SO WHAT DO ALL YOUR 32 SENSES DO?

WHERE have all our ‘extra’ senses come from? A ‘sense’ involves a specialist ‘sensor’ (or receptor) that is triggered by a specific change. The brain’s processing of this sensory signal might then lead to a conscious perception, such as hearing music. But it is not just about an obvious response. Our senses monitor events that we never become aware of. We even have sensors that detect important changes and mount responses that keep us alive without us needing to become conscious of them. Based on this definition, we have gone from five human senses to 32. They are:

1. SIGHT 2. ‘LIGHT-DETECTING’ SENSE (which helps your body clock ascertain the time of day). 3. HEARING 4. SMELL

TASTE: When it comes to taste, because we have five very different kinds of receptor for detecting different groups of chemicals for taste (and because they’re not just on the tongue), our old idea of ‘ taste’ is better thought of as five related senses: 5. SALTY 6. SWEET 7. BITTER 8. SOUR 9. UMAMI (SAVOURY)

TOUCH: This is our ‘contact’ sense — but it is really a group of three senses, each of which has its own sensors and involves different responses. These are: 10. PRESSURE 11. VIBRATION 12. GENTLE, SLOW-MOVING CONTACT (the sort you get from another person). 13. ITCH (this isn’t touch, and it isn’t pain — it is pruriception, as it’s properly called).

PAIN: We are capable of registering three distinct types of physical damage or potential damage, each of which can generate distinct pain perceptions. These senses relate to: 14. DANGEROUS TEMPERATURES 15. DANGEROUS CHEMICALS 16. MECHANICAL DAMAGE (pinching, tearing, cutting, slicing).

TEMPERATURE: We divide ‘temperature sense’ into two, partly because we have distinct ‘warm’ and ‘cool’ receptors but also their signals result in different responses: 17. COOLNESS ( causing shivering). 1 8 . WARMTH ( causing sweating).

19. BODY MAPPING ( or proprioception. This is our intuitive sense of limb location — where our various body parts are located in space. It is vital for descending a staircase, say, or drinking from a champagne glass. Attempting these actions without this sense could be lethal).

BALANCE: Next we move into the ‘balance’ senses. Here, receptors help our brain work out where we are. 20. HEAD ROTATION RECEPTORS (detect your head position in relation to gravity to ensure that you stay upright). 21. VERTICAL MOTION RECEPTORS (as in detecting if you are moving in a lift). 22. HORIZONTAL MOTION RECEPTORS (for instance, that you are moving in a car).

‘STAYING ALIVE’ SENSES: These receptors, in different tissues inside the body, send signals to keep the brain informed of our bodily states and will (consciously or unconsciously) change our behaviour accordingly — they are vital for our ability to stay alive. 23. HEARTBEAT RECEPTORS 24. BLOOD PRESSURE RECEPTORS 25. CARBON D I OX I D E RECEPTORS (how much carbon dioxide is in the blood). 2 6 . OXYGEN RECEPTORS ( detects oxygen levels in the blood). 27. LUNG STRETCH RECEPTORS (monitor the increase in lung volume as we breathe in). 28. CEREBROSPINAL FLUID pH RECEPTORS (these receptors monitor carbon dioxide in cerebrospinal fluid, the liquid that bathes the brain and spinal cord — when signals indicate that carbon dioxide levels are rising, you are prompted to inhale).

APPETITE AND WASTE SENSES: And finally, we have sensors that govern hunger, thirst and waste: 29. PLASMA OSMOTIC PRESSURE RECEPTORS (cells in the brain that sense the concentration of salts in your blood. If this strays the tiniest bit outside a tight range of acceptability, measures to adjust this kick in. For instance, you feel thirsty, which prompts you to drink and dilute the concentration). 30. STOMACH FULLNESS 31. BLADDER FULLNESS 32. RECTAL FULLNESS