Chemical Senses Flashcards
Describe the role of chemoreceptors in the chemical senses.
Chemoreceptors are specialized cells that detect chemicals in the environment, allowing the senses of smell (olfaction) and taste (gustation) to identify whether a substance should be savored or avoided.
Explain how chemicals must be processed for detection by chemoreceptors.
Chemicals must be dissolved in an aqueous solution to be detected by chemoreceptors, which are sensitive to these dissolved substances.
Define the olfactory epithelium and its function.
The olfactory epithelium is the organ of smell located in the roof of the nasal cavity, containing olfactory sensory neurons that detect odorants.
How are olfactory sensory neurons structured?Describe the regeneration process of olfactory neurons.
Olfactory sensory neurons are unusual bipolar neurons with thin apical dendrites that terminate in a knob, from which long, largely nonmotile olfactory cilia radiate.
What is the significance of supporting cells in the olfactory epithelium?
Supporting cells surround and cushion olfactory receptor cells, providing structural support and possibly assisting in the maintenance of the olfactory environment.
Describe the regeneration process of olfactory neurons.
Olfactory neurons have stem cells at the base of the epithelium that allow for the regeneration of new neurons every 30–60 days.
Explain the relationship between odorants and olfactory receptors.
Each odorant can bind to multiple receptors, and each receptor cell has one type of receptor protein, allowing for a complex interaction where one odorant activates multiple receptors.
How many ‘smell’ genes do humans have, and what is their role?
Humans have approximately 400 active ‘smell’ genes in the nose, each encoding a unique receptor protein that responds to specific odors.
Describe the organization of olfactory neurons in relation to their receptors.
Olfactory neurons with the same receptor type are confined to one zone in the olfactory epithelium but are scattered within that zone, ensuring a structured yet diverse response to odors.
What is the function of glomeruli in the olfactory system?
Each glomerulus is dedicated to one type of receptor and receives input from multiple olfactory neurons with the same receptor type, allowing for the processing of specific odor signals.
Describe the process required for a substance to be smelled.
A substance must be volatile, in a gaseous state, and able to dissolve in the olfactory epithelium fluid.
Explain the role of olfactory sensory neurons in the smelling process.
Olfactory sensory neurons are activated when dissolved odorants bind to receptor proteins in their cilium membranes, generating a receptor potential.
What is the role of the G protein in smell transduction?
The G protein, referred to as Golf, is activated when an odorant binds to its receptor, leading to the synthesis of cAMP, which is a second messenger.
How does the activation of olfactory sensory neurons lead to an action potential?
When the receptor potential reaches threshold, an action potential is conducted to the first relay station in the olfactory bulb.
Define olfactory adaptation and its effect on smell perception.
Olfactory adaptation is the decreased response to a sustained stimulus, causing individuals to be unable to smell a certain odor after prolonged exposure.
Explain the significance of cAMP in the olfactory transduction pathway.
cAMP opens Na+ and Ca2+ channels, causing Na+ influx that results in depolarization and impulse transmission.
Describe the relationship between olfactory nerves and mitral cells.
Filaments of olfactory nerves synapse with mitral cells in the olfactory bulb, where mitral cells act as second-order neurons that form the olfactory tract.
What occurs at the glomeruli in the olfactory bulb?
Synapses occur in structures called glomeruli, where axons from neurons with the same receptor type converge.
How do mitral cells process olfactory signals?
Mitral cells amplify, refine, and relay signals from activated olfactory sensory neurons.
Explain the pathway of olfactory impulses after leaving the mitral cells.
Impulses from activated mitral cells travel via olfactory tracts to the piriform lobe of the olfactory cortex and some information is sent to the hypothalamus, amygdala, and other regions of the limbic system.
What emotional responses can be elicited by odors?
Odors can elicit emotional responses due to their connections with the hypothalamus, amygdala, and limbic system.
Define anosmias and their impact on olfactory function.
Anosmias are olfactory disorders that affect the ability to smell.
Describe the common causes of olfactory hallucinations.
Olfactory hallucinations commonly result from head injuries that tear olfactory nerves, aftereffects of nasal cavity inflammation, neurological disorders such as Parkinson’s disease, and temporal lobe epilepsy that involves the olfactory cortex.
Explain the relationship between temporal lobe epilepsy and olfactory hallucinations.
Temporal lobe epilepsy can cause olfactory hallucinations, also known as phantosmia, and some individuals may experience olfactory auras prior to experiencing epileptic seizures.
