Lecture 23 and 24
Lecture 23 and 24 Biol 202
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This 0 page Class Notes was uploaded by Natasha on Saturday December 12, 2015. The Class Notes belongs to Biol 202 at St. Cloud State University taught by Schoenfuss, Heiko in Spring 2015. Since its upload, it has received 16 views. For similar materials see Human Anatomy and Physiology I in Biology at St. Cloud State University.
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Date Created: 12/12/15
Biol 202 Lecture 23 amp24 The Special Senses Development 0 Special senses are formed early in embryonic development 0 The eyes are direct outgrowths of the brain 0 All special senses are functional at birth 0 Special sensory receptors are confined to the head region in mammals 0 Special receptor cells not free nerve endings are utilized by special senses The Senses 0 General Senses to touch 0 Temperature 0 Pressureclosely related to pain 0 Pain closely related to pressure 0 Special senses O Smellolfaction 0 Taste gustation O Sight 0 Hearing 0 Equilibrium balance Chemical Senses Taste and Smell 0 Both senses use chemoreceptors O Stimulated by chemicals in a solution 0 Taste has four types of receptors some have a fifth 0 Small can differentiate a large range of chemicals 0 Both senses complement each other and respond to many of the same stimuli Olfaction Smell 0 Receptors are part of the olfactory epithelium 0 Olfactory epithelium composed of 0 Cell bodies of olfactory receptor cells 0 Supporting cellscolumnar cells O Basal cells make new cells 0 Axons of olfactory epithelium 0 Gather into bundles filaments of the olfactory nerve 0 Pass through the cribriform plate of the ethmoid bone 0 Attach to the olfactory bulbs interpretation of smells is made in the cortex Taste 0 Taste buds house the receptor organs papillae 0 Location of taste buds O Tongue O Cheeks 0 Soft palate The Tongue and Taste 0 The tongue is covered With projections called papillae 0 Filiform papillae sharp With no taste buds 0 Fungifiorm papillaerounded taste buds fungus looking 0 Circumvallate papillae large papillae With taste buds 0 Taste buds are found on the sides of papillae 0 Sweet sour salty bitter and 20 have umami 0 There is no structural differences among taste buds Gustatory Pathway 0 Taste information reaches the cerebral cortex 0 Primarily though the facial VII nerve and glossopharyngeal IX nerve 0 Sometimes taste information through the vagus nerve X 0 Sensory neurons synapse in the medulla The Eye and Vision from a contact lens box 0 70 of all sensory receptors are in the eyes 0 Each eye has over a million nerve fibers 0 Projections for the eye 0 Most of the eye is enclosed in a bony orbit O A cushion of fat surrounds most of the eye insulates eye so it cannot freeze Accessory Structures of the Eye 0 Eyelids 0 Eyelashes I Meibomian glandsmodified sebaceous glands produce an oily secretion to lubricate the eye I Ciliary glands modified sweat glands between the eyelashes I Conjunctive O O O Membrane that lines the eyelids Connects to the surface of the eye Secretes mucus to lubricate the eye 0 Lacrimal apparatus 0 O O O O O O Lacrimal glandproduces lacrimal uid Lacrimal canals drain lacrimal uid from the eye Lacrimal sac provides passage of lacrimal uid towards nasal cavity Nasolacrimal duct empties lacrimal uid into the nasal cavity Properties of the lacrimal uid I Dilute salt solution tears I Contains antibodies and lysozyme Protects moistens and lubricates the eye Empties into the nasal cavity Structures of the Eyes 0 Wall is made of three layers or tunics O O O Fibrous tunic outside layer I Sclera 0 White connective tissue 0 Seen anteriorly as the White of the eye I Cornea 0 Transparent central anterior portion 0 Allows for light to pass through 0 Repairs itself easily 0 The only human tissue that can be transplanted without fear of rejection Choroid middle layer I Choroid Layer 0 Bloodrich nutritive tunic 0 Pigment prevents light from scattering 0 Modified interiorly into two structures 0 Ciliary body smooth muscle 0 Iris I Pigmented into layer that gives eye color I Pupil rounded opening in the iris I tatetum lucidumanimals glow in the