Spinal Cord - Ascending Systems Flashcards
What information is relayed in the Dorsal Column Pathway? (DCP)
PROPRIORECEPTION
position due to conscious perception of muscle spindle & goalie tendon
Which receptors are involved in DCP?
1. Meissner's Corpuscle (2 pt. discrimination) 2. Merkel's Receptor (touch) 3. Pacinian Corpuscle (vibration) 4. Ruffini Corpuscle (stretch, pressure) 5. Joint capsule (joint position)
Which receptors are not encapsulated?
- Free Nerve Ending
- Merkel’s Disk
- Hair Follicle
What contains long ascending fibers from LOWER limb? From upper limb? Which vertebral segments?
- which of these two is more medial?
- F. Gracilis
- F. Cuneatus
C1-C8, T1-T6
F. Gracilis is more MEDIAL
How do the second order neurons travel for F. Gracilis & F. Cuneatus in the DCP?
INTERNAL ARCUATE FIBERS
Where do the medial lemniscus fibers of DCP fibers terminate? Where do the axons of 3rd order neurons terminate?
VPL (synapse here)
Ventral posterolateral nucleus of THALAMUS
- terminate in area 312 (sensory-> post-central)
What are the Brodman’s numbers for the pre-central and post-central gyrus?
pre = 4 (motor)
post = 312 (sensory)
What are the key players in the DCP, step wise? (7)
- Dorsal Root Ganglion (pseudo-unipolar)
- F. Gracilis or F. Cuneatus
- Nucleus Gracilis or Cuneatus
- Internal Arcuate Fibers
- decussate medially in MEDIAL LEMNISCUS of medulla
- VPL
- 312 area
Where do first order axons from the upper limb in the DCP synapse?
Nucleus Cuneatus (more Lateral)
- synapse here
What function is the DCP pathway responsible for? What receptors?
- Vibration
- 2 pt sensation
- Proprioreception
- Pacinian Corpuscle
- Meisner’s Corpuscle
- Joint Position
Where do third order axons of the DCP project on the parietal lobe?
Post-Central Gyrus
= Area 312 (sensory)
What is the result of cutting the DCP tract in the cord? What about a stroke on the right cortex?
Cut = ipsilateral loss (deficits ons game side = loss of vibration, proprioreception,etc)
STROKE = opposite side –> LEFT
What are decussating 2nd order fibers of the DCP called? Where do they cross?
INTERNAL ARCUATE Fibers
- cross in midline at the MEDIAL LEMNISCUS of MEDULLA
How many axons are involved in the DCP pathway?
3
- Receptor to Medulla
- Medulla to Thalamus
- Thalamus to cortex
What vertebral levels are covered by F. Cuneatus? Which part of the body is it in charge of?
C1-C8
T1-T6
UPPER LIMB
- more LATERAL***
A 59-year-old man is evaluated for lower limb ataxia and bladder dysfunction. Physical examination demonstrates small irregular pupils that constrict with accommodation but not in response to light. A VDRL test is positive. A CT scan of the spinal cord would most likely demonstrate atrophy of which of the following structures? (A) Dorsal column (B) Dorsal horn (C) Lateral column (D) Ventral column (E) Ventral horn
A) Dorsal Column
What area does syphillis destroy? What does it usually cause?
DORSAL COLUMN
- stoping gait (no receptors for this any longer)
What is Tabes Dorsalis?
Destruction of dorsal column
- no F> Gracilis or F. CUneatus
What is a positive Romberg Sign? Negative?
unsteady with eyes closed = POSITIVE
steady w/ eyes closed = negative
- ** positive in SENSORY ATAXIA
- negative in CEREBELLAR ATAXIA
What type of function is the Spinothalamic Tract responsible for? (STT)
PAIN & SENSATION
think: pain up your spine
Which nucleus do the STT neurons synapse in?
Where do the 2nd order neurons decussate?Where do they ascend?
- NUCLEUS PROPRIUS
- Anterior White Commissure (ventral) of the SPINAL CORD
- Lateral FUniculus
Where do the 3rd order neurons of the STT synapse? Where do the axons of 3rd order neurons project?
- VPL
2. area 312 (sensory cortex)
Whee is nucleus proprius found?
DORSAL HORN
Where do the fibers of DCP decussate? STT?
- MEDULLA
2. Spinal Cord (cervical & lumbar)
Where do fibers from nucleus proprius cross the midline? Where do they pile up?
anterior commissure
- lateral funiculus (& Anterior)
What will occur if you cut the STT in the spinal cord?DCP?
affect OPPOSITE side of the body –> has not crossed yet
DCP = same side if cut
List the 6 steps of the STT?
PAIN & SENSATION
- Dorsal Root Ganglion
- Nucleus Proprius
- cross ANTERIOR COMMISURE
- ascend/pile up in Lateral Funiculus
- synapse in VPL
- 3rd order axons in area 312 (sensory cortex)
What is Syringomyelia?What is brought about by?
