Exam #1: Sensory I

Question 1

Where is the dorsal column– medial lemniscus (DC-ML)?

Answer 1

This is the white matter between the two “wings” of the gray matter butterfly

Question 2

What does the DC-ML pathway relay?

Answer 2

• Discriminative (fine/detailed) touch
• Stereognosis
• Flutter- Vibratory sense
• General porprioception
• Light touch

Question 3

What is stereognosis?

Answer 3

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

Question 4

What is two-point discrimination testing? Inability with this test could indicate a problem with what anatomical structure?

Answer 4

This test determines the ability to distinguish between two stimuli; abnormality would indicate possible damage to the ML

Question 5

Where is 2-point discrimination finest? Where is it the least discrimate?

Answer 5

• Fingertips

- Legs & back

Question 6

What type of pathway is the DC-ML?

Answer 6

Ascending

Question 7

How many neurons are in the DC-ML?

Answer 7

3

Question 8

Where are the three cell bodies of the DC-ML?

Answer 8

1) DRG
2) NG or NC
3) VPL of Thalamus

Question 9

What is the function of the FG?

Answer 9

Sensory information form the lower trunk & limb

Question 10

What is the function of the FC?

Answer 10

Sensory information from the upper trunk & limb

Question 11

What is the difference between the presence of FG & FC? Why?

Answer 11

• FC is only present from C1-T6

- FG is present throughout the entire cord

Question 12

Where is the FC present in the spinal cord?

Answer 12

C1-T6

Question 13

What is the last level where new fibers are added to the FG?

Answer 13

T7; the one superior are the ascending tracts from the levels below

Question 14

What type of fibers does C1 have?

Answer 14

Motor ONLY; no sensory

Question 15

Describe the morphology of ascending & descending tracts as they progress up/down the spinal cord.

Answer 15

Ascending tracts increase in diameter as they go upward

Descending tracts decrease in diameter as they go downward

Question 16

List the receptor types that are involved in the DC-ML pathway.

Answer 16

Free nerve endings
Peritrichial nerve endings
Muscle spingle 
GTO 
Merkel's disc
Meissner's corpuscles 
Pacinian corpuscles 
Ruffini's end organs

Question 17

Outline the DC-ML pathway.

Answer 17

Lower limb:

• Receptor
• FG
• Medulla- NG

Upper limb:

• Receptor
• FC
• NC

Question 18

Where are first order cell bodies? What type of axons are sent to the second order neurons?

Answer 18

DRG

*A-alpha or beta i.e. heavily myelinated

Question 19

Where are second order cell bodies?

Answer 19

Medulla–nuclei

Question 20

Where do axons of the second order medullary nuclei go?

Answer 20

Arcuate

Medial Leminsicus

Question 21

Where is the medial lemniscus?

Answer 21

Medulla

Question 22

Where do axons of the ML go?

Answer 22

VPL of the Thalamus

Question 23

Where do axons of the VPL of the Thalamus go?

Answer 23

Sensory cortex in the parietal lobe

Question 24

Describe the organization of fibers in the FG & FC from medial to lateral.

Answer 24

SLTC

Medial to lateral=

• Sacral
• Lumbar
• Thoracic
• Cervical

Question 25

What arteries supply blood to the dorsal column?

Answer 25

Posterior spinal arteries

Question 26

What happens when there is a lesion in the spinal cord?

Answer 26

Damage of the ipsilateral dorsal column pathways at & below the level of the lesion

Question 27

What happens when there is a lesion in the NG?

Answer 27

• Damage of the dorsal column pathways & their nuclei

- Deficits on the ipsilateral side

Question 28

Where does crossing over occur?

Answer 28

After the NC/ NG

Question 29

What happens if the lesion affects the ML itself? What artery supplies the ML?

Answer 29

Anterior spinal arteries

Note that there will be deficits on BOTH side of the body

Question 30

A lesion above the sensory decussation will result in deficits on the _____ side of the body.

Answer 30

Contralateral

Question 31

Where does the ML receive its blood supply in the rostral medulla? Occlusion will result in deficits on which side of the body?

Answer 31

Vertebral artery–opposite

Question 32

Where does the ML receive its blood supply in the pons? Occlusion will result in deficits on which side of the body?

Answer 32

Basilar–opposite

Question 33

Where does the ML receive its blood supply in the midbrain? Occlusion will result in deficits on which side of the body?

Answer 33

Posterior cerebral artery–opposite

Question 34

What are the lenticulostriate arteries?

Answer 34

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

Question 35

What part of the DC-ML pathways does the anterior cerebral artery supply?

Answer 35

Somatosensory cortex:

- Leg & foot

Question 36

What part of the DC-ML does the MCA supply?

Answer 36

Somatosensory cortex:

• Trunk
• Upper limb
• Face

Question 37

What is the presentation of a lesion in the DC-ML?

Answer 37

• Sensory ataxia= “stamp & stick ataxia”
• Rhomberg’s sign
• Tabes Dorsalis?

Grandpa

Question 38

What is the dorsal spinocerebellar tract?

Answer 38

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Question 39

What is the cuneocerebellar tract?

Answer 39

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