Test 1 Study Guide
Test 1 Study Guide BIOL 3020-001
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This 24 page Study Guide was uploaded by Maria Martinez on Monday September 21, 2015. The Study Guide belongs to BIOL 3020-001 at Middle Tennessee State University taught by Dr. Miller in Fall 2015. Since its upload, it has received 53 views. For similar materials see Comparative Anatomy of the Vertebrates in Biology at Middle Tennessee State University.
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Date Created: 09/21/15
Test 1 study guide Biology 3020 Chapter 16 Nervous System The nervous system is very complex and conservative to change helps regulate internal and external environment Is broken down into 2 major components 1 Central Nervous System CNS consists of the brain and spinal cord 2 Peripheral Nervous System PNS consists of the nerves off the brain and spinal cord 2 types of PNS nerves are 1 Afferent sensory nerves meaning they take information into the CNS via electrical waves 2 Efferent motor nerves meaning they carry out information to the muscles or glands 2 Types of Cells of the Nervous System 1 Neuroglia Cells do not transmit impulses they form myelin and provide support and protection for neurons myelin speeds up impulse transmission Oligodendroglial cells form myelination in CNS neurons Schwann cells form myelination in PNS neurons Ependymal cells line the central canal of the brain Astrocytes pass nutrients between blood capillaries and neurons Microglia are specialized neuronal cells that are involved in helping defend against pathogens 2 Neurons the structural and functional unit are composed of Perykaryon also called the cell body or the soma Axons carry electrical impulses from the cell body Dendrites carry electrical impulses to the cell body Telodondria store the vesicles Synoptic knobsturn the electrical impulses into a chemical message Synapseprevents two neurons from touching and this is important because since there are no charges on dendrites the lack of contact between the neurons keeps the information traveling one way has types of 3 neuron processes 1 Unipolar neuroncomes off a single process has a single stem that divides into a dendrite and axon 2 Bipolar neuron has two processes usually at opposite ends 3 Multipolar neurons have many processes associated with the cell body Areas of swelling where multiple neurons are located are called ganglia in the PNS nucleus in the CNS Nerves Vs Tracts Nerve is a bundle of axons in the PNS can ow either way Tract is a bundle of axons in the CNS Gross Morphological Components Meninges soft tissue coverings that cushion and thermally insulate the brain and spinal cord made up of 3 layers 1 Piamater layersmall innermost layer 2 Arachnoid layer middle weblike layer 3 Duramater layer tough outermost layer Spinal uid is between the arachnoid layer and the duramater layer Spinal Nerves Are a mix of sensory and motor information Dorsal Route Carries sensory information in and out of the neuron Visceral Route Carries motor information in and out of the neuron Central Canal Filled With cerebral spinal uid Forms large chambers of the brain called ventricles White Matter Consists of myelinated axons giving it the White coloring Grey Matter Is grey because there is no myelin Simple Re ex Arc Receptors are stimulated to go through sensory neurons and are carried to the brain Sensory neurons Will synapse With intemeurons and like up With motor neurons From there they Will go off to the organ or brain 3 Rami Branches on the spinal cord 1 Dorsal Ramus Goes to the back muscles 2 Ventricle Ramus Goes to the muscles on the belly 3 Visceral Ramus Goes to the internal organs intestines heart diaphragm etc Plexus is an intermingling of nerves Peripheral Nervous System 2 main components 1 Somatic component Voluntary movements motor neuron that travels to the skeletal muscle consists of one neuron chain before reaching the muscle one neuron from the ventral horn to effector organ 2 Autonomic component motor neuron that travels through the visceral ramus to the organs consists of a two neuron chain before reaching the organ typically 2 neurons from the ventral horn to effector organ includes a presynaptic neuron in front of the synapse and the post synaptic neuron before reaching the organ causes involuntary movements 2 divisions 1 Sympathetic Component Preganglionic fibers secret acetylcholine neurotransmitter that contracts muscles these axon are shorter Post ganglionic fibers release epinephrine norepinephrine this results