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Somatosensory Pathways
Neuroanatomy- Somatosensory- Dudas
73
Anatomy
Professional
03/19/2012

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Term
Meissner's corpuscles carry what sensation?
Definition
Tactile impulses- fine touch
Under epithelium
RAPIDLY adapting
Term
Paccinian corpuscles carry what sensation?
Definition
Vibration sense
Deep under skin and bigger
RAPIDLY adapting
Term
Merkel's disks carry what sensation?
Definition
Pressure
Inside epithelium
SLOWLY adapting
Term
Ruffini's endings carry what sensation?
Definition
Pressure
Deeper under skin
SLOWLY adapting
Term
Muscle spindles carry what sensation?
Definition
Proprioception- movement
Term
Golgi tendon organs carry what sensation?
Definition
Proprioception- tension
Term
Where does the PCMLS cross?
Definition
Internal arcuate fibers, AFTER synapsing in the Gracile and Cuneate nuclei
BRAINSTEM
Term
Where does the Anterior Trigeminothalamic tract cross?
Definition
In the brainstem, after synapsing in the Principal nucleus
Term
Where does the Posterior Trigeminothalamic tract cross?
Definition
IT DOESN'T
Term
Regions 3a and 2 of the primary sensory cortex are target areas for what receptors?
Definition
Muscle Spindle, GTO, joint receptors
Term
Regions 3b and 1 of the primary sensory cortex are target areas for what receptors?
Definition
Cutaneous receptors
Term
A lesion that causes loss of area 1 of the primary sensory cortex causes loss of what functions?
Definition
Texture discrimination
Term
A lesion that causes loss of area 2 of the primary sensory cortex causes loss of what functions?
Definition
Loss of shape and size discrimination
ASTEREOGNOSIS
Term
A lesion that causes loss of area 3b of the primary sensory cortex causes loss of what functions?
Definition
Loss of texture discrimination and shape/size discrimination
Term
The primary sensory cortex has a medial aspect near the longitudinal fissure, and a lateral aspect near the lateral sulcus. Senses for the head are located closer to which?
Definition
Lateral Sulcus
Term
The primary sensory cortex has a medial aspect near the longitudinal fissure, and a lateral aspect near the lateral sulcus. Senses for the feet and junk are located closer to which?
Definition
Medial region- longitudinal fissure
Term
The secondary somatosensory cortex receives input from where?
Definition
Ipsilateral primary sensory cortex
VPI thalamic nucleus
Term
What supplies blood to the secondary somatosensory cortex?
Definition
Middle Cerebral Artery
Term
What is the blood supply to the posterior column of the spinal cord?
Definition
Posterior spinal artery
Term
What is the blood supply to the medial lemniscus?
Definition
Anterior Spinal Artery
Term
What is the blood supply to the VPL and VPM?
Definition
Thalamogeniculate branches of the posterior cerebral artery
(Thalamogeniculate arteries)
Term
What is the blood supply to the primary sensory cortex?
Definition
Anterior cerebral artery- genitals and feet
Middle cerebral artery- everything else
Term
What is the blood supply to the principal sensory nucleus and the mesencephalic trigeminal nucleus?
Definition
Basilar and superior cerebellar arteries
Term
Loss of blood supply to the basilar and superior cerebellar arteries causes what?
Definition
Loss of function of the sensory pathway for CONSCIOUS PROPRIOCEPTION OF THE HEAD
Term
Where do the nerves for nonconscious proprioception send signals to, and what happens if we lose this area?
Definition
Cerebellum; ATAXIA
Term
What is FRIEDRICH ATAXIA?
Definition
Degeneration of spinal cord pathways including the major SPINOCEREBELLAR TRACTS- lack of coordination during walking and other movements
Term
What are the two nonconscious proprioceptive pathways of the Lower Limb?
Definition
Anterior and Posterior Spinocerebellar Tracts
Term
What are the two nonconscious proprioceptive pathways of the Upper Limb?
Definition
Rostral Spinocerebellar Tract
Cuneocerebellar Tract
Term
Where does the Anterior spinocerebellar tract synapse, and where does it cross?
Definition
Synapse: Lamina V,VII- spinal border cells of L3-L5 (anterior Horn)

