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Chapter 11

Sense Organs Chapter 11

Five major sense organs Sight Hearing Taste Smell Touch
2 Pain senses Fast Pain fibers Slow Pain Fibers
Fast pain fibers Abundant in the skin and mucous membranes, these fibers produce a sharp, localized, stabbing-type pain at the time of injury. This is the type of pain you experience when you stub your toe or slam your finger in a door.
Slow pain fibers These fibers are congregated on deep body organs and structures and produce a dull, aching pain. For example, pain sensations from a bowel obstruction or appendicitis would be carried along these fibers.
Referred pain Pain originating in a deep organ may be sensed as if its originating from the body's surface- sometimes at a totally different part of the body. This occurs because sensory fibers from an organ and those from an area of skin coverge in a single pathway.
Analgesic Drugs used to relieve pain
Gustation The sense of taste, results when chemicals come in contact with taste buds. Most taste buds are located around protrusions on the tongue.
Glossal Papillae Another name for Taste buds.
Vallate Papillae Large papillae found at the rear of the tongue, although few in number, they contain up to half of all taste buds.
Foliate Papillae Form ridges at the sides of the tongue
Filiform Papillae Are thread-like papillae that contain no taste buds; they play a role in helping us distinguish the texture of food.
Fungiform Papillae Are especially concentrated at the tip and sides of the tongue.
General Senses Are spread throughout the body
Special Senses Are localized by their respective sensory organ
How are gustatory impulses sent to the brain a hair-like tip projects into an opening called the taste pore, which is bathed in saliva. Chemicals dissolved in saliva stimulate the gustatory cells, which in turn stimulate certain cranial nerves.
Smell Olfactory
Ears Provide the sense of hearing, they're also essential for balance (equilibrium)
The ear has three sections. Outer ear, Middle ear, Inner Ear
Outer Ear Consists of auricle (pinna) and the auditory canal. The visible part of the ear.
Auditory canal leads through the temporal bone to the eardrum.
Middle Ear Consists of 3 structures
Auditory Ossicles The three smallest bones in the body connect to the ear drum to the inner ear; they are named for their shape. Malleus (hammer) Incus (anvil) Stapes (stirrup)
Middle Ear infections Called Otitis Media commonly occur in children.
Inner Ear Complicated system of passageways within the temporal bone contains the inner ear, which explains why this part of the ear is called Bony Labyrinth.
3 separate structures form the Bony Labyrinth Semicircular canals, Vestibule, Cochlea.
Semicircular Canals: These structures are crucial for the maintenance of equilibrium and balance.
Vestibule: This structure, which marks the entrance to the labyrinths contains organs necessary for the sense of balance.
Cochlea: This snail-like structure contains the structure for hearing
How does hearing occur Sound waves enter the ear & travel down the external auditory canal. Vibration spreads through the malleus & incus and stapes. Movement of stapes against oval window shakes perilymph. Movement stimulates hairs of the corti sends nerves to cochlear nerve.
Hearing loss is divided into 2 main categories Conductive hearing loss- fluid in the middle ear (being sick) will return to normal. Sometimes needs surgery to restore hearing.
Sensorineural nerve hearing loss This type of hearing loss most often results from the death of hair cells in the organ corti, usually caused by loud noise. usually a permanent hearing loss
Balance The vestibule and semicircular canals of the inner ear play a rold in the process of --
Inside the vestibule are 2 sense organs Utricle and saccule- A patch of hair cells lies inside both these organs. The tips of the hair cells are covered by a gelatin-like material. Embedded throughout the gelatin material are heavy mineral crystals called otoliths.
Vision Most complex of the senses.
Eyebrows Perhaps the most significant role is to enhance facial expressions, aiding nonverbal communication. Also shields eye from sweat and from eye glare.
Eyelids (palpebrae) Formed primarily by the orbicularis oculi muscle covered with skin, the upper and lower-- protect the eye from foreign bodies and block light
Palpebral Fissure Opening between the lids.
Eyelashes These hairs along the edge of the eyelids help keep debris out of the eye.
Conjunctiva Transparent mucous membrane that lines the inner surface of the eyelid.
