Page 150 - 2024-bfw-MyersAP4e

Smell, like taste, is a chemical sense. We smell something when molecules of a sub-
stance carried in the air reach a tiny cluster of receptor cells at the top of each nasal cavity
(Figure 1.6-24). By sniffing, you swirl air up to those receptors, enhancing the aroma. These
20 million olfactory receptors, waving like sea anemones on a reef, respond selectively — to
the aroma of a cake baking, to a wisp of smoke, to a friend’s fragrance. Instantly, they alert
the brain through their axon fibers.

Olfactory bulb

4. The signals are transmitted
to higher regions of the brain.
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
Olfactory nerve
3. The signals are relayed
Olfactory bulb
via converged axons.
Copyright © Bedford, Freeman & Worth Publishers.
Receptor cells
in olfactory Bone
membrane
Olfactory
receptor
cells 2. Olfactory receptor
cells are activated and
send electrical signals.

Odor molecules

1. Odorants bind
to receptors.
Odorant
receptor

Air with odorant molecules

Figure 1.6-24
The sense of smell
Olfactory receptor cells send messages to the brain’s olfactory bulb, and then onward to the temporal lobe’s primary smell cortex and to the parts
of the limbic system involved in memory and emotion.

TRY THIS Being part of an old, primitive sense, olfactory neurons bypass the brain’s sensory
Impress your friends with your new control center, the thalamus. Eons before our cerebral cortex had fully evolved, our mam-
word for the day: People unable to malian ancestors sniffed for food — and for predators. They also smelled molecules called
see are said to experience blindness. pheromones — olfactory chemical messages — especially those secreted by other members
People unable to hear experience
deafness. People unable to smell of their species. Some pheromones serve as sexual attractants. When straight men smelled
experience anosmia. The 1 in 7500 ovulating women’s T-shirts, the men became more sexually interested and experienced
people born with anosmia not only increased testosterone (Miller & Maner, 2010, 2011).
have trouble cooking and eating,
but also are somewhat more prone Odor molecules come in many shapes and sizes — so many, in fact, that it takes many
to depression, accidents, and different receptors to detect them. A large family of genes designs the 350 or so receptor
relationship insecurity (Croy et al., proteins that recognize particular odor molecules (Miller, 2004). Linda Buck and Richard Axel
2012, 2013). Loss of smell and
taste have been commonly reported (1991) discovered (in work for which they received a Nobel Prize in 2004) that these receptor
symptoms of Covid. proteins are embedded on the surface of nasal cavity neurons. Just as a key slips into a lock,
odor molecules slip into these receptors. Yet we don’t seem to have a distinct receptor for each
detectable odor. Odors trigger combinations of receptors, in patterns that are interpreted by

150 Unit 1 Biological Bases of Behavior

03_myersAPpsychology4e_28116_ch01_002_163.indd 150 15/12/23 9:27 AM