Other Senses

Psychology: Chapter 4, Section 4

Other Senses• Vision and hearing are just two of our senses• Other senses are smell, taste, and the skin and

body senses• With vision and hearing, physical energy in the

form of light or sound waves stimulates our sensory receptors

• Smell and taste are called chemical senses, as we sense molecules of substances

• The skin detects touch through pressure, temperature, and pain

• Body senses alert us to posture and movement

Smell• The olfactory system is the sensory system used for

olfaction, or the sense of smell• People do not have as strong a sense of smell as

many animals• Dogs use seven times as much of the cerebral

cortex for smell as people do• But smell is important for people too• Without smell, we could not taste things as well,

and onions and apples would taste the same as each other

Smell- Taste Relationship• The smell of food

not only goes through our nostrils (nasal odor) but also up the back of the throat (retronasal odor) to the nose. • These smells help

us sense flavor

Smell

• Odors happen when molecules (in the form of a gas) spread from the object causing the odor

• Receptor neurons high in the nostrils react to the gas, and send information to the olfactory nerve, which sends the message to the brain

• We adapt rapidly to odors• This may be good in a smelly locker room, but not

so good if there is a dangerous gas leak in the house

Olfactory Epithelium (smell)

• Inside your nose is the olfactory epithelium, which is a fancy word for “smell device.”

• In the olfactory epithelium are more than 10 million scent receptors.

• These receptors can distinguish up to 10,000 different smells.

Taste

• Never feed a dog chocolate (it could give him or her a heart attack), but dogs do love candy. Cats, on the other hand, don’t particularly like candy. Dogs can taste sweetness, while cats cannot

• People have at least four basic taste senses– sweet, sour, salty, and bitter. (Some say another sense is umami, Japanese for “meaty” or “savory.”)

Taste

• Our tongue has taste buds, which are receptor neurons

• People have different concentrations of taste buds, leading to some people really enjoying spicy food, while others do not tolerate it

• It is possible to damage taste buds from hot foods or scraping your tongue, but fortunately, taste receptor cells reproduce rapidly, unlike other sensory neurons (like hearing or vision)

Taste buds are organized and grouped together on the tongue in distinct areas

Skin Senses

• The sense of touch could more accurately be further categorized into senses of pressure, temperature, itch and pain, so they are collectively called the skin senses

The sense of “touch” is actually many different kinds of senses

Pressure• Certain areas of our body are more sensitive to

the sense of pressure than other areas• For example, your fingertips, lips, and cheeks are

more sensitive than your shoulders or calves• We have hair cells that help with our sensitivity to

pressure, as sensory receptors near the hair roots fire when skin is touched

• There are also other structures under the skin to help with sensitivity to pressure

• Touch is very important for a newborn baby to thrive

One way to measure touch sensitivity is to see how far apart two points need to be to be felt as two points

It’s very important for a baby to be held (they should not be just left alone in a baby seat all the time)

Temperature• Sensations of temperature on our skin are relative.

If we are feverish, things that might normally feel warm could actually feel cold.

• We have receptors just below our skin surface that sense either hot or cold temperatures, and thus fire accordingly

• We adapt to hot or cold rather quickly. A cold pool or a hot bath seems relatively comfortable after just a few minutes.

When we have a high fever, we can ironically feel

very cold

Pain• How can pain be helpful? • Pain can protect us from further harm, by either

having us pull away from a source of injury or immobilizing an injured area

• As with pressure receptors, pain receptors are not evenly divided around the body– the sole of your foot is not as sensitive to pain as your neck

A swelling can help immobilize a joint that shouldn’t move, and may work as a splint

Pain• The pain message travels quickly from the source of

the pain to the spinal cord, to the thalamus, to the cerebral cortex, where the location and severity of the pain is interpreted

• Chemicals called prostaglandins send pain messages to the brain

• Aspirin and ibuprofen curb production of prostaglandins, thus reducing how much pain we feel

While all four of these do relieve pain and fever, Tylenol does not reduce swelling

Pain• Why does rubbing an injured area sometimes help

relieve pain?• One possible answer is the gate theory of pain• Gate theory suggests that only a certain amount of

information can be processed by the nervous system at a time

• Rubbing an area may flood the brain with other sensations, reducing the amount of pain messages able to make it through

Large nerve fibers are fast and stimulated by non-painful

rubbing. They effectively close the gate on pain coming through

Pain• Many people who have lost a limb experience pain

in the limb that is no longer there• This is known as “phantom limb pain”• There are nerves in the remaining stump of the

missing limb that have memories connected with the limb

These are the characteristic sensations of phantom limb pain after a leg has been amputated below the knee

Body Senses• Body senses help you stay upright and put food in

your mouth without looking• There are two main body senses: the vestibular

sense and the kinesthetic sense• Your vestibular sense lets you know whether you

are upright or falling, or changing speeds in a vehicle

• Your kinesthetic sense also lets you know the position and motion of your body, and allows you to touch your nose with your eyes closed or feed yourself with a fork

The semicircular canals in your ear help you keep your balance via your vestibular sense

Alcohol affects your kinesthetic sense, and so a common roadside test is for suspects to close their eyes, tip back their head, and

touch their nose

Assessment

• Answer all three questions on page 92 and turn that in