How the Brain Works The Facts Visually Explained by DK (z-lib.org)

BRAIN FUNCTIONS AND THE SENSES

Feeling Pain

Feeling Pain

Although unpleasant, pain is a useful warning

sign that something isn’t right with the body and

that we need to act quickly to avoid further injury.

Pain signals

Pain receptors are located all over the body and respond to

heat, cold, overstretching, vibration, and chemicals released

by wounds. Electrical signals are sent from the site of injury

to the spinal cord, where they cross over and travel to the

opposite side of the brain to the injury. If sudden,

strong pain is experienced, a reflex

reaction occurs (see p.101) within

the spinal cord to make the

limb pull away from

whatever is causing the

pain, even before we

are aware of it.

BRUISE CUT

Nerve cell

Fast A-fiber

SKIN

Damaged cell

Prostaglandin

molecule

released by cell

NE

RV

E^ B

UN

DL

E

Axon

Pain receptors

activated

Injury prompts the

release of chemicals

called prostaglandins

from damaged cells.

These trigger the nerve

axons to send impulses

to the brain.

1

Pain signals travel up nerve bundles

Signals from the injury site travel along

nerve bundles toward the spinal cord. The

A-fiber signals get there within milliseconds

and trigger a withdrawal reflex away from

the source of the pain.

2

Slow C-fiber

Pain fibers

There are two types of nerve fibers, or axons.

Fast A-fibers carry sharp, localized pain from

an injury such as a cut. Slower C-fibers carry

the more persistent dull feelings from the

area around the injury.

Fast A-fiber

covered by

myelin sheath

Slow C-fibers

are widespread

in skin

SPINAL CO

RD SI

GNA

L

PAIN^ SIGNAL

WHO FEELS

THE MOST PAIN?

Women feel pain more

intensely than men

because they have

more nerve receptors

in their bodies.

Nerve bundle

contains multiple

axons, or nerve fibers

US_086-087_Feeling_Pain.indd 86 20/09/2019 12:35