---
title: "Nervous Communication"
book: "Primary & Middle School Biology"
subject: biology
language: en
chapter: 60
exercises: 12
source: https://one-course.com/books/biology/1/en/chapter/60-nervous-communication
---

# Chapter 60 — Nervous Communication

[Chapter 33](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#ch-g5-brain-in-command) drew the loop — report, decide, order — and measured its fifth of a second. This year we open the cables. What actually travels along a [nerve](#def-g8-nervous-communication-neuron)? What are [nerves](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) made of? And what happens at the gaps where one wire ends and the next begins — the gaps where, it will turn out, both memory and many poisons do their work?

## 60.1 The wiring and its cells

**Definition 60.1 (Neurons and nerve messages).**

The [nervous system](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s working [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) are the *neurons* ([Remark 45.6](https://one-course.com/books/biology/1/en/chapter/45-the-cell-unit-of-life#rem-g6-cell-unit-of-life-twoways) listed them): each has a [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) body and a long thin fiber — some fibers reach from [spine](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-skeleton) to toe, the body’s longest [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell). A *nerve* is a cable bundling thousands of such fibers. Along each fiber travel *nerve messages*: brief electrical signals, racing at up to $100\,\mathrm{m}/\mathrm{s}$ ([Definition 33.1](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s figure, now with its carrier).

**Proposition 60.2 (Coding by frequency).**

The signals themselves are all alike — what varies is their *rate*. A gentle touch sends a slow patter up the sensory fiber; a strong one, a rapid drumroll. The [nervous system](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s language has one word repeated at different speeds: intensity is coded as frequency, on every line, in and out.

**Proof.** *Admitted at this level.* ∎

**Example 60.3 (Three lines, one language).**

The loop’s cast ([Proposition 33.2](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#prop-g5-brain-in-command-loop)), rewired: *sensory [neurons](#def-g8-nervous-communication-neuron)* carry the reports — [skin](https://one-course.com/books/biology/1/en/chapter/5-the-five-senses#def-g1-the-five-senses-sense) to [spinal cord](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system), [eye](https://one-course.com/books/biology/1/en/chapter/5-the-five-senses#def-g1-the-five-senses-sense) to [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system); *motor [neurons](#def-g8-nervous-communication-neuron)* carry the orders — cord to [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle), ending where the fiber meets the [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) and its drumroll sets the contraction’s strength ([Definition 17.6](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle)); and between them, in [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) and cord, uncounted *connecting [neurons](#def-g8-nervous-communication-neuron)* do the deciding. Reflex or symphony, the traffic is the same signals at different rates on different lines.

## 60.2 The gaps: synapses

**Definition 60.4 (The synapse).**

[Neurons](#def-g8-nervous-communication-neuron) do not touch. Where one fiber’s end meets the next [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) lies a microscopic gap — the *synapse*. The electrical signal cannot jump it; instead the arriving fiber releases a *chemical messenger* into the gap, which crosses, docks on the far side, and — if enough arrives — starts the signal afresh in the next [neuron](#def-g8-nervous-communication-neuron). Electrical along the wire, chemical at every junction: the whole system alternates the two.

**Proposition 60.5 (Why gaps, not solder).**

The gaps look like a flaw and are the system’s genius:

- they make junctions *adjustable* — a [synapse](#def-g8-nervous-communication-synapse) crossed often grows stronger, one unused fades: learning ( [Remark 33.8](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#rem-g5-brain-in-command-training) ’s “better paths”, found — they are strengthened [synapses](#def-g8-nervous-communication-synapse) );
- they make signals *one-way* — messengers release on one side only, so traffic cannot run backward;
- they let one [neuron](#def-g8-nervous-communication-neuron) *weigh* thousands of inputs — excitatory and damping voices summed at each [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) before it fires: the deciding of the loop, performed at junctions.