reactions like pupil dilating these axons are longer fight or ight response is activated here Sympathetic chain ganglia is associated with the visceral rami Has a thoracolumbar thorax lumbar region out ow 2 Parasympathetic Component Preganglionic fibers release acetylcholine which can also relax the muscles as well as contract them these axons are longer Post ganglionic fibers will also release acetylcholine these axons are shorter Originate from the brain and the spinal cord and have a craniosacral ow nerves will release from the sacrum Visceral Ganglia Travel to the effector organ and synapse with the neuron in the second organ They are in the affected organ Collateral Ganglia 3 types 1 Cervical associated with the neck 2 Coelemic associated with the body cavity 3 Mesenteric associated with the mesentery of the gut Twelve Cranial Nerves Smallest from anterior to posterior Purely sensory I 11 VIII Eyeball extrinsic muscles III IV VI Branchiomeric pharyngeal region V VII IX X 0 Terminalis Nerve sensory I Olfactory Nerve sensory II Optic Nerve sensory III Oculomotor Nerve motor IV Trocholier Nerve motor V Trigenimal Nerve sensory motor VI Abducen Nerve motor VII Facial Nerve sensorymotor VIII Auditory Nerve sensory IX Glossopharyngeal Nerve sensory motor X Vegus Nerve sensory motor XI Spinal Accessory Nerve motor XII Hypoglossal Nerve motor Ternimalis Nerve Identified after the others were found and that is Why it is zero Used for pheromone detection Olfactory Nerve Shortest cranial nerve Is a small host of nerves used for smell detection Optic Nerve Is essentially an extension of the brain Used for light detection Oculomotor Nerve Integrates 4 extrinsic eye muscles Trocholier Nerve Integrates the trocholier muscles also known as the superior oblique muscle Trigenimal Nerve Has 3 major branches 1 Opthalamic branch 2 Maxillary branch 3 Mandibular branch goes into the jaw tongue and teeth controls chewing Abducen Nerve Intergrates the lateral rectus and the rector bulbi muscle Facial Nerve Associated with the face and tongue muscles Involved with salivary glands and taste In sharks it is associated with 2 structures 1 Ampullae 2 Lorenzini allow for eye protection when opening jaws Auditory Nerve Associated with the inner ear and the ability to hear sounds Also deals with equilibrium Glossopharyngeal Nerve Integrates the pharynx and middle ear Associated with taste buds especially bitter and sour as well as swallowing Vegus Nerve Travels to the diaphragm pharynx internal organs Is also called the wandering nerve because it travels long distances Spinal Accessory Nerve Extends from C1 to C6 Has a cranial accessory that leads to the Vegus Hypoglossal Nerve Integrates tongue and is involved in tongue movements Lateral Line Nerves Has up to 6 pairs of additional nerves below the cranial nerves Rooted in the medulla oblongata Evolution of Spinal Cord and Spinal Nerves Amphioxus J awed sh that have a series of intersegmental paired dorsal spinal nerves Have 3 types of fibers 1 Somatic sensory fibers from skin and muscles 2 Visceral sensory fibers form integral organs 3 Visceral motor to internal organs The cell bodies lie within the spinal cord This means they don t have dorsal route ganglia Their synapses originate within the core Lacks myelination in the core there is no distribution of white matter Jawless Fish 2 major groups 1 Lamprae Spinal Nerves Are intersegmental and contain somatic and visceral sensory neurons and some visceral motor neurons Most sensory neurons have their cell body outside the spinal cord so ganglia are present 2 Hagfish Similar to the lamprae in that they are intersegmental Dorsal and ventral spinal nerves unite outside cord The giant axons that descend form the brain and synapse the sensory neurons that will synapse the duramater called muller cells Are associated with rapid escape reaction to stimulate motor neurons and the animal will swim away Are the most easily identified nerve tracts since they develop the most prominent tract way Lack myelin J awed Vertebrates 2 major groups 1 Anamniotes Includes fish and amphibians Have no amniotic sacs Has a yolk sac With cells identical to the impermeable membrane it absorbs dissolved yolk and passes it on to the embryo Jelly coat surrounding the egg sac comes from the mother s uterus so it has identical cells 2 Amniotes Includes reptiles birds turtles mammals Has 4 extraembryonic membranes 1 Yolk Sac Absorbs dissolved yolk and passes it on to the embryo 2 Amnion Filled with embryonic uid protects the embryo this uid