Ascending Sensory pathways 2 Flashcards
What are somaesthetic pathways?
perception of bodily senses such as
- pain
- temperature
- touch
- position
Where are somaesthetic pathways?
in face and body
What number cranial nerve is the trigeminal nerve?
CN V
What are the 3 divisions of the trigeminal nerve?
- opthalmic nerve - V1
- Maxillary nerve - V2
- Mandibular nerve - V3
Where does the opthalmic division of the trigeminal nerve run in the skull?
superior orbital fissure
Where does the maxillary division of the trigeminal nerve run in the skull?
foramen rotundum
Where does the mandibular division run in the skull?
foramen ovale
What branch of V2 (maxillary nerve) supplies the upper teeth?
Superior alveolar nerve
What branch of V3 (mandibular nerve) supplies the lower teeth?
Inferior alveolar nerve
What is herpes zoster (shingles)?
infection of the sensory roots of trigeminal nerve
How does herpes zoster (shingles) spread/infect?
Along the dermatome - if it affects V2 the maxilla will have a group of shingles blisters on their face along the maxilla
What 2 groups do the somaesthetic modalities fall into?
- modalities that are essential for survival - pain, temp, some touch and pressure
- modalities that increase detail - discriminative touch and proprioception
What is meant by discriminative touch?
2 point discrimination
Vibration
How many neurones are involved in the chain from receptor to sensory cortex?
3 neuron chains
How do the first order neurones travel?
from PNS to CNS
Where are first order neurons found?
cell bodies in the peripheral ganglia
How do the second order neurons travel?
across midline
Where are the second order neurone found?
extend to thalamus
How do third neurones travel?
extend from the thalamus to the post-central gyrus
Where are cranial nerve nuclei located?
brainstem
they are very specific
Where does sensory information received in cranial nerve nuclei come from?
fibres entering brainstem n cranial nerves?
What does the cranial nerve nuclei also give rise to that leave the brainstem in cranial nerves?
motor fibres
What is the cranial nerve nuclei equivalent to?
dorsal grey horn in spinal cord
- collection of cell bodies
- where primary sensory neurons synapse withs secondary sensory neurons
What is the motor nucleus equivalent to?
ventral grey horn
What does the trigeminal central nucleus deal with?
fibres coming from trigeminal nerve
Which cranial nerves is general sensation from the head carried by?
CN V, VII, IX, X
Which cranial nerve is the major carrier of general sensory info from FACE, NOSE, SCALP and DURA?
trigeminal CNV
Which cranial nerve carries sensation for the external ear?
Facial CNVII
Which cranial nerve carries sensation from the posterior 1/3 of the tongue, pharynx and middle ear?
Glossopharyngeal CNVIX
Which cranial nerve carries sensation from auditory canal, larynx, pharynx and oesophagus?
Vagus CN X
Where does information from CN V, VII, IX and X travel? (which pathway?)
same pathway
trigeminal sensory pathway
What 3 nuclei make up the trigeminal nerve nuclei?
mesencephalic nucelus
principle sensory nucleus of trigeminal nerve
spinal nucleus of trigeminal nerve
Sensory fibres from cranial nerves run through the trigeminal nerve nucleus and to the thalamus?
trigeminal CNV
facial CN VII
Glossopharyngeal CN IX
Vagus CN X
Where does the motor nuclei of the trigeminal lie in comparison to the trigeminal nerve?
medial to the sensory nuclei
NOTE
LEARN SOMATOTOPIC MAP ON POST-CENTRAL GYRUS
WILL BE ASSESSED
In the trigeminal nuclei what are the 3 divisions in the sensory nucleus?
- mesencephalic nucelus
- pontine, chief nucleus
- spinal nucleus
Where is the mesencephalic nucleus?
midbrain
Where is the pontine/chief sensory nucleus?
Pons
Where is the spinal nucleus?
in medulla
What is pain and temp received by?
caudal part of the spinal nucleus
What is simple touch and pressure received by?
more rostral parts of the spinal nucleus
Which sides are the nuclei present?
present on both sides
In the pain and temperature pathway where are the primary neuron cell bodies found?
trigeminal ganglion
What is the fibre like in the pain and temperature pathway? (2)
thin
slow
How do the fibres run in the spinal tract of the trigeminal nerve nuclei in the pain and temp pathway?
caudally
Where does the primary neurone synapse with the secondary neurone in the pain and temp pathway?
in spinal nucleus
what happens after the synapsing in the spinal nucleus in the pain and temp pathway?
axon crosses over and ascends in trigeminothalamic tract to specific place on thalamus (VPM)
runs very deep to midbrain and pons etc
What is VPM and what does it stand for?
ventral posteromedial nucleus
a nucleus of the thalamus
conveys facial sensory information of the trigeminothalamic tract and projects to the post-central gyrus
Where is the primary neuron cells found in the touch and pressure pathway?
trigeminal ganglion
What are the fibres like in the touch and pressure pathway?
thin
slow
Where do the fibres descend in the touch and pressure pathway?
doesn’t descend as much as temp
in spinal tract of trigeminal
Where does synapsing between primary neurons and secondary neurons take place in the touch and pressure pathway?
more rostrally in spinal nucleus
What happens to the axon after synapsing occurs in the touch and pressure pathway?
axon crosses and ascends in trigeminothalamic tract
NOTE - TRANSVERSE SECTION THROUGH ROSTRA MEDULLA OBLONGATA
- arcuate fibres - gracile and cuneate tubercles
- spinal tract
- medial leminscus
- pyramids
- spinal nucleus
- central canal
- left trigeminothalamic tract - info from right side (vice versa)
What is the trigeminal sensory nucleus like?
dorsal column pathway
What kind of modality does the pontine chief sensory nucleus receive in trigeminal sensory nucleus?
discriminative touch
What kind of modality does the mesencephalic nucleus in the trigeminal sensory nucleus?
proprioception
How is the mesencephalic nucleus an exception?
as it contradicts the generalisation that the first order cell bodies are in the peripheral ganglia
Where are primary neurone cell bodies in the discriminatory touch pathway?
trigeminal ganglion
What are the fibres like in the discriminatory touch pathway?
fast
fat
Where does the primary neurone synapse with the secondary neurone in discriminatory touch pathway?
pontine nucleus
What happens after synapsing in the discriminatory touch pathway?
axon crosses and ascends in the trigeminothalamic tract to thalamus
What is a key feature of the discriminatory touch pathway?
It does’t ascend or descend significantly prior to synapsing
Where is the primary neurone found in the proprioception pathway?
mesencephalic nucleus
Where do most of the axons in the proprioception pathway travel?
In mandibular division of V
Where does the primary neurone synapse in the proprioception pathway?
alongside M nucleys (adjacent to the nucleus)
outside the trigeminal nuclei
Where does the axon cross and ascend to in the proprioception pathway?
after synapsing
ascends to thalamus in trigeminothalamic tract
What do other fibres in the proprioception pathway do in the proprioception pathway?
contact motor neurons in the trigeminal motor nucleus
- muscles of mastication - jaw jerk reflex
