Podcast
Questions and Answers
What is the primary mechanism behind adaptation of olfactory receptor neurons (ORNs)?
What is the primary mechanism behind adaptation of olfactory receptor neurons (ORNs)?
- Direct sensory input from the environment
- Increase in olfactory bulb activity
- Centrifugal fibers from CNS (correct)
- Enhanced receptor sensitivity
How quickly does the olfactory system show adaptation after stimulation?
How quickly does the olfactory system show adaptation after stimulation?
- Only after several minutes
- About 50% in the first second (correct)
- Approximately 10 seconds
- Approximately 30 seconds
What structure allows for the comparison of smell between the two sides of the brain?
What structure allows for the comparison of smell between the two sides of the brain?
- Olfactory bulbs
- Uncus
- Anterior perforated substance
- Medial olfactory stria (correct)
Where do second-order olfactory fibers synapse?
Where do second-order olfactory fibers synapse?
What is the role of collateral axons from the anterior olfactory nucleus?
What is the role of collateral axons from the anterior olfactory nucleus?
What is the effect of extinction in the olfactory system?
What is the effect of extinction in the olfactory system?
What is the primary innervation for the circumvallate papillae?
What is the primary innervation for the circumvallate papillae?
What is the primary function of the anterior olfactory nucleus?
What is the primary function of the anterior olfactory nucleus?
Which anatomical pathway allows olfactory information to travel to the opposite hemisphere?
Which anatomical pathway allows olfactory information to travel to the opposite hemisphere?
Which of the following taste modalities is most sensitive to ionized salts?
Which of the following taste modalities is most sensitive to ionized salts?
What percentage of taste buds are located in the vertical folds along the posterolateral edge of the anterior 2/3 of the tongue?
What percentage of taste buds are located in the vertical folds along the posterolateral edge of the anterior 2/3 of the tongue?
Which type of molecule is primarily associated with the bitter taste?
Which type of molecule is primarily associated with the bitter taste?
Which taste modality is NOT recognized as one of the five basic tastes?
Which taste modality is NOT recognized as one of the five basic tastes?
What is the anatomical landmark separating the anterior 2/3 of the tongue from the posterior 1/3?
What is the anatomical landmark separating the anterior 2/3 of the tongue from the posterior 1/3?
How many taste buds can be found approximately on each filiform papillae?
How many taste buds can be found approximately on each filiform papillae?
What is the term for solitary chemoreceptor cells located throughout the head?
What is the term for solitary chemoreceptor cells located throughout the head?
What is the role of the solitary nucleus in the gustatory system?
What is the role of the solitary nucleus in the gustatory system?
What is the role of second order neurons in the olfactory pathway?
What is the role of second order neurons in the olfactory pathway?
Which structures receive input from the primary gustatory cortex?
Which structures receive input from the primary gustatory cortex?
Which of the following is true about the innervation of the tongue?
Which of the following is true about the innervation of the tongue?
What distinguishes the SVA axons in cranial nerves VII, IX, and X from other sensory pathways?
What distinguishes the SVA axons in cranial nerves VII, IX, and X from other sensory pathways?
What is the function of the amygdala in relation to taste perception?
What is the function of the amygdala in relation to taste perception?
What contributes primarily to the difference in taste between different flavors, such as jellybean and grape jellybean?
What contributes primarily to the difference in taste between different flavors, such as jellybean and grape jellybean?
Where do the medial and lateral olfactory striae project after they split from the olfactory tract?
Where do the medial and lateral olfactory striae project after they split from the olfactory tract?
Where do axons of ganglia neurons synapse in the gustatory ascending pathway?
Where do axons of ganglia neurons synapse in the gustatory ascending pathway?
Which nerve is responsible for taste sensation from the posterior one-third of the tongue?
Which nerve is responsible for taste sensation from the posterior one-third of the tongue?
In the olfactory pathway, which cortex is involved in odor identification and categorization?
In the olfactory pathway, which cortex is involved in odor identification and categorization?
Which structure is primarily involved in autonomic responses related to olfactory stimuli?
Which structure is primarily involved in autonomic responses related to olfactory stimuli?
What type of sensory innervation provides the sensation of touch and temperature to the anterior two-thirds of the tongue?
What type of sensory innervation provides the sensation of touch and temperature to the anterior two-thirds of the tongue?
What is the primary receptor type for olfaction?
What is the primary receptor type for olfaction?
How many functional olfactory receptor genes are there approximately?
How many functional olfactory receptor genes are there approximately?
Which type of encoding is primarily associated with gustation?
