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Visual Pathway Anatomy of the Ear Optic tracts * The ear is divided into three areas Thalamus (axons form optic radiation) -Outer (external) ear Right eye -Middle ear Left...

Visual Pathway Anatomy of the Ear Optic tracts * The ear is divided into three areas Thalamus (axons form optic radiation) -Outer (external) ear Right eye -Middle ear Left eye -Inner ear Visual cortex of the occipital lobe The External Ear * Involved in hearing only * Structures of the external ear -Pinna (auricle) - External auditory canal The Middle Ear or Tympanic Cavity *Air-filled cavity within the temporal Bones of the Tympanic Cavity bone * Three bones span the cavity * Malleus (hammer) *Only involved in the sense of hearing * Incus (anvil) * Stapes (stirrip) *Two tubes are associated with the inner ear Vibrations from eardrum move the malleus -The opening from the auditory canal is covered by the tympanic These bones transfer sound to the inner ear membrane Inner Ear or Bony Labrynth -The auditory tube connecting the A maze of bony chambers within the temporal middle ear with the throat bone -Allows for equalizing -Cochlea pressure during yawning or swallowing -Vestibule -This tube is otherwise -Semicircular canals collapsed Organs of Hearing Mechanisms of Hearing *Organ of Corti * Vibrations from sound waves move -Located within the cochlea tectorial membrane -Receptors = hair cells on the basilar * Hair cells are bent by the membrane membrane * An action potential starts in the -Gel-like tectorial membrane is capable of cochlear nerve bending hair cells * Continued stimulation can lead to -Cochlear nerve attached to hair cells adaptation transmits nerve impulses to auditory cortex on temporal lobe Nasa next page itong graph nato di kasya here  Static Equilibrium Organs of Equilibrium * Maculae - receptors in the vestibule * Receptor cells are in two structures * Report on the position of the head * Vestibule * Send information via the vestibular nerve * Semicircular canals * 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 Dynamic Equilibrium - Crista ampullaris - receptors in the semicircular canals * Tuft of hair cells * Cupula (gelatinous cap) * covers the hair cells Function of Maculae Dynamic Equilibrium *Action of angular head movements -The cupula stimulates the hair cells -An impulse is sent via the vestibular nerve to the cerebellum 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 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 Olfactory Epithelium The Sense of Taste * Taste buds house the receptor organs * Location of taste buds * Most are on the tongue * Soft palate * Cheeks 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 Structure of Taste Buds * Gustatory cells are the receptors -Have gustatory hairs (long microvilli) -Hairs are stimulated by chemicals dissolved in saliva Taste Sensations * Sweet receptors Sugars Saccharine Some amino acids * Sour receptors Acids * Bitter receptors Alkaloids * Salty receptors Metal ions Anatomy of Taste Buds Developmental Aspects of the Special Senses * Formed early in embryonic development * Eyes are outgrowths of the brain * All special senses are functional at birth