Crosses at level of spine but crosses back so is FUNCTIONALLY UNCROSSED
Term
Where does the Posterior spinocerebellar tract synapse, and where does it cross?
Definition
Synapse: DORSAL NUCLEUS OF CLARK

DOESE NOT CROSS
Term
What are the receptors for the Anterior Spinocerebellar and Posterior Spinocerebellar Tracts and where are they found?
Definition
Anterior ST- Lower Limb- Cutaneous Mechanoreceptors

Posterior ST- Lower Limb- Proprioceptors with few cutaneous receptors
Term
Where do the Anterior and Posterior Spinocerebellar tracts end up, and how do they get there?
Definition
Anterior- travels through Superior Cerebellar Peduncle to reach the LATERAL cerebellar vermis

Posterior- travels through the restiform body (inferior cerebellar peduncle) to reach the MEDIAL cerebellar vermis
Term
If there is a cerebellar lesion, where do we find the deficits?
Definition
IPSILATERAL
Term
Where does the
Definition
Term
Where does the Rostral Spinocerebellar Tract synapse and where does it cross?
Definition
Synapse: Lamina VII of cervical enlargement at C4-C8

Cross: It doesn't
Term
What does the Rostral Spinocerebellar Tract travel in and where does it end up?
Definition
The Anterior Spinocerebellar Tract;
LATERAL CEREBELLAR VERMIS
Term
What does the Cuneocerebellar Tract travel in and where does it end up?
Definition
The conscious pathways of the dorsal horn; ends up in the MEDIAL cerebellar vermis
Term
Where does the cuneocerebellar tract synapse and where does it cross?
Definition
The synapse is up in the LATERAL CUNEATE NUCLEUS
It does not cross
Term
What are the receptors for the Rostral Spinocerebellar Tract?
Definition
Cutaneous Mechanoreceptors
Term
What are the receptors for the Cuneocerebellar Tract?
Definition
Proprioceptors with few cutaneous mechanoreceptors
Term
What are the two nuclei of the trigeminocerebellar pathways, and what do they carry?
Definition
Mesencephalic Nucleus;
Spinal Trigeminal Nucleus- pars interpolaris

Both carry non-conscious proprioception of the head to the cerebellar hemispheres and cerebellar nuclei
Term
Where are the receptors for the trigeminocerebellar pathways?
Definition
Facial and masticatory muscles
Term
MOST of the spinal trigeminal nucleus carries what kind of sense?
Definition
PROTOPATHIC sense
Term
How does the spinal trigeminal- pars interpolaris pathway of the trigeminocerebellar tract end up in the cerebellum?
Definition
RESTIFORM BODY (Inferior Cerebellar Peduncle)
Term
How does the mesencephalic nucleus pathway of the trigeminocerebellar tract end up in the cerebellum?
Definition
Superior Cerebellar Peduncle
Term
Name the two types of nociceptors and their level of myelination:
Definition
Adelta- mechanical nociceptors- THINLY myelinated
C fibers- unmyelinated
Term
What are the protopathic senses?
Definition
Pain, temperature, and crude touch
Term
Where does the ALS Spinothalamic tract synapse and where does it cross?
Definition
Synapses: Lamina I, V for A deltas
Lamina II for C fibers

Crosses at the anterior commissure of the same spinal level
Term
Where does the ALS Spinothalamic tract end up?
Definition
It travels to the VPL, then the cortex MAINLY, but gives collaterals to the reticular formation of the brainstem
Term
Whee does the ALS spinoreticular tract synapse and where does it cross?
Definition
Synapse: Lamina II and III for C fibers
HAS INTERNEURONS THAT SYNAPSE IN LAMINA V, AND VIII
Crosses at the anterior commisure of the same level
Term
Where does the ALS spinoreticular tract end up?
Definition
It travels with the anterolateral system to synapse in the reticular formation, and from there goes to the INTRALAMINAR and POSTERIOR NUCLEI OF THE THALAMUS
Term
The ALS spinoreticular tract sends some fibers to the intralaminar nuclei of the thalamus. What kind of pain is transmitted here, and where does it end up?
Definition
LOCALIZED pain, ends up in the primary somatosensory cortex
Term
The ALS spinoreticular tract sends some fibers to the posterior nuclei of the thalamus. What kind of pain is transmitted here, and where does it end up?
Definition
DULL, persistent pain- ends up in the SECONDARY somatosensory cortex
Term
What is another name for Lamina II?
Definition
Substantia Gelatinosa
Term
What is interesting/important about the Spinocervicothalamic tract?
Definition
It carries protopathic sensation independent of the ALS system, so if one is lost there is still transmission of pain by the other

