Chapter 9_Chemical Senses Flashcards
Olfaction
The sense of smell, which detects volatile chemicals (odorants) in the air, allowing organisms to identify and respond to environmental stimuli.
Odorants
Chemical compounds that activate the olfactory system by binding to specific olfactory receptors.
Olfactory Epithelium
A mucus-covered tissue located in the nasal cavity that contains olfactory receptor neurons responsible for detecting odorants.
Olfactory Receptor Neurons (ORNs)
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.
Olfactory Bulb
A brain structure that receives input from olfactory receptor neurons and processes olfactory information before sending it to higher brain regions.
Glomerulus
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.
Mitral Cells
Secondary neurons in the olfactory bulb that relay olfactory signals from the glomeruli to the olfactory cortex.
Piriform Cortex
The main region of the olfactory cortex responsible for processing olfactory information and integrating it with other sensory inputs.
Gustation
The sense of taste, which detects flavorants (chemical compounds in food) through taste receptors located primarily on the tongue.
Flavorants
Chemical compounds that activate taste receptors, contributing to the perception of taste.
Taste Buds
Sensory structures located on the tongue and other parts of the oral cavity that contain taste receptor cells responsible for detecting taste stimuli.
Taste Receptor Cells
Specialized epithelial cells within taste buds that detect the five basic taste modalities: salty, sweet, sour, bitter, and umami.
Salty Taste
Mediated by sodium ions (Na+), which pass through epithelial sodium channels (ENaCs) in the taste receptor cells, leading to depolarization and neurotransmitter release.
Sour Taste
Mediated by proton (H+) channels, which respond to acidic foods, leading to depolarization of taste receptor cells.
Sweet Taste
Mediated by G-protein-coupled receptors (T1R2/T1R3) that respond to sugars and sweeteners, triggering signaling cascades that lead to taste perception.
Bitter Taste
Detected by T2R receptors, which respond to toxic or aversive substances, often triggering avoidance behaviors.
Umami Taste
Mediated by T1R1/T1R3 receptors that respond to the amino acid glutamate, associated with the savory taste found in foods like meat and aged cheese.
Internal Chemosensory Systems
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.
Vomeronasal Organ
A specialized structure found in some animals, responsible for detecting pheromones, which are chemicals that influence the behavior of others in the same species.
Pheromones
Chemical signals secreted by individuals that affect the behavior of other members of the same species, commonly involved in mating and social behaviors.
Hyposmia
A reduced ability to smell, which can be caused by nasal congestion, aging, or neurological conditions such as Parkinson’s disease.
Anosmia
A complete loss of the sense of smell, which can result from head injuries, infections, or neurodegenerative diseases.
Phantosmia
The perception of phantom smells (olfactory hallucinations), often associated with conditions like seizures, brain tumors, or psychiatric disorders.
Gustatory Cortex
The region of the brain responsible for processing taste information, located in the insular cortex and frontal operculum.
Lingual Papillae
Large structures on the surface of the tongue that contain taste buds.
Solitary Nucleus
A nucleus in the medulla that receives taste information from the facial, glossopharyngeal, and vagus nerves and relays it to the gustatory cortex.
Capsaicin
A chemical compound found in chili peppers that activates TRPV1 receptors, causing the sensation of heat or spiciness.
TRPV1 Receptors
Ion channels that respond to heat, acids, and chemical irritants like capsaicin, contributing to the sensation of pain and spiciness.
TRP Channels
A family of ion channels involved in the detection of temperature, pain, and other stimuli, including in the gustatory system.
Chemoreceptors
Sensory receptors that detect chemical changes in the environment, such as changes in blood pH or CO2 levels, and trigger physiological responses like respiration.
Area Postrema
A region in the medulla that detects toxins in the blood and cerebrospinal fluid, triggering the vomiting reflex to expel harmful substances.
Olfactory Cortex
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.
Entorhinal Cortex
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.
Orbitofrontal Cortex
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.
Olfactory Tubercle
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.
Medial Dorsal Nucleus of the Thalamus
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.
