s&p exam 4

tufted cells

A secondary class of output neurons in the olfactory bulbs.

What are chemosignals?

Impartial way to discuss human chemical communication Chemicals emitted by humans that are detected by the olfactory system that may have an effect on the mood or behavior of other humans. Example- androstadienone- chemically related to androstenone

What effects do pheromones have?

Social Insects: • ants, termites, and bees Ants are really socially complex in their ability to communicate with each other in order to get things done. Emit pheromones to get help carrying something, movement to different places, etc. They have super sophisticated signaling. -EahWilson Termites also have ridiculous signaling. Bees (in book). When a bee stings you, it is sending out pheromones to alert to the other bees that they are under attack and need help. Primates too! Sexual Behavior: Often provide signals to males about when a female is fertile and provide signals to males to initiate sexual behavior • Male rhesus monkey will ignore a female rhesus monkey in heat if his nose is blocked • A female sow will not go into lordosis(the position necessary for impregnation) if she isn't exposed to the male pig pheromone androstenone

Specific hungers theory

The idea that deficiency of a given nutrient produces craving (a specific hunger) for that nutrient. • Cravings for salty or for sweet are associated with deficiencies in those substances • Has not been supported for other nutrients, such as vitamins • Theory only holds for sweet and salty foods

Specific Anosmia

The inability to smell one specific compound amid otherwise normal smell perception Sig. portion of population has specific anosmia to androstenone, a molecule found in armpit sweat and pork • Perceive as "sweet muskyfloral" • Majority perceive it as an unpleasant "urinous" odor Sensitivity to androstenonecan be increased with training • This cannot be explained by vibration theory, nor can the differences in perceived smell • Shape-pattern theory can explain these findings Some people cannot smell the sulfur in urine that comes from eating asparagus. Some may be very sensitive to the smell of sweat. You can increase your sensitivity to certain smells. Or, some people can't smell what everyone else is complaining about even though they have a sense of smell.

Olfactory Receptor (OR)

The region on the cilia of OSNs where odorant molecules bind. 1:1:1 = each OSN express only one type of OR, and all OSNs expressing the same type of OR project to the same type of glomerulus. To initiate an action potential = it takes 7 or 8 odor molecules binding to a receptor It takes about 40 nerve pulses for a smell sensation to be reported. How long it takes for us to experience the smell. very specific to odorants.

Anosmia development statistics

.06% - born with it 30% - head trauma

cribriform plate

A bony structure riddled with tiny holes, at the level of the eyebrows, that separates the nose from the brain Axons from OSNs pass through the tiny holes to enter the brain

Pheromone

A chemical emitted by one member of a species that triggers a physiological or behavioral response in another member of the same species. May or may not have any smell.

olfactory cleft

A narrow space at the back of the nose into which air flows, where the main olfactory epithelium is located

Entorhinal cortex

A phylogenetically old cortical region that provides the major sensory association input into the hippocampus. Also receives direct projections from olfactory regions. Rhino nose, plastic on nose, old region (genetically)

olfactory epithelium

A secretory mucosa in the human nose whose primary function is to detect odorants in the air. The "retina" of the nose, which is where receptors are located. One inch to two inch. three cells in there

Are Olfactory hedonics nature or nurture?

Are hedonic responses to odors innate or learned? • Debate over this Evidence from infants: • Odor preferences often very different from adults Cross-cultural data: • Support associative learning (most familiar with this specific odorant because I associate it with this experience) An evolutionary argument: • Some animals exhibit an instinctive aversion to smells from predators, etc. Our predator varies on our environment, so we have a wide array of aversion. Learned taste aversion: • Avoidance of a novel flavor after it has been paired with gastric illness • Associated with negative experience so now you avoid it because it made you sick Learning occurs in utero. (with smell, about third month of gestation) Expose them to whatever you want to expose them to in utero. Wintergreen products are popular in America, but not in Britain. Familiarity breeds content.

Amygdala-hippocampalcomplex

Conjoined regions of the amygdala and hippocampus. Two components of limbic system - emotional center of brain Critical for the unique emotional and associative properties of olfactory cognition

olfactory tract

Axons from the mitral and tufted cells of each bulb combine and form the olfactory tract. They do this as they leave the olfactory bulb. One in each hemisphere of the brain. (ipsilateral) Conveys information ipsilaterally to the primary olfactory cortex.

