Chemical Senses and Vision I
Chemical Senses and Vision I Bil 268
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This 16 page Study Guide was uploaded by Anchy Sanan on Sunday March 15, 2015. The Study Guide belongs to Bil 268 at University of Miami taught by Dr. Zhongmin in Spring2015. Since its upload, it has received 107 views.
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Date Created: 03/15/15
BIL 268 02172015 I Light A The ER Radiation know what wavelength frequency and amplitude are and how they re tired into it B Visible Light 400 700 nanom Energy is proportional to frequency C Optics In refraction you have two different mediums Due to the density difference the light is bent and the speed is changed This is an example of how our eyes work and is an example of refraction If the image is not well focused on your retina you will get a blurry image II The Eye A Structure of the Eye Front view of the eye shows the Iris Iris is a circular muscle that can cause and retract to change the central hole Pupil central hole that allows the light to get into our eye The color of your eye is the color of the iris The peripheral area of the eye has sclera If you flip the eyeball you can find the conjunctiva know the term Conjunctive inside area of the eyelid The way you learn the structure of the eye is by following the light ray and its path The light first hits the cornea Shape of the cornea is fixed and that is extremely important Cornea gives you a very high focusing power even greater than your lens The lens can change the structure and the curvature which is basically different from the fixed structure of the cornea Lasik eye surgery is basically a laser that reshapes the curvature of the cornea The eyeball is controlled by three pairs of muscles Because of the three pairs of muscles you can move your eyeball Extraoccular muscles The end of your eyeball is connected to the optic nerve which is the axons at the end of your eyeball that go all the way to the brain If the muscles have a problem say the lateral muscles then your medial side muscles will overpower the lateral muscles and you will be cross eyed If vice versa you will get the opposite Amblyopia is actually known as the lazy eye But for some reason the visual acuity is extremely low and the person can only see the largest number in the reading chart Strabismus is due to the disease in the muscle that controls the eyeball Your eye starts drifting Wall eye or cross eye Cataract due to cloudiness of the lens which blocks light from getting into the eye Getting into more detail the light pathway hits the cornea and the iris Between the iris and the cornea you have a small chamber filled with aqueous humor The lens is connected to the ciliary muscle and via zonule fibers The ciliary muscle helps contract and relax and it helps change the curvature of the lens to fatter and thinner On the back of the lens you have a jelly like structure called vitreous humor Supposed to be transparent At the back you have the retina where you have receptor cells The most important spot in the retina is the fovea Whenever you look at something clearly the image is formed on your retina Surrounding the spot gives you the highest visual acuity In addition to the fovea you have another spot that has the optic nerve going out along with blood vessels going in and out In that spot there are no photo receptors and it is called our blind spot Know all the structures What is Glaucoma That is due to the inner pressure of the eyeball getting high which will press your eyeball and eventually the pressure moves to your optic nerve which can cause damage It s a very serious disease Know the elasticity of your lens the ability to retain certain shapes Your lens can change the shape from fatter to flatter which is due to the circular muscles The retina The doctors use this device to look at your retina ophthalmoscope It is the image of a human retina It allows you to see the yellowish area known as the macula It differs from the fovea which is the central regionpit of your macula The blind spot optic disk is the location of the optic nerve and the blood vessels Know the relative locations of the two spots The fovea is on your left retina Your blind spot is medial to your fovea The fovea will receive the light and the light source from the blind spot will go towards the temporal side Need to be able to form an image in your mind and be able to draw Cancer in the eye retinoblastoma caused by a mutation of the R81 gene B Image Formation Schematic drawing of the eyeball that shows light rays being focused on the fovea allowing us to see the sharp image This is the refractive power diopeters 1focal distance Emmetropia normal vision Myopia near sight Hyperopia far sight What is near sight and what is far sight Near sight is the focal distance is larger You need a lens to spread out the light rays Copyright 200339 Wolters Kluwer Health Lippincott Williams ampWilkins There are two shapes for lens concave and convex For near sightedness you need to use a concave lens Will cause the light to spread Convex lens have the same shape as your eye and are used for far sightedness A combination is to change the curvature of the lens to bring the image right on the retina Need to know what type of lens to use III Retina A Structure Your retina is laminar organization Means has different cell