Exam 2: The Chemical Senses

Question 1

Olfaction

Answer 1

The sense of smell, which detects volatile chemicals (odorants) in the air, allowing organisms to identify and respond to environmental stimuli.

Question 2

Odorants

Answer 2

Chemical compounds that activate the olfactory system by binding to specific olfactory receptors.

Question 3

Olfactory Epithelium

Answer 3

A mucus-covered tissue located in the nasal cavity that contains olfactory receptor neurons responsible for detecting odorants.

Question 4

Olfactory Receptor Neurons (ORNs)

Answer 4

Sensory neurons in the olfactory epithelium that detect odorants and send signals to the brain. These neurons are the only type exposed to the outside environment.

Question 5

Olfactory Bulb

Answer 5

A brain structure that receives input from olfactory receptor neurons and processes olfactory information before sending it to higher brain regions.

Question 6

Glomerulus

Answer 6

Structures within the olfactory bulb where the axons of olfactory receptor neurons converge and synapse with mitral and tufted cells, responsible for the initial processing of olfactory signals.

Question 7

Mitral Cells

Answer 7

Secondary neurons in the olfactory bulb that relay olfactory signals from the glomeruli to the olfactory cortex.

Question 8

Piriform Cortex

Answer 8

The main region of the olfactory cortex responsible for processing olfactory information and integrating it with other sensory inputs.

Question 9

Gustation

Answer 9

The sense of taste, which detects flavorants (chemical compounds in food) through taste receptors located primarily on the tongue.

Question 10

Tastants (Flavorants)

Answer 10

Chemical compounds that activate taste receptors, contributing to the perception of taste.

Question 11

Taste Buds

Answer 11

Sensory structures located on the tongue and other parts of the oral cavity that contain taste receptor cells responsible for detecting taste stimuli.

Question 12

Taste Receptor Cells

Answer 12

Specialized epithelial cells within taste buds that detect the five basic taste modalities: salty, sweet, sour, bitter, and umami.

Question 13

Salty Taste

Answer 13

Mediated by sodium ions (Na+), which pass through ionotropic epithelial sodium channels (ENaCs) in the taste receptor cells, leading to depolarization and neurotransmitter (serotonin) release.

Question 14

Sour Taste

Answer 14

Mediated by ionotropic proton (H+) channels, which respond to acidic foods, leading to depolarization and neurotransmitter (serotonin) release.

Question 15

Sweet Taste

Answer 15

Mediated by metabotropic receptors (T1R2/T1R3) that respond to sugars and sweeteners, triggering secondary messenger signaling that results in neurotransmitter (ATP) release.

Question 16

Bitter Taste

Answer 16

Mediated by metabotropic T2R receptors, triggering secondary messenger signaling that results in neurotransmitter (ATP) release. Bitter taste prompts avoidance because bitter tastes often indicate toxicity.

Question 17

Umami Taste

Answer 17

Mediated by metabotropic T1R1/T1R3 receptors that respond to the amino acid glutamate, triggering secondary messenger signaling that results in neurotransmitter (ATP) release. Associated with the savory taste found in foods like meat and aged cheese.

Question 18

Internal Chemosensory Systems

Answer 18

Systems that detect changes in the body’s internal chemical environment (e.g., blood CO2 levels or pH) to maintain homeostasis and trigger involuntary physiological responses such as respiration or vomiting.

Question 19

Vomeronasal Organ

Answer 19

A specialized structure found in some animals, responsible for detecting pheromones, which are chemicals that influence the behavior of others in the same species.

Question 20

Pheromones

Answer 20

Chemical signals secreted by individuals that affect the behavior of other members of the same species, commonly involved in mating and social behaviors.

Question 21

Hyposmia

Answer 21

A reduced ability to smell, which can be caused by nasal congestion, aging, or neurological conditions such as Parkinson’s disease.

Question 22

Anosmia

Answer 22

A complete loss of the sense of smell, which can result from head injuries, infections, or neurodegenerative diseases.

Question 23

Phantosmia

Answer 23

The perception of phantom smells (olfactory hallucinations), often associated with conditions like seizures, brain tumors, or psychiatric disorders.

Question 24

Gustatory Cortex

Answer 24

The region of the brain responsible for processing taste information, located in the insular cortex and frontal operculum.

Question 25

Lingual Papillae

Answer 25

Large structures on the surface of the tongue that contain taste buds.

Question 26

Solitary Nucleus

Answer 26

A nucleus in the medulla that receives taste information from the facial, glossopharyngeal, and vagus nerves and relays it to the gustatory cortex.

Question 27

Capsaicin

Answer 27

A chemical compound found in chili peppers that activates TRPV1 receptors, causing the sensation of heat or spiciness.

Question 28

Menthol

Answer 28

The cooling compound in mint, activates TRP Melastatin 8 (TRPM8) which is found on nerve fibers that respond to cold.

Question 29

Chemoreceptors

Answer 29

Sensory receptors that detect chemical changes in the environment, such as changes in blood pH or CO2 levels, and trigger physiological responses like respiration.

Question 30

Area Postrema

Answer 30

A region in the medulla that detects toxins in the blood and cerebrospinal fluid, triggering the vomiting reflex to expel harmful substances.

Question 31

Olfactory Cortex

Answer 31

The region of the brain responsible for processing olfactory (smell) information. It includes areas such as the piriform cortex and parts of the amygdala and entorhinal cortex. The olfactory cortex is involved in the perception and identification of odors.

Question 32

Entorhinal Cortex

Answer 32

A region of the brain that serves as a hub in the memory and navigation systems. It receives olfactory information and is part of the limbic system, which links smell to memory and emotion.

Question 33

Orbitofrontal Cortex

Answer 33

A prefrontal cortex region involved in sensory integration, decision-making, and emotional processing. In the context of olfaction, it helps evaluate the reward value of smells and integrates them with taste to create flavor perception.

Question 34

Olfactory Tubercle

Answer 34

A structure located at the base of the forebrain that plays a role in processing olfactory signals and integrating them with other sensory modalities, motivation, and reward.

Question 35

Medial Dorsal Nucleus of the Thalamus

Answer 35

A thalamic nucleus that relays olfactory information to higher cortical regions, including the orbitofrontal cortex. It is involved in memory, emotion, and the higher-order processing of odors, contributing to the conscious awareness and emotional response to smells.