Somatosensory Ascending Pathway - Part II Flashcards
Why do you feel “funny” when your funny bone gets irritated?
Ulnar nerve: Meissner Corpuscle causes tingling sensation
What does the DCML synapse with? Where?
2nd order neurons in Clarke’s nucleus
Where is Clarke’s nucleus?
lamina 7
What does the DCML do?
fine touch, vibration, proprioception
- participates in spinal reflex
What are the type of joint capsule receptors in the posterior root ganglion of the DCML?
Ia, Ib
- Ia most posteriorly, proproception, muscle spindle
- Ib from GTO
What are 1st order neurons in the DCML?
- cell body location
- located at dorsal root ganglia
What are AB receptors for in the DCML?
for meissner corpuscle, Pacini corpusle, Ruffini ending, Merkle cell, etc.
- conduct to more medial, anterior compared to proprioception part
What does lamina 7 form?
synapse where 2nd order neuron for posterior spinocerebellar trat and anterior spinocerebellar tract
Where is Clarke’s nucleus?
Lamina 7
What are the components of the Dorsal Column?
- fasciculus gracilis below T6
- fasciculus cunetus above T6
- lissauer’s tract
- fasciculus interfascicularis (b/w FG and FC)
- septomarginal fascuiculus
What does the fasciculus interfascicularis and septomarginal fasciculus do?
visceral and some somatic pain pathways
What kind of tracts are in the septomarginal fasciculus and fasciculus interfascicularis?
ascending tracts for visceral pain
What is the pathway of Lissauer’s tract?
ascend to C2 level of spinal cord, continue to be spinal trigeminal tract for trigeminal nerve functions
Is somatotopy maintained in the DCMLs pathway?
Yes
What are the third order neurons of the DCML?
- ventral posterolateral nucleus of the thalamus
What are the two parts of the ventral posterolateral nucleus of the thalamus?
- shell: proprioception (outside of VPL)
- core: vibration and fine touch (inside VPL)
Where do the parts of the VPL project?
to S1
Where are the 2nd order neurons of the DCML?
caudal medulla
What are the 2nd order neurons for the DCML? Where is sensory decussation?
- fasciculus gracilis: gracile nnucleus
- fasciculus cuneatus: cineate nucleus
- sensory decussation in internal arcuate fibers of medial leminiscus
What is the 1st order neuron of the trigeminothalamic pathway?
- trigeminal ganglion and mesencephalic nucleus
What is the trigeminal ganglion for?
fine touch, vibration, and proprioception
- outside of dura matter in medial cranial fossa
What is the messencephalic nucleus for? Location?
PNS structure, proprioception (CN V)
- located at CNS, midbrain but part of PNS
Where does the mesencephalic nucleus project to?
CN V motor nucleus for myotatic reflex
What reflex is mesencephalic nucleus responsible for?
CN V = tongue depressor flip - close jaw
Where is the 2nd order neuron of the trigeminothalamic pathway?
- main sensory nucelus in pons
(mid pons, where trigeminal nerve attaches)
What is the function of the 2nd order neuron of the trigeminothalamic pathway?
- fine touch and vibration
(left over, to main sensory nucleus)
What are the two pathways of the 3rd order neuron of the trigeminothalamic pathway?
shell and core
Where is the 3rd order neuron of the trigeminothalamic pathway?
ventral posteromedial nucleus
Where does the 3rd order neuron of the trigeminiothalamic pathway project?
- VPL and VPM project to S1
Is the somatotopy maintained with the projection of the 3rd order neuron of the trigeminothalamic pathway?
yes
What is the pathways of the 3rd order neuron of the trigeminothalamic pathway?
- cross over in caudal medulla, ascend to contralateral side of thalamus for head fine touch/vibration
What mechanoreceptors are in the hairy skin?
superficial
- hair follicle
- merkel cell
deep
- ruffini endings
- pacinian corpuscle
What does blood supply of the DCMLs?
- anterior spinal artery and posterior spinal artery
Where does the anterior spinal artery go?
to internal arcuate fibers: medial lemniscus
Where does the posterior spinal artery go?
- dorsal column
- caudal nuclei
What happens after the synapse of the 2nd order neurons of the DCML?
- they crossover, form the internal arcuate fibers aka medial lemniscus, go forwards, and the anterior spinal artery supplies
What happens until spinal cord to caudal medulla where 2nd order neuron is located?
get blood supply from posterior spinal artery
Where does the blood supply of the DCMLS in the medial lemniscus of the pons come from?
