Sensory System: Eye and Sight - PDF

The Sensory System Part 1: Introduction TERMS OF USE Today Please place your phones on the wall rack 1) Finish resolution presentations 2) Notes on Sensory systems 3) Go over Podcast Assignment 4) Eye Anatomy assignment Introduction: Sensory System The special senses include sight, hearing, s...

The Sensory System Part 1: Introduction TERMS OF USE Today Please place your phones on the wall rack 1) Finish resolution presentations 2) Notes on Sensory systems 3) Go over Podcast Assignment 4) Eye Anatomy assignment Introduction: Sensory System The special senses include sight, hearing, smell, taste, touch, and equilibrium SIGHT TASTE All senses rely on specialized sensory receptors, which enable the body to detect changes in the external and internal environment, which HEARING TOUCH are also called stimuli The senses are closely linked to the nervous system, which allows the body to interpret SMELL EQUILIBRIUM the stimuli and produce an appropriate response Sensory Receptors There are 5 kinds of sensory receptors in the body. CHEMO- PHOTO- MECHANO- THERMO- PAIN RECEPTORS RECEPTORS RECEPTORS RECEPTORS RECEPTORS Stimulated Stimulated Stimulated Stimulated Stimulated by certain by light by touch or by heat or by tissue chemicals wavelengths movement cold damage Sensory Receptors for Senses Sense / Organ Receptor Receptor Type Stimulus rods and Sight (eye) photoreceptor light wavelengths cones hair Hearing (ear) mechanoreceptor vibrations cells olfactory Smell (nose) chemoreceptor chemicals in air cells taste Taste (tongue) chemoreceptor chemicals in food buds Pacinian Touch (skin) mechanoreceptor pressure corpuscles maculae Equilibrium (ear) mechanoreceptor deflection and cristae Sensory Areas of the Brain All stimuli received by the different sensory receptors is carried along sensory neurons to specific areas of the brain The sensory cortex refers to the multiple areas of the brain where sensory information is received and processed There are 6 cortices in total linked to the 6 different senses: visual cortex, auditory cortex, olfactory cortex, gustatory cortex, somatosensory cortex, and vestibular cortex Sensory Cortices of the Brain VESTIBULAR CORTEX SOMATOSENSORY CORTEX (position, movement) (touch, pressure, pain) GUSTATORY CORTEX (taste) OLFACTORY CORTEX (smell) VISUAL CORTEX (vision) AUDITORY CORTEX (hearing) The Sensory System Part 2: The Eye and Sense of Sight Today Please place your phones on the wall rack 1) Notes on vision 2) Structure of the eye worksheet 3) Continue working on Podcast assignment Introduction to the Eye The eye is the sensory system’s organ of sight The eye gathers light, or radiant energy, from the environment and focuses it on sensory receptors found on the retina to form an image The image is then converted into nerve impulses, which are carried along sensory neurons to the brain The visual cortex interprets the impulses to form an image  Anatomy of the Eye CORNEA) SCLERA IRIS) CHOROID PUPIL RETINA FOVEA ANTERIOR CAVITY WITH AQUEOUS HUMOR OPTIC NERVE LENS “BLIND SPOT” SUSPENSORY LIGAMENT CILIARY BODY POSTERIOR CAVITY RETINAL BLOOD & MUSCLES WITH VITREOUS HUMOR VESSELS Outer Layers of the Eye The wall of the human eye is SCLERA CORNEA) comprised of 3 layers CHOROID The outer, fibrous coat consists of the white sclera, and the RETINA transparent front area of the sclera called the cornea, which allows light into the eye The choroid is the middle layer which is highly vascular with numerous blood vessels The retina is the innermost layer, which contains the receptors that detect light Cavities of the Eye The eye contains 2 fluid filled SCLERA CORNEA) cavities found at the front and back of the eye CHOROID The anterior cavity is found at RETINA the front of the eye, located between the cornea and lens and contains a watery fluid called aqueous humor The posterior cavity is found at the back of the eye, located between the lens and retina and contains a gel-like fluid called vitreous humor ANTERIOR CAVITY & POSTERIOR CAVITY & AQUEOUS HUMOR VITREOUS HUMOR Anterior Anatomy of the Eye The pupil is an opening that CORNEA) allows light to enter the eye The iris is a ring of smooth muscle that constricts or PUPIL dilates to alter the diameter of the pupil; it contains pigments that gives the eye its color The lens is a transparent, biconcave disk behind the iris IRIS that focuses light on the retina LENS The ciliary body consists of muscles that change the shape of the lens for focusing CILIARY BODY What advantage is a tiger orange coat? Posterior Anatomy of the Eye The retina is a sensory layer SCLERA covering the back of the eye CHOROID It is lined with over 120 million photoreceptor cells called rods and cones, which detect light RETINA and send nerve impulses to the brain along the optic nerve FOVEA The fovea is a dip in the center of the retina where most color- sensitive cone cells are located OPTIC NERVE The “blind spot” is small part of the retina where the optic nerve passes through; it contains no BLIND photoreceptor cells so no light is SPOT detected in this area Today Please Place your phone on wall rack 1)Notes on phototransduction 2)Experiment: How Your Eye Detects Color and Motion 3)Work on Podcast Assignment Rods and Cones Rods and cones are sensory RODS CONES cells that detect the different properties of incoming light Cones detect the color of light and come in 3 forms for the primary colors of light they detect: red, green, and blue; cones are found in the center of the retina and are highly concentrated at the fovea Rods detect brightness of light and therefore only “see” in black and white; they are found at the retina’s edges  Retina Cells Light enters the eye and strikes the retina must pass through all the neuronal cell layers before reaching and activating the photoreceptors. Horizontal and amacrine cells allow for communication laterally between the neuron layers. The photoreceptors then initiate the synaptic communication back toward the ganglion