Which type of encoding is primarily associated with gustation?
Which neurotransmitters are involved in taste signal transduction?
Which neurotransmitters are involved in taste signal transduction?
What is the condition of complete loss of taste called?
What is the condition of complete loss of taste called?
Which disorder involves misperception of normal odors?
Which disorder involves misperception of normal odors?
What type of receptor do salty and sour taste modalities utilize?
What type of receptor do salty and sour taste modalities utilize?
What physiological change occurs in the membrane potential upon stimulation of olfactory receptors?
What physiological change occurs in the membrane potential upon stimulation of olfactory receptors?
What percentage of flavor is commonly attributed to smell?
What percentage of flavor is commonly attributed to smell?
Which type of receptors are primarily involved in detecting odorants?
Which type of receptors are primarily involved in detecting odorants?
How many action potentials per second can Olfactory Receptor Neurons (ORNs) generate?
How many action potentials per second can Olfactory Receptor Neurons (ORNs) generate?
What is the primary role of Olfactory Cilia in Olfactory Receptor Neurons?
What is the primary role of Olfactory Cilia in Olfactory Receptor Neurons?
What distinguishes the olfactory receptor proteins expressed by individual ORNs?
What distinguishes the olfactory receptor proteins expressed by individual ORNs?
The process through which odorants bind to Olfactory Receptors and generate receptor potentials is an example of what type of mechanism?
The process through which odorants bind to Olfactory Receptors and generate receptor potentials is an example of what type of mechanism?
In the context of ORN tuning, what does it mean that each Olfactory Receptor can bind to multiple odors?
In the context of ORN tuning, what does it mean that each Olfactory Receptor can bind to multiple odors?
Which brain area is primarily associated with processing olfactory and gustatory information?
Which brain area is primarily associated with processing olfactory and gustatory information?
What is the primary function of the ventral posteromedial (VPM) nucleus of the thalamus in the gustatory pathway?
What is the primary function of the ventral posteromedial (VPM) nucleus of the thalamus in the gustatory pathway?
Which structure is involved in coordinating conscious taste and smell, contributing to flavor perception?
Which structure is involved in coordinating conscious taste and smell, contributing to flavor perception?
From where do the SVA axons in cranial nerves VII, IX, and X converge?
From where do the SVA axons in cranial nerves VII, IX, and X converge?
What role does the amygdala play in the gustatory system?
What role does the amygdala play in the gustatory system?
Which cortical region receives information directly from the primary gustatory cortex?
Which cortical region receives information directly from the primary gustatory cortex?
What type of receptors are involved in the sensory transduction of both taste and smell?
What type of receptors are involved in the sensory transduction of both taste and smell?
Which part of the brain is primarily responsible for integrating olfactory and gustatory information?
Which part of the brain is primarily responsible for integrating olfactory and gustatory information?
Which type of chemoreceptors are responsible for detecting chemical changes within the body, such as pH levels?
Which type of chemoreceptors are responsible for detecting chemical changes within the body, such as pH levels?
What is the primary function of chemical exteroceptors in relation to taste?
What is the primary function of chemical exteroceptors in relation to taste?
What sensory deficit is likely to occur as a result of a lesion in the gustatory pathway?
What sensory deficit is likely to occur as a result of a lesion in the gustatory pathway?
How do peripheral chemoreceptors contribute to homeostasis in the body?
How do peripheral chemoreceptors contribute to homeostasis in the body?
What role do specialized receptor cells play in the gustatory and olfactory systems?
What role do specialized receptor cells play in the gustatory and olfactory systems?
What is the consequence of a lesion in the olfactory pathway?
What is the consequence of a lesion in the olfactory pathway?
What is the role of centrifugal fibers in the adaptation process of olfactory receptor neurons?
What is the role of centrifugal fibers in the adaptation process of olfactory receptor neurons?
After stimulation, olfactory receptor neurons adapt at what rate during the first second?
After stimulation, olfactory receptor neurons adapt at what rate during the first second?
The medial olfactory stria primarily connects neurons from the anterior olfactory nucleus to which structure?
The medial olfactory stria primarily connects neurons from the anterior olfactory nucleus to which structure?
What anatomical structure allows olfactory fibers to communicate between the two sides of the brain?
What anatomical structure allows olfactory fibers to communicate between the two sides of the brain?
The anterior olfactory nucleus plays a key role in providing which aspect of olfactory perception?
The anterior olfactory nucleus plays a key role in providing which aspect of olfactory perception?
What percentage of adaptation do olfactory receptor neurons undergo after the first second of stimulation?
