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