Australian_Science_Illustrated_Issue_52_2017

76 | SCIENCE ILLUSTRATED

SCIENCE DISAGREE

ON STATUS

OF DÉJÀ VU

Scientists disagree

about how many senses

we have. Some believe

that déjà vu – the

feeling of having

experienced something

before – is a sense,

whereas others say that

"agency" – the sense of

ownership of your own

decisions – is also a

sense. 12 senses are

widely recognised:

1. Sense of smell


2. Sense of vision


3. Sense of hearing


4. Sense of taste


5. Sense of touch


6. Sense of balance


7. Sense of time


8. Kinaesthetic sense


9. Sense of itch


10. Temperature sense


11. Sense of pain


12. Sense of hunger/
    fullness

One of the most important senses measures

your temperature, which should be 36.4-37.1

°C, - the temperature at which most of the

body’s enzymes work most efficiently. The

hypothalamus brain region controls your

temperature and regulates metabolism, blood

flow, and sweat production based on data from

sensors in the skin, etc. If you are too cold, the

hypothalamus makes the muscles, etc.,

tremble, producing extra heat.

Pain is the body’s way of warning us. Like the skin,

the internal organs are ripe with sensitive nerve

cells, which detect temperature changes, pressure,

and chemicals. The nociceptors sound the alarm,

when they encounter temperatures of 40+ °C and

below minus 5 °C, or if they suddenly detect a

pH factor change, which could harm the cells

with lack of oxygen, etc.

If you move your hand over a scalding

hot cooking plate, nociceptors in the skin

immediately send signals to the brain.

Brain cells now produce a sensation of

pain, making you remove your arm,

before the heat burns through all

the layers of skin.

Mosquitoes, bugs, and other parasites tease

a sense which scientists recently began to

map out: the sense of itch. When parasites

penetrate your skin, they use special

enzymes known as proteases. They make

the body’s white blood cells produce the

histamine neurotransmitter, which

activates nerve cells in the skin. The result is

a pricking itch in the place in which the

parasite has taken hold. In this way, the

sense of itch warns the brain of invading

enemies. The sense can also be activated by

other foreign bodies such as pollen.

Body thermostat

makes you shiver

Pressure and heat

cause pain

Warns you of

uninvited guests

Itching makes you

aware of ticks and other

parasites on your skin.

SHUTTERSTOCK

ALEXANDER DEMIANCHUK/GETTY IMAGES

SHUTTERSTOCK

5 SENSE OF ITCH

6 TEMPERATURE SENSE

7 SENSE OF PAIN

Temperature changes

activate sensory

cells in your skin,

alerting your brain.

HUMANS SENSES