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MODULE 8:
NERVOUS TISSUE
PART 2 OF 7
Exam notes: intact strength, but reduced light-touch and vibration sense in both feet — “likely positional / accident-related.” The symmetry was recorded but never questioned.
Slide 1 Transcript
PATIENT CHART
STINA
THIS PART
Age 35
PRESENTING WITH
Numbness, tingling, and a hot stripe of pain down her left leg, slowly creeping, symmetric foot numbness
DIAGNOSIS
Anti-MAG peripheral neuropathy
DRUGS ORDERED
Rituximab
CHART CLUES
COLLECTED AS YOU GO
Radiating Leg Pain & Numbness After a ‘Clear’ Crash
Symmetric Loss of Light-Touch & Vibration
Slowed Nerve Conduction
Synapse Intact — the Fault Is Upstream
Anti-MAG Antibodies
A Map Pointing at Two Nerve Roots
Anti-MAG, Sensory-Predominant Peripheral Neuropathy
Put your money down: Both feet, from a one-sided crash?
A one-sided crash, yet numbness in both feet — can the accident really explain a symmetric loss?
Pick the answer you believe now. We’ll come back to it later!
Symmetric Numbness After a One-Sided Crash
When a neurologist finally tested Stina months later, her strength was fine — she could push, pull, and stand on her toes. But light touch and the buzz of a tuning fork faded in both feet, not just the leg that hurt. The note read “likely positional, accident-related,” and the visit ended. Nobody lingered on the strangest detail: a single car crash hits one side of a body, yet her sensory loss was symmetric, climbing up from both feet like waterThe universal solvent essential for life. filling a glass. That symmetry was a fingerprint, written down and ignored.
Glia of the CNS
Four support cellsThe basic structural and functional units of life. inside the brain and cord — each with one headline job.
Slide 2 Transcript
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Drag the Words: Drag each CNSComposed of the brain and spinal cord; integrates and processes information. glial cell to the job it does.
Glia of the PNS
Only two support cells out in the peripheral nervesNerves that extend beyond the brain and spinal cord. — but one of them is the whole case.
Slide 3 Transcript
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Multiple Choice: Which PNS cell wraps the myelin around Stina’s nerves?
The Neuron, Its Insulation, and a Protein Called MAG
A neuron is built for one job: carry a signal fast and far. Dendrites receive incoming signals; the soma (cell bodyThe central part of a neuron containing the nucleus and organelles.) holds the nucleusThe control center of the cell that contains DNA and directs cellular activities. and integrates them; a single axon carries the outgoing signal to axon terminals that hand it to the next cell. Neurons don’t work alone — neuroglia support them, and the most important here make myelin, a fatty insulating sheath wrapped around axons that lets signals jump quickly down the wire. The cell that makes myelin differs by location: in the PNS, Schwann cellsPNS glial cells that form the myelin sheath around peripheral nerve fibers. each wrap one segment of one axon; in the CNS, oligodendrocytesGlial cells in the CNS that form the myelin sheath around axons. wrap many axons at once. Gripping that innermost wrap of peripheral myelin to the axon is a sticky anchor protein called MAG (myelin-associated glycoproteinA protein with a carbohydrate chain attached, important for cell signaling.) — a small molecule that becomes the whole point of this case.
Myelin & MAG
The fatty sheath that speeds the signal — and the sticky anchor where Stina’s story turns.
Slide 4 Transcript
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Fill in the Blanks: Fill in what myelin does, and what MAG holds together.
The Blood-Brain Barrier
Astrocytes stand guard at the brain’s gates — a quiet preview of a wall the Brain module will breach.
Slide 5 Transcript
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Summary: Pick the one true statement about the barrier in each set.
The Exact Protein Her Antibodies Attack
Hold onto MAG. It is the exact protein that Stina’s own antibodies will be found to attack, loosening her insulation from the inside and producing the slow, symmetric numbness no crash could explain.
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Slide 6 Transcript
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Slide 7 Transcript
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FINDING!
Symmetric Loss of Light-Touch & Vibration — an Insulation (Myelin) Problem
Strength intact, but light touch and vibration faded symmetrically in both feet — recorded, then dismissed as ‘positional.’ New evidence: symmetry doesn’t come from a one-sided crash. It’s the fingerprint of a systemic myelin problem, and it introduces MAG (myelin-associated glycoprotein), the glue on the innermost wrap that her disease will target.
Confirm or refute your bet:
A one-sided crash, yet numbness in both feet — can the accident really explain a symmetric loss?
Now that you’ve read the story, confirm or overturn it — step by step, with the evidence in hand.
Slide 8 Transcript
NEXT PART
A well-wrapped wire is useless until something runs through it. Next: the electrical spark that turns a quiet neuron into a firing one.
QUICK QUESTIONS
QUICK QUESTIONS
PREVIOUS
The Crash
NEXT
The Spark
List of terms
- water
- cells
- CNS
- peripheral nerves
- cell body
- nucleus
- Schwann cells
- oligodendrocytes
- glycoprotein