Exam #1: Sensory I Flashcards
Where is the dorsal column– medial lemniscus (DC-ML)?
This is the white matter between the two “wings” of the gray matter butterfly
What does the DC-ML pathway relay?
- Discriminative (fine/detailed) touch
- Stereognosis
- Flutter- Vibratory sense
- General porprioception
- Light touch
What is stereognosis?
This is the ability to perceive and recognize the form of an object in the absence of visual and auditory information, by using tactile information to provide cues from texture, size, spatial properties, and temperature, etc
What is two-point discrimination testing? Inability with this test could indicate a problem with what anatomical structure?
This test determines the ability to distinguish between two stimuli; abnormality would indicate possible damage to the ML
Where is 2-point discrimination finest? Where is it the least discrimate?
- Fingertips
- Legs & back
What type of pathway is the DC-ML?
Ascending
How many neurons are in the DC-ML?
3
Where are the three cell bodies of the DC-ML?
1) DRG
2) NG or NC
3) VPL of Thalamus
What is the function of the FG?
Sensory information form the lower trunk & limb
What is the function of the FC?
Sensory information from the upper trunk & limb
What is the difference between the presence of FG & FC? Why?
- FC is only present from C1-T6
- FG is present throughout the entire cord
Where is the FC present in the spinal cord?
C1-T6
What is the last level where new fibers are added to the FG?
T7; the one superior are the ascending tracts from the levels below
What type of fibers does C1 have?
Motor ONLY; no sensory
Describe the morphology of ascending & descending tracts as they progress up/down the spinal cord.
Ascending tracts increase in diameter as they go upward
Descending tracts decrease in diameter as they go downward
List the receptor types that are involved in the DC-ML pathway.
Free nerve endings Peritrichial nerve endings Muscle spingle GTO Merkel's disc Meissner's corpuscles Pacinian corpuscles Ruffini's end organs
Outline the DC-ML pathway.
Lower limb:
- Receptor
- FG
- Medulla- NG
Upper limb:
- Receptor
- FC
- NC
Where are first order cell bodies? What type of axons are sent to the second order neurons?
DRG
*A-alpha or beta i.e. heavily myelinated
Where are second order cell bodies?
Medulla–nuclei
Where do axons of the second order medullary nuclei go?
Arcuate
Medial Leminsicus
Where is the medial lemniscus?
Medulla
Where do axons of the ML go?
VPL of the Thalamus
Where do axons of the VPL of the Thalamus go?
Sensory cortex in the parietal lobe
Describe the organization of fibers in the FG & FC from medial to lateral.
SLTC
Medial to lateral=
- Sacral
- Lumbar
- Thoracic
- Cervical
What arteries supply blood to the dorsal column?
Posterior spinal arteries
What happens when there is a lesion in the spinal cord?
Damage of the ipsilateral dorsal column pathways at & below the level of the lesion
What happens when there is a lesion in the NG?
- Damage of the dorsal column pathways & their nuclei
- Deficits on the ipsilateral side
Where does crossing over occur?
After the NC/ NG
What happens if the lesion affects the ML itself? What artery supplies the ML?
Anterior spinal arteries
Note that there will be deficits on BOTH side of the body
A lesion above the sensory decussation will result in deficits on the _____ side of the body.
Contralateral
Where does the ML receive its blood supply in the rostral medulla? Occlusion will result in deficits on which side of the body?
Vertebral artery–opposite
Where does the ML receive its blood supply in the pons? Occlusion will result in deficits on which side of the body?
Basilar–opposite
Where does the ML receive its blood supply in the midbrain? Occlusion will result in deficits on which side of the body?
Posterior cerebral artery–opposite
What are the lenticulostriate arteries?
Deep branches of the MCA that supply the anterior & posterior limbs of the internal capsule
*****These arteries supply the 3rd order neurons of the DC-ML pathways in the VPL of the thalamus
What part of the DC-ML pathways does the anterior cerebral artery supply?
Somatosensory cortex:
- Leg & foot
What part of the DC-ML does the MCA supply?
Somatosensory cortex:
- Trunk
- Upper limb
- Face
What is the presentation of a lesion in the DC-ML?
- Sensory ataxia= “stamp & stick ataxia”
- Rhomberg’s sign
- Tabes Dorsalis?
Grandpa
What is the dorsal spinocerebellar tract?
asdf
What is the cuneocerebellar tract?
asdfa