**Proof.** *Admitted at this level.* ∎

**Example 60.6 (The juggler’s synapses).**

[Remark 33.8](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#rem-g5-brain-in-command-training)’s juggler, explained at last: a month of practice conducted the same signals across the same junctions until those [synapses](#def-g8-nervous-communication-synapse) strengthened — the routing that was laboriously weighed now runs pre-weighted. Skill is chemistry consolidated at the gaps; “practice makes permanent” is a statement about [synapses](#def-g8-nervous-communication-synapse).

![Three balls flying themselves: a month of strengthened synapses, photographed.](https://one-course.com/images/onecourse/chapters/biology-1/g8-nervous-communication/img-1132e9edec1e.jpg)

*Three balls flying themselves: a month of strengthened [synapses](#def-g8-nervous-communication-synapse), photographed.*

**Remark 60.7 (The gaps are the vulnerable points).**

Whatever acts on the [nervous system](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) from outside acts at the [synapses](#def-g8-nervous-communication-synapse) — the one place the signal becomes chemistry, dockable and dupable. Anesthetics quiet them; venoms jam them (some paralyze by blocking the muscle-junction’s messenger, some by flooding it); and [Proposition 36.5](https://one-course.com/books/biology/1/en/chapter/36-healthy-choices#prop-g5-healthy-choices-substances)’s alcohol, and every drug that changes mood or perception, works by imitating, blocking or exhausting the gaps’ messengers. [Chapter 62](https://one-course.com/books/biology/1/en/chapter/62-protecting-the-nervous-system#ch-g8-protecting-the-nervous-system) builds on exactly this point.

## 60.3 Fast wires, slow mail: two systems compared

**Proposition 60.8 (Nerves against hormones).**

The body now shows two communication systems, built for opposite jobs:

- *nervous* : signals in milliseconds, along dedicated lines, to precise addresses — one [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) , one gland — and gone when the signal stops: the system of catches, speech and reflexes;
- *hormonal* ( [Definition 56.4](https://one-course.com/books/biology/1/en/chapter/56-puberty#def-g8-puberty-hormones) ): messengers in minutes to months, broadcast by [blood](https://one-course.com/books/biology/1/en/chapter/25-the-journey-of-food#prop-g4-journey-of-food-absorb) to every organ built to hear, ordering slow, body-wide programs — growth, cycles, [puberty](https://one-course.com/books/biology/1/en/chapter/56-puberty#def-g8-puberty-puberty) ’s rebuild.

Telegraph and postal service: the body runs both, and [Chapter 61](https://one-course.com/books/biology/1/en/chapter/61-hormonal-communication#ch-g8-hormonal-communication) gives the postal service its own chapter.

**Proof.** *Admitted at this level.* ∎

**Method 60.9 (Diagnosing a communication, system by system).**

Given any bodily coordination, assign its system:

1. time it: milliseconds — nervous; minutes to years — hormonal (or both, in relay);
2. map its reach: one precise address — nervous; body-wide — hormonal;
3. find the route: nameable wire path — nervous; bloodstream broadcast — hormonal;
4. check persistence: gone with the signal — nervous; running while the messenger circulates — hormonal.

**Example 60.10 (The method on three cases).**

The blink at a puff of air: milliseconds, one [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) ring, wired path, gone at once — nervous. The growth burst: years, whole-body, bloodstream, running for seasons — hormonal. The racing [heart](https://one-course.com/books/biology/1/en/chapter/27-the-heart-and-the-blood#def-g4-heart-and-blood-heart) of the sprint ([Proposition 49.4](https://one-course.com/books/biology/1/en/chapter/49-organs-at-work#prop-g7-organs-at-work-supply)): both in relay — [nerve](#def-g8-nervous-communication-neuron) signals set the pace up within a beat, and a bloodstream messenger (the famous surge you feel as a fright’s hot wave) holds the whole body’s alert for minutes. Telegraph first, post to follow.

