Psychology 135

C.F.Tiangco

UPDEPP

1. The sense of smell is mature at birth.

2. Newborn males have a keener sense of smell than newborn females.

3. Different aromas can make us happy, sad, alert or sleepy.

4. People can recall entire events with the whiff of a specific scent.

5. Our sense of smell shuts off when we sleep.

What’s your SQ (Smell Quotient)?

6. The only time we smell is when we inhale.

7. Everyone who smells the same thing perceives it in the same way.

8. Each individual human being has a unique odor-identity or smell fingerprint.

9. What we call the “taste” of food is mostly the “smell” of food.

10. Many animals use their scents to mark the path to and from a food source.

What’s your SQ (Smell Quotient)?

Influence of smell

Enhancement of taste

Purchasing behavior

Danger warnings

Identification of sex

- Wallace (1977) hand-sniff experiment: over 80% accuracy

- Doty et al. (1982) breath-sniff experiment: over 50% accuracy

- Russel (1976) “Stinky Tee” experiment

81% of the males and 69% of the females identified their own shirts correctly

General level of arousal:

peppermint vs bergamot experiment

Evoke old memories

Detecting diseases : (e.g.,trimethylaminuria)

Sexual behavior?aksepek.flv

Sex and the Nose

Vomeronasal organs (VNO) embedded in vomer bone

VNO neural messages are carried to the brain by their own special nerve fibers, bypassing the olfactory bulb

From there, projects to limbic system

Stimulus for Smell

The stimulus for smell consists of airborne molecules or vapors

To be odorous, a substance must be volatile

The volatile molecules be soluble in fat

Classification of Odors

Hans Henning’s smell prism

Crocker-Henderson system : four classifications of odor (burned, fragrant, acid and caprylic)

Stereochemical theory : seven odors (camphoraceous, musky, floral, minty, ethereal, pungent and putrid)

• Multidimensional scaling

Schiffman (1974) odor space

Considered several molecular characteristics in an attempt to uncover what physical properties, if any, similar smells have in common.

Examining the molecular shapes of various substances, she found no relation between the shapes of various compounds and the odors produced by these compounds .

Theories of Olfactory Perception Shape-pattern theory: Match between

shapes of odorants and odor receptors; dominant biochemical theory.

Vibration theory- the odorant molecule must first fit in the receptor's binding

site.

- it must have a vibrational energy mode compatible with the difference in energies between two energy levels on the receptor, so electrons can travel through the molecule and trigger the signal transduction pathway

- the odor character is encoded in the ratio of activities of receptors tuned to different vibration frequencies

Anatomy and Physiology of Smell: The Nose Inhaling pulls

vapors into the nostrils and circulates them through the nasal cavity

(a hollow region inside the nose where the olfactory receptors are located)

• Air entering the L and R nostrils (or wafting back from the back of the mouth) passes into the corresponding nasal cavities.

• There, the air circulates around a series of baffles formed by three, small, mucous-covered bones (turbinates)

As air circulates around this series of baffles, it is warmed and humidified, and tiny hairs lining the nasal cavity remove debris such as dust

In most people, L and R nasal airways appear to work in alternating shifts (nasal cycle)

At any given time, the mucous lining in one nasal passage is more engorged than the other, which narrows one nasal passage and creates greater resistance to the inflow of air

Olfactory Sensory Transduction The receptor cells that

register the presence of odorous molecules sit on a patch of tissue called the olfactory epithelium

The OE forms part of the ceiling of the nasal cavity

Olfactory Sensory Neuron (OSN) – a bipolar nerve cell that captures odorant molecules and initiates the neural signals for smell

At one end, this bipolar nerve cell has a single dendrite that terminates in a number of tiny cilia.

At its opposite end, the nerve cell terminates in a single axon that, together with the axons of several neighboring nerve cells, form a sensory fiber that threads through one of the perforations in the spongy, relatively thin bone that forms the roof of the nasal cavity and the upper 2/3 of the nasal septum.

After the axons pass through this bone, the axons’ terminals synapse with neurons in the olfactory bulb

The typical human nose contains somewhere between 40 and 50 million olfactory sensory neurons

OSNs differ from receptor neurons in the eye and ear:

- Genuine neurons

- Have very short lives, lasting about 5 to 8 weeks. When they die, they are replaced

- Do two jobs at once—transduce and carry impulses to the brain along their axons (which make up the olfactory nerve)

They are not mediated by any protective barrier, make direct contact with brain.

Extending from the dendritic end of each OSN are clumps of cilia – thin, hairlike structures embedded in the thin layer of mucus that coats the nasal cavity

The receptor sites for olfaction are embedded in the membrane surface of these cilia

the greater the surface area, the greater the opportunity for receptor sites to be exposed to airborne odorant molecules

To reach these receptor sites, molecules of odorant must pass from the inhaled air into the nasal cavity’s mucous layer

Odorants are aided in this process by olfactory binding proteins (traps and concentrates odorous molecules, transporting them into the nasal mucus, where they have a chance to make contact with receptors)

A gland located in the OE produces this protein, which occurs only in nasal tissue. A duct carries the protein toward the tip of the nose where, every time you inhale, molecules of the protein are mixed into the incoming air.

The protein in the newly inspired air traps molecules of potential odorants and carries these bound molecules to the olfactory receptors.

The steps to the perception of an odor begin when odorant molecules bind to specific sites on the receptor proteins.

