BIOL 232 Biology II: Anatomy of Sense Organs Lecture Outline PDF

BIOL 232 BIOLOGY II General  Anatomy of Sense Organs Lecture Outline COURSE INSTRUCTOR: DR. NOURA ABOU ZEINAB Email: [email protected] 2 Sense Organs 3 General Sense Organs 4 Speci...

BIOL 232 BIOLOGY II General  Anatomy of Sense Organs Lecture Outline COURSE INSTRUCTOR: DR. NOURA ABOU ZEINAB Email: [email protected] 2 Sense Organs 3 General Sense Organs 4 Special Sense Organs 5 Classification of Sense Organs 6 Classification of Sense Organs 7 Converting Stimuli into Sensation 8 General Sense Organs 9 General Sense Receptors 10 General Sense Organs 11 Outline  Sensory Receptors  Chemical Senses  Sense of Vision  Senses of Hearing and Balance  Somatic Senses 12 Sensory Receptors  Sensory receptors  Specialized cells capable of detecting changes in internal or external conditions, and of communicating that information to the central nervous system  Capable of facilitating sensory transduction 13 Sensory Receptors  Sensory receptors  Capable of facilitating sensory transduction  Conversion of an event (stimulus) occurring in the environment into a nerve impulse  There is no difference between the nerve impulses carried by different types of sensory nerves  Perceptions – Any sensory stimuli of which humans, and perhaps other animals, become conscious 14 Sensory Receptors  Sensory receptors (continued)  Chemoreceptors  Sensory receptors responsible for taste and smell  Photoreceptors  Sensory receptors responsible for responding to light  Mechanoreceptors  Sensory receptors stimulated by mechanical forces, such as pressure  Thermoreceptors  Sensory receptors stimulated by changes in temperature 15 Chemical Senses  Chemoreception is found almost universally in all animals  Thought to be the most primitive sense  Allow organisms to locate food, find a mate, detect dangerous environmental chemicals, etc. 16 Chemical Senses  Sense of Taste in Humans  In humans, taste buds are located primarily on the tongue  Taste buds open at a taste pore  Taste buds have supporting cells and elongated taste cells that end in microvilli  Five primary tastes  Sweet, sour, salty, bitter, and umami (savory)  Taste buds for each are located throughout the tongue, although certain regions may be more sensitive to particular tastes 17  Taste Buds in Humans Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. tonsils epiglottis sensory nerve fiber supporting cell taste pore 10 µm papillae taste bud connective tissue taste cell microvilli a. Tongue b. Papillae c. Taste buds d. One taste bud b(All): © Omikron/SPL/Photo Researchers, Inc. 18 Chemical Senses  Sense of Smell in Humans  Dependent on olfactory cells  Located within olfactory epithelium in the roof of the nasal cavity  Nerve fibers from olfactory cells lead to the same neuron in the olfactory bulb  Sense of taste and smell  Work together to create a combined effect  Interpreted by the cerebral cortex 19 Olfactory Cell Location and Anatomy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. olfactory bulb neuron olfactory tract frontal lobe of cerebral hemisphere olfactory bulb olfactory epithelium nasal cavity odor molecules sensory nerve fibers olfactory epithelium a. supporting olfactory cell cell olfactory cilia of b. olfactory cell odor molecules 20  Sense of Vision  How Animals Detect Light  Photoreceptors are sensory receptors that are sensitive to light  Arthropods  Contain compound eyes composed of many independent ommatidia  Photoreceptors generate nerve impulses which pass to the brain by way of optic nerve fibers  Insects have limited color vision 21 Compound Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Compound cornea eye crystalline cone photoreceptor cells pigment cells optic nerve fibers Fly head Ommatidium © Farley Bridges 22  Nectar Guides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. nectar guides (Both): © Heather Angel/Natural Visions 23 Sense of Vision  How Animals Detect Light (continued) Vertebrates and certain molluscs have a camera- type eye  Single lens focuses an image of the visual field on closely- packed photoreceptors  Stereoscopic vision  Found in animals with two eyes facing forward  Common in predators  Panoramic vision  Wide visual field  Common in prey animals 24 Extrnal Eye Structure 25 Sense of Vision  The Human Eye  Three Layers  Sclera - Opaque outer layer  Fibrous layer covering most of the eye  In front of the eye, the sclera becomes the transparent cornea  Conjunctiva – covers surface of the sclera and keeps the eyes moist 26 Sense of Vision  The Human Eye  Three Layers  Choroid - Thin middle layer  Contains blood vessels  In front of the eye, the choroid thickens to form the ciliary body and the iris  The iris regulates the size of the pupil  The lens helps form images  Retina - Inner layer  Contains photoreceptors called rod cells and cone cells  Contains the fovea centralis  Region of densely packed cone cells where light is focused 27  Anatomy of the Human Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sclera choroid retina ciliary body retinal blood vessels lens iris optic nerve pupil fovea centralis cornea posterior compartment anterior filled with vitreous humor