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Chapter Summary:
This chapter covered the sensory organs.The sensory organs include the nose, eyes, ears, mouth, and the sensory receptors that our bodies are covered with. Our sensory organs are vital to our survival as human beings. Without them, we would not be able to detect pain, smell a fire, see a dangerous situation or appreciate the beauty in life. They help us to know where we are, what is going on around us and to determine our body position. They can warn us of danger, like getting out hand to close to a hot stove, or can envoke emotional feelings like love when a tender touch from a significant other is felt. The sensory organs play a vital role in determining our bodies' next course of action based on present stimulus.

Lasagna, Grandma's apple pie, lemonade, vinegar, pretzels. When you read these words, your sense of taste is evoked. Savory, sweet, sour, bitter, and salty. The sensation of taste is called gustation. Our tongues are covered with taste buds that detect chemical messages that are in the foods we eat and beverages we drink. Each taste bud consists of microvilli which increase the surface area of the taste bud that is exposed to the chemicals. The taste buds all have cells that are sensitive to each of the types of taste senses. There is no longer a belief that the area of the tongue is separated into different portions for different taste senses. each type of taste sense has special devoted sensory nerves that detect that type of taste and carry the message to the brain. Each taste is due to chemical presence in the substance that carries that taste. For example, foods that taste salty taste that way because of the sodium ions that are present in that substance. Things that taste sour taste that way because of Hydrogen ions present in the substance. Bitter is an interesting taste in that it is usually associated with something toxic. Our senses believe bitter to be a bad thing and it is not a taste that evokes good feelings in our brains. The savory taste is a newly discovered taste sensation. When we think of savory, meat usually comes to mind and that is exactly what this sense is for. This sense is also activated by the chemical monosodium glutamate, otherwise known as MSG.

Middle Ear:
The section of the ear that contains the 3 smallest bones in the human body is called the middle ear. The middle ear is located between the external auditory meatus and the cochlea on the inside. The malleus, incus and stapes are called the middle-ear ossicles. The vibration of these three tiny bones is set into motion by the tympanic membrane, which is also known as the ear drum. When the ear drum vibrates, it in turn vibrates the malleus, which then vibrates the incus whhich then vibrates the stapes. When the stapes vibrates, it transfers this vibration to the oval window which it is attached to. Vibrations are then transferred to the inner ear where they are processed further and recognized as sound.
The middle ear also acts as a protection mechanism again sounds that are too loud. If a sound comes into the ear that is vibrating too aggressively (too loud) the stapedius muscle will contract and dampen the movement of the stapies. When the movement of the stapies is dampened, less vibrations are sent to the cochlea and the sound is then interpreted as not being as loud as it actually is.

When a person has an astigmatism, objects that are both close and far away are distorted. This is caused because the curvature of the cornea and the curvature of the lens do not match up symmetrically. Because of this asymmetry, light is refracted at different angles at different parts of the eye. The blurriness is caused by the inability of the retina to clearly focus the light rays. Astigmatism is usually present with nearsightedness or farsightedness. I chose to talk about this condition, because I have an astigmatism present in both of my eyes. No matter how close or far away objects are when I am without my glasses, they are distorted. In order for a person to be diagnosed with astigmatism, the asymmetry must be significant. For correction of this condition, glasses or special contact lenses are worn. Astigmatism is also very common.

Application to Nursing:
Sensory organs play a huge role in the field of nursing. Nurses use their sensory organs all day, every day. They are the essential tools for doing their jobs properly. Nurses must be able to see, hear and smell problems that arise during their shift. The sensory organs are also the tools that nurses use to assess their patients. Information sent to the brain from the sensory organs dictates the decisions that the nurse will make. If a nurse were to lose her sight, her days as a nurse would be over. If a nurse were to lose her hearing, she would lose her ability to receive communicated information from her patients. If a nurse were to lose her sense of smell or taste, she could still function in her job but would be slightly limited, especially with a loss of sense of smell. There are some conditions that the first indicator of their presence can be a foul odor. For example, a GI bleed has a very characteristic smell and would signal the need for further testing of the patient's stool. A loss of the sense of taste would not inhibit the nurse in her job function.

Essential Question:

When light enters into our eyes, the cornea and lens focus the light onto the photoreceptors on the retina in the back of our eyes. The photo receptors consist of rods and cones. The rods detect black and white and the cones detect colors. The eyes and the eye muscles will change position to maintain the focus on the object when the distance between the eye and the object changes. The thickness and curvature of the lens will also change with a change in distance. This helps to maintain the focus on the object. The eyes convert the energy from the visible light spectrum and change this energy into nerve impulses that are transmitted to the brain via the optic nerve. The optic nerve transfers these impulses These nerve impulses are the converted to colors on the visible light spectrum.