A&PII Exam 2 Study GuideThe Chemical Senses1. Define and identify the anatomy of the olfaction receptor cells and epithelium.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 electrical insulation for receptor cells. -Basal Cells: Base of the Epithelium, these divide to create more Olfactory Receptor CellsOlfactory 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- Nasal cavity contains pain receptors that respond to irritants2. Explain in detail the transduction of smell and its process and adaptation through the somatosenstory system.Transduction of Smell1. Odor binds to a receptor2. G-Protein ( a signaling molecule) is activated by Adenylate Cyclase in order to make cAMP which is a secondary messenger3. cAMP allows a cation membrane channel to open up from the extracellular to intracellular space4. Na+ and CA2+ flow in, causing depolarization, or smell transductionCircuit 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, Amygdala, or limbic system (sympathetic emotional responses to odors)Odor Thresholds and Adaptation- 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 or so and more slowly thereafter- Complete adaptation to certain strong odors occurs in about 1 min after exposure3. Describe and locate the types of taste buds associated with gustation. Gustation (Stratifies Squamous Cells)- Taste Buds: sensory receptors for taste -Located on the tongue, cheeks, soft palate, pharynx, epiglottis- Taste buds primarily in the tongue housed in papillae - hence the abrasive feel of the tongue -Fungiform Papillae - Top -Foliate Papillae - Lateral -Circumvallate Papillae - Back (largest and least available)4. Describe the gustatory cells.Gustation Cells- Each taste bud has between 50-100 cells of which there are 2 types: -Gustatory Receptor Cells and Basal Cells- Gustatory Receptor Cells - Gustatory Hairs -Project through at the taste pore into saliva, just like the olfactry cilia into the mucus- Dendrites in each cell take signal from receptor cells to the brain -2 types of Gustatory Receptor Cells: one releases its neurotransmitter serotonin, the other uses ATPTaste Bud Sensations- Taste: 5 major classes of stimuli that can be distinguished -Sour: Acids (acidic H+) -Sweet: Elicited by organics (sugars/ salts) -Salty: Inorganic Salts (metal ions/ NaCl -Bitter: Alkaloids (caffeine/ nicotine) -Umami: AAs (glutamine/ aspartate)- All other tastes such as chocolate, coffee, pepper, are combinations of these 5, plus accompanying olfactory sensations5. Name the major types of taste stimuli and where they most commonly occur.Taste Type Location- Sweet Receptors: tip of tongue- Salty and Sour: Sides-Bitter: Back- Umami: Pharynx- However, all taste can come from all areas. These are just primary regions6. 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 synapse- binding of the NT to the associated afferent fiber (dendrite) moves info to the 1st order neuronsChemical 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 release of intracellular calcium which opens cation channels allowing for depolarizationGustatory 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) Cortex7. Define the disorders of the chemical senses.Smell- Anosmias: absence of smell- Hyposmia: impaired sense of smell- Dysosmia: distorted sense of smellTaste- Ageusia: absence of taste- Hypogeusia: decreased sensitivity to taste- Hypergeusia: increased sensitivity to taste- Dysgeusia: distorted sense of tasteThe Eye Part 11. Locate and describe the accessory structures of the eye in detail along with the path through the lacrimal apparatus.Accessory Structures- 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
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