Home > Health A – Z > Olfactory System

Olfactory System

The parts of the body involved in sensing smell, including the nose and many parts of the brain. Smell may affect emotion, behavior, memory, and thought.

PubMed Health Glossary
(Source: NIH - National Cancer Institute)

How the Sense of Smell Works

Your sense of smell - like your sense of taste - is part of your chemosensory system, or the chemical senses.

Your ability to smell comes from specialized sensory cells, called olfactory sensory neurons, which are found in a small patch of tissue high inside the nose. These cells connect directly to the brain.

Each olfactory neuron has one odor receptor. Microscopic molecules released by substances around us—whether it's coffee brewing or pine trees in a forest—stimulate these receptors.

Once the neurons detect the molecules, they send messages to your brain, which identifies the smell. There are more smells in the environment than there are receptors, and any given molecule may stimulate a combination of receptors, creating a unique representation in the brain. These representations are registered by the brain as a particular smell.

Smells reach the olfactory sensory neurons through two pathways. The first pathway is through your nostrils.

The second pathway is through a channel that connects the roof of the throat to the nose. Chewing food releases aromas that access the olfactory sensory neurons through the second channel. If the channel is blocked, such as when your nose is stuffed up by a cold or flu, odors can't reach the sensory cells that are stimulated by smells. As a result, you lose much of your ability to enjoy a food's flavor. In this way, your senses of smell and taste work closely together...Read more about Smell and Smell Disorders NIH - National Institute on Deafness and Other Communication Disorders

Terms to know

Axons
Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.
Cell Body
The bulbous end of a neuron, containing the cell nucleus.
Dendrites
A long, branching outgrowth or extension from a neuron, that carries electrical signals from synapses to the cell body.
Myelin Sheath
A fatty covering that forms a protective sheath around nerve fibers and dramatically speeds the transmission of nerve signals.
Nerves
A bundle of fibers that receives and sends messages between the body and the brain. The messages are sent by chemical and electrical changes in the cells that make up the nerves.
Neurons (Nerve Cells)
A type of cell that receives and sends messages from the body to the brain and back to the body. The messages are sent by a weak electrical current. Also called nerve cell.
Neurotransmitters
A chemical that is made by nerve cells and used to communicate with other cells, including other nerve cells and muscle cells.
Olfactory Bulb
A rounded mass of tissue that contains several types of nerve cells that are involved in the sense of smell. The olfactory bulbs receive information about smells from the nose and send it to the brain by way of the olfactory tracts.
Olfactory Nerve
The olfactory nerve carries the sensory information for the sense of smell. The olfactory nerves consist of a collection of many sensory nerve fibers.
Olfactory Receptor Cells (Odor Receptor Cells)
A specialized nerve cell, embedded in the mucous membrane of the nose.
Olfactory Tract
The olfactory tract is a bundle of axons connecting the olfactory bulb to several regions in the brain. It is a narrow white band.
Olfactory Transduction
A series of events in which cells in the nose bind to scent-bearing molecules and send electrical signals to the brain where they are perceived as smells.
Oligodendrocyte
A cell that forms the myelin sheath (a layer that covers and protects nerve cells) in the brain and spinal cord.
Postsynaptic Membrane
Cell membranes associated with synapses.
Receptors
A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific effect in the cell.
Synapses
The space between the end of a nerve cell and another cell. Nerve impulses are usually carried to the neighboring cell by chemicals called neurotransmitters, which are released by the nerve cell and are taken up by another cell on the other side of the synapse.
Synaptic Terminals (Axon Terminals)
An area at the end of an axon that contains neurotransmitters.

Terms to know

Axons
Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body....
Cell Body
The bulbous end of a neuron, containing the cell nucleus....
Dendrites
A long, branching outgrowth or extension from a neuron, that carries electrical signals from synapses to the...
See all 17

PubMed Health Blog...

read all...