The five Senses

Traditionally, there are five senses; sight, smell, taste, touch and hearing.  Each of the five senses consists of organs with specialized cells that have receptors for specific stimuli. These cells contain links to the nervous system and to the brain.  These senses are essential for our survival and reproduction in the world.  In Principles of Neural Science, it’s written that sensory organization provides us with the ability to interpret information about our body and environment from our sense receptors. This occurs in the development of human beings before motor organization.

The eye is the organ of vision.  It is a complex structure in which a transparent lens focuses light on the retina.  The retina is protected by light sensitive cell-rods and cones.  The rod cells have a great sensitivity to light and are responsible for our peripheral and night vision.  The eye is connected to our brain through what is called the optic nerve.  The point of this connection is often referred to as the “blind spot” because it is insensitive to light. The brain combines the input of our two eyes into a single three-dimensional image.  Even though the image on the retina is upside-down, the brain compensates to provide the right-side up perception.  Color blindness or Daltonism is a very common abnormality in the human vision that makes it impossible to distinguish certain colors accurately. 

The ear is the organ of hearing.  The outer ear protrudes away from the head and has a cup-like shape in order to direct sounds towards the tympanic membrane.  The tympanic membrane transfers vibrations to the inner ear through a series of small bones located in the middle ear called the malleus, incus, and stapes.  The inner ear, also known as the cochlea, is covered by nerve fibers that react to the vibrations and transfers impulses to the brain through the auditory nerve.  The brain then combines the input of our two ears to determine the direction and distance of sounds. 

The mouth is the organ for taste.  The receptors for taste, more commonly known as taste buds, are located throughout the mouth including on the tongue, the roof of the mouth and near the pharynx.  They are able to detect the four basic tastes; salty, sweet, bitter and sour.  The taste buds located close to the tip of the tongue are sensitive to sweet taste, whereas those in the back of the tongue are sensitive to bitter tastes.  The taste buds on the top and sides of the tongue are more sensitive to sour or salty tastes.  Each taste bud contains a nerve that sends these sensations to the brain.  The sense of taste also functions with the sense of smell. 

The nose is the organ responsible for our sense of smell.  The inside of the nose, or the cavity, is lined with mucus membranes that contain smell receptors connected to the olfactory nerve.  Most smells themselves consist of vapors from various substances.  In order for these sensations to be transmitted to the brain, the smell receptors must interact with the molecules from such vapors.  The smell receptors are sensitive to seven known sensations.  These sensations are camphor, musk, flower, mint, ether, acrid and putrid.  The sense of smell can sometimes be lost when we have a cold. 

There is no specific part of the body responsible for the sense of touch.  Nerve endings are located under the skin and other parts of the body which transmit sensations to the brain.  However, the fingertips and the sexual organs have the greatest concentration of nerve endings.  There are four kinds of touch sensations that have been identified.  They are cold, heat, contact and pain.  The hairs located on the skin magnify our sensitivity and act as an early warning system for the body. 

In addition to sight, smell, taste, touch and hearing, the human body also contains an awareness of balance, temperature and motion, all of which may involve the coordinated use of multiple sensory organs.  Sensory systems are specific and no species could survive without them.  People can sense another person’s energy by their thought waves, and our senses of knowing and feeling tie together as one. So basically, each kind of species has its own unique sensory system according to its particular behavior and environment.  As the sensory inputs of sight, sound, touch, smell and taste are reproduced in the brain, so are the thought waves of the environment, which are reproduced by the brain as well. Emotion is everything , whereas everything is feelings, and all energy is emotion.

It’s unique to me how all our senses work.  Like, in a case of color blindness, some people are insensitive to certain taste.  Also, how our mood can change based on the type of people we are around.  If we didn’t relate everything back to thought, we wouldn’t have the knowledge of each sense. I can’t imagine a world without our senses, let alone how some people survive without one or two senses. That to me is amazing how all their other senses kick in to replace the ones they’re missing.