Time To Read
Date Last Modified
Nervous Tissue & the Senses · Chapter 1 of 7
Clear scans, a hot line of pain down one leg, and feet that “fall asleep.” Before anyone can say what is wrong, you need a map of where a signal travels — and the cell that carries it.
The question you will answer
Where would you look first for Stina’s problem: the central nervous systemComposed of the brain and spinal cord; integrates and processes information. (brain and spinal cordThe central nervous system structure that relays signals between the brain and body.) or the peripheral nervesNerves that extend beyond the brain and spinal cord. — and what in the chart tells you?
About 45 minutes. Work the steps in order.
Animation · in production · 1 min 30 s
A Signal’s Round Trip
Step on a tack and follow the signal in to the spinal cord and back out again — and see where the decision is made.
Watch the opener first. It sets the question; the chapter answers it.
1
Read the chart
Patient chart · Stina
2010, age 35 · emergency department, then a follow-up clinic
| Event | T-boned at an intersection on the driver’s side; walked away from the car. |
|---|---|
| ER | CT of the spineProminent ridge on the posterior scapula dividing it into supraspinous and infraspinous fossae.: no fractureBreaks in bones due to stress or injury., alignment normal. Discharged as “lucky” with ibuprofen and a whiplash / muscle-strain note. |
| Day 2 | A hot, electric line of pain from the low back down the back of the left leg; a muffled patch on the outer left shin and the top of the foot. |
| Triage aside | “Both my feet fall asleep easily.” She blames her shoes. |
| Exam | Strength normal in both legs; walks normally. |
| Follow-up clinic | “Pinched nerve from the accident.” |
This chapter writes line 1 of Chart Clue #8.
Your prediction
Where would you look first? Open the one you’d bet on. Nothing is graded, and the answer isn’t here — the scenes will test your bet.
The spinal cord (CNS) — a spinal injury could explain symptomsSubjective experiences reported by the patient (e.g., nausea, fatigue). in both legs
You’re betting on the cord. Fair: the crash was hard, and both legs are involved. In Scene 5, check what else a cord injury would bring with it — and whether any of it is on her chart.
The peripheral nerves — the problem is out in the wiring
You’re betting on the nerves. Fair: the pain follows one leg and the numbness sits in her feet. In Scene 3, see how long those wires are — and ask why a nerve problem would show up in both feet at once.
I can’t say yet
An honest bet. Decide what you’d need to know first — a scan? a strength test? a map of the numbness? — and look for it as you go.
2
The story
Three short movements. Read them once now; each links to the scene where you’ll see it move.
I · The Crash the Scans Called Lucky
Stina was thirty-five, in the year her mother died, when another car ran the light and caught her door. The ER did its job: the CT showed no fracture and nothing out of line, and the resident called her lucky and sent her home with ibuprofen and a note about whiplash. For a day she believed him. Then, on the second morning, a hot, electric line switched on from her low back and ran straight down the back of her left leg, and a patch of her outer shin and the top of her foot felt muffled, as if it were wearing a sock that wasn’t there. At triage she had mentioned, almost as an aside, that both her feet “fall asleep” easily. Nobody wrote a plan beside that line.
See it move: Scene 1 · The Map: Divisions and Directions
II · Two Divisions, Two Directions of Traffic
To read that chart you need the map. The central nervous systemThe organ system that controls body functions using electrical and chemical signals. (CNS) — brain and spinal cord — is where information is integrated and decisions are made. The peripheral nervous systemPNS All nervous tissue outside the CNS; includes nerves and ganglia. (PNS) is every nerve outside it. Traffic runs two ways: sensory (afferent) neuronsThe functional cells of the nervous system that transmit signals. carry messages in toward the CNS, and motor (efferent) neurons carry commands out to muscles and glands, through the somatic division to skeletal muscle and the autonomic division to the heart, smooth muscle and glands. Every message rides on one kind of cell, the neuron: dendritesBranch-like extensions from a neuron that receive signals from other neurons. receive, the cell bodyThe central part of a neuron containing the nucleus and organelles. integrates and keeps the cell alive, and a single axon carries the signal away, sometimes for a meter or more.
