1 / 31

Chapter 8 Special Senses

Chapter 8 Special Senses. The Senses. Special senses Smell Taste SIGHT Hearing Equilibrium Lady website. The Eye and Vision. Of all the sensory receptors in the body 70% are found in the eyes Optic tracts Carry information from the eyes to the brain

turner
Download Presentation

Chapter 8 Special Senses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 8Special Senses

  2. The Senses • Special senses • Smell • Taste • SIGHT • Hearing • Equilibrium • Lady website

  3. The Eye and Vision • Of all the sensory receptors in the body • 70% are found in the eyes • Optic tracts • Carry information from the eyes to the brain • Consists of over a million nerve fibers per eye

  4. The Eye and Vision • Protection for the eye • Only 1/6th of the eye’s surface can be seen • Remaining portion of the eye • Enclosed in a bony orbit • Cushioned by a layer of fat • Accessory Structures • Eyelids • Conjuctiva • Extrinsic eye muscles • Lacrimal apparatus

  5. Accessory Structures of the Eye • Eyelids • Meet at the medial & lateral corners of the eye = (Medial & lateral canthus) • Nictitating membrane • Eyelashes

  6. Accessory Structures of the Eye

  7. Accessory Structures of the Eye • Conjunctiva • Delicate membrane • Lines the eyelids & covers part of the outer surface of the eyeball • Connects to the surface of the eye • Secretes mucus to lubricate the eye • Conjuctivitis?

  8. Accessory Structures of the Eye

  9. Conjunctivitis • PINKEYE • Common condition • Inflammation of the conjunctiva • Clear membrane that covers the white part of the eye & lines the inner surface of the eyelids • No danger to the eye or your vision • Causes • Bacteria, viruses, allergies (hay fever), irritants

  10. Accessory Structures of the Eye • Lacrimal apparatus • Consists of the lacrimal glands and ducts  drain lacrimal secretions into the nasal cavity • Lacrimal glands • Continually release tears • Tears • Antibodies • Lysozyme • Enzyme that destroys bacteria • Clean, protect and moisten the eye surface

  11. Accessory Structures of the Eye • Extrinsic (external) eye muscles • 6 muscles attached to the outer surface of each eye • Produce eye movements

  12. Internal Structures: The Eyeball • Eyeball • Hollow sphere • Its wall is composed of three tunics (layers) • Sclera or fibrous tunic • “White of the eye” • Outermost layer • Choroid or vascular tunic • Middle layer • Sensory tunic • Innermost layer • Retina • Interior is filled with fluids called humors

  13. Internal Structures: The Eyeball

  14. The Fibrous Tunic • Sclera • White connective tissue layer • “White of the eye” • Cornea • Transparent “window”- central anterior portion • Allows for light to pass through • Repairs itself easily • Only human tissue that can be transplanted from one person to another without the fear of rejection • No blood vessels  beyond the reach of the immune system

  15. Choroid Layer • Middle layer • Blood-rich nutritive tunic • Pigment prevents light from scattering • Modified anteriorly into two structures • Cilliary body – smooth muscle to which the lens is attached • Iris • Pigmented layer that gives eye color • Pupil – rounded opening in the iris through which light passes

  16. Sensory Tunic (Retina) • Contains receptor cells (photoreceptors) • Rods • Cones • Signals pass from photoreceptors and leave the retina toward the brain through the optic nerve • Photoreceptors • Distributed over the entire retina, except where the optic nerve leaves the eyeball • Optic disc or blind spot*

  17. Neurons of the Retina

  18. Neurons of the Retina & Vision • Rods • Most are found towards the edges of the retina • Allow dim light vision and peripheral vision • Test fact of rod location by looking “off-center” at objects at night…stars/glow-in-the-dark objects on ceiling • Perception is in all gray tones

  19. Neurons of the Retina & Vision • Cones • Densest in the center of the retina • Fovea centralis • Area of the retina with only cones • Greatest visual acuity • 3 types of cones  respond to a particular wavelength of light • Blue light • Green light • Both green & red light • ** Color blindness  lack of one to all cone types

  20. Color-Sensitive Cones

  21. Lens • Focuses light entering the eye on the retina • Flexible biconvex crystal-like structure • Held in place by a suspensory ligament  attached to the ciliary body • Divides the eye into 2 segments • Anterior (aqueous) segment • Posterior (vitreous) segment

  22. Lens

  23. Internal Eye Chamber Fluids • Anterior (aqueous) Segment • Contains a watery fluid  Aqueous humor • Found in chamber between the lens and cornea • Similar to blood plasma • Helps maintain intraocular pressure • Provides nutrients for the lens and cornea • Reabsorbed into venous blood • Blocked drainage = Glaucoma

  24. Internal Eye Chamber Fluids • Posterior (Vitreous) Segment • Vitreous Fluid • Gel-like substance behind the lens • Keeps the eye from collapsing • Lasts a lifetime and is not replaced

  25. Lens Accommodation • Light must be focused to a point on the retina for optimal vision • Resting eye is set for distance vision (over 20 ft away) • The lens must change shape to focus for closer objects

  26. Vision • Emmetropia • Correct focus • Myopia  nearsightedness • Focus of light in front of retina • Eyeball too long or lens too strong • Distant objects are blurry • Hyperopia  farsightedness • Focus of light beyond the retina • Short eyeball or lazy lens • Near objects are blurry.

  27. Emmetropia

  28. Hyperopia

More Related