Somatosensory Pathways Flashcards
Dr. Mokha's content
Spinal nerve root C6-C8
hand and fingers
Spinal nerve root T4
Nipples
Spinal nerve root T10
Umbilicus
Merkel cell
sensation
Anterior 2/3 of the tongue is innervated by which nerve?
Trigeminal provides pain, temperature and touch
Does the Trigeminal nerve provide motor or sensory innervation?
It provides both
Which branch of the Trigeminal nerve has a motor component?
The mandibular nerve it provides motor to the muscles of mastication
Where does the trigeminal nerve enter the brain?
In the level of the mid pons
Which nerve supplies the TMJ
the auriculotemporal joint (posteriorly)
Meissner cells
flutter
Two point discrimination
ability of the brain to discriminate between two closely spaced touch stimuli as two separate stimuli
Greater the receptor density in a body region, _________ is the distance between two stimuli that the brain can perceive as two separate stimuli.
smaller
What receptor type allows us to have proprioception?
Muscle fibers axon type Ia and II
Pacinian cells
vibration
Axon type of cells providing touch sensory
A-beta
What receptor type allows use to feel pain and temperature?
Free nerve endings of axon A-delta
Dorsal column-medial lemniscal system (DCML)
Allows us to feel touch and propioception.
Anterolateral system (ALS)
Allows us to feel pain and temperature from the neck down.
Trigeminothalmic tract
Allows us to feel pain, temperature, touch, propiception from the face, sinus, oral cavity etc.
Steps of the DCML
- mechanoreceptors (spinal cord) from the upper body synapse at the cuneate nucleus (medulla)
- lower body mechanoreceptors (spinal cord) synapse at the gracilis nucleus (medulla)
- upper and lower fibers merge to form the medial lemniscus any lesions here or higher will manifest in contralateral issues with touch and propioception
- Medial lemniscus travels through mid pons, mid brain
- 2nd order neurons synapse in the VENTRAL POSTERIOR LATERAL NUCLEUS in the somatosensory region of the post central gyrus
What fibers synapse in the ventral posterior LATERAL nucleus (thalamus)
fibers from the neck, trunk and extremities
What fibers synapse in the ventral posterior MEDIAL nucleus (thalamus)
fibers from the head
Where does crossing over happen in the DCML pathway
In the medulla
Cuneate nucleus (medulla)
Where fiber from upper extremities synapse (above T6)
Cuneate gracilis (medulla)
Where fiber from lower extremities synapse (below T6)
Where do 3rd order neurons synapse in the DCML pathway?
In the somatosensory cortex of the post central gyrus
Where do the 2nd order neurons synapse in the DCML and AML pathways?
In the ventral posterior lateral nucleus of the thalamus
Proprioception fibers follow the same pathway as the DCML pathway except?
Propiocetion fibers below L2 travel to the gracilis nucleus
Propioception fibers from L2-T1 (upper extremities) travel to the CLARK NUCLEUS
Form the spinocerebellar tract
Clark nucleus
Where propioception fibers from L2-T1 (upper) synapse
Dorsal spinocerebellar tract
Where crossing over happens in propioception fibers
Morphosynthesis
recognition of objects by touching them
Graphesthesia
recognition of numbers or letters traced on skin
Anterolateral System (ALS)
fibers for pain and and temperature
Where does crossing over happen in the ALS
in the dorsal horn of the spinal cord at the anterior white commissure
Where does crossing over happen in the DCML pathway?
in the medulla
Where does 3rd order neuron synapse in the ALS
Primary somatic sensory cortex
Where does all sensory information leave the thalamus?
through the thalamo-cortical projections in the internal capsule (posterior limb)
Brown Sequard Syndrome
damage to one side of the spinal cord
DCML damage on the same side
ALS damage on opposite side
Corticospinal tract damage on the same side unable to move limbs
Babinski signs
Corticospinal tract
motor fibers coming from the PRIMARY MOTOR CORTEX OF THE PRECENTRAL GYRUS the muscles
Where does crossing over occur in the corticospinal tract
In the medulla
In the cortical tract damage below what will show ipsilateral damage?
damage after the pons will show on the same side.
Anything above the pons (medulla, cortex, midbrain) will show on opposing side
How to test damage of the cortical spinal tract
with the babinski sign
if toes flex down (normal)
if toes fan up (damage to the corticospinal tract)
Main sensory nuclei in the pons
Pontine trigeminal nucleus for sensory and touch
mesencephalic nucleus
propioception
nucleus of the the spinal tract
pain and temperature
Touch pathway of the face
mechanoreceptors go through the trigeminal ganglion
synpase and crossover in the pons
Pain fibers in the face
enter through the pons
travel down in the the spinal trigeminal tract
synapse in the spinal nucleus (medulla)
cross over at the trigeminothalmic tract
Vertebral artery give rise to what?
Anterior Spinal artery &
Posterior Inferior Cerebellar artery
Wallenberg syndrome
Stroke that damages PICA
damage of the trigeminal nucleus
Pain and temperature loss ipsilateral of face
contralateral rest of the body