What percentage of adaptation do olfactory receptor neurons undergo after the first second of stimulation?
Which fibers are primarily responsible for the extinction of olfactory sensations?
Which fibers are primarily responsible for the extinction of olfactory sensations?
Which of the following structures is NOT involved in the olfactory system's processing of sensations?
Which of the following structures is NOT involved in the olfactory system's processing of sensations?
Which taste modalities are detected by Type II taste receptor cells?
Which taste modalities are detected by Type II taste receptor cells?
What triggers the activation of TRPV1 receptors found on polymodal nociceptors?
What triggers the activation of TRPV1 receptors found on polymodal nociceptors?
Which trigeminal nerve primarily transmits the sensation of spicy stimuli?
Which trigeminal nerve primarily transmits the sensation of spicy stimuli?
How do Type III cells contribute to taste perception?
How do Type III cells contribute to taste perception?
What is a key characteristic of the response from trigeminal nociceptors to certain tastants?
What is a key characteristic of the response from trigeminal nociceptors to certain tastants?
What anatomical feature is primarily associated with the detection of taste stimuli?
What anatomical feature is primarily associated with the detection of taste stimuli?
What is the primary role of Type I taste receptor cells?
What is the primary role of Type I taste receptor cells?
Which substance is known to activate trigeminal receptors as an irritant?
Which substance is known to activate trigeminal receptors as an irritant?
What type of chemicals are primarily responsible for the sweet taste modality?
What type of chemicals are primarily responsible for the sweet taste modality?
Which taste modality is primarily linked to the detection of acidic compounds?
Which taste modality is primarily linked to the detection of acidic compounds?
How are taste buds distributed across the circumvallate papillae?
How are taste buds distributed across the circumvallate papillae?
Which cranial nerve primarily innervates the vertical folds located along the posterolateral edge of the tongue?
Which cranial nerve primarily innervates the vertical folds located along the posterolateral edge of the tongue?
Which statement about the concept of a taste map on the tongue is accurate?
Which statement about the concept of a taste map on the tongue is accurate?
Which of the following statements about the bitter taste modality is true?
Which of the following statements about the bitter taste modality is true?
What percentage of total taste buds is located in the circumvallate papillae?
What percentage of total taste buds is located in the circumvallate papillae?
Which type of cells are found throughout the head and resemble taste cells?
Which type of cells are found throughout the head and resemble taste cells?
What primarily distinguishes the taste of different jellybeans, such as a regular jellybean and a grape jellybean?
What primarily distinguishes the taste of different jellybeans, such as a regular jellybean and a grape jellybean?
Which cranial nerve is responsible for taste sensation in the anterior two-thirds of the tongue?
Which cranial nerve is responsible for taste sensation in the anterior two-thirds of the tongue?
What type of information does the piriform cortex process in relation to olfactory stimuli?
What type of information does the piriform cortex process in relation to olfactory stimuli?
In the olfactory pathway, which structure acts as the first relay for olfactory signals after the olfactory bulb?
In the olfactory pathway, which structure acts as the first relay for olfactory signals after the olfactory bulb?
Which of the following statements about the olfactory receptor neurons is true?
Which of the following statements about the olfactory receptor neurons is true?
Which structures are part of the general sensory innervation of the tongue?
Which structures are part of the general sensory innervation of the tongue?
In relation to olfactory stimuli, what role does the amygdala serve?
In relation to olfactory stimuli, what role does the amygdala serve?
Which region integrates memory aspects with olfactory processing in the brain?
Which region integrates memory aspects with olfactory processing in the brain?
What anatomical feature does the olfactory system utilize to pass through the ethmoid bone?
What anatomical feature does the olfactory system utilize to pass through the ethmoid bone?
What is the significance of ORNs projecting to the same glomerulus?
What is the significance of ORNs projecting to the same glomerulus?
What type of axons do ORNs bundle into as they enter the olfactory bulb?
What type of axons do ORNs bundle into as they enter the olfactory bulb?
What type of synapses do periglomerular cells form within the olfactory bulb?
What type of synapses do periglomerular cells form within the olfactory bulb?
Which of the following is stated about the glomeruli in the olfactory bulb?
Which of the following is stated about the glomeruli in the olfactory bulb?
Which cells serve as the primary inhibitory interneurons in the olfactory bulb?
Which cells serve as the primary inhibitory interneurons in the olfactory bulb?
What is the approximate number of olfactory receptor neurons (ORNs) in a typical mouse olfactory epithelium?