dark eyes Sensory tunic inside layer retina Contains receptor cells photoreceptors 0 Rods lightdark 0 Cones color Signals pass from photoreceptors via a twoneuron chain 0 Bipolar neurons 0 Ganglion cells Signals leave the retina toward the brain through the topic nerve Optic nerve blood vessels enter eye amp spread out among eye Neurons of the Retina and Vision 0 Rods 0 Most are found towards the edges of the retina 0 Allow dim light vision and peripheral vision 0 Perception is all in gray tones 0 Cones 0 Allow for detailed color vision Densest in the center of the retina Fovea centralis area of the retina with only cones Different cones are sensitive to different wave lengths I Blue420 nm 39 Green 530 nm I Red 560nm 0 Color blindness is the lack of one type of cone 000 0 No photoreceptor cells are at the optic disk or blind spot Eye Chamber Fluids 0 Aqueous humor 0 Watery uid found in the anterior chamber of the eye 0 Similar to blood plasma 0 Helps maintain intraocular pressure 0 Provides nutrients for the lens and cornea O Reabsorbed into venous blood though the ccanal of Schlemm 0 Vitreous humor 0 Gellike substance posterior to the lens 0 Keeps the eye from collapsing O Lasts a lifetime and is not replaced Lens 0 BiconveX crustallike structure 0 Held in place by a suspensory ligament attached to the ciliary body Lens Accommodation 0 Light must be focused to a point on the retina for optimal Vision 0 The eye is set for distant Vision over 20 ft away 0 The lens must change shape to focus for closer objects Visual Pathway 0 Photoreceptors of the retina 0 Optic nerve 0 Optic nerve crosses at the topic chiasma 0 Optic tracts 0 Thalamus axons form optic radiation 0 Fibers of the optic radiation reach the Visual cortex of the occipital lobe The Ear 0 Has two senses 0 Hearing 0 Equilibrium 0 Receptors are mechanoreceptors 0 Different organs house receptors for each sense 0 Ear Ossicles fully formed at birth 0 Maleus 0 Incus O Stapes Middle EarTympanic CaVity 0 Two tubes are associated with the inner ear 0 The openings from the auditory canal is covered by the tympanic membrane 0 The auditory tube connects the middle eat with the throat I Allows the equalizing pressure during yawning or swallowing I This tube is otherwise collapsed Inner Ear Bony Labyrinth 0 Includes sense organs for hearing and balance 0 Filled with perilymph 0 A maze of bony chambers within the temporal bone 0 Cochlea O Vestibule O Semicircular canals Organs or Hearing 0 Organ or Corti 0 Located Within the cochlea O Receptors hair cells on the basilar membrane 0 Gellike tectorial membrane is capable of bending hair cells 0 Cochlear nerve attached to hair cells transmit nerve impulses to auditory cortex on the temporal lobe Mechanisms of Hearing 0 Vibrations from sound waves move tectorial membrane 0 Hair cells are bent 0 An action potential starts in the cochlear nerve 0 Continued stimulation can lead to adaptation Organs of Equilibrium 0 Equilibrium has two parts 0 Static equilibrium 0 Dynamic equilibrium Static Equilibrium 0 Maculaereceptors in the vestibule 0 Report on the position of the head 0 Send information via the vestibular nerve 0 Anatomy of the maculae 0 Hair cells are embedded in the otolithic membrane 0 Otoliths are tiny crystals that oat in the gel around hair cells 0 Movements cause otoliths to bend the hair cells Dynamic Equilibrium 0 Crista ampullaris receptors in the semicircular canals O Tuft of the hair 0 Cupula covers the hair cells 0 Action of angular head movements 0 The cupula stimulates the hair cells 0 An impulse is sent from the vestibular nerve to the cerebellum Disorders of Equilibrium and Hearing Motion Sickness 0 Motion sickness carsickness seasickness 0 Popular theory for the cause a mismatch of sensory inputs from Vision and equilibrium Disorders of Equilibrium and Hearing Meniere s Syndrome 0 The equilibrium is greatly disturbed 0 Excessive amounts of endolymph in membranous labyrinth Disorders of Equilibrium and Hearing Conduction Deafness 0 Conduction deafness 0 Sound Vibrations cannot be conducted to the inner ear I Ruptured tympanic membrane otitis media otosclerosis
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