Genetic Basis of Olfactory Receptors

Buck and Axel (1991): Study showed that genome contains about 1,000-2,000 different olfactory receptor genes; each codes for a single type of OR. All mammals have pretty much the same set of 1000 genes. However, some genes are non-functional pseudogenes • Dogs and mice: About 20% are pseudogenes • Humans: Between 60% and 70% are pseudogenes • Each person has a different number of pseudogenes, resulting in individual differences in sensitivity to smells There may be an evolutionary trade-off between vision and olfaction.

What is the special case of umami?

Candidate for fifth basic taste but not perceptible in many foods. Advertisers of monosodium glutamate (MSG) as a flavor enhancer • Glutamate: Important neurotransmitter Safety issues in human consumption: • Can lead to numbness, headache, flushing, tingling, seating, and tightness in the chest if sensitive individuals consume a large amount • For most people, MSG does not pose a problem in small doses People who are prone to migraines are more sensitive to MSG in foods, so they avoid them. There used to be the idea that MSG would enhance good flavors and eliminate bad ones.

circumvallate papillae

Circular structures that form an inverted V on the rear of the tongue (three to five on each side). Moundlike structures surrounded by a trench. Much larger than fungiform papillae

Sour

Comes from acidic substances. Like lemons and grapefruit At high concentrations, acids will damage both external and internal body tissues. We avoid sour things because of that. Usually viewed less enjoyable when becomes intense. It's okay at minimal levels.

Papillea

Contain taste buds -Have taste receptors

Olfactory nerves

Cranial Nerve I The axons of the OSNs bundle together after passing through the cribriform plate to form the olfactory nerve. makes up olfactory tract.

taste buds

Create neural signals conveyed to brain by taste nerves Embedded in papillae (bumps on tongue) Each taste bud contains taste receptor cells: • Each receptor responds to a limited number of molecule types. Information is sent to brain via cranial nerves

Sweet

Evoked by sugars Many different sugars that taste sweet: • Sucrose: sugar cane, sugar beets, corn. natural source of sugar. Combination of glucose and fructose • Glucose: Principle source of energy for most animals - need this for ATP • Fructose: Even sweeter than glucose Single receptor responsible for all sweet perception! • Different sweeteners stimulate different parts of receptor • Artificial sweeteners stimulate this receptor as well - want to try to avoid these because even though you're satisfying the sweetness, they do tend to increase appetite and eating. Sugar is no longer being processed properly which is a drawback

What is the McClintock effect?

Example of primer pheromone. Women who are in physical proximity (e.g., live together) over time start to have menstrual cycles that coincide • Women who move into a college dorm together will likely have their menstrual cycles synchronized by winter break • Relevant to consider what you share with the other women that you sync up with.

Foliate papillae

Folds of tissue containing taste buds. Located on the rear of the tongue lateral to the circumvallate papillae, where the tongue attaches to the mouth.

Connection between taste and smell

Food industry: • Adds sugar to intensify sensation of fruit juice • Increase in sweetness (a pure taste sensation) increases perceived olfactory sensation of fruit The reverse? • Adding volatiles to reduce the amount of sugar and salt.

What is the vomeronasal organ?

Found in nonhuman animals A chemical sensing organ at the base of the nasal cavity with a curved tubular shape. Evolved to detect chemicals that cannot be processed by the olfactory receptors, such as pheromones. Humans don't have this the same way other animals do. Snakes flick tongue to try to detect pheromones that are out there to activate this. Cats rub up on things to mark their territory.

cilia

Hairlike protrusions on the dendrites of OSNs. Contain receptor sites for odorant molecules. These are the first structures involved in olfactory signal transduction. chemical transduction: activated by odorants.

Why do we need to taste?

Helps us figure out what we can and cannot digest! Is a chemical sense just like smell Helps us figure out what will taste good. Things that taste bitter (naturally) are more likely to be toxic. Things that taste sweet are likely to be safer.

What is the importance of patterns when it comes to smell?

