Study Guide Exam 2 Fall 2011 Olfaction 1 Know the organization of the structures neurons associated with the sense of smell i e olfactory epithelium through olfactory nerve a Knew the various cells i e supporting cells basal cells olfactory cells mitral cells of olfaction also the structure of olfactory cells Olfactory epithelium 3 different kinds of cells all located in roof of nasal cavity poorly positioned for survival Olfactory Cells first order neurons of olfactory pathway bipolar neurons olfactory cilia project from dendrites axons form filaments of olfactory nerves replaced every 30 60 days replace basal cells Supporting cells surround cushion olfactory cells make up bulk of epithelial membrane contain yellow brown pigments mucous membrane lining in nose help detoxify chemicals that come in contact w olfactory epithelium Basal cells at base of epithelium Produce new olfactory receptors Mitral cell output cell 2nd order neurons Refine signal amplify it relay it b Know why olfactory receptors are different than the other special senses i e think generator potential vs receptor potential Basal cells produce new olfactory receptors which are neurons and usually mature neurons aren t generally replaced 2 Describe the transduction of smell i e G protein activation of adenylate cyclase cAMP depolarization of the cell 1 Odorant binds to its receptor 2 Receptor activates G protein Golf 3 G protein activates adenylate cyclase 4 Adenylate cyclase converts ATP to cAMP 5 cAMP opens a cation channel allowing Na and Ca2 influx and causing 6 depolarization triggering action potential then generator potential nerve impulse through olfactory nerves olfactory bulbs olfactory tract primary olfactory area of the cerebral cortex hypothalamus and limbic system 3 Briefly describe the threshold and adaptability of olfactory cells how quickly do olfactory receptors adapt Olfaction has a LOW threshold like all special senses only a few molecules need to be present Adaptation to odors occurs rapidly olfactory receptors adapt by 50 in the first second or so and more slowly thereafter Complete adaptation to certain strong odors occurs in about 1 minute after exposure Nasal cavity contains pain receptors that respond to irritants like ammonia 4 Know what area s of the brain are associated with olfaction 2 pathways 1 OLFACTORY CORTEX via the thalamus and part of the frontal lobe conscious interpretation and identification 2 To LIMBIC SYSTEM via the subcortical route emotional response to odor like Smells like cooking gas smoke or skunk trigger sympathetic fight or flight response appetizing odors increase salivation and stimulate digestive system activities and reflexes unpleasant odors induce sneezing coughing Hypothalamus amygdala and others Axons of the olfactory receptor cells makeup the olfactory nerves that synapse in the overlying olfactory bulbs on the end of the olfactory tracts There filaments of olfactory nerves synapse with mitral cells 2nd order neurons Mitral cells refine the signal amplify it and relay it When mitral cells are activated impulses flow from the olfactory bulbs via the olfactory tracts to 2 main destinations the olfactory cortex or the limbic system SMELL PHYSIOLOGY PATHWAY Odorant binds to receptor of an olfactory hair G protein activation activation of adenylate cyclase production of cAMP opening of Na channels inflow of Na generator potential nerve impulse through olfactory nerves olfactory bulbs olfactory tract primary olfactory area of the cerebral cortex hypothalamus and limbic system Gustation 5 Know the various cells associated with the papillae i e gustatory cells basal cells and the structure of the gustatory cells specifically Tongue cheeks soft palate pharynx epiglottis Taste buds primarily on the tongue housed in papillae Fungiform papillae scattered over entire tongue surface mushroom shaped Contain about 5 taste buds each Foliate papillae foliate because the look like folds on side walls of tongue most taste buds degenerate in early childhood Circumvallate papillae large round and least numerous they form an inverted V at back of tongue Each has 100 300 taste buds Each taste bud consists of epithelial cells of 2 major types Gustatory or taste cells have gustatory hairs like microvilli that are bathed in saliva The gustatory hairs are sensitive portion receptor portion of the gustatory cells Basal cells act as stem cells dividing and differentiating into new gustatory cells and basal cells 6 Know the major classes of taste i e what stimulates each and the differences between the transduction pathways of each i e which are G protein which are ion channels 1 Sour Hydrogen ions acids Acids have H 2 Sweet sugar like sucrose 3 Salty sodium ions like NaCl 4 Bitter alkaloids quinine Lowest threshold or high sensitivity 5 Umami amino acids glutamate and aspartate give a hearty savory flavor Sweet and salty threshold is higher than bitter or sour Complete adaptation to specific taste can occur in 1 5 mins of continuous stimulation a Briefly describe how the process differs for the various taste classes i e which classes use G protein mediated pathways Salty and sour direct influx of cations and depolarization of the cell these are the only 2 cation caused flavors Na and H Bitter sweet umami activation of a G protein which will ultimately cause depolarization of the cell 7 Describe the transduction physiology of taste i e binding of taste chemical to gustatory hairs graded potential release of neurotransmitters initiation of action potential Physiology of gustation Chemicals dissolved in saliva contact gustatory hairs Binding of chemical to gustatory cell induces a graded potential Graded potential results in the release of neurotransmitters from synaptic vesicles Binding of nt to the associated dendrite triggers an action potential in 1st order neurons gustatory fibers 8 Explain the gustatory pathway including the cranial nerves and areas of the brain included in this pathway Facial Nerve VII anterior 2 3rds of tongue Glosspharyngeal Nerve IX posterior 1 3 of tongue and oropharynx Vagus nerve X throat region and epiglottis from taste buds nerve impulses propagate along cranial nerves to gustatory nucleus in medulla oblongata Medulla 2nd order neurons from here some axons project to limbin system and hypothalamus and others to the thalamus Thalamus 3rd order neurons fom here froject to primary gustatory area in parietal lobe of cerebral cortex to give perception of
View Full Document
Unlocking...