Week 4 lecture notes Biology 3020
Week 4 lecture notes Biology 3020 BIOL 3020-001
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This 8 page Class Notes was uploaded by Maria Martinez on Friday September 18, 2015. The Class Notes belongs to BIOL 3020-001 at Middle Tennessee State University taught by Dr. Miller in Fall 2015. Since its upload, it has received 58 views. For similar materials see Comparative Anatomy of the Vertebrates in Biology at Middle Tennessee State University.
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Date Created: 09/18/15
Week 4 Lecture Notes Biology 3020 m Has 3 primary layers 1 Fiberous Tunic Referred as such because it has a lot of blood running through it Includes the sclera Forms the light of the eye Forms a tough coating capsule of connective tissue for the eyeball Forms eye shape Eye muscles connect to the sclera and that allows for eye movement In chickens the sclerotic ossicles will form the schlerate ring In amphibians and fish the schlerate cartilage will develop instead of bones In birds the sclera will be tougher so as to protect the eyes in ight Also includes the cornea Its transparency allows light into the eyeball Has a refractive Index of 1336 refractive index is a value placed on different media through which the light can penetrate through air has a refractive index of 1008 water has a refractive of 1330 this is important for animals trying to view through air or water as the refractive value causes the image to look bent An example of this is looking a stick in water it will look bent and and that is the refraction causing that effect Because the light bends when light enters the eye the cornea will focus the image while the lens will work on fine focus In water the water will do the majority of the focusing because the cornea s refracting value is already met with that of the water This refraction is What causes astigmatism because some people have lenses that are too circular causing the light to come in at an angle that over stimulates the receptor cells Conjunctivitis is When the sheet of epithelia coating on the surface of the eye becomes in amed due to infection 2 Vascular Tunic Includes the choroid heavily pigmented lots of melanin the light that comes into the eye is absorbed by the pigment to keep from over stimulating the receptors in the eyes In some lowlight environment animals the choroid is used to bounce back the the light in the eye to restimulate the sensory cells This is done by the tapetum lucidum Which evolved to be able to see at night the eye shine effect seen in some mammals like dogs cats and deer is the tapetum lucidum bouncing back extra light humans get red eye because of the blood vessels in the eye Also includes the iris Circular muscle that has the ability to contract and dilate located at the anterior end of the eye Surrounds the pupil The pigmented portion of the eye that gives it its color blue green brown etc Has multiple layers that portray color Many groups of fish have a fixed pupil diameter meaning the only way to change the amount of light received is to change positions to limit light intensity Sharks bonyfish lizards snakes turtles and mammals all have sphincter and dilator muscles The iris becomes elliptical in nocturnal animals vertical in cats horizontal in some amphibians is some animals the eye opening and closing more rapidly has evolved independently Geckos have pupils that in low light look like key holes and this allows super imposed images to go to the retina Includes the ciliary body sometimes called a ciliary muscle A circular muscle that helps support eyes and is around the lens Responsible for supporting the lens The ripped fibers in the lens are the remains of the suspensory ligaments The ciliary body s circular shape allows the lens to atten they the pupils dilate causing the suspensory muscles to contract Short distance vision will require a rounder lens while long distant vision will require a atter lens In amniotes the shape of the lens changes to be able to accommodate In anamniotes the position of the lens is changed to accommodate an advantage to this is that the curvature of the lens allows the light to cross and focus the object 2 different methods of accommodation 1 Anamniotes will have spherical lens Lampreys Don t have good vision in general Spherical lens at rest will be against on the cornea Have corneal muscles that will deform the cornea and pus the lens posteriorly so when the lamprey s pupils contract they will have better distant vision When relaxed the cornea will be pulled back out by the humerous Teleost advanced bony fish Spherical lens Positioned near not on the cornea at rest this gives them good near focus To see distant objects or to focus on a faraway object an intrinsic eye muscle will retract the lens posteriorly To see near objects the lens will go back to its original resting place Sharks and Amphibians Spherical lens The lens is positioned near the retina giving them distant vision To see nearby objects the lens is moved anteriorly by the protractor lenti muscles and once they are relaxed the lens will go back In sharks the protractor lenti muscles are mesodermal In amphibians the protractor lenti muscles of the endodermal origin 2 Amniotes The lens will be held in place and will change shape to accommodate Birds and most groups of lizards Have a series of paths that are between the ciliary in cornea these will constrict the suspensory muscles