How can we detect so many different scents if our genes only code for about 1000 olfactory receptors? 600-700 nonfunctional - some don't work (psuedogenes) We can detect the pattern of activity across various receptor types. Intensity of odorant also changes which receptors will be activated • Weak concentrations of an odorant may not smell the same as strong concentrations of it Specific time order of activation of OR receptors is important - can bind to more than one as long as it fits. Some odorants can fit in multiple receptor types through movement or can bind to more than one. Timing matters for everything.

Odor Imagery

Humans have little or no ability to conjure odor "images" • We do not think in smell very well • We do not imagine smells very well—dreams with olfactory sensations are very rare. We can describe it (what it looked like, where you were). • Some exceptions, such as perfumers show activation of the piriform cortex. Trained to detect different odorants. Other animals for whom smell plays a more central role, such as rats, may very well think and dream smells. A greater part of cortex is devoted to processing smell compared to ours.

What happens if you remove salt and sugar from your diet?

If you remove salt and sugar from your diet, you will see differences in your body responses, especially when you have it again after a long time.

limbic system

It is the emotional center of the brain that also plays roles in smell, motivation and memory. Olfaction is unique among the senses for its direct and intimate connection to the limbic system Olfaction's unique connection to the limbic system explains why scents tend to have such strong emotion associations. Memories may be better or sense of smell in relation to the memory may be stronger, but may not always be accurate. ex. smelling someone's scent who died

How easy is it to identify smells with a verbal label?

It's not. We are bad at being able to describe smells. Anthropologists have found that there are fewer words for experience of smells compared to other sensations Ex. Stinky, sweet, fruity, good, bad, disgusting, etc

two subdivisions of the olfactory system

Main Olfactory Bulb (MOB): • First region of the brain where smells are processed. Accessory Olfactory Bulb (AOB): • A smaller neural structure found in nonhuman animals. • Located behind the MOB. • Receives input from the vomeronasal organ. This is a chemical sensing organ that is sensitive to detect pheromones. We cannot detect them the same way other animals do that do have it.

What types of scent cause physical sensations?

Menthol - feels cool Cinnamon - feels warm Ammonia - feels burning

What is the staircase method?

Method for determining the concentration of a stimulus required for detection at a threshold level. Stimulus is presented in increasing concentrations until detection is indicated. Then, concentration is decreased until detection ceases. Detecting an individual's sensitivity to odor; determine the threshold. Be given exposure to an odor that would gradually increase in concentration until you say you can smell it. Then they decrease it till you can't smell it. They repeat this until they can determine an average to find your overall threshold. There are differences in olfactory receptors

Fungiform papillae

Mushroom-shaped structures (maximum diameter 1 mm) that are distributed most densely on the edges of the tongue, especially the tip. An average of six taste buds per papilla are buried in the surface. There are variations among individuals in how many we have.

Olfactory Hedonics

Odor Hedonics: The liking dimension of odor perception Scales measure perceived pleasantness, familiarity, and intensity. Familiarity and Intensity: We tend to like odors we've smelled many times before. Intensity has a more complicated relationship with odor liking: • Inverted U-shape function • Linearly decreasing function

What is responsible for scent feeling physical?

Odorants can stimulate somatosensory system through polymodal nociceptors (touch, pain, temperature receptors). Trigeminal nerve (cranial nerve V (nerve 5)): mediate these sensations - gets mixed with info from #1 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.

Are odors really the best cues to memory?

Other modalities can elicit memory as well (e.g., vision, touch, taste). Memories triggered by odor cues are distinctive in their emotionality. Emotion and evocativeness of odor-elicited memories lead to false impression that such memories are especially accurate. All memories have a degree of error. While people think smell provides more accurate memories, it's really just an increase in emotional memories.

Orbitofrontal cortex

Part of the frontal lobe that integrates pleasure and displeasure from food. • Also the cortical area for assigning affective value (i.e., hedonic judgment) • Called the secondary olfactory cortex and the secondary taste cortex. These two factors help explain the increased emotionality of smells as opposed to other senses. Right behind eyes. This is where we have the associated judgement for liking and disliking things. Taste and smell go hand in hand when making judgements. Think of limbic system! Emotional center of the brain. All that info is associated with the orbitofrontal cortex

retronasal olfaction

Perceiving odors through the mouth while breathing and chewing. Eating also involves breathing, not just chewing. Gives us the experience of flavor.

Is it possible that there is a disconnect between smell and language?