layers The structure is inside out The photoreceptor cell layer the bipolar cell layer and the ganglion cell layen Why do you need the pigment layer Can absorb excessive photons It s called inside out because the light coming in doesn t directly hit your photoreceptor cells First goes through the ganglion cell layer the bipolar cell layer and then the photoreceptor cell layer Why Any design always has a trade off and is a design that is dependent on the environment If our environment had less light then maybe the photoreceptor cells would be on the outside The bipolar cells are neurons that do not generated AP s They make the MP change and can release NT s The ganglion cells are neurons and the axons are collectively called the optic nerve Optic nerve comes from the neurons of the ganglion cell Between the photoreceptors and the bipolar cells you have the horizontal cells Between the ganglion cells and the bipolar cells you have the amacrine cells Both have unique functions Do the comparison between the two types of PR cells B Photoreceptors Can be divided into two structures Cone and rod They can detect light because of the disc like structures Membrane of the disks have photo pigments that are sensitive to light If you flip them then you are looking at the SEM photo which shows the rods and the cones Two types of receptor cells with different functions Cone works in the bright light situation and do not work well in the dim light Rods are more sensitive to light and they work well in dim light The vision in dim light is scotpic and is photopic in the bright light situation Cones give you a higher resolution of the image If you want to have a high resolution image you must be in the bright light situation If you try to count the number of the receptor cells the number of rods is greater Rods can be found in the peripheral region of the lens They work well in the dim light What is the fovea It ahs no rods and has the highest visual acuity It has three structural bases The fovea has the cones There is also 1 cone connected to one ganglion cell and one bipolar cell One to one Fovea is the pit which means the ganglionbipolar cells are pushed aside which allows the light to directly stimulate Three things put together gives you high visual acuity Photo transduction Receptor cells In the dark there is no stimulation For the regular neurons at rest they are hyper polarized Why are the photoreceptor cells in the dark depolarized Due to the dark current and an influx of ions in the dark It is basically the influx of sodium ions The sodium ion channels are open and are they are regulated by cGMP sodium ion channels In the darkness the concentration is high which keeps the channels open and causes DP Stimulation to light closes the sodium ion channels Through this process the intracellular cGMP is reduced and is turned into GMP which closes the ion channels and causes the cell to become hyperpolarized Mechanisms underlying photo transduction In the membrane of photoreceptor cells light stimulate the gate The pigment has rhodopsin photo pigment with two parts opsin protein and retinal chemical Stimulation of light changes the structure of the photoreceptor which affects the gprotein For humans we can perceive color because we have different kinds of cones which have different kinds of opsins RGB sensitive to different wavelengths 31515 1020 AM 31515 1020 AM BIL 268 02122015 Lecture 8 Chemical Senses I Gustation Five basic tastes There are five basic tastes saltiness sourness sweetness bitterness and umamL The taste of deliciousness for umami Sugars like fructose and artificial sugars are for sweetness and ions like potassium and magnesium are for bitter Taste Organs If you stick your tongue out and look at it in the mirror you can see the surface of it If you open your mouth the taste sensitivity is different 0 Maybe a portion of your tongue is especially sensitive to bitterness Tip of the tongue is more sensitive to sweetness while back of the tongue is more sensitive to bitterness The sides of the tongue are sensitive to saltiness and sourness The palate and the epiglottis are evolved for sensation and are not as strong as your tongue 0 Tongue has the taste receptor cells The taste organs what are they The tongue isn t entirely flat It has bumps 0 These bumps are called papillae Leaf shaped papillae are foliate papillae You can find receptor cells in the taste bud along with basal cells marked in green on the PowerPoint Some of the taste receptor cells are innervated by the nerve fibers The receptor cells are regenerated and they have a short life span 2 wks at which point the basal cells develop into the receptor cells 0 Same thing is true for the olfactory receptor cells When you are born you have a fixed number of auditory receptor cells 0 Which is why as you get older you have hearing loss Sensory Transduction Very important concept Applied to taste and smell along with hearing It s basically the process to convert a natural stimulus into an electrical signal at the receptor cell level If you have sugar directly stimulated to the brain directly you will not get any taste at all 0 Your brain cannot take the natural stimulations 0 You must have something at the peripheral level to convert natural stimulation unto signals that can be recognized by the brain Refer to the schematic drawing in the ppt When you re