Syrinx/hole near the central canal
–> trauma, hydrocephaly, idopathic also
- can transect he cord
What fibers does a Syrinx affect? What are the last fibers of the to be destroyed by a SYRINX? What kind of a loss of sensation results?
- STT
- SACRAL fibers –> last to be destroyed (leg)
- fibers spared above & below the lesion
VESTED loss of sensation
(syrinx wipes out crossing fibers)
If you hemisect the Thoracic spinal cord, what pathways are transected? Symptoms (what loss and on which side: ipsilateral or contralateral?)
- STT & DCP
- STT - loss of pain & sensation CONTRALATERAL (opposite)
- DCP - loss of proprioreception, vibration IPSILATERAL (same side)
A 66 year old anatomy professor with a beard wakes up one morning and finds that he cannot feel the lower left side of his body and right face. He calls to his wife but she cannot understand what he is saying. What may be the cause?
Left MCA stroke ALS Diabetic neuropathy Right medullary stroke Thoracic syringomyelia
D) Right Medullary Stroke
What causes a “vest-like” loss of sensation? Which tract is affected
SYRINX
- STT tract affected
What causes a lateral medulla stroke? What is the term for the characteristic symptoms?
blood flow is interrupted in either the:
- vertebral artery or
- posterior inferior cerebellar artery (PICA)
WALLENBURG SYNDROME
What type of function are the Spinocerebellar Tracts responsible for? (DSCT, VSCT, CCT)
Unconscious Proprioreception
Which nucleus does the Dorsal Spinocerebellar Tract utilize? (DSCT) What information does it relay?
- Clark’s Nucleus
- MUSCLE STRETCH
(think: Dick Clark –> Dsct & Clark)
What vertebral levels does Clark’s Nucleus cover?
C8-L2
What info does the VSCT relay?
Reflexes, interneurons
from dorsal horn & intermediate gray
Which part of the spinal cord do the Spinocerebellar tracts reside in?
LATERAL FUNICULUS
dorsal & ventral
What is Nucleus Dorsalis (Clark’s Nucleus) homologous for in the Medulla?
Lateral (Accessory) Cuneate Nucleus
- N. dorsalis = DSCT
- Lateral Cuneat N. = CCT
What fibers (DSCT or CCT) innervate the upper limb? Lower limb?
DSCT = LOWER limb
(nucleus dorsalis is only C8-L2)
CCT = UPPER LIMB (C1-C7)
Which tracts are uncrossed?
DSCT & CCT
VSCT is crossed
State the 4 steps of the DSCT. What function is it responsible for?
UNCONSCIOUS PROPRIORECEPTION
- Muscle spindle & golgi tendon in LOWER LIMB
- Nucleus Dorsalis (Clark’s)
- axons ascend on same side to INFERIOR PEDUNCLE in medulla
- terminate in Cerebellar VERMIS
State the 5 steps of the CCT. What function is it responsible for?
UNCONSCIOUS PROPRIORECEPTION
1.Muscle spindle & golgi tendon in UPPER LIMB
- afferent fibers ascend ipsilaterally in F. CUNEATUS (C1-C7)
- Project neurons to LATERAL CUNEATE N.
- axons ascend on same side to INFERIOR PEDUNCLE (medulla)
- terminate in Cerebellar VERMIS
Where doe unconscious spindle info from the upper limb synapse?
LATERAL CUNEATE NUCLEUS
What is responsible for C8-L3? C1-C7?
- Nucleus Dorsalis (Clark’s Nucleus)
2. Lateral Cuneate Nucleus
Where does the VSCT cross 1st? 2nd? What is VSCT responsible for?
1st = SPinal Cord
2nd = SUPERIOR PEDUNCLE
RELAY STATION!!!
double crossed
What tract is double crossed and what will happen if it is cut?
VSCT
- cut = IPSILATERAL LOSS
- -> same side, crosses twice
What tract(s) use the Inferior Peduncle? What tract(s) use the Superior peduncle?
Inferior = DSCT & CCT
Superior = VSCT
What tract relays spinal motor “interneuronal” info? Via which peduncle?
Ventralspinocerebellar Tract
VSCT
- SUPERIOR PEDUNCLE (crosses twice)
Lesions in the SPinocerebellar Tracts cause what kind of loss?
all are IPSILATERAL loss (same side)
- DSCT, CCT, VSCT
What do muscle afferents below L3 use to reach Clark’s Nucleus? How does muscle info from the upper body reach f. cognates?
F. Gracilis
- LATERAL CUNEATE N.
A ten year old boy comes to the neurologist with weakness in his lower limbs, little or no reflexes in his legs, a slight scoliosis, and an enlarged heart. Upon testing with a tuning fork, it is found that he cannot sense vibration in his legs. His gait is ataxic and his voice is hoarse. What is the diagnosis?
ALS MS VD MD Friedreich's Ataxia
Freidrich’s Ataxia
What is the autosomal recessive disease that causes sclerosis of the posterior and lateral columns of the spinal cord; characterized by muscular weakness and abnormal gait; occurs in children?
Friedrich’s Ataxia