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. We don't have the words to describe smell. Because processing occurs in different hemispheres, may lead to disconnect between words to describe the smell and the smell itself. SMELL DOES NOT GO TO THE THALMUS. IT. DOESN'T. GO. THERE. Trouble with smelling can be an indicator of Alzheimer's or Parkinson's. (It diminishes as you age).

basal cells

Precursor cells to olfactory sensory neurons.

supporting cells

Provides metabolic and physical support for the olfactory sensory neurons.

Pheromone types

Releaser pheromone: • Triggers an immediate behavioral response among conspecifics (another member of the same species. • Example- sexual cues and behavioral cues (lordosis) • Example: Bee stinging you, immediately other bees come and sting you. Primer pheromone: • Triggers a physiological (often hormonal) change among conspecifics (member of the same species) • This effect usually involves prolonged pheromone exposure. • Ex. When female rodent in same container as other female rodents, they will sync cycles with each other.

Do taste and smell mix?

Retronasal Olfactory Sensation: • The sensation of an odor that is perceived when chewing and swallowing force an odorant in the mouth up behind the palate into the nose and stimulate the olfactory receptors. Flavor: • The combination of ttaste (sweet, salty, sour, bitter) and retronasal olfaction

Infant behavior when tasting

Reveal innate preferences for certain foods. Different flavored foods placed on tips of infants' tongues: • Sweet food evokes a "smile like" expression followed by sucking. • Sour produced pursing and protrusion of lips • Bitter produced gaping, movements of spitting, and sometimes vomiting movements

salty (sodium chloride)

Salt is made up of two charged particles: Cation and anion (NaCl) Ability to perceive salt is not static: • Low-sodium diets will increase in intensity of salty foods over time. does not the stay the same Liking for saltiness is not static: • Early experiences can modify salt preference. Chloride-deficiency in childhood leads to increased preference for salty foods later. • Gestational experiences may affect liking for saltiness early exposure influences tolerance for salty depends how much salt is in your food for you to notice it - we eat so much prepackaged food that has high levels of salt that it's hard for us to detect it. we do need salt for action potentials and we do increase sodium levels when we sweat, so we do need salt in our diet to compensate.

Olfactory Adaptation

Sense of smell is essentially a change detector: • Examples: Walking into a bakery and can only smell fresh bread for a few minutes. Someone who wears perfume every day cannot smell it and might put a lot on. • Ex: Being exposed to odor in stinky room: if you stay there for at least 15 minutes, eventually you will not be able to smell the odor anymore. Only works to a certain extent; relationship between attention and concentration on it.

Shape-Pattern Theory

Shape-Pattern Theory: Different scents activate different arrays of olfactory receptors in the olfactory epithelia. These various arrays produce specific firing patterns of neurons in the olfactory bulb, which then determine the particular scent we perceive. They each of their own shape and overall smell is from which receptors are activated, which leads to perceived scents.

Microvilli

Slender projections of the cell membrane on the tips of some taste bud cells that extend into the taste pore. Contain the sites that bind to taste substances. Not tiny hairs (as the name implies) part of tastebud extension of cell membrane that includes receptors

Filiform papillae

Small structures on the tongue that provide most of the bumpy appearance. Have no taste function. Just kind of there.

Anosmia

Smell blindness The total inability to smell, most often resulting from sinus illness or head trauma. A hard blow to the front of the head can cause the cribriform plate to be jarred back or fractured, slicing off the fragile olfactory neurons. Anosmia causes a profound loss of taste as well as smell. Hard to make adjustments when you lose sense of smell. You won't want to eat because food won't taste right and you can't receive pleasure from something you can't smell.

orthonasal olfaction

Sniffing in and perceiving odors through our nostrils, which occurs when we are smelling something that is in the air.

Foods and Perception

Somatosensory System - touch, temperature, pain receptors in tongue and throughout entire mouth. Helps protect: • Burn of acid • Heat pain • Pain of biting tongue Fat content: • Oily • Viscous • Thick • Creamy Texture thing -people don't want to eat stuff because they hate the texture.

Glomeruli

Spherical conglomerates containing the incoming axons of the OSNs. Each OSN converges on two glomeruli (one medial, one lateral). Combine to form one thing. Receptors and cells combine and go through the spherical conglomerates.