Tarsal Glands Lie along the thickened area at the edge of the eye, secrete oil to slow the evaporation of tears and help form a barrier seal when the eyes are closed.
Lacrimal Gland Small gland secretes tears that flow onto the surface of the conjunctiva.
Nasolacrimal duct Passageway carries tears into the nasal cavity. which explains why crying causes a runny nose.
Ophthalmology Study of the eye and treatment of its disease.
3 layers of eye tissue A Fibrous outer layer A Vascular middle layer A neural inner layer
Fibrous outer layer contains Scleara and Cornea
Vascular Middle Layer Choroid, Ciliary body, and Iris
Neural Inner Layer Retina, Optic nerve, and blood vessels
Sclera Formed from dense connective tissue- the outermost layer of the eye. "White of the eye"
Cornea Transparent extension of the sclera in the anterior part of the eye. It sits over the iris. (color portion of the eye)
Iris Ring of colored muscle: it works to adjust the diameter of the pupil. (central opening of the iris)
Ciliary Body Thickened extension f the choroid that forms a collar around the lense.
Choroid Highly vascular layer of tissue that supplies oxygen and nutrients to the retina and sclera.
Retina Thin layer of light- sensitive cells.
Optic Nerve Exiting from the posterior portion of the eyeball is the -- which transmits signals to the brain.
Whats inside the retina Photoreceptors- called rods and cones. that are stimulated by light rays to produce an electrical or chemical signal.
The space between the lens and the cornea Anterior cavity
Clear watery fluid that fills the anterior cavity Aquenous Humor
Lens A transparent disc of tissue just behind the pupil, between the anterior and posterior cavities. Changes shape for near and far vision.
Posterior Cavity Larger cavity lying posterior to the lens and anterior cavity. It is filled with a jelly-like substance. Keeps the eyes from collapsing.
Jelly-like substance found in the posterior cavity Vitreous Humor
Ciliary Body Secretes aqueous humor that fills the anterior cavity. The fluid flow from the posterior chamber, through the pupil, and into the anterior cavity. It then drains into a blood vessel called the Canal of Schlemm.
Pupil The center of the cornea
Pupillary Contrictor Muscle encircles the pupil. When stimulated by the parasympathetic nervous system, the muscle constricts, narrowing the pupil to admit less light.
Pupillary Dilator Looks like the spokes of a wheel. When stimulated by the sympathetic nervous system, this muscle contracts, pulling the inside edge of the iris outward. This widens the pupil and admits more light.
Photopupillary Reflex When pupils constrict automatically when exposed to bright light.
Rods Located at the periphery of the retina, are active in dim light, are responsible for night vision, cannot distinguish colors from each other
Cones Are concentrated in the center of the retina, are active in bright light, are primarily responsible for sharp vision, are responsible for color vision.
Glaucoma Narrowed field of vision and colored halos around artificial lights. Can be treated with drugs or surgery any resulting vision loss is permanent.
Cataracts Common cause of visual disturbances, especially among the elderly. Clouding of the lens, making vision cloudy or blurry. Part of age, other risk factors include diabetes mellitus, smoking, and prolonged exposure to light. Surgery is possible.
Color Blindness Person sees colors but has difficulty distinguishing certain colors. Most common colors are red-green color deficit.
Common Visual defects Emmetropia Myopia Hyperopia Astigmatism Presbyopia
Emmetropia When light rays focus on the retina without the need of corrective lens, normal vision results.
Myopia (nearsightedness) When light rays focus in front of the retina instead of directly on it, distant objects appear blurry while those up close are clear.
Hyperopia (farsightedness) When light rays focus at a point behind the retina, objects up close appear blurry,
Astigmatism Results when an uneven or asymmetrical curvature of the cornea, causing light to be focused unevenly.
Presbyopia With age, the lens loses flexibility- interfering with its ability to change shape and the focusing muscles in the eye weaken usually begins between ages 40 and 50.
Cerumen Earwax
Ceruminous Glands Glands in the auditory canal that produce cerumen (earwax)
Equilibrium Sense of hearing and Balance
Inner ear functions Maintain balance
Key role in balance are Vestibule and Semicircular canals
Inner ear is sometimes referred to simply as Labyrinth
Created by: kayley911



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