compartment filled with aqueous humor retina suspensory ligament choroid sclera 28 The Eye and Vision 29 The Eye and the Eye Fluids 30 Sense of Vision  Focusing of the Eye  Light rays pass through the pupil and are focused on the retina  Focusing starts at the cornea and continues as rays pass through the lens, which provides visual accommodation  Shape of lens is controlled by the ciliary muscle  Distant object – ciliary muscle is relaxed  Near object – ciliary muscle is contracted 31 Focusing of the Human Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ciliary muscle relaxed lens flattened light rays suspensory ligament taut a. Focusing on distant object ciliary body ciliary muscle contracted lens rounded b. Focusing on suspensory ligament relaxed near object 32 Sense of Vision  Photoreceptors of the Eye  Both rods and cones have an outer segment joined to an inner segment by a stalk  Pigment molecules are embedded in membrane of the disks in the outer segment  Rhodopsin - pigment composed of opsin and retinal, a derivative of vitamin A  Rods permit vision in low light  Peripheral vision and motion  Cones permit vision in bright light  Fine detail and color 33 Sense of Vision  Photoreceptors of the Eye (continued)  Rods permit vision in low light  Peripheral vision and motion  Cones permit vision in bright light  Fine detail and color  Three different types of cones, each containing a different type of photopigment  B (blue)  G (green)  R (red) 34  Photoreceptors in the Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ion membrane of disk channels close rod cell light rays outer segment cone cell ion channels in plasma membrane retinal inner segment cell body opsin nucleus synaptic membrane Rhodopsin molecule vesicles synaptic endings of disk (opsin + retinal) 20 µm © Lennart Nilsson, from The Incredible Machine 35 Sense of Vision  Integration of Visual Signals in the Retina  The retina has three layers of neuronsa  Layer closest to choroid contains rod and cone cells  Middle layer contains bipolar cells  Innermost layer contains ganglion cells  Rod and cone cells synapse with the bipolar cells, which in turn synapse with ganglion cells responsible for initiating nerve impulses 36 Sense of Vision  Integration of Visual Signals in the Retina  Human retina has approximately  150 million rod cells  6 million cone cells  1 million ganglion cells  Since more rod cells synapse on a ganglion cell than cone cells, cone cells provide sharper more detailed images of an object than rod cells 37 Structure and Function of the Retina Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sclera choroid rod cell and cone cell layer choroid bipolar retina cell layer optic nerve ganglion cell layer axons of b. Micrograph of retina ganglion cells blind spot to optic nerve light rays a. Location of retina b: © Biophoto Associates/Photo Researchers, Inc. 38 Cells of the Retina 39 The Eye and Vision Structures 40 Pathway of light rays and Refraction 41 Visual Pathways 42 Visual Pathway 43 Sense of Vision  Disorders of Vision (Disorders of Retina)  Diabetic retinopathy  Capillaries to the retina become damaged  Macular degeneration  Capillaries supplying the retinas become damaged, resulting in hemorrhage and blocked vessels  Retinal detachment  Retina peels away from the supportive choroid layer 44 Retinal Detachment 45 Retinal Disorders 46 Sense of Vision  Disorders of Vision (continued)  Glaucoma  Drainage system of the eyes fail, leading to the buildup of aqueous humor and intraocular pressure  Cataracts  Lens becomes opaque and incapable of transmitting light rays 47 Retinal Disorders 48 Color Vision Screening Figures 49 Disorders of the Visual Pathway 50 Sense of Vision  Disorders of Vision (continued)  With normal aging, the lens loses its ability to accommodate for near objects  Nearsighted (myopic)  Elongated eyeball  Wear concave lenses  Farsighted (hyperopic)  Shortened eyeball  Wear convex lenses 51 Sense of Vision  Disorders of Vision (continued)  Astigmatism  Uneven cornea or lens, leading to a fuzzy image  Can sometimes be corrected with the use of an unevenly ground lens 52 Common Abnormalities of the Eye with Possible Corrective Lenses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. normal a. Nearsightedness eyeball Long eyeball; rays focus in front of Concave lens allows subject retina when viewing distant objects. to see distant objects. b. Farsightedness normal eyeball Short eyeball; rays focus behind Convex lens allows subject retina when viewing close objects. to see close objects. c. AstigmatismUneven cornea; Uneven lens allows subject rays do not focus evenly. to see objects clearly. 53 Artificial Retinas Come into Focus  Artificial retinas can help provide vision for blind and visually-impaired patients  Argus II  Digital camera in glasses transmit information to receiver implanted near the eye  Receiver stimulates ganglion cells which send impulses to the brain through the optic nerve  New research indicates that studying the pattern associated with the way ganglion cells send information to the brain can be used to engineer mechanisms to provide vision to blind patients 54 Refraction Disorders 55 Muscles of the Eye 56 57