Other secondary sexual characteristics, such as the bright red sides and hooked upper jaw, appear at this time. Upon reaching the natal stream, the salmon spawn. The female deposits her eggs and the male quickly fertilizes them. After spawning the aged salmon die, leaving the potential offspring to remain at the graveled stream bottom where the parents once began their lives. Because the salmon rely on olfactory information for migration, I will briefly review the components of the olfactory system.
Odors initially interact with receptor neurons in the olfactory epithelium.
These receptor neurons send axons to the olfactory bulb. Insert figure 1 here. Receptors Primary receptor neurons, which make up the first stage of olfactory information processing, express one or a few receptor proteins. The receptors consist of a seven-transmembrane domain that forms a basket for ligand binding. Most receptors contain two second messenger systems, cAMP and IP3.