© 2009 The McGraw-Hill Companies, Inc. All rights reserved Special Senses Chapter 12

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Introduction  Special senses  Sensory receptors located in head Nose – smell Tongue – taste Eyes – vision Ears – hearing and equilibrium  Touch is a generalized sense

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved How do senses work?  Receptors collect information  Stimulate neurons  Information is sent to the brain  The cerebral cortex integrates the information with that from other senses  Forms a perception (a person’s particular view of the stimulus)

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Receptor Structure  Receptors are structured in two basic ways:  Nerve endings  Cells which are associated with nerve endings  When these are stimulated, they produce graded potentials. If they hit threshold, nerve fires.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear and the Senses of Hearing and Equilibrium: Structures External Ear  Auricle (pinna) Collects sound waves  External auditory canal Guides sound wave to tympanic membrane Ear

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear and the Senses of Hearing and Equilibrium: Structures (cont.)  Tympanic membrane Concave shaped membrane Separates external canal and middle ear Vibrates when sound hits it  Ear ossicles Malleus, Incus, Stapes  Ossicles vibrate in response to vibration of tympanic membrane  Tympanic Cavity Surrounds ossicles  Eustachian tube Connects middle ear to throat Equalizes pressure on eardrum  Oval window Separates middle ear from inner ear The Middle Ear Ear

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Middle Ear Diagram

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear and the Senses of Hearing and Equilibrium: Structures (cont.) Inner Ear Labyrinth of communicating chambers  Semicircular canals (3): detect balance of the body  Vestibule : central part of labyrinth; equilibrium  Cochlea : coiled canal ofdense bone tissue of the skull; shaped like a snail;  Filled with two fluids ( endolymph and perilymph ).  The Organ of Corti is the sensory receptor inside the cochlea which holds the hair cells, the nerve receptors for hearing. Ear

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved Ear Wax  Cerumen; naturally produced by your body  Produced in sebaceous and modified apocrine glands of the ear  Coats the ear canal to moisturize it, fight off infection, keep dust, dirt, and other debris from getting inside ear  20 to 50 percent fat

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear and the Senses of Hearing and Equilibrium: Hearing Process  Sound waves collected through external ear canal  Waves cause tympanic membrane to vibrate  Ossicles amplify vibrations  The mechanical energy from movement of the middle ear bones pushes in a membrane ( the oval window ) in the cochlea.  This force moves the cochlea's fluids that, in turn, stimulate tiny hair cells.  Movement of hairs lining cochlea are converted into nerve impulses  Impulses are transmitted by auditory nerve to the brain for interpretation 35-13

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear and the Senses of Hearing and Equilibrium: Hearing Process (cont.)  Bone conduction  Alternative pathway  Bypasses external and middle ear directly to inner  Useful in determining cause of hearing problem 35-14

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Equilibrium Position of Body/Movement  Above the cochlea are two interconnecting chambers filled with endolymph, the sacculus and utriculus.  On their inner surface are patches of hair cells to which are attached thousands of tiny spheres of calcium carbonate (CaCO 3 ).  Gravity pulls these downward. As the head is oriented in different directions, these ear stones ( otoliths ) shift their position. Impulses initiated in the hair cells are sent back to the brain.  Motion of the body is detected in the semicircular canals  Whenever the head is moved, the fluid within the canals lags; this stimulates the hair cells to send impulses back to the brain.  When the hair cells send messages that are incongruent with what the eyes are seeing and our body is feeling, as may occur in a boat or aircraft during rough weather, motion sickness can result.  Some people also suffer severe dizziness because otoliths have become dislodged from their utriculus (following a blow to the head) and settled in a semicircular canal

© 2009 The McGraw-Hill Companies, Inc. All rights reserved How to Recognize Hearing Problems in Children  Guidelines  Infants to 4 months Startled by loud noises Recognize mother’s voice  4 to 8 months Regularly follow sounds Babble at people  8 to 12 months Respond to the sound their name Respond to “no” 35-16

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Aging Ear  External ear larger / earlobe longer  Cerumen dryer and prone to impaction  Ear canal narrower  Eardrum shrinks and appears dull and gray  Ossicles do not move as freely  Semicircular canals less sensitive to changes in position – affects balance

