Sensory Receptors and the Senses
1. Sensory Receptors: What are they and how do they work?
Sensory receptors are responsible for capturing information from the environment and relaying it to the nervous system. They can be nerve endings or specialized cells, usually grouped together to form sensory organs. Sensory receptors are activated by changes in their surrounding environment. For a stimulus to excite a receptor, it must have a minimum intensity, called the intensity threshold, below which no action occurs. Once the stimulus is grasped, the sensory cells convert it into a nerve impulse, which is then transmitted to a higher nerve center where it creates what we call sensation. The nerve centers that receive information from the sensory receptors process, regulate, integrate, and develop an appropriate response to the effector organs. The response can be of two types: secretory, if conducted by the endocrine system, or motor, if produced by the locomotor system.
2. Types of Sensory Receptors
Sensory receptors capture information from outside or inside the body. We can distinguish:
-Photoreceptors. They detect light stimuli and are located in ojos.-Mechanoreceptors. Are stimulated by mechanical changes, such as pressure, contacts or waves sonoras.-Chemoreceptors. Capture information of chemical changes. The receptors of taste and smell are of this Grupo.-thermoreceptors. Are stimulated by temperature changes, as some receptors in the skin. 3-Explains the role of the eyeball, retina, choroid and lens
-Eyeball: it is a hollow spherical structure, housed in a cavity in the skull called the orbit.
-Retina: innermost layer of the eyeball. It contains the photoreceptor cells, which may be of two types: rods and cones. The rods are excited by any kind of visible light, but not different colors. The cones are able to distinguish colors, but need a light intensity mayor.-Choroid: second layer of the eyeball. It is black, but the rainbow has a different color for each person. In the center of the iris there is a hole, pupila.-Crystalline and transparent elastic body shaped convex lens. The lens separates two chambers: the former is occupied by a fluid (aqueous humor) and further contains a substance more viscous, also clear (vitreous humor). 4-The accessory structures. He explains his role
-Eyebrows: Deflect the brow to protect the ojo.-Lids: protect the eyeball. In its innermost part are lined by the conjunctiva, a layer which also covers the front of globo.-tabs: hairs located on the edge of the eyelids screened making it more diffuse light.-Eye muscles: move the eyeball upward, downward or lateralmente.-lachrymal glands: secrete tears kept wet the front of the eyeball to prevent drying. 5-eye operation
The role of the eyeball is to allow light to excite the rods and cones of the retina, which produce a nerve impulse that is transmitted to the brain by the optic nerves. Before reaching the retina, the light passes through the eyeball, then comes two processes:
“Regulating the intensity of light. If this is excessive, it may not cause injury to the photoreceptor cells, and if very poor, the visual process can not be performed. In this regulatory mechanism involving the pupil, which opens more or less depending on the intensity of light due to the contraction or relaxation of some very small muscles located in the iris.
6-The Ear: What is it? Explains the parts and functions
The ears are sensory organs that are housed in cavities of the temporal bones located in the temples. These organs captured in different areas, two different types of stimuli: sounds and changes in body position (balance). In the ear there are three parts: ‘Outer ear: Shaped by the pinna (ear) and ear canal, which enters the bone. In this canal is a protective wax producing glands. The canal ends in an elastic membrane, the tÃmpano.-Middle Ear: It is a cavity in the temporal bone that begins at the eardrum and reaches a small membrane called the oval window and round window. Contains within it three small bones, which are called ossicles, which are the hammer, anvil and stirrup. The hammer is resting on the eardrum and the stirrup, the window-oval. Inner Ear: Part deeper by the membranous labyrinth, a series of membranes that cover a range of complex temporal bone cavities, which form the bony labyrinth. Between them lies a liquid labyrinth, perilymph, and inside the membranous labyrinth is another fluid called endolymph. The membranous labyrinth consists of several parts. One of them, the snail, is responsible for detecting sounds, and another, the vestibular apparatus is responsible for the spatial control and balance. The vestibular apparatus consists, in turn, through three channels or semicircular canals and two vesicles, the utricle and saccule. 7 – How does the audition?
The sound waves are produced by vibrations of air molecules or of any object. When these waves reach the eardrum, it begins to vibrate and transmit the vibrations to the ossicles. The greater the intensity of sound, the greater the vibration. The last ossicle (stapes) transfers the vibration to the oval window in which it rests. This, in turn, causes vibration of the inner ear perilymph and, therefore, there is the excitement of certain cells in the interior of the snail, which constitute the so-called organ of Corti. Is generated, thus, a nerve current that travels through a nerve to the brain where information is interpreted. 8 – How do you detect the balance?
The term balance information encompasses two very different understanding of body position and the detection of the movements realizan. “Knowledge of body position or perception of static equilibrium occurs in the utricle and saccule. Within these structures there are sensory cells, provided with cilia and covered by a gelatinous mass that contains a small mineral particles. By changing head position, these particles give rise to a change in the position of the cilia, and generating a nerve impulse that is driven by a few nerves in the cerebellum, an organ that receives the information equilibrio.-movement detection or perception dynamic equilibrium takes place in the semicircular canals. When we move, they also move the head and ears. The endolymph of the inner ear, however, remains motionless for a moment of inertia. Thus, there is a relative motion between it and certain cells in the interior of the vestibular apparatus. These cells are covered by a gelatinous mass and have a few hairs that bend, which generates a current is transmitted by nerve cerebelo.Algo such is what happens when we stop moving. In this case, the endolymph continues to move by inertia, and the cilia of cells in the vestibular fold and produce nerve impulses.