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

The skin is the biggest organ of the body

and also the largest sense organ. Packed

with sensors, it enables us to experience

a wide variety of sensations, as well as

an awareness of where we are.

Receptors in the skin

Skin sensors consist of receptors connected by axons.

Found at various levels in the skin, there are around

20 types that respond to different sorts of stimuli. The

receptors register mechanical, thermal, and, in some cases,

chemical stimuli and convert them into electrical signals.

These travel up peripheral nerves to the spinal cord, then

to the brain stem, and finally to the somatosensory cortex,

where they are translated into a touch.

Touch

Net of nerve fiber

endings wrapped

around base of shaft

Hair movement

triggers nerve

impulse

Root hair plexus

Nerves wrapped around the base of a hair

shaft are triggered by things that have not

touched the skin, such as air currents or

objects that brush against the hair.

Free nerve endings

extend into skin’s

surface layer

Free nerve endings

Extending up into the spinous layer of

the epidermis, these bare, rootlike nerve

endings are sensitive to cold, heat, light

touch, and pain.

Merkel’s disks

Found slightly lower than free nerve

endings, Merkel’s disks are particularly

dense in the lips and fingertips. They

respond to light touch.

Well-defined

borders make

Merkel’s disks

sensitive to

shapes and

edges

LIGHT BREEZE TEMPERATURE CHANGE BRUSH OF A FEATHER

DERMIS (DEEP LAYER OF SKIN)

EPIDERMIS

TOP, DEAD LAYER OF EPIDERMIS

SPINOUS LAYER

H

A

RI

S

H

A

TF

BASAL

(^) LAY
ER
Mechanoreceptors
Proprioceptors
Nociceptors
Thermoreceptors
Chemoreceptors
Sensory receptors that respond to
mechanical pressure or distortion.
This can range from a light touch
to deep pressure.
Receptors that receive stimuli from
within the body, particularly in
relation to position and movement.
Sensory neurons that respond
to damaging stimuli by sending
“possible threat” signals to the
spinal cord and the brain.
Specialized nerve cells that are able
to detect differences in temperature.
They are found all over the skin and
in some internal areas.
Extensions of the peripheral nervous
system that respond to changes in
blood concentrations to maintain
homeostasis (see pp.90–91).

TYPES OF RECEPTORS FUNCTION

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