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Hearing Loss  Interruption in transmission to inner ear  Causes  Obstruction of ear canal  Infection of middle ear  Reduced movement of stirrup  Sound waves not perceived by brain as sound  Causes  Hereditary  Repeated exposure to loud noises / viral infections  Side effect of medication Conductive hearing loss Sensorineural hearing loss Symptom of a disease, not a normal part of aging

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Hearing and Diagnostic Tests  Hearing tests  Tuning forks – differentiate between types of loss  Audiometer – measures hearing acuity  Diagnostic testing  Tympanometry Measures the ability of the eardrums to move Detects diseases and abnormalities of the middle ear

© 2009 The McGraw-Hill Companies, Inc. All rights reserved “Cauliflower Ear”  Cauliflower ear is medically known as an auricular hematoma.  The external ear is made of cartilage and it is the shape of the cartilage that gives the ear its distinctive shell-like shape. The cartilage is lined by perichondrium, a tight layer of connective tissue.  Auricular hematoma occurs when the ear cartilage is injured  Trauma results in fluid or blood collecting between the perichondrium and the cartilage. This blood or fluid can become permanent and scarred, resulting in the appearance of cauliflower ear.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Olfaction – Sense of Smell  Olfactory epithelium in roof of nasal cavity  Pseudostratified columnar epithelium  Has millions of bipolar neurons = olfactory receptor cells Only neurons undergoing replacement throughout adult life  Olfactory cilia bind odor molecules  Mucus captures & dissolves odor molecules  Each receptor cell has an axon – the cells are bundled into “filaments” of olfactory nerve  Penetrate plate of ethmoid bone & enter olfactory bulb

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved Olfaction  Olfactory receptors  Chemoreceptors – respond to changes in chemical concentrations Chemicals must be dissolved in mucus 35-23

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Day 2 - Taste Chapter 12 – Special Senses

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Olfaction Smell sensation that send the information along olfactory bulbs and tracts to different areas of the cerebrum; cerebrum interprets the information as a particular type of smell Activation of smell receptors  information sent to olfactory nerves

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Nose and Sense of Smell (cont.)  Sensory Adaptation  Chemical(s) can stimulate receptors for limited amounts of time  Chemoreceptors fatigue and stop responding to chemical  Result = no longer smell odor 35-26

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Tongue…  The tongue is a muscular organ in the mouth.  Covered with moist, pink tissue called mucosa.  Tiny bumps called papillae give the tongue its rough texture.  Thousands of taste buds (receptor cells) cover the surfaces of the papillae. Taste buds are collections of nerve-like cells that connect to nerves running into the brain.  The tongue is anchored to the mouth by webs of tough tissue and mucosa.  The tether holding down the front of the tongue is called the frenum.  In the back of the mouth, the tongue is anchored into the hyoid bone.  The tongue is vital for chewing and swallowing food, as well as for speech.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Tongue and Sense of Taste  Taste buds: detect chemicals dissolved in saliva from food in the mouth and throat ( chemoreceptors )  Taste buds send their sensory information through neurons to the gustatory center of the brain.  The average person has around 10,000 taste buds in their mouth and throat, although the number of taste buds peaks in early childhood and declines throughout our lives.  Location  Papillae of the tongue  Roof of mouth  Walls of throat Tongue } fewer than on tongue

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Papillae Types  Foliate papillae: these are ridges and grooves towards the posterior part of the tongue found at the lateral borders.  Fungiform papillae: small, on entire surface of tongue  Vallate papillae : inverted “V” near back of tongue  Filiform papillae : these are thin, long papillae "V“ shaped cones that don't contain taste buds but are the most numerous. These papillae are mechanical and not involved in gustation 35-29

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Taste Buds

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved Tongue and Sense of Taste (cont.)  Taste sensation  4 primary Sweet Sour Salty Bitter  Umami  5 th basic taste  Glutamic acid  Spicy foods  Activate pain receptors  Interpreted by brain as “spicy” Tongue

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Tongue and Sense of Taste (cont.) Taste sensation Activation of taste cells Cranial nerves Gustatory cortex of cerebrum interprets information