Processes thought to underlie odor recognition. Ways odors may affect human behavior. Strategies for helping people whose sense of smell is diminished or lost. The nose contains specialized sensory nerve cells, or neurons, with hairlike fibers called clilia on one end. Each neuron sends a nerve fiber called an axon to the olfactory bulb, a brain structure just above the nose.
Most animals can distinguish thousands of odors.
Early studies showed that different olfactory neurons respond to different odors and that odors stimulate specific patterns of activity in the olfactory bulb. Scientists also found that the olfactory cilia in fish contain binding sites, or receptors, for odor molecules. Recently, researchers identified a surprisingly large family of genes in rats that appears to code for odor receptors. Scientists think this large and diverse group of genes is what helps animals detect such a huge variety of odors. In rats and mice, the olfactory lining is divided into four zones, each containing neurons with different odor receptors.