cells. Photoreceptor Density Visual information from our peripheral vision is generally detected by our rod cells, Cone photoreceptor cells allow for high-acuity vision. They are most densely packed at the fovea, corresponding to the very center of your visual field. cone cells make up the minority of photoreceptors in the human retina, outnumbered by about 20-times more rod cells. Retina Synaptic Convergence photopic vision, uses cone photoreceptors of the retina, and is responsible for high-acuity sight and color vision in daytime. scotopic vision, uses rod photoreceptors and is best for seeing in low-light conditions, such as at night. mesopic vision, when there are intermediate lighting conditions, such as indoor lighting or outdoor traffic lighting at night. Synaptic Convergence Rod cells are organized to have high synaptic convergence advantage of a high-convergence network is the ability to add many small signals together to create a seemingly larger signal A disadvantage of this type of organization is that it is difficult to identify exactly which photoreceptor is activated by the incoming light, which is why accuracy is poor when seeing stimuli in our peripheral vision. cone cells are highly effective at precisely identifying the location of incoming light. Phototransduction Photoreceptors do not fire action potentials; they respond to light changes with graded receptor potentials (depolarization or hyperpolarization). The amount of glutamate released changes along with the membrane potential Photoreceptors hyperpolarize in light and depolarize in dark. Phototransduction When the photoreceptor moves into the light, the cell hyperpolarizes. Light enters the eye, reaches the photoreceptors, and causes a conformational change in a special receptor protein called an opsin. The opsin receptor has a pre-bound chemical agonist called retinal (vitamin A). Together, the opsin + retinal makes up the photopigment rhodopsin. In the dark, the photoreceptor has a membrane potential that is more depolarized than the “typical” neuron o the photoreceptor membrane potential is approximately -40 mV. Eye Accessory Structures Eyebrows and eyelashes protect against foreign particles entering EYEBROW & the eye or scratching its surface EYELASHES EYELID Eyelids protect the anterior portion of the eye The conjunctiva is a thin, clear membrane that covers the front surface of the eye and inner eyelid; it keeps the eye surface moist and lubricated The lacrimal apparatus contains glands that produce tears which act to moisten the eye and kill CONJUNCTIVA LACRIMAL microbes; tears are spread APPARATUS across the eye during blinking Today Please place your phones on the wall rack 1)Notes on Vision 2) Last two presentations 3) Vision Lab Camera vs Eye Vison Step 1 DIM LIGHT R L BRIGHT LIGHT Light rays pass through the transparent cornea The cornea focuses the rays through the pupil into the lens In dim light, the pupil dilates (widens) to allow in more light In bright light, the pupil constricts (narrows) to allow in less light Vison Step 2 DISTANT OBJECTS R L NEAR OBJECTS Light passes through the lens, which focuses it onto the retina The ciliary muscles can constrict or relax to make the lens thicker or thinner, depending on the distance of the object For distant objects, ciliary muscles contract; lens pulled thinner For nearby objects, ciliary muscles relax; lens made thicker Vison Step 3 CONES - COLOR R LRODS - BRIGHTNESS Light rays hit a layer of sensory receptor cells in the retina Cone cells detect color of light and come in 3 types according to the colors of light they detect: red, green, and blue Rod cells detect brightness or intensity of light and therefore only “see” in black and white Vison Step 4 OPTIC NERVE FLIPS IMAGE FROM EYE R L VISUAL CORTEX FLIPS IMAGE BACK Rod and cones send nerve impulses along the optic nerve to the visual cortex, which interprets the signals as visual images How the Brain “Sees” Sensory information from each LEFT RIGHT eye is carried by the optic nerve VISUAL VISUAL FIELD FIELD Optic nerves from each eye cross at the optic chiasm OPTIC `` OPTIC Information from the right visual NERVE CHIASM field of both eyes is carried to the left side of the brain LEFT RIGHT Information from the left visual OPTIC OPTIC field of both eyes is carried to CORTEX CORTEX the right side of the brain Neurons in the visual cortex flip the image horizontally so that LEFT RIGHT humans “see” images correctly SIDE OF SIDE OF BRAIN BRAIN IMAGE Today Please place your phone on wall rack 1) Vision Lab 2) Therapeutic Technologies for Blindness Assignment o You will look up 3 technology for "curing" blindness" ▪ Genetic ▪ Brain implant ▪ pharmaceutical Today Please, place your phones on the wall rack 1) Kahoot on vision 2) Continue notes on vision 3) Discuss Therapeutic Technologies Please read ch.1 of The Man who Mistook his wife for a Hat by next Tuesday Visual Fields The fovea separates the retina into two sections: the nasal retina and the temporal retina. The nasal retina is the medial portion that is located toward the nose. The temporal retina is the lateral portion that is located toward the temples and temporal lobe Pathways to the Brain all information from the left visual field enters the right hemisphere of the brain, while visual information from the right visual field enters the left hemisphere of the brain. The nasal retina from one eye along with the temporal retina from the other eye are able to view an entire hemifield. Striate Cortex (Primary Visual Cortex) This organizational pattern, where a section of retinal inputs map onto neurons of a specific section of V1, is called retinotopic organization Post-Striatal Processing Ventral Stream is responsible for object recognition o Fusiform face area Dorsal Stream is responsible for motion and spatial information Therapeutic Technologies for Blindness Assignment Make a slide for each of the therapies o You have 15 minutes to work on your slides and then you will present