## 60.4 Exercises

**Exercise 60.1 ★.**

What is a [neuron](#def-g8-nervous-communication-neuron)? What is a [nerve](#def-g8-nervous-communication-neuron), in terms of [neurons](#def-g8-nervous-communication-neuron)?

**Solution of Exercise 60.1.**

A [neuron](#def-g8-nervous-communication-neuron) is the [nervous system](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s working [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell): a [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) body with a long thin fiber — some spine-to-toe. A [nerve](#def-g8-nervous-communication-neuron) is a cable bundling thousands of such fibers.

**Exercise 60.2 ★.**

What travels along a fiber, at what speed — and how is intensity coded?

**Solution of Exercise 60.2.**

Brief electrical signals, at up to $100\,\mathrm{m}/\mathrm{s}$. The signals are all alike; intensity is coded as their rate — gentle patter to rapid drumroll.

**Exercise 60.3 ★.**

Name the three [neuron](#def-g8-nervous-communication-neuron) kinds of the loop and each one’s line.

**Solution of Exercise 60.3.**

Sensory [neurons](#def-g8-nervous-communication-neuron): the report lines, [sense organ](https://one-course.com/books/biology/1/en/chapter/5-the-five-senses#def-g1-the-five-senses-sense) to cord and [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system). Motor [neurons](#def-g8-nervous-communication-neuron): the order lines, cord to [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle). Connecting [neurons](#def-g8-nervous-communication-neuron): the deciding, within [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) and cord.

**Exercise 60.4 ★.**

What is a [synapse](#def-g8-nervous-communication-synapse), and what crosses it?

**Solution of Exercise 60.4.**

The microscopic gap where one [neuron](#def-g8-nervous-communication-neuron)’s fiber end meets the next [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell). A chemical messenger crosses it, docks, and — if enough arrives — restarts the signal in the next [neuron](#def-g8-nervous-communication-neuron).

**Exercise 60.5 ★.**

Give the three services the gaps provide, by [Proposition 60.5](#prop-g8-nervous-communication-whygaps).

**Solution of Exercise 60.5.**

Adjustability ([synapses](#def-g8-nervous-communication-synapse) strengthen with use and fade without — learning); one-way traffic (release happens on one side only); and weighing (each [neuron](#def-g8-nervous-communication-neuron) sums thousands of exciting and damping inputs before firing).

**Exercise 60.6 ★.**

Contrast [nerves](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) and [hormones](https://one-course.com/books/biology/1/en/chapter/56-puberty#def-g8-puberty-hormones) on speed, reach, route and persistence.

**Solution of Exercise 60.6.**

[Nerves](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system): milliseconds, one precise address, dedicated wire paths, effect gone with the signal. [Hormones](https://one-course.com/books/biology/1/en/chapter/56-puberty#def-g8-puberty-hormones): minutes to years, body-wide, bloodstream broadcast, effect running as long as the messenger circulates.

**Exercise 60.7 ★★.**

Rewrite the ball-catch of [Example 33.3](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#ex-g5-brain-in-command-catch) in this chapter’s vocabulary: name the [neuron](#def-g8-nervous-communication-neuron) kinds and where [synapses](#def-g8-nervous-communication-synapse) do the weighing.

**Solution of Exercise 60.7.**

The [eyes](https://one-course.com/books/biology/1/en/chapter/5-the-five-senses#def-g1-the-five-senses-sense)’ sensory [neurons](#def-g8-nervous-communication-neuron) drum the ball’s positions to the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system); connecting [neurons](#def-g8-nervous-communication-neuron) weigh the streams at their [synapses](#def-g8-nervous-communication-synapse) — the path computed is inputs summed junction by junction; motor [neurons](#def-g8-nervous-communication-neuron) drum the orders out, their rates setting each [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle)’s strength for step, lean and close of the hand.

**Exercise 60.8 ★★.**

“Practice makes permanent.” Explain the slogan at the gaps, with the juggler.

