The senses are how we collect information about our environment. Without senses, we would have no idea what is going on around us and we would be in complete mental isolation. Obviously, the existence of the senses are very important to our survival and well being. There are three main types of senses. These include energy senses, chemical senses, and body position senses.
Energy senses include vision, hearing, and touch. All of these senses detect a type of energy that gives information about the environment.
Vision, for one, is used in the detection of light. Vision is used to gather the most information out of all of the human senses. This makes it very important.
Light enters the eyes through the cornea and is focused by the lens. The muscles in the eye change the shape of the lens in order to focus on different objects. The light is flipped upside down and inverted as it is passed through the lens and strikes the retina. Specialized cells known as cones and rods are what the light reaches first. Cones are activated by color, while rods are activated by black and white. Our number of rods outnumber the cones by approximately 20:1. Most of the cones are concentrated in a curved part of the retina called the fovea. Most of the rods are around the outside of the retina, and this is why we have difficulty determining color when using peripheral vision.
Once the rods or cones have been activated, they activate the bipolar cells, which activate the ganglion cells, which make up the optic nerve. From there the image is sent to the brain. The images from the left side of each retina go to the left hemisphere and vice versa. At this point, there are only theories as to what happens as science has yet to produce significant evidence of what exactly happens.
Hearing is a sense that detects vibrations in a medium such as air or water. Sound waves are collected in the outer year and travel down the auditory canal until they reach the tympanic membrane. This membrane is vibrated by the sound energy and transfers the energy to a series of bones. The order of the bones is malleus, incus, and stapes, followed by a membrane known as the oval window, which transfers the energy to the cochlea. The cochlea is a structure filled with fluid that absorbs the energy and causes tiny hairs to move. The hairs are connected to the organ of corti, which is made up of neurons that are activated by the hair cells. The neurons transmit the energy to the brain via the auditory nerve.
Touch is a sense that is triggered by sensors covering our skin. The sensors are specialized nerve endings that are activated by pressure or temperature. The amount of pressure or temperature affects the intensity of the signal sent to the brain, which is very useful. We are also able to determine the location of the source of these disturbances since the brain has faculties to determine where exactly the signals come from. When sharp changes in pressure or temperature are detected, special nerve endings known as pain receptors transmit signals, which we feel as pain.
Taste is a chemical sense that involves specialized cells on the tongue. Chemicals from food and other things are absorbed by taste buds on our tongue. The taste buds are located on papillae, which appear to be tiny bumps on the surface of the tongue. What some people do not know is that taste buds are not confined to the tongue itself. There are also taste buds located on the roof of the mouth and walls of the cheeks. The sensitivity of taste is specific to each person. One person may have more taste buds than another and report something as too strong, while the other may report it is weak.
Smell works closely together with taste to create the "flavor" of food and other things. Our noses contain specialized cells known as olfactory cells. These cells absorb chemicals that we inhale and create the sensation known as smell. Researchers estimate that there are approximately 100 different types of olfactory cells.
The vestibular sense creates our ability to sense how our body is oriented in space. The initial sensations for body orientation are collected by canals in the ear. These canals are partially filled with fluid which shifts as the position of the body shifts. The movement of fluid causes the movement of hair cells in the canals. The movement of the hair cells causes nerve impulses to be sent to the brain. When the fluid in these canals shifts too much, the messages sent to the brain are confused, causing the feeling of nausea and dizziness.
The kinesthetic sense gives us information about the position of certain body parts. There are specialized receptors in muscles and joints that report the position of our limbs.