cavity breaks and that s when the water breaks 3 Allantois Takes part in making the placenta 4 Chorion Acts as an extra embryonic lung and helps in gas exchange J awed Anamniotes Spinal cord is larger in diameter more rounded and cross sectioned allowing for an increase in blood ow Grey matter and White matter are going to be distinct but Will regulate the environment better Ventral grey matter horns are evident of an increase of tracts Both the dorsal median fissure and the ventral median fissure are formed due increase in activity The dorsal and ventral nerves join outside the spinal cord and outside the vertebral column All sensory information is going to enter via the dorsal root Visceral motor fibers are going to depart by the dorsal and ventral root Somatic motor fibers exit only through the ventral root J awed Amniotes Spinal cord With distinct grey matter White matter consists of neurons sending information up and down the cord All visceral motor fibers exit via ventral roots All synapses Will occur in the brain matter Vascularization is increased meaning there Will be more blood ow The more synapses the more information that can be sent and released Brain 3 primary brain swellings vesicles 1 Prosencephalon forebrain 2 Mesencephalon midbrain 3 Rhombencephalon hindbrain 5 brain vesicles 1 Myelencephalon Also known as the medulla oblongata Is essentially a cord extension of the spinal cord to brainstem Composed of tracts that carry signals from the brain to the body A damaged nerve in the part of the brain can result in death Houses nuclei and cranial nerves Nerves VIIXII in mammals Nerves VIX in sharks the telochordia which are thin membranes forming the medulla oblongata are posterior to the choroid plexus is one of the sites where cerebral uid will be produced Holds some sensory neurons Facial lobes responsible for gustation Vagal Lobes responsible for olfaction Houses the solitary nucleus a clustering of cell bodies that is associated with the sense of taste in fish Holds the octavolateris a pair of nuclei associated with the lateral system which is responsible for perception equilibrium and hearing in fish 2 Metencephalon Has 2 prominent features 1 Pons Latin for bridge Grown out ventrally It is the connection between the cerebellum and the medulla oblongata Serves as communication and coordination center between both hemispheres 2 Cerebellum Associated with involuntary movements Hagfish have no cerebellum Lamprey have a very rudimentary cerebellum Has 2 components 1 Auricles Receive information from the lateral line systems and vestibular portion of the inner ear deal with equilibrium 2 Body Receives mostly sensory information No association with olfaction or gustation Has propiorecptors that wrap around the skeletal muscle fibers to connect with the brain to tell it what degree of contraction is happening Its connections off the cerebellum allow it to integrate information auditory visual to the brain Some fishes have the ability to interpret their electrical output because of the cerebellum called electrical sense The larger the cerebellum the larger the receptors It is enlarged in birds and mammals and becomes folded this is termed folia and increase brain matter surface area which allows more synapses 3 Mesencephalon The dorsal portion is called tectum The oor or ventral portion is called tegmentum Contains the nuclei for the oculomotor and trochlier nerves Some of the nuclei are associated with the Vth cranial nerve Some motor sensory activity originates here In fish There are bulges located off the tectum that are associated with visual responses The larger the eyes the larger the part of the optic nerves will be on the brain Below the optic nerves are auditory nerves that receive and sent sound information In mammals anmniotes In the optical lobes and auditory nerves is referred to as the superior colliculi Are associated with eye movements and visual re exes Below the superior colliculi are the inferior colliculi Are associated with hearing and auditory re exes Both of these swellings the superior and inferior colliculi make up the corpora quadrigemina 4 Diencephalon Has 3 distinct regions 1 Epithalamus Contains the habenula which serves as an interface for the limbic and motor pathways Basic emotions like fear pleasure anger are centered here The limbic system is associated hunger and sex drive These pathways sizes will increase in animals with larger habenula meaning they have better memory In birds the small habenula means less developed sense or smell