Also, a lesion of this tract is not a permanent disability since it is a backup
Term
Where does the Spinocervicothalamic tract synapse, and where does it cross?
Definition
Synapse is in Lamina III, IV-
Doesn't cross until the Lateral Cervical Nucleus at C1-C2
Term
The spinocervicothalamic tract carries protopathic sensation to synapse in the lateral cervical nucleus via what tract?
Definition
Ipsilateral Lateral Funiculus
Term
The spinocervicothalamic tract, after synapsing, crosses and travels in what system to what ultimate destination?
Definition
After synapsing in the Lateral Cervical Nucleus, it crosses and travels in the MEDIAL LEMNISCUS to the VPL of the thalamus and on to the cortex
Term
PROTOPATHIC sensation from the anterior trigeminothalamic tract synapses where and travels where? Does it cross?
Definition
Synapse is in the spinal trigeminal nucleus
Crosses there, and travels to the VPM of the thalamus and on to the cortex
SOME FIBERS GO TO RETICULAR FORMATION
Term
The mesencephalic nucleus is associated with what senses?
Definition
Non-conscious proprioception
Term
The principal nucleus is associated with what senses?
Definition
Conscious Proprioception
Term
The Spinal Trigeminal nucleus is associated with what senses?
Definition
Protopathic and some non-conscious proprioception
Term
What vessels supply the SPINAL ALS?
Definition
Anterior and Posterior Spinal Arteries
(arterial vasocorona)
Term
What vessels supply the MEDULLARY ALS and the spinal trigeminal nucleus?
Definition
PICA- VERY IMPORTANT
Posterior Inferior Cerebellar Artery
If lesioned, takes out the ALS, and the Spinal Trigeminal Nucleus
Term
If there is a lesion/occlusion of the PICA, what regions are lost, what are the symptoms, and what is the syndrome called?
Definition
Medullary part of ALS, spinal trigeminal nucleus
CONTRALATERAL loss of protopathic senses over the body
IPSILATERAL loss of protopathic senses over the face
Term
A patient presents to you unable to feel pain, temperature, and crude touch on the left half of their body and the right side of their face. You suspect a lesion where, on which side, involving what artery?
Definition
The lesion would be on the RIGHT side, in the medullary ALS and trigeminal nucleus, involving the PICA
This is Wallenberg Syndrome
Term
What vessels supply the VPL and VPM?
Definition
Thalamogeniculate branches of the posterior cerebral artery
Term
What vessels supply the primary sensory cortex?
Definition
Anterior and Middle Cerebral arteries
Term
A patient presents with loss of fine senses on one side, protopathic senses on the other side, and paralysis on the same side as loss of fine senses. What do they have?
Definition
Brown-Sequard Syndrome- Supply to half the cord is gone
Posterior column loss- same side
ALS- contralateral side
Motor- same side
(ALL BELOW MIDBRAIN SYNAPSES)
Term
What gets destroyed in syringomyelia?
Definition
Decussating ALS fibers in the anterior commissure- ONLY THE CROSSING FIBERS AT THAT LEVEL
Term
What is the clinical presentation of syringomyelia?
Definition
Bilateral loss of nociception, crude touch, and thermal sensations, beginning several segments below the level of injury
Term
Name two treatments for deafferentation pain:
Definition
Thalamic Lesioning-
Deep brain electrical stimulation
Term
How do we treat central (thalamic) pain?
Definition
TENS, posterior column, and deep brain stimulation
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