**Solution of Exercise 60.8.**

Each practiced pass conducts signals across the same junctions, and crossed junctions strengthen: after a month the juggle’s routing is pre-weighted — what needed effortful weighing now runs of itself. The permanence is stronger [synapses](#def-g8-nervous-communication-synapse).

**Exercise 60.9 ★★.**

Why does everything that acts on the [nervous system](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) from outside act at the [synapses](#def-g8-nervous-communication-synapse)? What is special about them?

**Solution of Exercise 60.9.**

Because the [synapse](#def-g8-nervous-communication-synapse) is where the signal becomes chemistry — a released messenger, docking sites, a gap open to whatever molecules arrive. A wire’s electricity is hard to counterfeit; a chemical courier can be imitated, blocked or exhausted — so that is where anesthetics, venoms and drugs all act.

**Exercise 60.10 ★★.**

Run [Method 60.9](#met-g8-nervous-communication-diagnose) on: (a) pulling back from a hot pan; (b) [puberty](https://one-course.com/books/biology/1/en/chapter/56-puberty#def-g8-puberty-puberty)’s voice change; (c) the fright’s hot wave that outlasts the scare.

**Solution of Exercise 60.10.**

(a) Milliseconds, one [arm](https://one-course.com/books/biology/1/en/chapter/4-my-body#def-g1-my-body-parts)’s [muscles](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle), wired path, gone at once: nervous. (b) Years, body-wide, bloodstream, running for seasons: hormonal. (c) The relay: a nervous split-second start, then the bloodstream messenger holding the alert for minutes after the scare — both, in order.

**Exercise 60.11 ★★.**

A venom blocks the messenger at the [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) junction. Predict the victim’s state, and name the loop stage cut.

**Solution of Exercise 60.11.**

The order arrives at the junction and cannot cross: [muscles](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) receive nothing. The victim is progressively paralyzed — conscious, sensing, deciding — with the loop cut at its last link, order-to-muscle.

**Exercise 60.12 ★★★.**

“Electrical along the wire, chemical at the junction — and everything interesting happens at the junctions.” Defend the last clause three ways: learning, deciding, and vulnerability.

**Solution of Exercise 60.12.**

Learning: skills are [synapses](#def-g8-nervous-communication-synapse) strengthened by use — the juggler’s month lives at junctions. Deciding: each [neuron](#def-g8-nervous-communication-neuron) fires or not by summing its junctions’ voices — the loop’s “decide” is junction arithmetic. Vulnerability: anesthetics, venoms and drugs act where signal becomes chemistry — at the gap. Wires only carry; junctions learn, choose and can be fooled.

## 60.5 Problem: The Reflex Bench

**Problem 60.1.**

Weekend problem — the knee-jerk, instrumented

The classic bench demonstration: the seated volunteer, the little hammer below the kneecap, the foot’s involuntary kick — now instrumented with timers and this chapter.

**Part I — The circuit.**

1. The hammer stretches a tendon; the foot kicks about a fiftieth of a second later. Lay out the circuit: which [neuron](#def-g8-nervous-communication-neuron) kinds, through where — and why the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) is not on this loop.
2. A fiftieth of a second is faster than the ball-catch’s fifth. Account for the difference with the circuit’s length and junction count.
3. The volunteer cannot suppress the kick, though warned. What does this say about where the reflex is decided — and about one-way traffic at the [synapses](#def-g8-nervous-communication-synapse) ?
4. Immediately after the kick, the volunteer *feels* the tap. Explain the delay’s second, slower journey.

**Part II — Bench variations.**

5. Tap harder: the kick strengthens. Which coding rule of [Proposition 60.2](#prop-g8-nervous-communication-code) showed itself?
6. The class doctor explains that this reflex is tested at every check-up. What does a present, symmetrical knee-jerk certify about cord, [nerves](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) and junctions?
7. A volunteer clenching their jaw kicks harder — a known amplification. What does this reveal about connecting [neurons](#def-g8-nervous-communication-neuron) ’ voices reaching even “brainless” loops?
8. Local anesthetic in the [leg](https://one-course.com/books/biology/1/en/chapter/4-my-body#def-g1-my-body-parts) abolishes both kick and feeling. Name the point of attack, by [Remark 60.7](#rem-g8-nervous-communication-vulnerable) .

