Chapter 9 The Sensory System
Chapter 9 The Sensory System BIO 1004
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This 4 page Bundle was uploaded by Juliane Notetaker on Sunday February 21, 2016. The Bundle belongs to BIO 1004 at Mississippi State University taught by Jeffery Echols in Spring 2016. Since its upload, it has received 37 views. For similar materials see Anatomy & Physiology in Biology at Mississippi State University.
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Date Created: 02/21/16
Chapter 9 The Sensory System General Receptors o Neurons: found throughout the entire body esp. skin and the internal organs. Some are concentrated in the muscles and joints. o General Receptors detect temperature; detects pressure; detect pain(2 separate types of pain receptors) one found in the skin and other in the internal organs(one in internal organs is more sensitive than those in the skin) There are separate receptors for hot, cold, warm and cool. Detects pain (2 types for pain) One found in skin One found in internal organs o One in internal organs is more sensitive than the one found in the skin Chemoreceptors: Sensitive to chemicals; when chemoreceptors are exposed to a very specific chemical, they generate an electrical response which travels to the brain. The brain interprets what the electrical impulse means; there are 2 senses that use chemoreceptors (sense of taste and smell) o Sense of taste receptors are found in the taste buds; they are far less sensitive than the chemoreceptors in the nose; they are more abundant on the edge of the tongue than in the center; certain areas on the tongue are more sensitive to specific tastes (sweet, salty, sour, bitter) Olfactory Cells: chemoreceptors found in the nasal cavity, extremely sensitive to chemicals, the oldest of the senses, there is no cranial nerve associa ; instead chemoreceptors attach directly to the brain; they attach at the olfactory bulb and the diencephalon in the brain. Chemicals stimulate specific receptors causing them to generate an electrical impulse that travels to the brain, the brain itself determines what you smell; chemoreceptors are located at the very top of the nasal cavity Photoreceptors: sensitive to light; eyes; stimulated by light causing them to product an electrical impulse that travels to the brain, the brain itself interprets the impulse; accessory organs of the eye: eyelids and eyelashes o Extrinsic muscles are the skeletal muscles attached to the eye; allows the eye to move in the socket o Eyelids, eyelashes and eyebrows are for protections; eyebrows block light from entering your eyes o Lacrimal apparatus: 2 parts (lacrimal gland: produces tears; constantly producing fluid, contains antimicrobial chemicals)(lacrimal ducts: a hollow tube that starts in the corner of the eye and drains into the nose) o Eyes are only area free of bacteria. Structure of the Eye: o Retina: inner lining of the eye; contains the photoreceptors; which are rods and cones. (Some are sensitive to low light and movement; others detect color) o Stereoscopic Vision o Optic Nerve: cranial nerve, connects eye to brain o Fovea: indentation in the retina; contains 90% of the photoreceptors responsible for color vision o Choroid Layer: middle layer of tissue surrounding the eye; it absorbs stray light rays o Sclera: outer layer of the eye; The white of the eye. o Cornea is an extension of the sclera; front of the eye; and is clear (so light can pass through) o Pupil: a hole in the eye which allows light to pass through o Iris: the colored muscle of the eye that controls the size of the pupil o Lens: a hardened portion behind the pupil; focuses light on the retina The eye is divided into 2 regions: both are hollow and filled with fluid; o Anterior Cavity: between the lens and the cornea (filled with fluid called aqueous humor: has a consistency of water) o Posterior Cavity: from the lens to the retina; filled with victrious humor; has the consistency of jello; it is clear; maintains the shape of the posterior cavity; commonly has hardened areas which are called floaters Photoreceptors stimulate the eye, generates an electrical impulse which travels to the brain and the brain interprets what you saw Rods are photoreceptors which are sensitive to low light and movement. They are responsible for black and white vision Cones are stimulated by intense light (must be bright). They are responsible for color vision. 90% of cones are found in the Fovea (back of the retina). Color vision sensitivity decreases in lower light. Most mammals have strong black and white vision Fish and amphibians have strong color vision Birds have color vision Reptiles have color vision Mammals are not active in times of intense light Mechanoreceptors: stimulated by pressure, causes them to generate an electrical impulse, impulse travels to the brain, brain determines what the information is involved with sense of touch, they are not evenly distributed throughout the body. They are concentrated in the hands, feet, the face, and groin regions. Involved in sense of hearing. Structures of the Ear: o Outer Ear: Pinna (coneshaped, outer fleshy part of ear, concentrates pressure waves) o Ear Canal: conducts pressure waves to the middle ear o Tympanum: ear drum; it vibrates in the presence of pressure waves o Middle Ear: infections occur here, consists of 3 small bones (malleus, incus, and stapes). They connect the tympanum to the inner ear o Eustachian Tube: hollow tube, connects the middle ear to the throat, drains excess fluid from the middle ear; if fluid accumulates in the middle ear, bacteria may begin to grow, causing an ear infection o Inner Ear: o Cochlea: snailshaped; fluid filled, lined with mechanoreceptors, vibrations from the middle ear transfer to the cochlea where they stimulate the mechanoreceptors o Semicircular Canals: there are 3; partially filled with fluid, they are lined with mechanoreceptors, they are responsible for balance
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