See it move: Scene 1 · The Map: Divisions and Directions · Scene 2 · Anatomy of a Neuron · Scene 3 · Classifying Neurons — and the Longest Cells in the Body
III · Where Would You Look?
Every complaint on Stina’s chart is a message arriving, not a command failing to leave: her strength is normal. But arriving messages cross two territories — long peripheral wires out in the leg, and the spinal cord that receives them — and a crash could have bruised either one. A clear CT clears bone. Which territory fits a stripe down one leg, and which fits two feet going quiet? The chapter won’t tell you. Collect the evidence.
See it move: Scene 4 · Nerves, Tracts, Nuclei, Ganglia — and What a Scan Can See · Scene 5 · Two Patterns on One Patient
3
Watch · explore · think · check
Five scenes. Each one has a short animation or a slide, something to explore, a true/false spot-check of your thinking, and a quick check. Every scene gives you an evidence card for your board.
How to read the scenes
- Animation (dark teal) — a short animated explainer, one idea each
- Slide (dark teal) — a still to study: a micrograph or a map
- Explore (purple) — something to push on while you watch
- Game (purple) — a quick challenge
- Think (gold) — reason it out, then spot-check yourself with a few true/false questions; not graded
- Check (gold) — a quick H5P that scores itself
Scene 1 of 5
The Map: Divisions and Directions
Follow one signal in and one command out, and learn where decisions are made.
Animation · in production · 2 min
Building the Map
The brain and cord light up as the CNS, the nerves as the PNS; arrows run in on sensory lanes and out on motor lanes — then a step on broken glass shows serial and parallel processing at once.
Game
Signal Traffic Controller
Route each signal into its lane: coming in or going out, from skinThe body’s largest organ, providing protection and regulation. and muscle or from organs.
Think · not graded
Stina’s strength is normal, yet two sensations are wrong. Where along the incoming route could a problem make a foot feel numb?
Spot-check your thinking: true or false?
Check · Drag the Words
Drag CNS, PNS, afferent and efferent into the sentences that define them.
Evidence card 1
Add it to your evidence board
Every complaint is sensory; her strength is normal.
Scene 2 of 5
Anatomy of a Neuron
Build the cell that carries every signal, part by part.
Animation · in production · 1 min 40 s
Build a Neuron
A neuron assembles part by part, then a signal runs dendrite → cell body → axon hillockCone-shaped region of the neuron where the axon originates and where action potentials begin. → axon → terminals.
Explore
Parts of a Neuron
Open each marker to see what that part does.
Think · not graded
Adult neurons can’t divide to replace themselves, yet a cut peripheral axon can regrow. Which part of the neuron has to survive for that to happen?
Spot-check your thinking: true or false?
Check · Fill in the Blanks
Name the neuron’s four working parts, from signal-in to signal-out.
Evidence card 2
Add it to your evidence board
An axon depends on its cell body; a break silences everything beyond it.
Scene 3 of 5
Classifying Neurons — and the Longest Cells in the Body
Sort neurons by shape and by job, and meet the sensory neuron that feels the toes.
Animation · in production · 1 min 50 s
Three Shapes, Three Jobs
Multipolar, bipolar and unipolar neurons line up; then one sensory axon unrolls from a ganglionA cluster of neuron cell bodies located in the peripheral nervous system (PNS). beside the spine all the way to the big toe.
Explore
Neuron Shapes
Five neurons, five shapes. Open each marker to learn what that shape is built for.
Think · not graded
The sensory neuron that feels Stina’s big toe has its cell body next to her spine. Which part of that cell is most exposed to damage — and who would notice it first, tall people or short?
Spot-check your thinking: true or false?
Check · Multiple Choice
Which functional class of neuron carries Stina’s pain toward the cord?
Evidence card 3
Add it to your evidence board
The neurons that feel the feet have the longest axons in the body.
Scene 4 of 5
Nerves, Tracts, Nuclei, Ganglia — and What a Scan Can See
Name bundles and clusters by where they live, then look at the real tissue.
Slide · a still to study
Under the Microscope: a Neuron
Open each marker to tour a real section A cut or slice of the body or an organ for study. of nervous tissue.
Explore
Where Does It Live?
