Topic: the senses. The five human senses. How do human senses help us to navigate the world?

Topic: the senses.
The five human senses.
How do human senses help us to navigate the world?

There are five basic human senses: touch, sight, hearing, smell and taste. The sensing organs associated with each sense send information to the brain to help us understand and perceive the world around us. However, there are in fact other human senses in addition to the basic five that you couldn't live without. These lesser-known senses include spatial awareness and balance. Here's how the human senses work.

TOUCH
Touch is thought to be the first sense that humans develop, according to the Stanford Encyclopedia of Philosophy(opens in new tab). Touch consists of several distinct sensations communicated to the brain through specialized neurons in the skin. Pressure, temperature, light touch, vibration, pain and other sensations are all part of the touch sense and are all attributed to different receptors in the skin.
Touch isn't just a sense used to interact with the world; it also seems to be very important to a human's well-being. For example, touch has been found to convey compassion from one human to another, according to a study published by the University of California, Berkeley(opens in new tab).
SIGHT
Sight, or perceiving things through the eyes, is a complex process. First, light reflects off an object to the eye. The transparent outer layer of the eye called the cornea bends the light that passes through the hole of the pupil. The iris (which is the colored part of the eye) works like the shutter of a camera, retracting to shut out light or opening wider to let in more light.

"The cornea focuses most of the light. Then, it [the light] passes through the lens, which continues to focus the light," explained Dr. Mark Fromer, an ophthalmologist and retina specialist at Lenox Hill Hospital in New York City.
People without sight may compensate with enhanced hearing, taste, touch and smell, according to a March 2017 study published in the journal PLOS One(opens in new tab). Their memory and language skills may be better than those born with sight, as well.

"Even in the case of being profoundly blind, the brain rewires itself in a manner to use the information at its disposal so that it can interact with the environment in a more effective manner," Dr. Lotfi Merabet, senior author on that 2017 study and the director of the Laboratory for Visual Neuroplasticity at Schepens Eye Research Institute of Massachusetts Eye and Ear, said in a statement(opens in new tab).
HEARING
This sense works via the complex labyrinth that is the human ear. Sound is funneled through the external ear and piped into the external auditory canal. Then, sound waves reach the tympanic membrane, or eardrum. This is a thin sheet of connective tissue that vibrates when sound waves strike it.
Have you ever listened to a recording of your voice and thought it didn’t sound like you? This is because some qualities of your voice sound different to those around you as you speak. For someone standing next to you, the sound of your voice will be detected as it is channelled through their ear canals, according to the BBC. The same will happen in your ears, but as the speech is being produced from within you, vibrations will also reach your eardrums via another route.
SMELL
Humans may be able to smell over 1 trillion scents, according to the National Institutes of Health(opens in new tab). They do this with the olfactory cleft, which is found on the roof of the nasal cavity, next to the "smelling" part of the brain, the olfactory bulb and fossa. Nerve endings in the olfactory cleft transmit smells to the brain..
Dogs are known as great smellers, but research suggests that humans are just as good. Research published in the May 11, 2017, issue of the journal Science(opens in new tab) suggests that humans can discriminate among 1 trillion different odors; it was once believed that humans could take in only 10,000 different smells.
"The fact is the sense of smell is just as good in humans as in other mammals, like rodents and dogs," John McGann, a neuroscientist at Rutgers University-New Brunswick in New Jersey and the author of the new review, said in a statement(opens in new tab). The Rutgers study backs up a previous study at the Rockefeller University in New York, whose findings were published in the March 2014 issue of the journal Science.
TASTE
The sense of taste aided in human evolution, according to the NLM, because taste helped people test the food they ate. A bitter or sour taste indicated that a plant might be poisonous or rotten. Something salty or sweet, however, often meant the food was rich in nutrients.

Taste is sensed in the taste buds. Adults have 2,000 to 4,000 taste buds. Most of them are on the tongue, but they also line the back of the throat, the epiglottis, the nasal cavity and the esophagus. Sensory cells on the buds form capsules shaped like flower buds or oranges, according to the NLM. The tips of these capsules have pores that work like funnels with tiny taste hairs. Proteins on the hairs bind chemicals to the cells for tasting.
It is a myth that the tongue has specific zones for each flavor, according to NLM. The five tastes can be sensed on all parts of the tongue, although the sides are more sensitive than the middle. About half of the sensory cells in taste buds react to several of the five basic tastes. The cells differ in their level of sensitivity.

The other half of the sensory cells are specialized to react to only one taste. It's their job to transmit information about the intensity — how salty or sweet something tastes.

Source: livescience.com