Chemical Senses

CHEMICAL SENSES  The gustation (taste) and olfaction (smell) and both dependent on chemoreceptors that detects specific chemicals (dissolve in aqueous solution) in the environment.  Taste receptor excited by food chemicals dissolve in saliva  Smell receptor excited by airborne chemicals that dissolve in fluid coating nasal membrane.

OLFACTION a) Olfactory receptor cells – neuron that lines the upper portion of nasal cavity and sends impulse directly to olfactory bulb of the brain. b) The receptive ends of the cells contain cilia that extend into mucous layer coating the nasal cavity. c) Odorant diffuse  binds to specific protein called odorant receptors (ORs) on the plasma membrane of the cilia  depolarize the membrane  receptor cells generate action potentials.

GUSTATION Gustation receptor cells – modified epithelial cells called taste buds.  Most taste buds : papillae.  Two cells of taste buds: i.Taste/gustatory cells ◦  Gustatory hairs project from the tips of taste cells and extend through taste pores. ii. Basal cells ◦  Act as stem cell, dividing & differentiating into new gustatory cells.

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