Kaila Strauss
Human Body Systems
West Career and Technical Academy
Period 3
February 19, 2014

The five senses of sight, hearing, touch, taste and smell are all sensations throughout the human body. Sensation is the involvement of sensory receptors as well as the central nervous system in order to allow us to experience outside stimuli. The system that allows us to experience sensation is the sensory system.
The sensory system’s organs are the sense organs of the body. The purpose of the sensory system is to allow us to experience outside stimuli and identify alterations in the environment by sensory receptors and eyes, nose, ears, tongue, and skin, which are the sensory organs. The sensory system is actually one of the main elements of the body used to process sensory information. The sensory system is not a system by itself in the human body; it is actually a sub system or a part of the nervous system. When sensory receptors/neurons from the sensory organs detect a stimulus, this information is sent to the brain through sensory neurons and the reaction to that stimulus is sent back to that area of the body where the stimulus was present. Another strong relationship between the nervous system and the sensory system is that there are parts of the brain (the brain is part of the central nervous system) that are involved in sensory perception such as thalamus as well as the lobes of the brain such as the parietal lobe (this is mainly involved in the senses of smell, touch, and taste). One sub-system under the sensory system is the visual system; the main sense organs of this are the eyes. The eye is the sensory organ that allows us to detect light from external stimuli. When a light ray is detected, the eye converts these rays into electrical signals that can be sent to the brain in order to process the information and give a clear image to the human. The main receptors in the eye’s retina (photoreceptors) are rods and cones. Rods are in charge of providing scotopic vision, being able to indicate vision with dim light; however, they are unable to detect color. Cones are responsible for providing color sensitivity to the eye and photopic vision, which is indicating vision in bright light. Cones are divided into three categories of red (lowest sensitivity), green (medium sensitivity), and blue (highest sensitivity). In the retina, there are about 120 million rods and 6-7 million cones. There are many parts of the eye that include the cornea, iris, pupil, lens, sclera, retina, etc. A light ray begins to enter the eye through the cornea; next, when the ray reaches the pupil, the pupil is contracted or dilated by the iris depending of brightness or intensity of the light; then, the light enters the lens so that it can assist in focusing the light on the retina; fourth, the light passes through the vitreous humor and is finally gets to the retina; next, the retina then processes the information to be sent through the optic nerve to the visual cortex of the brain; last, the brain processes the information and enables a human to see a clear image. The somatosensory system is a part of the sensory system involved in the sense of skin sensations; therefore, making the sensory organ the skin. The somatosensory system informs the body about external stimuli, as well as monitoring components of the internal body. From the body, the skin monitors its internal temperature in order to maintain homeostasis. For external stimuli, when one stimulus is present for touch, the somatosensory receptors (usually the nerve endings, which are usually nocioceptors), which are in the skin as well as the hair follicles that detect this stimuli and send these signals to the brain and back to the sense organ in order to react to the stimuli. The main four kinds of information that skin is responsible for sending to the brain when referring to the environment is pain, warmth, coldness, and pressure. The somatosensory system’s