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Special Senses The Senses General senses of touch Special senses Function of the lacrimal apparatus ___________________________________ the eye Empties into the nasal cavity Properties of lacrimal fluid Dilute _____________ solution (tears) Contains antibodies and lysozyme Extrinsic eye muscles _________ muscles attach to the outer surface of the eye Produce eye _____________________ Structure of the Eye The Eye and Vision ______ of all sensory receptors are in the eyes Each eye has over a ___________ nerve fibers Protection for the eye Most of the eye is enclosed in a __________ ________ A cushion of ______ surrounds most of the eye Accessory Structures of the Eye Tarsal glands lubricate the eye Ciliary glands are located between the eyelashes Membrane that lines the eyelids Connects to the surface of the eye Secretes mucus to lubricate the eye Lacrimal apparatus _____________gland—produces lacrimal fluid Lacrimal _____________—drain lacrimal fluid from eyes Lacrimal _____________— provides passage of lacrimal fluid towards nasal cavity ___________________—empties lacrimal fluid into the nasal cavity Layers forming the wall of the eyeball Outside layer Middle layer Inside layer Structure of the Eye: The Fibrous Layer White __________________ tissue layer Seen anteriorly as the “___________________________” ________________________, central anterior portion Allows for ________________ to pass through _____________ itself easily The only human tissue that can be _________________ without fear of rejection Structure of the Eye: Vascular Layer _________________ is a blood-rich nutritive layer in the posterior of the eye _________________ prevents light from scattering Modified anteriorly into two structures _________________ —smooth muscle attached to lens ____________—regulates amount of light entering eye Pigmented layer that gives eye _____________ Pupil—rounded __________________ in the iris Structure of the Eye: Sensory Layer Retina contains two layers Outer __________ layer Inner __________ layer Contains receptor cells (photoreceptors) ________ ________ Signals pass from photoreceptors via a two-neuron chain Bipolar neurons Ganglion cells Signals leave the retina toward the brain through the ______________ nerve ______________ (blind spot) is where the optic nerve leaves the eyeball ______________ see images focused on the optic disc Neurons of the retina and vision Rods Most are found towards the __________ of the retina Allow ______ light vision and _____________ vision All perception is in ___________ tones Cones Allow for ___________ ______________ vision Densest in the ________________ of the retina _______________—area of the retina with only cones ____photoreceptor cells are at the optic disc, or blind spot Cone sensitivity ____________ types of cones Different cones are sensitive to different wavelengths Color _________ is the result of the lack of one cone type Lens ____________ crystal-like structure Held in place by a suspensory ligament attached to the ciliary body Cataracts result when the lens becomes hard and __________ with age Vision becomes _________ and distorted Eventually causes blindness in affected eye Two Segments, or Chambers, of the Eye Anterior (________________) segment Anterior to the lens Contains aqueous humor Posterior (_______________) segment Posterior to the lens Contains vitreous humor Anterior Segment ________________ humor ______________ fluid found between lens and cornea Similar to blood _____________ Helps maintain intraocular _________________ Provides ________________ for the lens and cornea Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm Posterior Segment _________________ humor _______________ substance posterior to the lens Prevents the eye from ________________ Helps maintain intraocular pressure Ophthalmoscope Instrument used to illuminate the interior of the eyeball Can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina Pathway of Light Through the Eye Light must be focused to a point on the ______________ for optimal vision The eye is set for ______________ vision (over 20 feet away) Accommodation—the _____________ must change ________ to focus on closer objects (less than 20 feet away) Image formed on the retina is a real image Real images are _______________ from left to right _______________ down _______________ than the object Eye Reflexes Internal muscles are controlled by the ____________________ nervous system Bright light causes pupils to ______________ through action of radial, circular, and ciliary muscles Viewing close objects causes accommodation External muscles control eye ____________ to follow objects Viewing close objects causes _____________________ (eyes moving medially) A Closer Look ______________—eye focuses images correctly on the retina ______________ (nearsighted) Distant objects appear ____________ Light from those objects fails to reach the retina and are focused in _____________ of it Results from an eyeball that is too long ______________ (farsighted) Near objects are blurry while distant objects are clear Distant objects are focused ______________ the retina Results from an eyeball that is too short or from a “lazy lens” _______________________ Images are ___________________ Results from