Senses+NLL

Sensory receptors are dendrites specialized to detect certain types of stimuli. Sensory receptors are the structure that receives either external or internal environmental stimuli and is a part of a sensory neuron or transmits signals to a sensory neuron. The sensory receptors are organized as chemoreceptor’s, photoreceptors, mechanoreceptors, and thermoreceptors. Exteroceptors are sensory receptors that detect stimuli from outside the body, such as those that result in taste, smell, vision, hearing, and equilibrium. Excteroceptors such as those in the eyes and ears are not directly involved in homeostasis and continually send messages to the central nervous system regarding environmental conditions. Interceptors receive stimuli from inside the body. For example, among interoceptors, pressoreceptors respond to blood pressure, osmoreceptors detect changes in blood volume, and chemoreceptors monitor the pH of the blood. Interoceptors are directly involved in homeostasis and are regulated by a negative feedback mechanism. For example, when blood pressure rises, pressoceptors signal a regulatory center in the brain, which sends out nerve impulses to the arterial walls, causing them to relax; the blood pressure then falls. Therefore, the pressoreceptors are no longer stimulated, and the system shuts down. Thermoreceptors are sensory receptors that are the first element in a relax arc. We are only aware of a reflex action when sensory information reaches the brain. At that time, the brain integrates this information with other information received from other sensory receptors. After all if you burn yourself and quickly remove your hand from a hot stove, the brain receives information not only from your skin, but also from your eyes, nose, and all sorts of sensory receptors. The functioning of our sensory receptors makes a significant contribution to homeostasis. Without sensory input, we would not receive information about our internal and external environment. This information leads to appropriate reflex and voluntary actions to keep the internal environment constant. Sensation occurs when nerve impulses reach the cerebral cortex of the brain.
 * Define sensory receptors. 274**
 * Give examples of exteroceptors. 274**
 * Give examples of interoceptors. 274**
 * Which type of receptors only detects information and send information to the brain but do not regulate the body's homeostasis. 274**


 * __Describe (in detail) and give examples of each of the following receptor types...(274)__**


 * Chemoreceptors**-Chemoreceptors respond to chemical substances in the immediate vicinity. Taste and smell depend on this type of sensory receptor, but certain chemoreceptors in various other organs are sensitive to internal conditions. Chemoreceptor’s that monitor blood pH are located in the carotid arteries and aorta. If the pH lowers, the breathing rate increases. As more carbon dioxide is expired, the blood pH rises.
 * Pain receptors**- Pain receptors are a type of chemoreceptor. They are naked dendrites that respond to chemicals released by damaged tissues. Pain receptors are protective because they alert us to possible danger. For example, without pain of appendicitis, we might never seek the medical help needed to avoid a ruptured appendix.
 * Photoreceptors**- Photoreceptors respond to light energy. Our eyes contain photoreceptors that are sensitive to light rays and thereby provide us with a sense of vision. Stimulation of the photoreceptors known as rod cells results in black-and-white vision, while stimulation of the photoreceptors known as cone cells results in color vision.
 * Mechanoreceptors**- Mechanoreceptors are stimulated by mechanical forces, which most often result in pressure of some sort. When we hear, airborne sound waves are converted to fluid-borne pressure waves that can be detected by mechanoreceptors in the inner ear. Similarly, mechanoreceptors are responding fluid-borne pressure waves when we detect changes in gravity and motion, helping us keep our balance. These receptors are in the vestibule and semicircular canals of the inner ear, respectively. The sense of touch depends on pressure receptors that are sensitive to either strong or slight pressures. Pressoreceptors located in certain arteries detect changes in blood pressure, and stretch receptors in the lungs detect the degree of lung inflation. Proprioceptors, which respond to the stretching of muscle fibers, tendons, joints, and ligaments, make us aware the position of our limbs.
 * Thermoreceptors**- Thermoreceptors located in the hypothalamus and skins are stimulated by changes in temperature. Those that respond when temperatures rise are called warmth receptors, and those that respond when temperatures lower are called cold receptors.

//**Smell**// Approximately 80-90% of what we perceive as “taste” actually is due to sense of smell, which accounts for how dull food taste when we have head cold or a stuffed-up nose. Our sense of smell depends on olfactory cells located within olfactory epithelium high in roof of the nasal cavity. Olfactory cells are modified neurons. Each cell ends in a tuft of about five olfactory cilia, which bear receptor proteins for odor molecules. Each olfactory cells has only one out of 1, 000 different types of receptor proteins. Nerve fibers from like olfactory bulb, an extension of the brain.
 * Explain in a five-point paragraph the sense of taste (278), smell (278) or vision (280).**