**Part III — The write-up.**

9. Draw the reflex as [Proposition 33.2](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#prop-g5-brain-in-command-loop) ’s three-step loop, marking where this one shortcuts.
10. Compare reflex and catch in a two-column table: path, junctions, time, suppressibility, role of practice.
11. The write-up’s last section asks: “why do fast protective loops bypass the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) ?” Answer with the hot-pan logic ( [Exercise 33.5](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#exo-g5-brain-in-command-5) ).
12. One sentence to close: what the bench showed about the [nervous system](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) ’s language, wiring and junctions at once.

**Solution of Problem 60.1.**

**1.** The tendon stretch fires sensory [neurons](#def-g8-nervous-communication-neuron); they run to the *[spinal cord](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)*, [synapse](#def-g8-nervous-communication-synapse) there directly onto motor [neurons](#def-g8-nervous-communication-neuron), and the motor drumroll kicks the thigh [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle). Two [neuron](#def-g8-nervous-communication-neuron) kinds, one junction, cord-level — the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) is bypassed because protection cannot wait for deliberation.

**2.** The catch’s loop runs [eye](https://one-course.com/books/biology/1/en/chapter/5-the-five-senses#def-g1-the-five-senses-sense) to [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) to [arm](https://one-course.com/books/biology/1/en/chapter/4-my-body#def-g1-my-body-parts) — metres of fiber and many weighing junctions; the knee-jerk runs tendon to cord to [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) — centimetres and essentially one [synapse](#def-g8-nervous-communication-synapse). Shorter wire, fewer junctions, a tenth the time.

**3.** The decision is made in the cord, before any [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) veto can arrive — and the [synapses](#def-g8-nervous-communication-synapse)’ one-way traffic means the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s later objection cannot run backward down the sensory line. Warning changes nothing: the loop closes below the will.

**4.** The feeling is a second journey: the same tap’s report also climbs the cord to the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) — a longer path with more junctions — arriving after the kick is already history.

**5.** Frequency coding: the harder stretch sends a faster drumroll, and the motor line answers in kind — stronger contraction from a higher rate, the one-word language at both ends.

**6.** That the whole circuit is sound: sensory line, cord junction, motor line and [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) — and symmetry certifies both sides alike. One tap audits four components.

**7.** That connecting [neurons](#def-g8-nervous-communication-neuron)’ voices from elsewhere in the system reach even this loop’s junction, raising its readiness: the “brainless” reflex is still wired into the whole, its [synapse](#def-g8-nervous-communication-synapse) hearing more than the tendon.

**8.** The [synapses](#def-g8-nervous-communication-synapse) — and the fibers’ signalling generally: the anesthetic quiets the chemistry at the junctions and the message traffic with it, kick and feeling together.

**9.** Report (tendon stretch) — decide (one cord junction) — order (motor line): the loop with its middle step reduced to a single [synapse](#def-g8-nervous-communication-synapse), the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s weighing bypassed.

**10.** Reflex: tendon-cord-muscle, one junction, a fiftieth of a second, unsuppressible, practice-free. Catch: eye-brain-arm, uncounted junctions, a fifth of a second, fully voluntary, practice-built.

**11.** Because the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system)’s weighing costs time, and a burn deepens by the millisecond: loops that protect tissue are soldered short, cord-level, and inform the [brain](https://one-course.com/books/biology/1/en/chapter/33-the-brain-in-command#def-g5-brain-in-command-system) afterward — feel it late, saved already.

**12.** “One hammer tap showed the one-word frequency language, the two-line wiring through the cord, and a junction that decides faster than its owner can.”