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Unformatted text preview: 1 The Sensory The Sensory System System Classification of Sensory Receptors Classification of Sensory Receptors s Structurally a sensory receptor may be very simple (e.g. naked nerve ending of pain receptors), or very elaborate and sensitive (e.g. visual & auditory receptors) Type of stimulus receptors respond to: s Chemoreceptors : detect chemicals in solution (taste & smell) s Photoreceptors : respond to light (rods & cones of the retina) s Thermoreceptors : detect temperature changes s Mechanoreceptors : respond to movement (stretch, pressure, body position, equilibrium) The Senses The Senses s General Senses (throughout the body) s Pressure s Heat & Cold s Pain s Touch s Position s Special Senses (localized in sense organ) s Vision s Taste s Smell s Hearing, and s Equilibrium The Eye The Eye The Eye The Eye s 70 % of all sensory receptors are in the eyes s Each eye has over a million nerve fibers s Protection for the eye: s Bony orbit (eye socket) s Surrounded by a cushion of fat s Eyelids (protection from foreign material) s Blinking (lubrication) s Eyelashes & eyebrows (protection from foreign material) s Conjunctiva (lubrication) Eye Eye Protection: Conjunctiva Protection: Conjunctiva s Thin transparent membrane s Lines the inner surface of the eyelid s Cells secrete mucous for lubrication s Covers the sclera s Conjunctivitis c bloodshot eyes Conjunctival sac s Extends from the eyelid to the anterior of the eye s Site for eye-drops 2 Eye Eye Protection: Eye Muscles Protection: Eye Muscles s Orbicularis oculi s closes eyes s Used for blinking & winking s Levator palpebrae superioris s attached to the upper eyelid s contracts to keep the eyes open s weakness c ptosis (drooping of the eyelids) Eye Protection Eye Protection Lacrimal gland s Upper lateral part of the eyes orbit s Produces tears s Lubricates eyes s Washes out foreign bodies Nasolacrimal duct s Drains the tears from the eyes into the nose Properties of Lacrimal Fluid Properties of Lacrimal Fluid s Lacrimal fluid = tears s a dilute salt solution s contains antibodies & lysozymes (enzymes that destroy bacteria) s Protects, moistens, and lubricates the eye Coats/Tunics of the Eye Coats/Tunics of the Eye 1. Fibrous Tunic : avascular outermost layer: s Sclera + cornea (transparent center window) 2. Choroid : vascular middle layer 3. Sensory Tunic : innermost layer (retina) The Fibrous Tunic The Fibrous Tunic The Sclera: s Outermost coating s Appears white due to the presence of collagen and absence of blood vessels The Cornea s Anterior transparent continuation of the sclera s Main refracting structure s Avascular s can be transplanted with no fear of rejection The The Choroid Choroid s The vascular middle layer s blood provides nutrition to the internal eye structures s Contains dark brown pigments which prevent the scatter of incoming light rays s Modified interiorly into 2 intrinsic muscles, the 1. Ciliary body s the muscle used in accommodation 2. Iris: s the pigmented layer that gives eyes its color 3...
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This note was uploaded on 05/04/2008 for the course HP 320 taught by Professor Islam during the Spring '08 term at USC.
- Spring '08