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Ch11 Sensory System

Ch11 Sensory System - Classification of Sensory Receptors...

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1 The Sensory System Classification of Sensory Receptors square6 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: square6 Chemoreceptors : detect chemicals in solution (taste & smell) square6 Photoreceptors : respond to light (rods & cones of the retina) square6 Thermoreceptors : detect temperature changes square6 Mechanoreceptors : respond to movement (stretch, pressure, body position, equilibrium) The Senses square6 General Senses (throughout the body) square6 Pressure square6 Heat & Cold square6 Pain square6 Touch square6 Position square6 Special Senses (localized in sense organ) square6 Vision square6 Taste square6 Smell square6 Hearing, and square6 Equilibrium The Eye The Eye square6 70 % of all sensory receptors are in the eyes square6 Each eye has over a million nerve fibers square6 Protection for the eye: square6 Bony orbit (eye socket) square6 Surrounded by a cushion of fat square6 Eyelids (protection from foreign material) square6 Blinking (lubrication) square6 Eyelashes & eyebrows (protection from foreign material) square6 Conjunctiva (lubrication) Eye Eye Protection: Conjunctiva Protection: Conjunctiva square6 Thin transparent membrane square6 Lines the inner surface of the eyelid square6 Cells secrete mucous for lubrication square6 Covers the sclera square6 Conjunctivitis c3right “bloodshot” eyes Conjunctival sac square6 Extends from the eyelid to the anterior of the eye square6 Site for eye-drops
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2 Eye Eye Protection: Eye Muscles Protection: Eye Muscles square6 Orbicularis oculi square6 closes eyes square6 Used for blinking & winking square6 Levator palpebrae superioris square6 attached to the upper eyelid square6 contracts to keep the eyes open square6 weakness c3right ptosis (drooping of the eyelids) Eye Protection Lacrimal gland square6 Upper lateral part of the eye’s orbit square6 Produces tears square6 Lubricates eyes square6 Washes out foreign bodies Nasolacrimal duct square6 Drains the tears from the eyes into the nose Properties of Lacrimal Fluid square6 Lacrimal fluid = tears square6 a dilute salt solution square6 contains antibodies & lysozymes (enzymes that destroy bacteria) square6 Protects, moistens, and lubricates the eye Coats/Tunics of the Eye 1. Fibrous Tunic : avascular outermost layer: square6 Sclera + cornea (transparent center window) 2. Choroid : vascular middle layer 3. Sensory Tunic : innermost layer (retina) The Fibrous Tunic The Sclera: square6 Outermost coating square6 Appears white due to the presence of collagen and absence of blood vessels The Cornea square6 Anterior transparent continuation of the sclera square6 Main refracting structure square6 Avascular square6 can be transplanted with no fear of rejection The The Choroid Choroid square6 The vascular middle layer square6 blood provides nutrition to the internal eye structures square6 Contains dark brown pigments which prevent the scatter of incoming light rays square6
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