Contains the pineal and parietal complex Are photoreceptive and are also known as the third eye In some fish their functions could serve as actual eyes In mammals the pineal gland is associated with light detection and helps regulation cyclic behavior Has 4 evaginations swellings 1 Paraphysis not much is known about the paraphysis 2 Dorsal sac not much is known about the dorsal sac 3 Epiphysis also known as the pineal organ lizards have well developed epiphysis In mammals is an independent structure 4 Parietal organ also known as the parapineal or the parietal eye Will include a cordia lens and photoreceptor cells Not well developed in frogs Not developed at all in mammals 2 Thalamus all sensory pathways coming from spinal cord are going to synapse in nuclei located in the thalamus In reptiles the thalamus is smaller where as in humans it is going to be bigger Contains large mass swellings found between the thalamus and the 3rd ventricle called massa intermedia 3 Hypothalamus Found in the anterior boundary next to the optic chiasm Gives rise to the infundibulum also known as the pituitary stalk The infundibulum will connect to the pituitary gland that develops from the roof of the mouth in embryo created the anterior pituitary pituitary gland associated with the endocrine system so it deals with horomones posterior pituitary produced oxytocin also produces antidiuretic hormone that conserves uid passing through kidneys this is inhibited when drinking alcohol and that is what causes people to go to the bathroom often because the kidneys aren t ltering the liquid it s just going straight though anterior pituitary Associated with growth hormones thyroid stimulating hormone prolactin follicle stimulating hormone leuteinizing hormone and the Adentrocotropic hormone regulates homeostatic activities contains some olfactory centers contains the tuber cinerium which helps regulate circadian rhythms 5 Telencephalon includes the cerebral hemispheres and Rhombencephalon which includes olfactory tracts bulbs and lobes the bigger the Rhombencephalon the better the sense of smell 4 Central canals enlarged cavities are called ventricles 4th ventricle is going to be in the Rhombencephalon cerebral aqueduct of sylvius is in the mesencephalon 3rd ventricle Is located in the diencephalon 1St and 2nd are Within the telencephalon are called the lateral ventricles of the cerebral hemispheres produces some cerebral spinal uid that ows from the central canal to be produced from the posterior plexus in the medulla oblongata Sense Organs Specialized cells responsible for detecting or monitoring changed internal or external changes or stimuli Responsible for translating environmental energy into an electrical impulse neurons at rest are polarized ions of one charge on the outside membrane and different charge on the inside of the membrane When information passes through it it Will depolarize the neuron causing the information to pass through the neurons via electrical impulses all cells of the body can detect stimuli some are just specialized Sensory receptors become transducers a sense organ is formed When dendrites of that sensory receptor neurons are embedded in the tissue Sensory Organs Somatic sensory organs associated With skin going to the skeletal muscle Visual sensory organs Associated With the visceral organs Extrasensory organs monitor external environment Intersensory organs monitor internal environment General sensory organs Wide distribution in the body Deal with touch heat and degree of contraction Specialized sensory organs deal with light touch and equilibrium form sense of olfaction sight gustation General sensory receptors Free naked receptors the dendrites are branched out but nerve endings empty into tissues that aren t specialized associated with pain extreme heat or cold stimulated when swelling from damaged tissue abundant in areas like eyes mouth and intestines Encapsulated sensory receptors dendrites will be enclosed and associated with specialized functions Meissner s Corpuscles sensitive to touch Embuldge of Krause sensitive to cold Corpuscles of Ruffini sensitive to touch Pacinian Corpuscles located in skin joints body Viscera sensitive to pressure Associated receptors dendrites wrap around organs house proprioceptors which wrap around the skeletal muscle so that when it contracts it sends the information to the brain Specialized Sensory Receptors localized in distribution Sensitive to information like light waves or chemicals Specialized for specific stimuli Has chemoreceptors a