recording from the membrane you re recording the Action Potentials yellowish box Taste receptor cells are capable of conducting action potentials even though they are receptor cells Transduction Mechanisms Ionic processes underlying the basic tastes You need to know the flow chart and pay attention to whether ion channels or Gprotein coupled receptors are used If you have a drop of table salt on your tongue the sodium ions will go in via diffusion Amiloride The positive ions going in will cause depolarization of the cell membrane which in turn will effect the voltagegated sodium channels and cause them to open 0 Synaptic Transmission will occur Sourness Increasing the Hydrogen ion concentrations 0 The H ions getting in will cause depolarization The potassium ion channels are open 0 The influx of the hydrogen ions will cause the potassium ion channels to close It will cause depolarization which in turn will open voltage gated ion channels Sourness looks at acidity and pH Sweetness Bitterness and Umami All three use Gprotein coupled receptors The taste binds to the receptor When the IP3 concentration is high it will cause the release of interceuar calcium into the cytosol which will sort of depolarize Different receptor cells have different receptors Taste Receptors There are three different taste receptors and two families of genes 0 One is called T1R gene family and the other is T2R o Transmembrane receptors that can generate about 30 membrane proteins depending on the different kinds of proteins 0 Different combinations will give you different taste sensations The T2R family has different shapes and groove patterns The sweet and umami receptors are from T1R 0 Overall the one receptor contains two proteins Capsaicin Why do hot peppers taste Kind of like something is burning on your tongue In the hot peppers you have the capsaicin which can activate the thermal nociceptor pain 0 Burning pain The heat opens the ion channel causing the influx of the cation Neural Coding of Taste There are two theories labeled line and population coding Labeled line is found in invertebrates The way the system is designed is that the receptors are tuned to one type of chemical Mwcom Type III receptors if isolated will only respond to salty and sour 0 However if you have the entire cell the cell will respond to all the different types of taste buds 0 Can be recorded in vitro and in vivo The ATP released by the type II receptor cells will bind to the receptor Central Taste Pathways Sensory neurons go to different levels in the brain and eventually reach the cortex 0 Gustatory cortex Impairment of taste ageusia II Olfaction Pheromones are body odors we all have them 0 It is basically the chemical released in response to the same species 0 It can be seen as a mode of communication for the rodents o Relegated to reproduction or territorial fights 0 Identification and aggression Smell Organ If you look at the medial view you ll see our nose chamber The dorsal wall has olfactory epithelium which has many receptor cells 0 If you make a cut you can find the receptor cells along with the basal cells in addition to supporting cells 0 The receptor cells go and die 4 8 wks The basal cells regenerate into the new smell receptor cells The function of the supporting cells is that you need to have a layer of mucus that is produced by the supporting cells The taste receptor cells are neurons because they look like neurons and they function like neurons The cilia found in the mucus layer generate action potential which travels to the brain The receptor cells go directly to the brain quite unique The axon cells of the receptor cells innervate the brain Olfactory Transduction Looking at the tip of the cilia you can find gprotein coupled receptors 0 ATP is converted to cAMP cAMP opens the ion channels and are also referred to cAMP gated channels 0 Causes an influx of positive ions which leads to depolarization 0 You cannot generate AP until the threshold is reached The influx of positive ions will open the chlorine channel which will cause Calcium gated ion channels These are different from normal neurons 0 The outside concentration for chlorine is higher in normal neurons 0 It s the opposite in these neurons 0 The IC side has a higher concentration of chlorines The glomerulus there are three receive input from many receptor cells 0 In each glomerulus you can find many synapses containing axons of receptor cells and dendrites of secondary olfactory neurons The glomeruli sort out the information sent to them Refer to ppt for the diagram of the Odor map Your different odors are mapped along the olfactory bulb Neural Coding of Smell Schematic drawings in ppt You can count the number of action potentials Temporal coding is for insects and not humans 0 By looking at the pattern of action potentials in time you ll see that the firing path in time is different Olfactory Maps You need to have voltage sensitive dye to label the olfactory bulbs When the dye is absorbed the receptor cells also have the dye You can play around with different stimulations and then look at the images caused which will cause the dye to emit light 0 The microscope will detect the pattern of the emissions so that you can form a map corresponding to different stimuli 0 Use fluorescent or confocal microscope 31515 1010 AM 31515 1010 AM
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