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how smell travels

how smell travels插图

How does the sense of smell travel through the air?

Some of the particles travel up toward an area in the nasal cavity where odor-sensing cells are located (this area is marked in white below the eye). Only a few particles are needed to trigger the sense of smell. The remaining particles travel down toward the lungs (through the pink circle marked at lower right) and are eventually breathed out.

How many particles are needed to trigger the sense of smell?

Only a few particles are needed to trigger the sense of smell. The remaining particles travel down toward the lungs (through the pink circle marked at lower right) and are eventually breathed out.

Where does smell begin?

Smell begins at the back of nose, where millions of sensory neurons lie in a strip of tissue called the olfactory epithelium. The tips of these cells contain proteins called receptors that bind odor molecules. The receptors are like locks and the keys to open these locks are the odor molecules that float past,…

How do odors affect the brain?

When an odorant stimulates the chemoreceptors in the nose that detect smell, they pass on electrical impulses to the brain. The brain then interprets patterns in electrical activity as specific odors and olfactory sensation becomes perception — something we can recognize as smell.

What happens when air currents sweep up odorant?

When an air current sweeps an odorant up through the nostrils, the molecules hit the olfactory epithelium – the center of ol factory sensation . The epithelium occupies only about one square inch of the superior portion of the nasal cavity. Mucus secreted by the olfactory gland coats the epithelium’s surface and helps dissolve odorants.

How many glomeruli are there in the olfactory bulb?

The brain interprets the "odorant patterns" produced by activity in the different glomeruli as smell. There are 2,000 glomeruli in the olfactory bulb — twice as many microregions as receptor cells — allowing us to perceive a multitude of smells.

How many genes are in the olfactory receptor family?

Axel and Buck discovered a large gene family — 1,000 genes, or 3 percent of the human total — that coded for olfactory receptor types. They found that every olfactory receptor cell has only one type of receptor. Each receptor type can detect a small number of related molecules and responds to some with greater intensity than others. Essentially, the researchers discovered that receptor cells are extremely specialized to particular odors.

Why does my car smell musty after rain?

Temperature and humidity affect odor because they increase molecular volatility. This is why trash smells stronger in the heat and cars smell musty after rain. A substance’s solubility also affects its odor. Chemicals that dissolve in water or fat are usually intense odorants.

Which nerve fibers are responsible for odor?

While receptor cells respond to olfactory stimuli and result in the perception of smell, trigeminal nerve fibers in the olfactory epithelium respond to pain. When you smell something caustic like ammonia, receptor cells pick up odorants while trigeminal nerve fibers account for the sharp sting that makes you immediately recoil.

Why is smell important?

Smell is often our first response to stimuli. It alerts us to fire before we see flames. It makes us recoil before we taste rotten food. But although smell is a basic sense, it’s also at the forefront of neurological research. Scientists are still exploring how, precisely, we pick up odorants, process them and interpret them as smells. Why are researchers, perfumers, developers and even government agencies so curious about smell? What makes a seemingly rudimentary sense so tantalizing?

What is the chemical sense of smell?

Smell, like taste, is a chemical sense detected by sensory cells called chemoreceptors. When an odorant stimulates the chemoreceptors in the nose that detect smell, they pass on electrical impulses to the brain.

Why does a smell conjure up memories?

This happens because the thalamus sends smell information to the hippocampus and amygdala, key brain regions involved in learning and memory.

How many different smells can you identify?

Although scientists used to think that the human nose could identify about 10,000 different smells, Vosshall and her colleagues have recently shown that people can identify far more scents. Starting with 128 different odor molecules, they made random mixtures of 10, 20, and 30 odor molecules, so many that the smell produced was unrecognizable to participants. The researchers then presented people with three vials, two of which contained identical mixtures while the third contained a different concoction, and asked them to pick out the smell that didn’t belong.

How many different types of olfactory receptors are there?

People have about 450 different types of olfactory receptors. (For comparison, dogs have about two times as many.) Each receptor can be activated by many different odor molecules, and each odor molecule can activate several different types of receptors.

What is the function of the olfactory bulb?

After receiving smell information from the nose’s sensory receptors, the olfactory bulb relays the information to a circuit of brain regions for processing.

Where does smell originate?

Smell begins at the back of nose, where millions of sensory neurons lie in a strip of tissue called the olfactory epithelium. The tips of these cells contain proteins called receptors that bind odor molecules. The receptors are like locks and the keys to open these locks are the odor molecules that float past, explains Leslie Vosshall, a scientist who studies olfaction at Rockefeller University.

What is the mouth of a mouse?

The “mouth” is the nasal cavity of a mouse, which is lined with specialized odor-sensing cells (in green). These cells signal to the olfactory bulbs — the round “eyes” in the image. Memi, et al. Journal of Neuroscience, 2013. After receiving smell information from the nose’s sensory receptors, the olfactory bulb relays the information …

Where does the smell come from in the brain?

Odors in the Brain. This neural code begins with the nose’s sensory neurons. Once an odor molecule binds to a receptor, it initiates an electrical signal that travels from the sensory neurons to the olfactory bulb, a structure at the base of the forebrain that relays the signal to other brain areas for additional processing.