PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART B 8 Special Senses The Ear, Taste and Smell

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Ear  Houses two senses  Hearing  Equilibrium (balance)  Receptors are mechanoreceptors  Different organs house receptors for each sense

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear  The ear is divided into three areas  External (outer) ear  Middle ear (tympanic cavity)  Inner ear (bony labyrinth)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The External Ear  Involved in hearing only  Structures of the external ear  Auricle (pinna)  External acoustic meatus (auditory canal)  Narrow chamber in the temporal bone  Lined with skin and ceruminous (wax) glands  Ends at the tympanic membrane

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity)  Air-filled cavity within the temporal bone  Only involved in the sense of hearing

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity)  Two tubes are associated with the inner ear  The opening from the auditory canal is covered by the tympanic membrane  The auditory tube connecting the middle ear with the throat  Allows for equalizing pressure during yawning or swallowing  This tube is otherwise collapsed

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Bones of the Middle Ear (Tympanic Cavity)  Three bones (ossicles) span the cavity  Malleus (hammer)  Incus (anvil)  Stapes (stirrip)  Function  Vibrations from eardrum move the hammer (malleus)  anvil (incus)  stirrup (stapes)  inner ear

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Inner Ear or Bony Labyrinth  Includes sense organs for hearing and balance  Filled with perilymph  A maze of bony chambers within the temporal bone  Cochlea  Vestibule  Semicircular canals

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Equilibrium  Equilibrium receptors of the inner ear are called the vestibular apparatus  Vestibular apparatus has two functional parts  Static equilibrium (monitoring)  Dynamic equilibrium

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Equilibrium

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Static Equilibrium  Maculae—receptors in the vestibule  Report on the position of the head  Send information via the vestibular nerve (VIII) to the cerebellum  Helps to keep our head erect  Anatomy of the maculae  Hair cells are embedded in the otolithic membrane  Otoliths (tiny stones) float in a gel around the hair cells  Movements cause otoliths to bend the hair cells

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of the Maculae

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of Maculae

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Dynamic Equilibrium  Responds to angular or rotatory movements of the head  Twirling around, etc.  Crista ampullaris—receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers the hair cells  Action of angular head movements  The cupula stimulates the hair cells  An impulse is sent via the vestibular nerve to the cerebellum  Message is sent to appropriate skeletal muscles to maintain balance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Hearing  Organ of Corti  Located within the cochlea  Receptors = hair cells on the basilar membrane  Gel-like tectorial membrane is capable of bending hair cells  Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings How We Hear Sound  1) Vibrating waves of air enter the outer ear (pinna) and strike the eardrum (tympanic membrane).  2) The eardrum transmits vibrations to 3 ossicles (hammer, anvil & stirrup).  3)The ossicles pass the vibrations to the cochlea (primary organ of hearing) in the inner ear.  4) The cochlea passes the vibrations along the basilar membrane (inside cochlea)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings How We Hear Sound  5) The swaying of tiny hairs on the basilar membrane stimulates sensory nerve endings and the excited neurons transform the mechanical vibrations into neural activity (action potential).  6) Now the neural message leaves the cochlea in a bundle of neurons called the cochlear nerve (VIII-vestibulocochlear).  7) The neurons from the two ears meet in the brainstem.  8) The brainstem passes the auditory information to the auditory cortex (temporal lobe) of the brain for interpretation of sound or hearing occurs.

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Hearing

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of Hearing

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Olfaction—The Sense of Smell  Olfactory receptors are in the roof of the nasal cavity  Neurons with long cilia  Chemicals must be dissolved in mucus for detection  Impulses are transmitted via the olfactory nerve  Interpretation of smells is made in the cortex

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Olfactory Epithelium

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sense of Taste  Taste buds house the receptor organs  Location of taste buds  Most are on the tongue  Soft palate  Cheeks

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Tongue and Taste  The tongue is covered with projections called papillae  Filiform papillae—sharp with no taste buds  Fungifiorm papillae—rounded with taste buds  Circumvallate papillae—large papillae with taste buds  Taste buds are found on the sides of papillae  The Structure of Tastebuds  Gustatory cells are the receptors  Have gustatory hairs (long microvilli)  Hairs are stimulated by chemicals dissolved in saliva

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Tongue and Taste  Impulses are carried to the gustatory complex by several cranial nerves because taste buds are found in different areas  Facial nerve  Glossopharyngeal nerve  Vagus nerve

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Taste Sensations  Sweet receptors(sugars)  Saccharine  Some amino acids  Sour receptors  Acids  Bitter receptors  Alkaloids  Salty receptors  Metal ions  Umami (delicious)  Steak, soy sauce

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Senses: Taste and Smell  Both senses use chemoreceptors  Stimulated by chemicals in solution  Taste has four types of receptors  Smell can differentiate a large range of chemicals  Both senses complement each other and respond to many of the same stimuli

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Special Senses  Formed early in embryonic development  Eyes are outgrowths of the brain  All special senses are functional at birth  Eye problems  Strabismus—“crossed eyes” results from unequal pulls by the external eye muscles in babies  Ophthalmia neonatorum—conjunctivitis resulting from mother having gonorrhea. Baby’s eyelids are swollen and pus is produced

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of Special Senses  Eye problems  Presbyopia—“old vision” results from decreasing lens elasticity that accompanies aging  Ear problems  Presbycusis—type of sensorineural deafness  Otosclerosis—ear ossicles fuse

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Hearing Loss  Conduction Hearing Loss  hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea  Conduction of the vibration has been affected.  Punctured eardrum, ossicles lose their ability to vibrate (middle ear infection), wax buildup, fluid accumulation  Hearing aids can possibly help  Sensorineural Hearing Loss  Aka nerve deafness  hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve  Most people who are born deaf have this type.  Causes: heredity, prolonged exposure to loud music, aging