BIEB 166 Lecture 25 (WI13)

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Department
Biol/Ecology, Behavior, & Evol
Course
BIEB 166
Professor
James Nieh
Semester
Spring

Description
Lecture 25 Reception of olfactory signals Tiger - The male was rubbing his face towards a tree - Female smells that, and when it encounters the actual male, she has to make sure the male is the one left the odor marks - Olfactory receptor cells have the highest turnover of any sensory cells ○ Most survive only for days to weeks Mechanism - Odor molecule binds to receptor - Same for all types of olfactory receptors - Receptor in a membrane - Odorant molecules bind to the receptor - Triggers cascade of events/open a channel to allow other ions to pass through - molecule binding to receptor - Oldest form: basic mechanism involved in regulating a wide variety of processes - Can be used specifically for communication Insect olfactory sensillum - Multipurpose sensors - Bent by a particle of a near-field sound - Pores inside the hair to allow odor molecules to diffuse inside - Often surrounded by a kind of liquid that the molecule must diffuse through before they can really enter to the receptors in the membrane Nose - Terminate at the olfactory cilia - Mucus ○ Surrounds the cilia, and allow the molecules to diffuse through ○ Protects the cilia ○ Not easily dried out Olfactory cells may be narrowly tuned to a single chemical 1. “Labeled line coding” - 1 cell class sensitive to a single odor - Binds onto the receptor cells, and transfer to the glomeruli ○ Collect information from multiple sensory neurons - Bring information to the olfactory bulb - Similar to light perception Advantage Disadvantage Very sensitive Very inefficient -More olfactory apparatus is more focused -Need a different set of neurons to detect on a single odor different types of molecules -Silk moth/tick -Evolve a new class of neurons to sense new odors Better at detecting a signal from a noisy chemical background 2. "Across neuron pattern coding" - Broadly tuned to many chemicals such that odor quality is a function of the combination of receptor cell types stimulated - Each sensory neuron is capable of detecting multiple odors and the identity of odors is encoded in the olfactory lobe by the pattern of neuron activation - Similar to sound perception - Similar to sound perception - Multiple neurons in the olfactory lobe is turned on ○ Specific neurons response to specific odors Honeybee - Antennal lobe - Calcium sensitive voltage guide ○ Cause change in Ca flux when the cell is active - Response to multiple odors Mixed odors -> mixed pattern - Few odors are pure - Summing up the different patterns, and can recognize the different combination of different molecules - Brain does add up the different odors Concentration difference - The bees are able to differentiate between two odors when one is 1.5x of the other - The brain is more activated in one area than the other Receptive organs Contact organs - Require direct physical contact with the surface carrying the odor molecules 1. Tongue - Bitter - Sweet - Salty - Sour - Umami ○ Response to glutamic acid ○ Meat/protein/soy beans ○ Adaptation of being an omnivore - Taste buds ○ Small openings ○ Molecules coming in can contact with the short, stiff microvilli that are sticking out  Less fragile ○ Human perception is a complex mix of the contact organ and our nose Fly proboscis - Labellum - Sensitive to very few things ○ Salt ○ Sugar Medium-borne organs - Can detect odor molecules dispersed or dissolved in a medium 1. Human nose - Cilia ○ Embedded in the
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