Quiz #3

What is retronasal olfaction?

"backwards smelling", and plays an important role in flavor detection. Odorants are forced up behind the palate, or expired, then diffused through the nasopharynx to the olfactory receptors. We can smell through our nose and our throat!

Be able to write out taste pathway (no abbreviations!)

-Cranial nerves -Nucleus of the solitary tract (NST, within medulla) -Thalamus -Insular cortex (Primary Gustatory Cortex) -(CATS Cranial nerves NEVER Nucleus solitary tract (medulla) THANK Thalamus PEOPLE Primary gustatory cortex)

What is the process of olfaction?

-Odorants dissolve in the mucus of the epithelium -Odorants bind to g-coupled protein receptors (located on the cilia of the OSNs) transduction -OSN axons (cranial nerve 1) travel through the cribriform plate and then synapse onto glomeruli (dendrites of mitral cells) -Mitral axons converge to form the lateral olfactory tract which goes to the limbic system

What are the properties of odorant molecules?

-Volatile (floats in air) -Hydrophobic (water avoiding) -Small mass/small in size (extremely light in weight)

What is orthonasal olfaction?

Air and odorants are inhaled, or inspired, through the nose. Passes through the olfactory cleft, olfactory epithelium, and reaches the olfactory receptors.

What are odorants?

Chemicals that activate odor receptors

What is the signal transduction process?

Cilia, olfactory epithelium, cribriform plate, olfactory bulb

What is olfaction?

Detection of chemicals called odorants that are dissolved in the air.

What are the five receptor tastes?

Each receptor responds to a limited number of molecule types. The five basic tastes are salty, sweet, bitter, sour, and umami.

What are the different types of papillae?

Fungiform, foliate, circumvallate, filiform

What is the cribriform plate?

Horizontal bone through which the olfactory nerve filaments passes and supports the olfactory bulb, which lies in the olfactory fossa.

Where are the receptors for tastants houses?

In taste buds which are located inside structures called papillae on the tongue. Each taste bud has several taste receptors.

What is circumvallate?

Large, posterior tongue, multiple taste buds/papilla

What is foliate?

Lateral surface of tongue, taste buds arranged in the folds

What are mitral cells?

Mitral cells transmit impulses along olfactory tract and form synapses in neuropils called glomeruli.

What is filiform?

No taste buds, Create rough texture which assists in cleansing the mouth as well as chewing and talking

What is olfaction and gustation?

Olfaction (smell) and gustation (taste) are referred to as the chemical senses because these senses detect chemicals in the environment

Where do olfactory sensory neurons synapse?

Olfactory bulb

What cranial nerve is associated with olfaction? What is it made up of? (I.e. axons of which cells from where to where?

Olfactory nerve, which is made up of sensory fibers.

What brain regions do the olfactory sensory neurons project to?

Olfactory neurons project from olfactory bulb to: pyriform cortex, amygdala, entorhinal cortex, and hippocampus

What is the glomerulus?

Receives its blood supply from an afferent arteriole of the renal arterial circulation.

What are turbinates?

Ridges that add turbulence to incoming air and send it to olfactory cleft ---> then olfactory epithelium. They regulate airflow and a large surface area.

What is papillae?

Small bumps on tongue

What physiological/anatomical quality makes some people super-tasters?

Supertasters have a greater number of fungiform papillae than non-tasters, Greater taste perception (all taste qualities), Dislike: extremely sweet things, spicy foods, black coffee, alcohol, green vegetables, Less vegetables = vitamin deficiency.

What are tastants?

Tastants - molecules that activate receptors in our tongue called taste receptors

What is taste vs. flavor?

Taste - stimulation of taste receptors located in taste buds -Allow us to determine taste quality- salty or sweet? Flavor - combination of taste receptors and odor receptors -Learn more about olfaction next week!

What are taste buds?

Taste buds- bundles containing taste receptors

Cranial nerves associated with tongue (taste/tactile/chemical)

Taste information is carried to the brain via three cranial nerves: the chorda tympani (CN VII), glossopharyngeal nerve (CN IX) and the vagus nerve (CN X). The cranial nerves carry taste information to the medulla, thalamus, and finally the insular cortex.

What are taste receptors?

Taste receptors- cells that send information to the brain

HOW do olfactory sensory neurons work? How are they activated, how do they transmit signals, where does the signal go afterwards.

The axons of OSNs travel through the tiny holes of the cribriform plate (a bony structure which separates the nose from brain) and converge to form the olfactory nerve (CN I) to enter the olfactory bulb in the brain. In the olfactory bulb, the OSN axons synapse onto glomeruli, along with the dendrites of mitral cells and tufted cells. Studies have shown that all neurons expressing a particular olfactory receptor type converge onto one glomerulus pair. This means that all ORs that detect mint, for example, all send their axons to the same glomerulus pair.

Know the types of cells in the olfactory epithelium and olfactory bulb.

The nasal epithelium is home to three cell types: olfactory sensory neurons (OSNs), supporting cells and basal cells. The OSNs have cilia that protrude into the mucus. The cilia have receptors on their tips, and these receptors detect odorants.

How does gustation work?

When food enters the mouth, it needs to be broken down into molecules that can activate taste receptor cells - this is done by chewing food, and chewed food is further broken down by enzymes in saliva. Once broken down, the molecules that can activate taste receptor cells are called tastants.

What is fungiform?

Widespread; mushroom-shaped; typically 1 taste bud/fungiform papilla

How is transduction initiated for each of the different types of receptors?

• Salty and sour tastants activate taste receptor cells differently than sweet, bitter, and umami tastants. Salty and sour tastes are detected as sodium or hydrogen ions pass through ion channels in the membrane of the taste cell. When this occurs, the cells become depolarized and fire action potentials. Sweet, bitter, and umami tastants activate what are known as G-protein coupled receptors, which in turn activate a cascade of molecular events inside the cell, ultimately causing the cell to depolarize and fire an action potential.