chemical molecule that will integrate with a receptor which are responsible for two things 1 Gustation associated with the upper part of the tongue or where there are taste buds taste buds acts as transducers fit in the receptors of the sensory cells and that will cause the depolarization of the cells that will send the message to the brain 3 primary cell types that make up taste buds l Basal cells Give support to the Sustentacular and gustatory cells 2 Sustentacular cells Give support to the basal cells 3 Gustatory sensory cells Live about a week and there are replaced Lack axons but when depolarized will link up with a sensory neuron causing a synaptic reaction The sensory neurons are associated with the facial glossypharyngial and vegus nerves There are 5 families of gustatory cells and each will send a different path of electrical voltage to the brain which allows for discrimination between them 1 salt taste is associated with ions 2 sweet taste is associated with sugar and carbohydrates 3 bitter taste is associated with alkaloids 4 sour taste is associated with acids and acid salts 5umami taste is associated with amino acids taste detection is the best in mammals 2 Olfaction associated with the nasal passage has 3 components 1 Olfactory epithalamium the surface layer of nasal passageways has 3 primary cell types 1 Basal cells replenish cells for the Sustentacular and olfactory cells 2 Sustentacular cells gives support for the basal cells 3 Olfactory sensory cells they send information to the brain has a series of dendritic process that have an axon processes that Will travel to the olfactory bulb the dendrite processes are special types of cilia called kinocilia they are not motile there are about 10000 different sensory cells identified so far 2 Olfactory bulb made of mitral cells synapse With axons of olfactory cells that send information into the olfactory tract in fish they are sacs in janess fish the sacs become fused and just have a single sac and bulb but the tract ways are still paired in sharks water has to move through nasal sacs to smell the water the septum helps the water ow by separating into a division to increase the water ow other fish have extracurrent and internal organs to help the water ow in some fish the water ows to the oral cavity Which is an evolutionary in the sarcopterygians eshfinned fish some have external and internal nares nostrils Amphibians have a vomeronasal organ also known as J acobson s organ which is a specialized sac that is associated With pheromone detection the olfactory bulbs are smaller compared to fishes unlike fishes where the nasal passage way is for olfaction and the nasal pathway is for respiration Lizards Snakes Vestibule has a duct nasopharyngeal duct that leads into the body have a more complex nasal passageway Vomeronasal organ is separated into pits and located in the oral caVity and used for detecting chemicals for mating or catching prey in snakes the tongue fork has receptors used to sense chemicals allowing it to track prey Mammals Birds m Has 3 primary layers 1 Fiberous Tunic nasal passageway has hair that allows air filtering to take place warming the air for the lungs and moistening the air so it s not too dry Vomemasal organ is only present in some like dogs and cats and used for the ehmin response located in the anterior end of the palate anterior palatine foramen are openings into the J acobson s organ allowing to detect chemicals use nasal passageways to warm air have really poor sense of smell but otherwise similar to the lizards 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 1 11 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 sacculus also known as sacule and is made up of soft tissue imbedded in either cartilage or bone depending on the vertebrate Saccular maculafound in the saccular sac cristae elongated cilia found in the utricle 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 saccular sac and lagena not so much with the utricle 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 small cartilage bone goes in to the oval window that leads in the perylymphatic duct of the inner ear and this will allow it to perceive sound Outer Ear In mammals it consist of the atlike projection allowing the ear to hear well The middle ear developed in the therian mala The Metatheorians are the marsupials like opossums the Eurothrous are animals that have placentas they are not present in the platypus Whales or dolphins basically the sound gathering deVice
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