22 - Chemical Senses Overview

Flashcards focusing on the vocabulary related to chemical senses, specifically taste and smell, as outlined in the lecture.

Chemical Senses

Systems that allow us to perceive our environment through taste, smell, and trigeminal sensations.

Gustation

The sense of taste, which distinguishes five basic taste qualities: sweet, sour, salty, bitter, and umami.

Olfaction

The sense of smell; involves the detection of volatile substances by olfactory receptors.

Trigeminal System

A sensory system that detects sensations such as irritation, burning, freshness, tingling through trigeminal nerve fibers, receptors on fibers of trigeminal nerve of the nasal and oral mucosa

Functions - Warning and nutrition

Taste Buds

Taste buds are located on the mucosa of the tongue (and elsewhere in the oral cavity), also papillae of the tongue ex. fungiform papillae, foliate papillae, circumvallate papillae, filiform papillae

Taste Map

Urban legends that some tastes are processed in certain areas, in reality all qualities processed everywhere

Anosmia

Complete loss of the sense of smell.

Hyposmia

Partial loss of the sense of smell.

Parosmia

A condition where odors are perceived differently than they are supposed to.

Phantosmia

The perception of smells in the absence of any odor source.

Olfactory Receptor Neurons (ORN)

Specialized neurons located in the roof portion of nasal cavity that detect odors, receptors in cilia, can regenerate from stem cells

Olfactory Code

400 different types of olfactory receptors, each ORN carries one type of receptor, each ORN can be activated by different substances, one odorant can activate multiple receptors

Olfaction Organization

Axons of all olfactory neurons carrying one type of receptor converge to one glomerulum within the olfactory bulb, processing occurs in olfactory bulb and tract

Olfactory Cortexes

Primary olfactory cortex 
• Piriform cortex 
• Amygdala 
• Entorhinal cortex 

Secondary olfactory cortex 
• Orbitofrontal cortex – Involved in perception of reward 
• Insula 

Orthonasal and Retronasal Olfaction

Orthonasal - Within respiration, air

Retronasal - During swallowing

Sniffing causes turbulence so more molecules reach olfactory muscosa, slurping is the retronasal equivalent

Cilia

Microscopic hair-like structures on olfactory receptor neurons that detect odorants.

Cribriform Plate

A bony structure in the skull through which olfactory axons pass from the nasal cavity to the olfactory bulb.

Glomerulus

A structure in the olfactory bulb where axons from ORNs of the same type converge.

Functions of Smell

Warning, fear, nutrition, social communication

Taste Functions

Warning (bitterness), nutrition, we are relatively insensitive to sweetness and umami, ex. when deficient for electrolytes, we crave salty and acidic foods

Main causes of olfactory dysfunction

Disease of the nose or nasal mucosa, neurological diseases, unknown, and aging

Factors that influence olfaction

Age

Sex - female better than male

Education level

Smokers

Alcohol consumption - Moderate drinkers better than abstainers

BMI - Normal better than obese

Blood pressure

Fast recovery rates, can be spontaneous