Today I found out humans have more than five senses. It turns out, there are at least nine senses, and many researchers think there are more than double that.
The commonly held definition of a “sense” is “any system that consists of a group of sensory cell types that respond to a specific physical phenomenon and that corresponds to a particular group of regions within the brain, where the signals are received and interpreted.”
The commonly held human senses are as follows:
This technically is two senses given the two distinct types of receptors present, one for color (cones) and one for brightness (rods).
You can argue this one should count for five senses by itself due to the differing types of taste receptors: sweet, salty, sour, bitter, and umami). But generally it’s considered one sense.
Umami receptors detect the amino acid glutamate, which is a taste generally found in meat and some artificial flavoring. Taste, unlike sight, is a sense based on a chemical reaction
Touch has been found to be distinct from pressure, temperature, pain, and even itch sensors.
Obvious sense is obvious.
Surprisingly, this is a distinct sensor system from other touch-related senses.
Ability to sense heat and cold. This also is thought of as more than one sense — not just because of the two hot/cold receptors, but also because there is a completely different type of thermoceptor, in terms of the mechanism for detection, in the brain. These thermoceptors in the brain are used for monitoring internal body temperature.
Detecting vibrations along some medium, such as air or water that is in contact with your ear drums.
Yet another sensor related to a chemical reaction. This sense combines with taste to produce flavors.
This sense gives you the ability to tell where your body parts are, relative to other body parts. It’s one of the things police officers test when they pull someone over who they think is driving drunk. The “close your eyes and touch your nose” test is testing this sense.
This sense is used all the time in little ways, such as when you scratch an itch on your foot, but never once look at your foot to see where your hand is relative to your foot.
10. Tension sensors
These are found in your muscles and allow the brain the ability to monitor muscle tension.
In a word, pain. This was previously considered the result of overloading other senses, such as touch. But now it’s viewed as its own unique sensory system. There are three distinct types of pain receptors: cutaneous (skin), somatic (bones and joints), and visceral (body organs).
The sense that allows you to keep your balance and sense body movement in terms of acceleration and directional changes. This sense also allows for perceiving gravity.
This sensory system is found in your inner ears and is called the vestibular labyrinthine system. Anyone who’s ever had this sense go out on them knows how important it is. When it’s not working or malfunctioning, you literally can’t tell up from down. Moving from one location to another without aid is nearly impossible.
13. Stretch receptors
Found in the lungs, bladder, stomach, and the gastrointestinal tract. A type of stretch receptor that senses dilation of blood vessels is also often involved in headaches.
These trigger an area of the medulla in the brain that’s involved in detecting blood borne hormones and drugs. It’s also involved in the vomiting reflex.
This system more or less allows your body to monitor its hydration level, so your body knows when it should tell you to drink.
This system allows your body to detect when you need to eat something.
The ability to detect magnetic fields. This sense is principally useful in providing a sense of direction when detecting the Earth’s magnetic field.
Unlike most birds, humans do not have a strong magnetoreception. However, experiments have demonstrated that we do tend to have some sense of magnetic fields. The mechanism for this is not completely understood; it is theorized that this has something to do with deposits of ferric iron in our noses. People who are given magnetic implants have been shown to have a much stronger magnetoreception than humans without them.
This one is debated. No singular mechanism has been found that allows people to perceive time. However, experimental data has shown humans have a startling accurate sense of time, particularly when younger.
The mechanism we use for this seems to be a distributed system involving the cerebral cortex, cerebellum, and basal ganglia. Long term time-keeping seems to be monitored by the suprachiasmatic nuclei (responsible for the circadian rhythm). Short term time keeping is handled by other cell systems.