Special Senses General Senses Widely distributed throughout the body –Examples Touch Pain...
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Special Senses
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General Senses
• Widely distributed throughout the body– Examples
• Touch• Pain• Proprioception (provides information
about the position of the body)
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Special Senses
• Produced by highly localized sensory organs– Examples
– Smell– Taste– Sight – Hearing
Model of the human nose
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The Inner Ear
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Structures of the outer and middle ear
• Outer ear – Pinna- collects and focuses sound waves– External auditory canal- passage way that leads to the ear
drum– Ear drum- also called tympanic membrane. It vibrates with
sound waves.• Middle ear
– hammer, anvil, and stirrup- bones that transmit vibrations – Oval and round windows- two openings that connect the
middle ear to inner ear– Auditory tube- angles air pressure to be equalized
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How We Hear• Sound waves are collected by the auricle and conducted through
external auditory meatus toward the tympanic membrane which causes vibrations
• The vibrations of the stirrup produce waves in the perilymph of the cochlea. This makes the perilymph move and this pushes against the membrane of the round window
• This causes the vestibular membrane to vibrate. It creates waves in the indolymph and the basilar membrane
• Cochlear nerves (located in the cochlar ganglion), send axons to the cochlar nueculas in the brain stream
• Neurons project to other areas of the brain stream to inferior collicuculus thalamus auditory cortex of the cererum.
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Smell- Olfactory
• Molecules in the air enter the nasal cavity and dissolve in the mucus lining of the uppermost shelf of the nose (chemoreceptors – cilia)
• The olfactory neurons of the molecules contact the olfactory receptors who send impulses to the axons.
• The olfactory bulbs send this to the brain which interprets each scent.
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Taste - tongue*
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Taste
• Saliva breaks down the food into fluid. The chemicals in the fluid attach to the taste cells.
• Nerve fibers send impulses to the facial nerves, which send impulses to taste cortex of parietal lobe for interpretation.
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Structures of the eye pictures
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Accessory structures of the eye
• Eyebrows-protect eyes by preventing perspiration from running down the forehead.
• Eyelids- protect the eyes from foreign objects• Conjunctiva- covers inner surface of the eyelids• Lacrimal Apparatus- produces tears• Extrinsic Eye Muscles- help movement of the eye
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Eye structures
• Sclera – outermost, white, hard, layer• Cornea – transparent part of sclera, light in• Choroid – 2nd layer, black, absorbs light• Retina – innermost layer, bipolar cells: rods-
night vision and cones- color vision• Ciliary body – holds the lens in place• Iris – colored part of eye, regulates light• Fovea Centralis – area producing sharpest
vision
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Chambers of the eye
• Anterior compartment- between the lens and cornea, divided into anterior chamber and posterior chamber
– Filled with aqueous humor• Helps maintain pressure in the eye• Bends light• Provides nutrients to inner eye• Circulates around the cornea
• Posterior compartment– Filled with a transparent jellylike substance called the vitreous
humor• Holds the retina in place
• Has many similar functions to the aqueous humor
• Unlike aqueous humor, it does not circulate
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Path of sight input
• The rods / cones synapse
• bipolar sensory cells
• to the optic nerve
• reaches the thalamus of brain
• Visual cortex of occipital lobe of cerebrum
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Eye Disorders
• Conjunctivitis- also called pink eye, an infection of the conjunctiva
• Chalazion- a small lump in the eyelid caused by obstruction of an oil producing gland
• Cataract- clouding of the natural lens • Glaucoma- malformation or malfunction of the eye’s
drainage structures• Myopia- nearsightedness • Presbyopia- an eye in which the natural lens can no
longer accommodate• Stye- same as chalazion