© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 36 The Sensory System

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Eye There are three layers: retina, sclera, and iris Made up of several parts that work together to allow vision to occur Vision receptors- allow the lens to focus on light sensitive cells and allow for day and night vision in animals

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The Eye Retina – inner layer of eye with two types of cells that aid in seeing color and determining depth Rod - cells that allow the eye to detect light and depth; makes up 95% of cells within the eye Cones – cells that allow an animal to see certain colors

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. The Eye Posterior chamber – behind the retina; holds the nerves, blood vessels, and optic vessels Iris – middle layer of eye; gives the eye color and holds pupil in center Anterior chamber – in front of the iris; holds the vitreous humor Sclera – the outer white layer of eye Cornea – clear layer

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Taking Ocular Pressure

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Flurosein Stain- checks for ulcers or scratches to cornea

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Reflex Testing Menance Response Test – reflex test of the eye –hand is moved quickly toward the eye without touching the eye or any hair around the eye –normal response: blink or close eye –abnormal response: shows no change in the eye and does not elicit a blink response

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Reflex Testing Pupillary Light Response Test –light source is shown into eyes to note constriction or shrinking of the pupil –both pupils should act in same manner –dilating or expanding when light source is removed from eye

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Reflex Testing Nystagmus –a condition where the eyes jump back and forth in rhythmic jerks due to damage in the inner ear, brain stem, or cranial nerves –causes symptoms such as motion sickness, vomiting, and incoordination

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Ear An organ that enables hearing and helps maintain balance Divided into the outer, inner, and middle portions Pinna – the external portion of the ear that catches sound waves and transmits them to the external auditory canal

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Ear External auditory canal – tube that transmits sound to the internal auditory canal Middle ear – consists of the tympanic membrane, the auditory ossicles, eustachian tube, oval window, round window, and tympanic bulla

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Ear Tympanic membrane – tissue that separates the outer and inner ear structures Auditory ossicles – three bones of the inner ear (malleus, stapes, and incus) Eustachian tube – narrow duct that leads from the ossicles to the nasopharynx and serves to maintain air pressure in middle ear

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Ear Oval window – membrane that separates the middle and inner ear Round window – membrane that receives sound waves Tympanic bulla – an osseous chamber at the base of the skull Inner ear – consists of the vestibule, semicircular canals, and the cochlea

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Ear Vestibule – contains receptors for balance and position Semicircular canals – contain sensory cells that detect changes in position Cochlea – spiral-shaped passage that vibrates and relays vibrations to allow sound to be heard

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Hearing Sound waves enter through the pinna, travel through the auditory canal, and strike the tympanic membrane Tympanic membrane moves the ossicles Ossicles conduct sound waves Sound vibrations reach inner ear Inner ear cells initiate nerve impulse which is relayed to the brain

© 2011 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Equilibrium A state of balance Static equilibrium – controlled by the organs of inner ear Dynamic equilibrium – controlled by the semicircular canals These structures maintain balance in response to rotational or angular movement of the head