AICA, SCA, pontine arteries
- AICA caudally, SCA rostrally
Where does the blood supply of the DCMLS in the medial lemniscus of the medulla come from?
anterior spinal artery
- after crossover, medial leminscus goes to the anterior part of the caudal/rostral medulla where anterior spinal artery supplies it
What is unique about the pons of the DCMLS?
180 degree turn
- medial to lateral
- UL to LL
What is unique about a pontine artery stroke?
patient can regain the sensation back, but lost motor functions bc basilar pons motor tracts compromised so cannot regain motor function but sensation comes back early
What supplies the lateral frontal/patrietal/superior temporal lobes?
MCA
What supplies the medial and superior frontal/parietal/limbic lobes?
ACA
What supplies the thalamus and postcentral gyrus(VPN)?
thalamogeniculate arteries from PCA
What are 1 and 3b from the S1 for?
fine/crude touch; sharp pain, temperature
What is 2 from the S1 for?
joint capsule: Vibration
What is 3a - the muscle spindle and GTO for in S1?
(Ia) and GTO (Ib)
- proprioception
What is 3a?
muscle spindle, GTO, Ib signal projects here for proprioception
What is 3B for?
fine touch, crude touch, pain, temp
What brodmanns area is S1?
3,1,2
What brodmanns area is M1?
4
What detects vibration?
Pacinian corpuscles
What is the clinical importance of the Pacinian corpuscles in DCMLS?
- Braille reading by blind people
- stereognosis test (identify objects without seeing them, just using feeling)
Where are the superficial mechanoreceptors?
finger, lips, sole
- smallest receptive area, most sensitive to differentiate two adjacent stimuli
Where do pacinian corpules project waves?
to nucleus gracilis
You get a kiss from your loved one on your lip. List out the 3 order neurons to your S1 that make you feel happy?
1st - trigeminal ganglion
2nd - main sensory nucleus in pons
3rd - ventral posteromedial nucleus
What happens at the inferior cerebellar peduncle of the posterior spinocerebellar tract?
no decussation
- adjusts body all the time
- unconcious proprioception
- balance, motor control
Where is the lateral cuneate nucleus of the posterior spinocerebellar tract?
T4 - C2
Where is Clarke’s nucleus of the posterior spinocerebellar tract?
Below T4
What are the functions of the posterior spinocerebellar tract?
unconscious proprioception
What is the pathway of the posterior spinocerebellar tract?
- ascend until cerebellum without crossover, ipsilateral side through inferior cerebellar peduncle, combines with other pathway to run ipsilateral cerebellum through inferior cerebellar peduncle, not crossing over
What happens in the anterior spinocerebellar tract above t4?
no decussation, ipsilateral inferior cerebellar peduncle to the cerebellum
What is Clarke’s nucleus?
below T4, decussation, and bilateral projection through the superior cerebellar peduncle
What is the function of the anterior spinocerebellar tract?
motor information
- how fast youre performing a movement, how far we reach out etc
ONLY _______________ information projects to anterior spinocerebellar tract
muscle spindle
What is the mesencephalic nucleus in the trigeminocerebellar pathway projecting to?
- ipsilateral cerebellum: the superior cerebellar peduncle
What is the function of the mesencephalic nucleus in the trigeminocerebellar pathway?
lake anterior spinocerebellar tract; motor info
What is the spinal triceminal nucleus in the trigeminocerebellar pathway projecting to?
the ipsilateral cerebellum: inferior cerebellar peduncle
What is the function of the spinal trigeminal nucleus?
like posterior spinocerebellar tract, mainly for pain by free nerve endings, AB
What is Tabes Dorsalis?
DCMLS functional loss
What are the symptomes of Tabes Dorsalis?
literally “flat back”, progressive locomotor ataxia and sensory ataxia
What is the infection that causes Tabes Dorsalis?
treponema pallidum, STD
causes DCMLS degeneration
- only affects DCMLS axons
What are signs of Tabes Dorsalis?
wide-based stance/feet grasping the floor/steppage gait, etc
-without shoes - claw feet, lost proprioception, no balance
- must watch feet when walking or cant walk
What can control Tabes Dorsalis?
penicillin
- now 5 mil infected
- back in USA, Japan
- rash everywhere, cant walk
Map the arteries supplying DCMLS pathway to the S1?
- spinal cord and caudal medulla: posterir spinal artery
- Medial lemniscus in medulla: anterior spinal artery
- Pons: AICA and SCA branches
- midbrain: SCA and PCA branches
- Thalamus: PCA branches
- S1: ACA (LE and trunk) MCA (UE and head)
