BIOL 252 1st Edition Lecture 7 Outline of Last Lecture I. GustationII. OlfactionIII. Hearing and EquilibriumIV. Poll EverywhereV. Sensory CodingVI. Cochlear TuningVII. Projection PathwayVIII. EquilibriumOutline of Current LectureI. EquilibriumII. VisionIII. Sensory Transduction in the RetinaIV. Generating Optic Nerve SignalV. How do we have different sensitivitiesVI. Color visionVII. Visual Projection PathwayCurrent LectureI. Equilibriuma. Static equilibriumi. Saccule and utricleii. When head is tilted, heavy otolithic membrane sags, bending the stereociliaiii.b. Semicircular DuctsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Sensory organ Gelatinous membraneCochlear ducts Organ of corti Tectorial membraneUtricle/Saccule Macula Otolithic membraneSemicircular ducts Crista Cupulac. Angular accelerationi. Crista Ampullarisii. When head is turning, cupula is pushed into endolymphiii. Cupula hangs into endolymph, as it turns, is pushed into endolymph which is stationary iv. Tells us which way we’re moving in space d. Vestibular Projection Pathwayi. Awareness of spatial orientation and movement (vestibular cortex)ii. Cerebellum controls muscle movements according to how head moving inspaceII. Visiona. Perception of objects in the environment by means of the light that they emit or reflectb. Conjunctivai. Membrane that covers eyeballii. Starts at margins of eyelidsiii. Only other visible structure = corneac. Lacrimal Apparatusi. Lacrimal gland – tears are produced (source)ii. Sink = medial, lacrimal punctumiii. Flows lateral to medial then to nasal cavity to help wash away foreign particles and prevent infection w/ lysozymed. Extrinsic Eyes Musclesi. Extrinsic = outside ofii. Ciliary body and iris are examples of intrinsiciii. Four of them (rectus muscles – straight) located at 12, 3, 6, 9 o’clockiv. 2 = oblique muscles (turning movements of eyeball)e. Fluids of the eyei. Aqueous humor: produced by ciliary body and absorbed through Scleral venous sinus1. Anterior to the lensii. Draining of extra fluid by scleral venous sinus (glaucoma – not enough absorption) iii. Maintains curvature of corneaf. Formation of imagei. Light through corneaii. Passes through pupil1. Light through small hole causes inversioniii. Neural components1. Fovea centralis: central pit2. Surrounding that is macula lutea (yellow patch)a. Where acute vision takes place (good resolution for spatial discrimination and color determination) 3. Job of extrinsic muscles: focus light on fovea4. Medially, have optic disca. What is coming out? Blood vesselsb. Axons headed for optic disc, so no room for photoreceptors (blind spot)c. If medially located on retina, lateral part of vision is missing d. Medial retina represents lateral fielde. Lateral retina represents medial field iv. Want to limit or enhance amount of light and want to focus the image1. Regulating lighta. Sympathetic nervous system stimulates dilators (contract) and pupil gets larger b. Parasympathetic nervous system stimulates constrictors sopupils get smaller g. Principle of Refractioni. How do we focus light?ii. Cornea is more dense, higher index of refraction (n=1.38) vs. air (n=1)1. Site of greatest refraction2. Lens can change shape a. Adjust through ciliary muscle: put tension on lens and can vary that tensioniii. Why do we do this?1.2. Light rays converge on focal plane behind the lens 3. Not always coming in parallelh. Emmetropia: true, unadjusted visioni. State in which the eye is relaxed and focused in an object more than 20 fii. Eyes are looking parallel to each otheri. What happens when we look at something right in from of it?i. Convergence: eyeballs turn inward ii. Light ways are not paralleliii. Image is in different locationiv. Near response: bends light waves more substantially by creating thick lens compared to thin dense j. Common Defects of image formationi. Hyperopia: farsightedness, focused beyond retinaii. Myopia: nearsightedness1. Image falls short of retina k. Accommodation: adjusting lens III. Sensory Transduction in the Retinaa.b. Sclera: white c. Retina: thick part of the eye walld. In front of the eye: vitreous body (thicker fluid vs. aqueous humor)e. Encountered many structures before getting heref. Rod and conei. Along w/ choroid: holds pigii. Photoreceptor cells1. RODa. Most sensitiveb. Used in low light circumstances (night vision, scotopic, monochromatic vision)c. All over the retina, 2. CONEa. Location: concentrated in fovea, sparse in periphery b. Can perceive color 3. Bipolar cells connected to both by synaptic vesicles4. Cones contain photopsin pigment w/ 3 different amino acid sequences and 3 sensitivities to colors5. S, M, L cones: short, medium, long wavelength 6. Rods contain rhodopsin: most sensitive to blue light but don’t perceive a color w/ it iii. Perception of everything happens in braing. Location and Action of Visual Pigmentsi. Membranous discsii. Produces a lot of surface areaiii. In membranes are pigment molecules called opsin1. Opsin signals change in permeability of cell membrane but ofen bound up and prevented from signaling by retinal (comes from Vitamin A)2. Has to different shapes3. At one particular location switches from cis to trans4. When no stimulation by light, are in cis conformation5. Photon comes in and energizes molecule => trans6. Retinal held by opsina. Each type of opsin is different (3 types of cone, 1 rod type)7. Pigment molecules bound up to opsin8. Membrane tells us how much cell membrane there isIV. Generating Optic Nerve Signala. Light comes in, dissociates retinal from opsin, opsin signals to membrane channelsb. Don’t memorize detailsV. How do we have different sensitivitiesa. Rods-signal to fewer number of bipolar cells, exact same signal sent no matter which rod is hit (converging circuit)i. Over given area, greater chance of detecting photons if photons are scarceii. But lose resolution qualityiii. Over vast distance, signal looks identical to the brainiv. High sensitivityb. Conesi. Photopic systemii. 1:1 ratioiii. Each one looks differentiv. High resolutionc. Single type of receptor cannot produce both high sensitivity and high resolutionVI. Color visiona. Color perception is based on mixture of nerves signals representing cones of different absorption peaksb.c. Color blindness: missing a cone or a cone is duplicatedi. Ofen hereditary alteration or