light focusing as lines, not points, on the retina due to unequal curvatures of the cornea or lens Homeostatic Imbalances of the Eyes Visual Fields and Visual Pathways Optic __________________ Location where the optic nerves _______________ Fibers from the medial side of each eye cross over to the opposite side of the brain Optic __________________ Contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye Night blindness—inhibited rod function that hinders the ability to see at night Color blindness—genetic conditions that result in the inability to see certain colors Due to the lack of one type of cone (partial color blindness) Cataracts—when lens becomes hard and opaque, our vision becomes hazy and distorted Glaucoma—can cause blindness due to increasing pressure within the eye The Ear Houses two senses Receptors are ____________________________ Different organs house receptors for each sense Anatomy of the Ear The ear is divided into three areas The Middle Ear (Tympanic Cavity) _____________________ cavity within the temporal bone Only involved in the sense of ____________________ Two tubes are associated with the inner ear The opening from the auditory canal is covered by the tympanic membrane The _______________________________ tube connecting the middle ear with the throat Allows for equalizing ___________________ during yawning or swallowing This tube is otherwise __________________ Bones of the Middle Ear (Tympanic Cavity) Three bones (_____________________) span the cavity ______________ (hammer) ______________ (anvil) ______________ (stirrip) Function Vibrations from eardrum move the _____________ _____________ _____________ _____________ Inner Ear or Bony Labyrinth The External Ear Involved in __________________________ only Structures of the external ear __________________ (pinna) External acoustic meatus (______________________) Narrow chamber in the temporal bone Lined with skin and _______________________ (wax) glands Ends at the ____________________________ Includes sense organs for _____________ and _____________ Filled with _________________ A maze of bony chambers within the temporal bone _____________ _____________ _____________ ____________ Organs of Equilibrium Equilibrium receptors of the inner ear are called the _____________ apparatus Vestibular apparatus has two functional parts _____________ equilibrium _____________ equilibrium Static Equilibrium _____________ —receptors in the vestibule Report on the _____________ of the head Send information via the vestibular nerve Anatomy of the maculae Hair cells are embedded in the _____________ membrane _________(tiny stones) float in a gel around the hair cells Movements cause otoliths to ___________ the hair cells Dynamic Equilibrium _____________ _____________ —receptors in the semicircular canals Tuft of hair cells _____________ (gelatinous cap) covers the hair cells Action of angular head movements The cupula _____________ the hair cells An impulse is sent via the vestibular nerve to the cerebellum Organs of Hearing Organ of _____________ Located within the _____________ Receptors = hair cells on the basilar membrane _____________ tectorial membrane is capable of _____________ hair cells Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe Mechanism of Hearing Vibrations from sound waves move _____________ membrane Hair cells are _____________ by the membrane An _____________ ___________ starts in the cochlear nerve _____________ stimulation can lead to adaptation Olfaction—The Sense of Smell Olfactory receptors are in the __________ of the nasal cavity Neurons with long _______________ Chemicals must be ____________ in mucus for detection Impulses are transmitted via the olfactory nerve Interpretation of smells is made in the cortex The Sense of Taste Taste____________ house the receptor organs Location of taste buds Most are on the _____________ _____________ palate _____________ Taste Sensations _____________ receptors (sugars) Saccharine Some amino acids _____________ receptors Acids _____________ receptors Alkaloids _____________ receptors Metal ions _____________ Chemical Senses: Taste and Smell Both senses use _____________ Stimulated by chemicals in _____________ Taste has _____________ types of receptors Smell can differentiate a _____________ range of chemicals Both senses _____________ each other and respond to many of the _____________ stimuli The Tongue and Taste The tongue is covered with projections called papillae _____________ papillae—sharp with no taste buds _____________ papillae—rounded with taste buds _____________ papillae—large papillae with taste buds Taste buds are found on the sides of papillae Structure of Taste Buds _____________ cells are the receptors Have gustatory hairs (long _____________) Hairs are stimulated by _____________ dissolved in saliva 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 Developmental Aspects of the Special Senses Formed early in embryonic development Eyes are _____________ of the brain All special senses are _____________ at birth Eye problems _____________ —“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 _____________ —“old vision” results from decreasing lens elasticity that accompanies aging Ear problems _____________ —type of sensorineural deafness _____________ —ear ossicles fuse