spinal tracts Flashcards
what kind of information is relayed on the dorsal column pathway?
2 point discrimination
vibration
conscious proprioception
(GSA)
what receptors are associated with DCP?
pacinian (vibration)
meissner’s (2 point discrimination)
Merkels (touch)
joint (position)
what is the terminal destination for the DCP?
contralateral area 312 of cortex
if the DCP is injured in the spinal cord, what happens?
loss of ipsilateral sensation
if the DCP is injured in the brainstem or if the cortex is injured, what happens?
loss of contralateral sensation
how many neurons are in the DCP?
3 neuron pathway
- receptor to medulla
- medulla to VPL
- VPL to area 312
describe the DCP route
- sensory information from receptors to DRG
- axons travel to the dorsal funiculus (myelinated)
- ascend to the medulla
- synapse at their respective nuclei
- 2nd order neurons cross at medulla midline (internal arcuate fibers)
- ascend on the contralateral medial lemniscus
- synapse at thalamus VPL
- 3rd order neurons enter area 312 (sensorimotor cortex/postcentral gyrus)
where do upper limb neurons travel in the DCP?
fasciculus cuneate (C1-T6)
nucleus cuneate
(lateral)
where do lower limb neurons travel in the DCP?
fasciculus gracilis (all levels)
nucleus gracilis
(medial)
neurosyphilis and DCP
- pupils do not constrict to light
- destruction of DCP and DRG cells
romberg sign
(+) patient closes their eyes, and cannot stand steadily
indicates cerebellar ataxia
tabes dorsalis/syphilis
damage to DCP
what receptors are involved in the spinothalamic pathway
free nerve endings
what information is relayed on the STT?
primarily a pain pathway
- temperature
Describe the route of the STT?
- sensory information from free nerve endings travel to DRG
- axons enter the dorsal fasciculus via the lateral division (unmyelinated)
- synapse in the nucleus proprius of the dorsal horn
- 2nd order fibers cross at the anterior commissure
- fibers ascend through the lateral funiculus
- fibers travel through the lateral tip of the medial lemniscus
- synapse in VPL
- 3rd order fibers travel to the contralateral area 312
what is the terminal destination for STT fibers?
travel from nucleus proprius to the contralateral area 312
if you damage the STT in the spinal cord, what will happen?
pain sensation would be lost on the contralateral side
if you cut right side of the cord, lose sensation from the left fingers
syringomyelia and STT
- vacuole forms within central canal
- transection of the cord
- sacral fibers are most lateral, last to be transected (sacral pain remains)
- syrinx wipes out fibers as they cross…only at the level of the lesion
brown-sequard lesion
- lesion caused by stroke or GSW that wipes out half of the spinal cord
- DCP: ipsilateral sensation loss
- STT: contralateral sensation loss
Wallenberg Syndrome
- due to stroke of vertebral artery or PICA
- damage to lateral medulla
- damage to contralateral STT sensation
- destruction of SCTs (ataxia)
- destruction of vestibular nuclei (N/V/vertigo)
Horner’s Syndrome
interruption of ipsilateral descending sympathetic fibers
- miosis (small pupils)
- ptosis
- anhydrosis (decreased facial sweating)
in general, spinocerebellar tracts reside in what part of the spinal cord?
- lateral funiculus
- clarke’s nucleus
what information is relayed through the Dorsal spinocerebellar tract?
- muscle stretch
- nonconscious proprioception
what vertebral levels of the spinal cord is DSCT associated with?
- clarke’s nucleus only exists at C8-L2
- muscle afferent neurons below L2 reach Clarke’s Nucleus via fasciculus gracilis of the dorsal funiculus
what receptors are associated with DSCT?
muscle spindles
GTOs
What is the DSCT pathway?
- first order neurons from muscle spindles and GTOs enter the DRG
- axons synapse in the nucleus dorsalis (Clarke’s)
- 2nd order neurons ascend ipsilaterally through the lateral fasciculus
- fibers reach the inferior cerebellar peduncles of the medulla
- fibers continue and terminate in the cerebellar vermis
If there was damage to the DSCT, what would happen?
ipsilateral loss of proprioception and coordination (regardless of location)
Describe the pathway of CCT?
- muscle afferent neurons from the upper limbs (above C8) enter DRG
- travel to fasciculus cuneatus of the dorsal funiculus
- ascend ipsilaterally and synapse in the accessory cuneate nucleus in the lower medulla
- 2nd order neurons continue into the inferior cerebellar peduncles and terminate in the cerebellar cortex
describe the information relayed in the VSCT
- no peripheral input
what do we need to know about the VSCT?
- enters the cerebellum via superior cerebellar peduncles
- double crossed
damage to the VSCT at any level leads to what?
ipsilateral loss of sensation
what are cells of the CST called?
upper motor neurons
how is the CST organized?
- somatotopically in a homunculus
- arm movements = lateral
- leg movements = medial
is the CST myelinated?
yes
what is a motor unit
alpha motor neuron (from ventral horn) + skeletal muscle fiber it innervates
what is the difference between small and large motor units
small = precise movements large = broad movements
what information is relayed along the CST/
control of fine motor movements
- efferent
- digital movement
- control of flexors
where does the CST originate?
pyramidal/Betz cells of Area 4/precentral gyrus
describe the pathway for CST?
- pyramidal cells extend their long axons through the corona radiata, internal capsule, through the cerebral peduncles of the midbrain
- fibers continue through pontine gray and medullary pyramids
- fibers cross over at the midline of the medulla (lateral CST)
- fibers enter the spinal cord at the lateral funiculus
- synapse in the lateral and medial motor nuclei of the anterior horn cells
- final common pathway of alpha motor neurons innervates the skeletal muscle
how many neurons are in the CST?
2
describe the anterior CST
- do not cross at the medulla
- continue to descend and enter the spinal cord at the anterior horn
- only at the cervical levels
- ipsilateral
damage in the cerebral cortex would do what with the CST?
contralateral impairment of motor function
damage to brainstem, CST?
contralateral impairment
damage to spinal cord, CST?
ipsilateral because it is after they have crossed over
lesions of upper motor neurons can cause the following..
- spasticity
- hyperreflexia
- hemiplegia
- babinski sign
describe the babinski sign
- rub the bottom of feet, eversion (normal)
- toes fan out => infants, UMN damage
lesions of lower motor neurons cause
- flaccid paralysis
- hypertonic muscles
- atrophy
loss of anterior horn cells leads to?
loss of CST
ALS/polio
LMN pathology
anterior spinal artery occlusion
loss of anterior horn cells
subacute combined degeneration
loss of DCP, lateral funiculus (affects SCTs, CST) (due to vitamin B deficiency)
ALS
loss of lateral funiculus and anterior horn cells
tabes dorsalis
loss of dorsal columns
syphilis
key grouping: nucleus proprius
STT
key grouping: area 312
STT, DCP
key grouping: area 4
CST
key grouping: crosses in cord
STT, VSCT, ACST
key grouping: medial lemniscus
DCP
key grouping: nucleus dorsalis
DSCT
key grouping: pyramids
CST
key grouping: crosses in medulla
CST, DCP
key grouping: lateral and medial motor nuclei
CST
key grouping: IML
sympathetics
key grouping: inferior cerebellar peduncle
DSCT
CCT
key grouping: superior cerebellar peduncle
VSCT
