Sense of Smell Suzanne DAnna 1 Olfactory Organs

Olfactory Organs lie in nasal epithelium mucous membrane n total area of olfactory epithelium

Olfactory Epithelium n Consists of three types of cells: - olfactory receptors - supporting

Olfactory Receptors 10 - 100 million n lifespan about 30 days n Suzanne D'Anna

Olfactory Receptors (cont. ) bipolar neurons with knob-shaped dendrite at distal end - cilia

Supporting Cells columnar epithelial cells of mucous membrane lining the nose n surround and

Basal Cells located around supporting cells n stem cells that produce new olfactory receptors

Olfactory Glands also called Bowman’s glands within connective tissue that supports epithelium n produce

Physiology of the Sense of Smell Suzanne D'Anna 9

Olfactory Stimulation n Primary scents: - floral - pungent - musky - minty -

Olfactory Stimulation (cont. ) irritating odors also stimulate lacrimal and nasal receptors producing tears

Olfaction or Transduction n chemical interaction with receptor sites - sodium channels open leading

Adaptation decreasing sensitivity to odors n occurs rapidly; about 50% in the first second

Olfactory Pathway olfactory receptors n olfactory nerves n olfactory bulbs n olfactory tract n

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Sense of Smell Suzanne D'Anna 1

Olfactory Organs lie in nasal epithelium mucous membrane n total area of olfactory epithelium is less than 1 square inch n located in superior portion of nasal cavity - superior nasal conchae - part of nasal septum n Suzanne D'Anna 2

Olfactory Epithelium n Consists of three types of cells: - olfactory receptors - supporting cells - basal cells Suzanne D'Anna 3

Olfactory Receptors 10 - 100 million n lifespan about 30 days n Suzanne D'Anna 4

Olfactory Receptors (cont. ) bipolar neurons with knob-shaped dendrite at distal end - cilia called olfactory hairs protrude from dendrite - cilia are sites of olfactory transduction n respond to chemical stimulation of an odorant molecule n single axon projects into olfactory bulb at proximal end n Suzanne D'Anna 5

Supporting Cells columnar epithelial cells of mucous membrane lining the nose n surround and support olfactory receptors n Suzanne D'Anna 6

Basal Cells located around supporting cells n stem cells that produce new olfactory receptors (neurons) n Suzanne D'Anna 7

Olfactory Glands also called Bowman’s glands within connective tissue that supports epithelium n produce mucus - moistens surface of olfactory epithelium - dissolves odorant gasses - continued production clears surface area and prevents continued stimulation by same odor n Suzanne D'Anna 8

Physiology of the Sense of Smell Suzanne D'Anna 9

Olfactory Stimulation n Primary scents: - floral - pungent - musky - minty - putrid - camphoraceous - etheral Suzanne D'Anna 10

Olfactory Stimulation (cont. ) irritating odors also stimulate lacrimal and nasal receptors producing tears and sniffles n Example: - onions n Suzanne D'Anna 11

Olfaction or Transduction n chemical interaction with receptor sites - sodium channels open leading to depolarization which causes action potential in axon leading to olfactory bulb n low threshhold - only a few molecules of a substance in the air are necessary to stimulate olfactory receptors Suzanne D'Anna 12

Adaptation decreasing sensitivity to odors n occurs rapidly; about 50% in the first second after stimulation and very slowly thereafter n even though adaptation to one odor has occurred, sensitivity to other odors remains unchanged n Suzanne D'Anna 13

Olfactory Pathway olfactory receptors n olfactory nerves n olfactory bulbs n olfactory tract n prepyriform cortex and limbic system n frontal lobes n Suzanne D'Anna 14