When an odorant molecule has firmly docked with its matching receptor protein, the receptor triggers a series of molecular events

The last of these intermediaries is an enzyme that triggers electrical changes in the cell membrane. At this point, the capture of an odorant molecule has been transduced into an electrical signal.

Neural Coding of Odor Quality The vast majority of olfactory nerve fibers

respond to a host of different odors, many bearing no qualitative similarity to one another.

Consequently, individual olfactory fibers can signal the presence of an odorous substance, but no single olfactory fiber provides unequivocal information about exactly what that substance is.

The Olfactory Pathways

Olfactory bulb receives all input from the olfactory nerve

Olfactory brain – a cluster of neural structures receiving projections from the olfactory bulb

The incoming axons from the olfactory epithelium activate neurons in the receiving stage of the bulb rather diffusely (glomeruli)

There is enormous convergence. Consequently, very weak neural signals, originating in many different olfactory neurons and carried by olfactory nerve fibers, may be summed within the bulb

Output of OB is carried by axons arising from several morphologically distinct classes of neurons in the bulb. Those axons project to the primary olfactory cortex, located below the anterior portion of the temporal lobe

Odor Perception

People are generally able to detect weak odors better in the morning than in the evening

Elderly people are less sensitive than young adults

Females are more sensitive, on average, than males

Smokers are less sensitive to odors than nonsmokers

Odor Identification

At near-threshold concentrations, people can smell an odor without being able to identify the odor

Females are significantly better at odor identification than males, with the best performance exhibited by individuals ranging in age from the mid-20s to late-40s (Doty, Shaman, and Dan, 1984)

Sense of smell and language:

Disconnected, possibly because

– Olfactory information is not integrated

in thalamus prior to processing in cortex

– Majority of olfactory processing occurs in

right side of brain while language

processing occurs in left side of brain

The Common Chemical Sense Free nerve endings – in

olfactory epithelium

Each of these membranes is very sensitive to potentially irritating chemicals

Responsible for the feeling that accompanies certain smells

The feel of scent:

– Odorants can stimulate somatosensory system through polymodal nociceptors (touch, pain,temperature receptors).

– These sensations are mediated by the

trigeminal nerve (cranial nerve V).

– Often, it is impossible to distinguish between sensations traveling up cranial nerve I from olfactory receptors and those traveling up cranial nerve V from somatosensory receptors.

Disorders of Smell

Some people have hyposmia, which occurs when their ability to detect certain odors is reduced.

This smell disorder is common in people who have upper respiratory infections or nasal congestion.

This is usually temporary and goes away when the infection clears up.

Other people can't detect odor at all, which is called anosmia.

This type of smell disorder is sometimes the result of head trauma in the nose region, usually from an automobile accident or chronic nasal or sinus infections.

It can sometimes be caused by aging. In rare cases, anosmia is inherited.

Sometimes a problem with smell can be a sign of a more serious health problem.

This might include diseases of the nervous system, such as multiple sclerosis, Parkinson's disease, or Alzheimer's disease, or, in rare cases, a brain tumor.

Sometimes a loss of smell can be accompanied by a change in the perception of odors. This type of smell disorder is called dysosmia.

Familiar odors may become distorted, or an odor that usually smells pleasant instead smells foul.

Sometimes people with this type of smell disorder also experience headaches, dizziness, shortness of breath, or anxiety.

1. The sense of smell is mature at birth.

2. Newborn males have a keener sense of smell than newborn females.

3. Different aromas can make us happy, sad, alert or sleepy.

4. People can recall entire events with the whiff of a specific scent.

5. Our sense of smell shuts off when we sleep.

1. Agree. In fact, smell is one of the first senses that a newborn baby experiences.

2. Disagree. It’s just the opposite. 3. Agree. Aroma-Chology research is

discovering more about the effect of odors on moods,feelings & emotions.

4. Agree. Researchers studying this phenomenon have found that our ability to recall a specific scent that we’ve experienced surpasses even our ability to recall what we’ve seen.

5. Disagree. Our sense of smell definitely does function while we’re asleep, although some scientists believe it is not as acute as when we are awake.

What’s your SQ (Smell Quotient)?

6. The only time we smell is when we inhale.

7. Everyone who smells the same thing perceives it in the same way.

8. Each individual human being has a unique odor-identity or smell fingerprint.

9. What we call the “taste” of food is mostly the “smell” of food.

10. Many animals use their scents to mark the path to and from a food source.

6. Disagree. It takes about 5s for humans to breathe --- 2 to inhale,3 to exhale – and in that time molecules of odor flood through our nasal cavity. Inhaling and exhaling, we smell odors.

7. Disagree. Our reactions to most odors are highly personal, depending upon our own unique odor receptors and odor/ memory associations.

8. Agree. Genes, skin type, diet, age, physical and mental conditions, and even the weather, are determining factors in each individual’s unique odor-identity.

9. Agree. Without the sense of smell, we vastly limit ourselves to only five taste sensations.

10. Agree. Animals also use their sense of smell to establish territories and to communicate with each other.

What’s your SQ (Smell Quotient)?

Next topic: Taste

Homework

List down 10 “fun” facts about the sense of taste. To be submitted and shared next meeting.

The five students who can share the most obscure, interesting, yet TRUE information about the human gustatory system get additional 5 points on exam 1!