Taste processing in the CNS

Taste Processing in the CNS: Pathway: • Taste buds to cranial nerves to medulla and thalamus and then on to cortex. Insular cortex: • Primary cortical processing area for taste. • The part of the cortex that first receives taste information. Orbitofrontal cortex: • The part of the frontal lobe of the cortex that lies above the bone (orbit) containing the eyes. • Receives projections from insular cortex. • Involved in processing of temperature, touch, smell, and taste, suggesting it may be an integration area.

Survival Values of Taste

Taste is a system for detecting nutrients and antinutrients: Bitter: Might signal poisons. Sour: Configured to detect acidic solutions that might harm the body. Sweet and Salty: Our bodies need sodium and sugar to survive.

Receptor adapation

The biochemical phenomenon that occurs after continuous exposure to an odorant, whereby the receptors stop responding to the odorant and detection ceases. Aka, the receptor will not be available for anymore binding for a period of time. The information is no longer available as long as the odorant stays bound to it. Smelling something else will mess this up, as it resets your receptors. If you keep paying attention to it, that won't help either.

olfactory bulb

The blueberry-sized extension of the brain just above the nose. Olfactory information is first processed here. There are two olfactory bulbs, one in each brain hemisphere, corresponding to the left and right nostrils. Connections are ipsilateral(same side of body). Sends info upwards.

Tip of the nose phenomenon

The inability name an odorant, even though it is very familiar It's there and we know we know it, but we can't come up with what it is. When we use a name to describe a smell, we're usually describing what we associate with or think of when we smell the smell. • Not the same as tip-of-the-tongue phenomenon! We do NOT have lexical access to the name of the odorant, such as first letter, rhyme, number of syllables, etc. There isn't semantic info to help us. Language and olfactory perception are deeply disconnected

olfactory sensory neurons (OSNs)

The main cell type in the olfactory epithelium • OSNs are small neurons located within a watery mucous layer in the epithelium • Contain odorant receptors. extend through mucosa. olfactory cilia on end of this contains receptors.

mitral cells

The main projective output neurons in the olfactory bulbs.

Primary Olfactory Cortex: "Piriform Cortex"

The neural area where olfactory information is first processed, which includes the amygdala-hippocampal complex and interacts with the entorhinal cortex

Cognitive Habituation

The psychological process by which, after long-term exposure to an odorant, one is no longer able to detect that odorant or has very diminished detection ability. • Example: Going out of town, coming back and noticing how your house smells. -It takes leaving for several weeks to break this because you're so used to it. Even drawing your attention to it won't do anything. Exposure to something for so long that you don't even sense it anymore.

Cross-adaptation

The reduction in detection of an odorant following exposure to another odorant. • Presumed to occur because the two odors share one or more olfactory receptors for their transduction, but the order of odorants also plays a role. Smells something else to reset receptors and make them available again. If things smell similar, you won't be able to smell the second thing because your receptors are already bound to something and are already activated; you can't smell anything new.

How are olfactory receptor cells different from all other sensory receptor cells?

They are not mediated by any protective barrier and make direct contact with the brain! Aka, there is no barrier. • Contrast with visual receptors that are protected by cornea, hearing receptors protected by eardrum, taste buds are buried in papillae. • Why so many drugs are inhaled. snorting and inhalation leads to quicker high bc no barrier. OSN axons are among the thinnest and slowest in the body • Takes longer to perceive odors compared to other sense. Relaying upward actually kinda slow

Types of taste

Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called "Umami" (MSG).

What is the triangle test?

Used to determine if someone can discriminate between two odorants. Participant is given three odors to smell, two of which are the same and one is different. Participant must identify the odd odor. (Will switch it up.) • Need to say which one is different and which ones are the same. Will switch the order to see if you can discriminate between them. The order of the three odors is varied and tested several times to increase accuracy

How important is attention when it comes to smelling?

We cannot smell while we are asleep Attention is cut off during sleep, so is our ability to respond to odors Attention increases our ability to detect odors Need to be awake to pay attention to something We have smoke detectors for this reason; we wouldn't be able to smell smoke; we need the alarm to wake us up to smell it. Need to pay attention to be able to sense it. Some may say they smell something even if they don't because of fear (expect it to be harmful). Attention can help us zone in on smell to make sure we smell it before. If you stay up for a really long time, your ability to pick up on smells diminishes the longer you stay awake. It effects everything. SLEEP AFFECTS EVERYTHINGGGGGGGGGGGGG

Do humans respond to pheromones?