Four words, two locations. Drag each term and example to the square where it belongs.
Think · not graded
A CT scan resolves about half a millimeter. A single myelinated axon is roughly 1 to 20 micrometers wide. What could the ER’s clear CT rule out, and what could it never see?
Spot-check your thinking: true or false?
Check · Single Choice
Three quick calls about what you just saw under the microscope.
Evidence card 4
Add it to your evidence board
A clear CT rules out broken bone, not damage to tiny nerve fibers.
Scene 5 of 5
Two Patterns on One Patient
Put Stina’s complaints on a body map and test each territory against them.
Animation · in production · 1 min 20 s
One Stripe, Two Stockings
Stina’s two numb areas drawn on one body — then tested against a spinal cord injury, and against the nerves.
Explore
Symptom Mapper
Sort each finding by its shape: one nerve route, every long nerve, or a spinal cord injury.
Think · not graded
A spinal injury from the crash could make both legs numb. What else would you expect to find if the cord were the problem — and is any of it on her chart?
Spot-check your thinking: true or false?
Check · Multiple Choice
Which finding would point most strongly to the spinal cord?
Evidence card 5
Add it to your evidence board
No weakness, no numb level on the trunk, no bladderA muscular organ that stores urine before excretion. change.
4
Your evidence board
Every scene gave you an evidence card, and the chart adds two more. Drag each card to the side it supports. Some cards belong in more than one place — that’s allowed, and the feedback tells you which cards decide the case.
5
Your verdict
Time to decide. Build your verdict from statements that hold up — no writing needed. At the end you’ll see your whole argument in one place.
Look back at your prediction
If you bet on the spinal cord
The crash was a fair reason to suspect it. What changed the picture is what’s missing: no weakness, no numb level on her trunk, no bladder change. Dropping a bet when the evidence doesn’t show up is exactly the skill this chapter practices.
If you bet on the peripheral nerves
Your bet held. Check that it held for the right reason — not just because the pain is in her leg, but because nothing points to the cord and the numbness sits where the longest axons end.
If you said you couldn’t say yet
That was honest. You now know what would have settled it fastest: a check for weakness, for a numb level on the trunk, and for bladder changes. Next time, look for those first.
6
The finding
Added to Stina’s chart · Chart Clue #8, line 1 of 7
Two patterns after a “clear” crash — a sensory, peripheral problem
Every complaint is sensory and her strength is intact. The pain runs in a stripe down one leg; the numbness sits in both feet, where the body’s longest axons end. Nothing points to the spinal cord. A clear CT cleared bone, not wiring — and two patterns may mean two problems. Keep both in view.
Next · Chapter 2
Wires and Insulation
If the trouble lives out in the wiring, you need to know how a wire is built — and who wraps it. Next: the glia, the myelin, and a small protein called MAG.
Reliable information on rare diseases
NORD · NIH GARD · Orphanet · MedlinePlus Genetics: FMF · FMF & AID Global Association · Autoinflammatory Alliance · Global Genes · Amyloidosis Foundation
Stina has one rare disease. In the United States, about 1 in 10 people live with one of the more than 7,000 known rare diseases. These organizations are where patients, families and clinicians go for trustworthy information.
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← Familial Mediterranean Fever — case home
All Modules
- Anatomical Language, Membranes & Homeostasis
- Just Enough Chemistry
- The Cell & Its Transport
- Making Cells & Proteins
- The Integumentary System
- The Skeletal System
- The Muscular System
- Nervous Tissue & the Senses
- The Spinal Cord
- The Brain & the Blood–Brain Barrier
- The Autonomic Nervous System
- Special Senses (in developmentThe process of growth and differentiation.)
- The Endocrine System
- Blood
- The Heart
- Blood Vessels
- The Digestive System
- The Respiratory System
- The Urinary System
- Fluids, Electrolytes & Acid–Base Balance
- The Reproductive System
- The Immune System
List of terms
- central nervous system
- spinal cord
- peripheral nerves
- spine
- fracture
- symptoms
- nervous system
- peripheral nervous system
- neurons
- dendrites
- cell body
- skin
- axon hillock
- ganglion
- section
- bladder
- development