cause loss of sensation?
Where would lesions to the anterior cerebral artery cause loss of sensation?
The anterior cerebral artery damage would eradicate sensation from the lower extremity.
Middle cerebral artery damage would eradicate damage from the upper extremity and face.
What are the three parts of the spinal nucleus of the trigeminal nerve?
Where do the dorsomedial and ventrolateral fibers of the main sensory nucleus of the trigeminal nerve synapse?
On the ventral posteromedial nucleus of the thalamus.
What nucleus in the thalamus does the PCML pathway synapse onto?
The ventral posteriolateral nucleus of the thalamus.
What artery supplies the PCML in the spinal cord?
What artery supplies the PCML in the medulla (and up from there)?
Spinal cord = posterior spinal artery
Medulla and up = anterior spinal artery
Where do the afferent first order fibers of the PCML system enter the spinal cord?
At the medial division of the posterior root.
What symptom is associated with damage to the secondary somatosensory area?
Agnosia – the loss of ability to recognize a limb as part of the body.
What artery supplies the ventral posterolateral nucleus?
What would happen if these were occluded?
The thalamogeniculate branches of the posterior cerebral artery.
Complete loss of discriminative touch, pressure sensation, and proprioception to the contralateral body.
Where are the cell bodies for first order sensory neurons?
What type of nerves are these?
From what layer are these nerves derived?
Dorsal root ganglion.
What are the two divisions of the fibers from the main sensory nucleus of the trigeminal nerve?
What are their contents?
Dorsomedial division: contiains afferent input from the oral cavity.
Ventrolateral division: contains afferent input from V1, V2, and V3.
What type of information is carried by the VPL pathway?
Two point touch
Where do we find the nuclei gracilis and cuneatus?
In the posterior medulla.
What is the purpose of the mesencephalic nucleus?
Primarily relays proprioceptive information related to chewing.
At the level of the pons, are fibers from the nucleus gracilis medial or lateral to the fibers of the nucleus cuneatus?
Fibers from the nucleus gracilis are lateral in the pons.
Where is the switch over from fibers coming together to form the fasciculus gracilis to becoming the fasciculus cuneatus?