We don't necessarily have the means to really detect this, but it is possible. Professional exotic lap dancers earn almost twice as much in tips ($335/night versus $185/night) during the ovulatory phase of their menstrual cycle. • Dancers taking birth control pills showed no change in tips over their cycle • Dancers not taking birth control pills earned more, overall, than those who did. • It is possible that when they are ovulating, they are emitting chemosignalsto the crowd. Or, it could be that way that they were dancing. It's possible that they were dancing different even if they didn't realize that they were doing it. Dancers may have been perceivedas more attractive to their male customers, increasing their tips. Question marks allllllllllover this. When women smell t-shirts while ovulating they are attracted to more testosterone.

Why do we smell odor mixtures rather than just pure odorants?

We rarely smell "pure odorants." Rather, we smell mixtures How do we process the components in an odorant mixture? Two possibilities: • Analyses: Example from auditory mixtures. High note and low note can be played together but we can detect each individual note. We can split these types apart. • Synthesis: Example from color mixtures. Mixing red and green lights results in yellow light, but we cannot separately perceive the red and green in the yellow. We cannot split these types apart.

Bitter

We try to avoid all bitter substances! • Many bitter substances are poisonous • Example - Quinine is a prototypical bitter-tasting substance and is found in tonic water (originally used to treat malaria). Sugar added to make palatable. Cannot distinguish between tastes of different bitter compounds Bitter sensitivity is affected by hormone levels in women, intensifies during pregnancy.

Who is more sensitive to detecting smells throughout the lifespan?

Women.

What do our detection thresholds depend on?

Women: Generally lower thresholds than men, especially during ovulatory period of menstrual cycles (more sensitive then), but their sensitivity is not heightened during pregnancy. Professional perfumers and wine tasters can distinguish up to 100,000 odors Age: By 85, 50% of population is effectively anosmic Durability: Our recognition of smells is durable even after several days, months, or years. We an recognize dead relatives perfumes even after a long time.

What happens when you eat fruit?

Your body responds differently to natural fruit than it does to just juice because of fiber differences. The sugar spike is different than if you had just eaten the piece of fruit.

What else can cause anosmia?

bad sinus infection, nasal polyps, medication: blood pressure, anti-depressants, antibiotics

nasal dominance

changes throughout the day, switch between dominant nostril. How neurons react depends on odorant

dogs

have greater sensitivity, detect smells at low levels. humans can likely detect same number of odors as dogs.

trigeminal system/nerve

enables us to feel gustatory and olfactory experiences such as cooling or burning when smelling, also cranial nerve #5

chocolate essential oils study

humans not bad at tracking smell for 10 meters

Olfactory Physiology

involves chemical compounds, but not every chemical is an odorant. In order to be smelled, the chemical must be in the air (volatile), small, and hydrophobic (repel water)

The map of taste buds that we are taught is usually bogus

it's not that drastic. taste buds aren't just on your tongue but also in other parts of your mouth. you could still taste sugar where they claim you can only taste bitter things.

African elephant study

longest nose with 2,000 receptor types

chemical detection systems

olfaction, gustation, and trigeminal nerve

odor

olfactory sensations made up of odorants

What happens to our sense of taste as we age?

our sensitivity declines, but this can also be sped up by alcohol and smoking.

gustation

sense of taste

Olfaction

smell

odorant

specific chemical entity

What is the pathway for taste?

tongue -> taste receptors -> cranial nerves -> medulla -> thalmus -> insulacortex -> orbitofrontal cortex

Supertasters

varies on sensitivity and number of tasters women are supertasters more often than men also more sensitive to sensations like burns

turbinates

when you breathe in air, the turbinates help kick air into olfactory cleft - the entry of the olfactory cleft is called the olfactory epithelium

gas

you can't actually smell methane but companies add a chemical to it so you can smell it

The human olfactory apparatus

your nose. Unlike other senses, smell is tacked onto an organ with another purpose - the nose. • Primary purpose: To filter, warm, and humidify air we breathe • Nose contains small ridges, olfactory cleft, and olfactory epithelium. Brings air to where it interacts with other parts of the nose.