Lesson 2 Special Senses 1 Describe the components of the different special senses a Five special senses i Olfaction smell chemoreceptor 1 Located in nasal cavity on either side of nasal septum 2 Made up of two layers a Olfactory epithelium where the magic happens i Contain ii Olfactory receptor cells high turnover rate 1 They are highly modified neurons iii Supporting cells iv Basal stem cells regenerates olfactory receptor cells v The high turnover rate is weird being that it is a nerve cell and they typically don t regenerate but they get replaced by the stem cells b Lamina propria i Contain ii Areolar tissue iii Blood vessels iv Nerves v Olfactory glands FORM MUCUS 1 Secretions coat surfaces of olfactory orgains 3 Olfactory Discrimination a Can distinguish thousands of chemical stimuli b CNS interprets smells by the pattern of receptor activity 4 Number of olfactory receptors and resulting sense of smell declines with age ii Gustation taste chemoreceptor 1 Taste Receptors a Distributed on tongue and portions of pharynx and larynx b Clustered into taste buds i Associated with epithelial projections lingual papillae on superior surface of tongue 2 Three types of lingual papillae a Filiform papillae i Do NOT contain taste buds ii They provide friction b Fungiform papillae i Contain FIVE taste buds each c Circumvallate papillae i Contain 100 taste buds each 3 Taste Buds Contain a Basal Cells b Gustatory cells i Extend taste hairs through taste pore ii Survive only 10 days before replacement c Monitored by cranial nerves that synapse within the medulla oblongata then on to thalamus and primary sensory cortex 4 Gustatory Discrimination a Four primary taste sensations i Sweet ii Salty iii Sour iv Bitter i Umami ii Water b Additional Human taste sensations 1 Receptors sensitive to amino acids small peptides and 2 Detects characteristic of beef chicken broths and nucleotides Parmesan cheese 1 Detected by water receptors in the pharynx 5 Taste Sensitivity a Exhibits significant individual differences i 1000x more sensitive to acids sour taste than sweet salty 100x more sensitive to bitter than acids WHY Because a lot of poisonous things are bitter Defense mechanism b Some conditions are inherited i Ex phenylthiocarbamide PTC 70 of White people taste it but 30 do not c Number of taste buds begin declining rapidly by age 50 d Spicy food stimulates nociceptors iii Vision motor receptor iv Equilibrium mechanoreceptor v Hearing mechanoreceptor 2 Describe the sensory transduction pathway of each sense how are the neurons connected to each other to reach the brain which part of the brain do they terminate a Olfaction i Odorants come in the nose and are detected by the olfactory epithelium The information is sent to the Olfactory Bulb then to the Olfactory tract then to the CNS and the Cerebrum ii Olfactory reception involves detecting dissolved chemicals as they interact with odorant binding proteins on cell membranes of olfactory receptor cells iii Olfactory Pathways 1 Axons leaving olfactory epithelium Axons are collected into 20 or more bundles penetrate the cribriform plate of ethmoid and reach olfactory bulbs of cerebrum where first synapse occurs 2 Axons leaving olfactory bulb travel along olfactory tract to reach olfactory cortex hypothalamus and portions of limbic system 3 Arriving info reaches information centers WITHOUT first synapsing in thalamus 4 Odors are strongly associated with memories and emotion because of connection with limbic system 5 Know that Olfaction uses a 2nd messenger system b Gustation i Dissolved chemicals contact taste hairs ii Bind to receptor proteins of gustatory cells iii Salt and sour receptors 1 Use chemically gated ion channels 2 Stimulation produces depolarization of cells iv Sweet bitter and umami stimuli v End result of taste receptor stimulation 1 Release of neurotransmiters by receptor cell 1 Bind to membrane receptor protein to activate G proteins 2nd MESSENGER c Vision a Neurotransmitters generate action potentials in afferent fiber i Begin at photoreceptors ii End at visual cortex of cerebral hemishpheres iii Message crosses two synapses before it heads toward brain 1 Photoreceptor to bipolar cell 2 Bipolar cell to ganglion cell iv Central Processing of Visual info 1 Axons from ganglion cells converge on optic disc 2 Penetrate wall of eye 3 Proceed toward diencephalon as opitc nerve II 4 Two optic nerves one for each eye reach diencephalon at optic chiasm 5 Half the fibers travel to the contralateral lateral geniculate nucleaus half to the ipsilateral side v Visual Data cotex 1 Optic radiation Bundle of projection fibers linking lateral geniculate with visual 2 From combined field of vision arrive at visual cortes of opposite occipital lobe a Left half arrive at right occipital lobe b Right half arrive at left occipital lobe vi The Field of Vison 1 Depth perception a Obtained by comparing relative positions of objects between left and right eye images vii Circadian rhythm some fibers from later geniculate nucleus goes to hypothalamus 1 It is tied to day night cycle affects other metabolic processes viii Remember that ANYTHING on the left gets processed on the right side of the brain ANYTHING on the right gets processed on the left side of the brain If something is viewed in the exact center then it gets processed by its respective side of the brain Ex If something is on the left and it is viewed by the right eye the light ray will hit the lateral side of the retina and go to the right side If that same image is viewed with the left eye it will hit the medial part of the retina and cross over the optic chiasm and go to the right side 3 Explain how olfaction and gustation are similar a Both are i Chemoreceptors ii Both their sensory receptors have a high turnover rate b Describe the way that chemicals are detected by both systems i Both use a 2nd messenger system ii For gustation 1 Salt and sour use a gated ion channel 2 Sweet bitter umami use a 2nd messenger 4 Describe the different taste sensations a Described above 5 Describe the structures of the eye a Which are the accessory structures of the eye What are their functions i Palpebrae eyelids Continuation of skin 1 Blinking keeps surface of eye lubricated free of dust and debris 2 Tarsal glands Secrete lipid rich product that helps keep eyelids from sticking together ii Superficial epithelium 1 Lacrimal caruncle contain glands producing thick secretions a Contributes to gritty deposits that
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