allowing the ciliary muscles to push down on the lens forming it to a rounder shape In mammals See up closes by allowing the lens to let the suspensory ligaments relax An inherent elasticity in lens allows it to become rounder and this allows near sight The lens are elliptical meaning they are at but are made rounder to see better When the lens loses that elasticity it causes the condition presbyopia Retina The major component associated with the sensory tunic Sensory cells are located on the backside of the retina but the axons are located on the in the front and will ow to and will form the optic nerve Has 2 major types of sensory cells 1 Rods are long rodshaped sensory cells are 2 orders of magnitude more sensitive than cones sensitive to all wavelengths of visible light result in low acuity in monochromatic Convergence when a lot rods or cones are sending the signal to only a few ganglion cells gives lower resolution 2 Cones 3 types of cone types 1 S cone Associated with short wavelengths of light Responsible for the blue coloration spectrum 2 M cone Associated with medium wavelengths of light Responsible for the green coloration spectrum 3 L cone Associated with long wavelengths of light Responsible for the red coloration spectrum Require a higher frequency of light to be stimulated and so will function poorly in low frequency Human eyes have 120 million rods in each eye and only 5 million rods in each eye Cones will be concentrated in the fovea center portion of the retina called the fovea centralis in the macula a part of the eye responsible for sharp image Macular degeneration is a condition where the cones in the eye die and the ability to sharpen image or see to a degree is lost resulting in vision loss The cone convergences provide higher resolution Vision is accomplished by the light enters the eye and goes to a specific place like the rods or the cones There will be a lll ratio between the cones bipolar receptors and ganglia In dogs there are also more rods than cones just as in humans Some turtles fish and birds have pigments sensitive to ultraviolate light allowing them to see outside the spectrum of light Eye position The eye position and the snout size will affect Vision greatly Humans have overlapped Vision because of their small snout this allows for stereoscopic Vision and depth of field Birds have 2 fovea one for near Vision and one for distant Vision Mechanical Reception Mechanoreceptors hair cells have a top layer composed of kinocilium cilia that can increase or decrease depolarization affecting the rate of discharge of the energy ow that will go to the brain Can be modified to detect electrical fields When the cells are clustered at the kinocilium they are going the same direction in the terms of energy ow The kinocilium are covered by the cupula a gelatinous mass covering that reinforces the signal that will change the rate of discharge The sterocilia will alert the fish animal when something is coming from what direction it is coming from and at what speed it is coming The kinocilium are usually at right angles to each other to have total directional detection This clustering forms a neuromast organ Can be modified in some fishes to become electroreceptor organs This allows them to detect weak electrical fields made by the muscle contractions of other animals These are called ampullary organs Ampullary organs Present in the ampullae of Loranzini Have cilia like structure In sharks the entire unit is filled with oil they do not have a scapula The jelly present will allow the shark to detect electrical fields and currents Inner Ear Includes the Membranous labyrinth which is composed of 3 semicircular canals edolymphatic duct in humans it will like up to the brain utriculus sac connects to the sarculus sac utricular neglecta was overlooked when all the other structures were found also known as the vestibule of the ear sarculus also known as sarcule and is made up of soft tissue imbedded in either cartilage or bone depending on the vertebrate Sacular macula found in the sacular sac cristae elongated cilia found in the utrical sac at the end of the semicircular canals basalar papillaeclustered sensory receptors found in or around the lagens lagena will be short in fishes large in amniotes In humans it is called the cochlear epdolymph uid in the membranous labyrinth perlymph uid that surrounds the membranous labyrinth Lagena length will vary between vertebrates deals with equilibrium and allows to detected rate of movement forward and backward Cristae overstimulation is the reason spinning around makes you dizzy because of the sensory overload Responsible for linear and angular acceleration associated with hearing this is associated with the sacular sac and lagen not so much with the utrical sac In amniotes hearing is associated with an enlarged lagena the longer the lagena them more sensory receptors there are the better the hearing capacity Organ of corti formed when the papilla in the lagena elongates and forms it Middle Ear Has 2 openings windows that go into the inner ear 1 Oval Window 2 Round Window Eustachian tube moves mucus in and out Where ear infections happen In lizards is I unusually small cartiage Outer Ear In mammalsit consist of the atlike projection allowing the ear to hear better that call The middle ear developed in the therian mala The Mediterranean did helped the seasoning the Eurothrous is the placenta toe They don t have the platypus Whales