A PII Exam 2 Study Guide The Chemical Senses 1 ithelium Define and identify the anatomy of the olfaction receptor cells and ep Olfactory Epithelium is a Pseudostratified epithelium meaning it is only 1 layer of cells but gives the impression that it is multi layered Located on the roof of the nasal cavity making contact with the Cribriform Plate and the Olfactory Bulbs The Olfactory Epithelium is composed of 3 types of cells Olfactory Receptor Cells millions on either side of the nasal septum Supporting Cells surround Olfactory Cells Provide physical support nourishment and elec trical insulation for receptor cells Basal Cells Base of the Epithelium these divide to create more Olfactory Receptor Cells Olfactory Receptor Cells Bipolar Neuron thin dendrite that ends w a knob giving way to olfactory cilia Olfactory Cilia increase receptive surface area They lie flat on the epithelium and are covered by mucus produced by the Supporting Cells which captures airborne chemicals Filaments of the Olfactory Nerves run superior to inferior through the cribriform plate Replaced every 30 60 days by the Basal Cells These cells can distinguish about 10 000 different smells Receptors are stimulated by at least 1 000 smell genes active in the nose Unique receptor protein Each cell has only 1 type of receptor protein each protein responds to some odorants more than others 2 Nasal cavity contains pain receptors that respond to irritants Explain in detail the transduction of smell and its process and adapta tion through the somatosenstory system Transduction of Smell 1 2 Odor binds to a receptor G Protein a signaling molecule is activated by Adenylate Cyclase in order to make cAMP which is a secondary messenger cAMP allows a cation membrane channel to open up from the extracellular to intracellu Na and CA2 flow in causing depolarization or smell transduction 3 4 lar space Circuit Level of Olfaction Olfactory receptor cells send the action potential AP to the second order neurons Mitral Cells which are inside the glomeruli of the Olfactory bulbs Different glomeruli respond to different odors which then excite the mitral cells Mitral Cells send info down olfactory tract to either the Thalamus Hypothalamus Amyg dala or limbic system sympathetic emotional responses to odors Odor Thresholds and Adaptation or so and more slowly thereafter Olfaction has a very low threshold which means few molecules need to be present Adaptation to odors occurs rapidly Olfactory receptors adapt by 50 in the first second 3 Complete adaptation to certain strong odors occurs in about 1 min after exposure Describe and locate the types of taste buds associated with gustation Taste buds primarily in the tongue housed in papillae hence the abrasive feel of the Taste Buds sensory receptors for taste Gustation Stratifies Squamous Cells Located on the tongue cheeks soft palate pharynx epiglottis tongue Fungiform Papillae Top Foliate Papillae Lateral Circumvallate Papillae Back largest and least available 4 Describe the gustatory cells Gustatory Receptor Cells Gustatory Hairs Each taste bud has between 50 100 cells of which there are 2 types Gustation Cells Gustatory Receptor Cells and Basal Cells Project through at the taste pore into saliva just like the olfactry cilia into the mucus 2 types of Gustatory Receptor Cells one releases its neurotransmitter serotonin the other uses ATP Dendrites in each cell take signal from receptor cells to the brain Taste 5 major classes of stimuli that can be distinguished Taste Bud Sensations Sour Acids acidic H Sweet Elicited by organics sugars salts Salty Inorganic Salts metal ions NaCl Bitter Alkaloids caffeine nicotine Umami AAs glutamine aspartate companying olfactory sensations All other tastes such as chocolate coffee pepper are combinations of these 5 plus ac 5 Name the major types of taste stimuli and where they most commonly Sweet Receptors tip of tongue Salty and Sour Sides occur Taste Type Location Bitter Back 6 Umami Pharynx However all taste can come from all areas These are just primary regions Describe the physiology and transduction of gustation including the afferent fibers that are involved Physiology of Gustation Chemicals dissolved in saliva come into contact w gustatory hairs Binding of chemical to gustatory cell induces depolarization At highest change in membrane voltage neurotransmitter NT is released from the binding of the NT to the associated afferent fiber dendrite moves info to the 1st order synapse neurons Chemical Depolarization Salty Na influx through Na channels causes depolarization Sour H blockade of K channels allows these cations to enter and cause depolarization Bitter Sweet Umami Receptor coupled w Gustducin G protein Gustducin causes re lease of intracellular calcium which opens cation channels allowing for depolarization Gustatory Pathway Afferent Fiber Origination Facial Nerve VII anterior 2 3 of tongue Glossopharyngeal Nerve IX posterior 1 3 of tongue and the oropharynx Vagus Nerve X Throat region Epiglottis Lower Pharynx Solitary Nucleus of the Medulla 2nd order neurons Elicit digestive reflexes through PNS on the way saliva into mouth Thalamus 3rd order neurons Gustatory Taste Cortex 7 Define the disorders of the chemical senses Smell Taste Anosmias absence of smell Hyposmia impaired sense of smell Dysosmia distorted sense of smell Ageusia absence of taste Hypogeusia decreased sensitivity to taste Hypergeusia increased sensitivity to taste Dysgeusia distorted sense of taste The Eye Part 1 1 Accessory Structures Locate and describe the accessory structures of the eye in detail along with the path through the lacrimal apparatus Eyebrows Overlie supraorbital margins of the skull Shade the eyes from sunlight and prevent perspiration from reaching the eyes Contraction of the Orbicularis Oris or Oculi Eyelids palpebrae separated by the palpebral fissure meet at the medial and lateral commissures of the eye They protect the eyes blink every 3 7 sec prevent drying through blinking Lacrimal Caruncle in medials commissure fleshy elevation that contains sweat glands Tarsal Plates connective tissue sheets support eyelid Eyelashes projecting follicles of which a touch prevents reflex blinking Conjunctiva transparent mucous membrane covering the eyelid Lacrimal Apparatus as saline solution Lacrimal Gland and ducts that drain secretions Lacrimal Gland In orbit above lateral end of the eye Releases lacrimal secretions tears As you blink tears are spread downward to
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