What is the approximate number of olfactory receptor neurons (ORNs) in a typical mouse olfactory epithelium?
Which cells are primarily responsible for the output of the olfactory bulb?
Which cells are primarily responsible for the output of the olfactory bulb?
What is a unique characteristic of periglomerular cells compared to other types of neurons in the olfactory bulb?
What is a unique characteristic of periglomerular cells compared to other types of neurons in the olfactory bulb?
Which anatomical organization of the olfactory bulb includes axons from olfactory receptor neurons and dendrites from mitral cells?
Which anatomical organization of the olfactory bulb includes axons from olfactory receptor neurons and dendrites from mitral cells?
What is the regeneration period for Olfactory Receptor Neurons (ORNs)?
What is the regeneration period for Olfactory Receptor Neurons (ORNs)?
What is the primary role of the olfactory epithelium?
What is the primary role of the olfactory epithelium?
Which statement best describes the tuning of Olfactory Receptor Neurons (ORNs)?
Which statement best describes the tuning of Olfactory Receptor Neurons (ORNs)?
Where are Olfactory Receptor Neurons (ORNs) located?
Where are Olfactory Receptor Neurons (ORNs) located?
What is the role of the hypothalamus in relation to gustatory processing?
What is the role of the hypothalamus in relation to gustatory processing?
Which structure receives sensory input from the primary gustatory cortex for processing emotional responses?
Which structure receives sensory input from the primary gustatory cortex for processing emotional responses?
Where do second-order synapses occur in the gustatory pathway?
Where do second-order synapses occur in the gustatory pathway?
What is the primary function of the gustatory association cortex?
What is the primary function of the gustatory association cortex?
What defines the role of SVA axons in cranial nerves VII, IX, and X?
What defines the role of SVA axons in cranial nerves VII, IX, and X?
Which structure is primarily responsible for the projection of second-order neurons in the olfactory pathway?
Which structure is primarily responsible for the projection of second-order neurons in the olfactory pathway?
What role does the medial olfactory stria serve in the olfactory pathway?
What role does the medial olfactory stria serve in the olfactory pathway?
In the olfactory system, which component is primarily responsible for autonomic responses?
In the olfactory system, which component is primarily responsible for autonomic responses?
Which cranial nerve is responsible for the taste sensation from the anterior two-thirds of the tongue?
Which cranial nerve is responsible for the taste sensation from the anterior two-thirds of the tongue?
Which area receives direct input from the olfactory tract, bypassing the thalamus?
Which area receives direct input from the olfactory tract, bypassing the thalamus?
What type of sensory information is processed by the lingual nerve (CN V3) in the anterior two-thirds of the tongue?
What type of sensory information is processed by the lingual nerve (CN V3) in the anterior two-thirds of the tongue?
Which structure distinguishes the olfactory system by allowing the comparison of smelling between the two hemispheres of the brain?
Which structure distinguishes the olfactory system by allowing the comparison of smelling between the two hemispheres of the brain?
Which type of sensory nerve endings serve the posterior one-third of the tongue responsible for taste?
Which type of sensory nerve endings serve the posterior one-third of the tongue responsible for taste?
What types of cells are primarily responsible for detecting sweet, umami, and bitter tastes in the taste bud?
What types of cells are primarily responsible for detecting sweet, umami, and bitter tastes in the taste bud?
Which nerve is primarily involved in carrying information about spicy stimuli?
Which nerve is primarily involved in carrying information about spicy stimuli?
What is the primary role of Type III cells in taste buds?
What is the primary role of Type III cells in taste buds?
Which of the following is considered a characteristic of TRPV1 receptors involved in spicy taste perception?
Which of the following is considered a characteristic of TRPV1 receptors involved in spicy taste perception?
Which of the following taste modalities is primarily processed by type II taste receptor cells?
Which of the following taste modalities is primarily processed by type II taste receptor cells?
Which cranial nerves are associated with the gustatory pathway as mentioned?
Which cranial nerves are associated with the gustatory pathway as mentioned?
What is the role of ammonia in the context of trigeminal nerve receptors?
What is the role of ammonia in the context of trigeminal nerve receptors?
How many taste receptor cells (TRCs) are typically found in a single taste bud?
How many taste receptor cells (TRCs) are typically found in a single taste bud?
Flashcards
Olfactory Adaptation
Olfactory Adaptation
The process where the olfactory receptor neurons (ORNs) become less responsive to a continuous odor stimulus.
Centrifugal Fibers
Centrifugal Fibers
A type of neural pathway that projects from the central nervous system (CNS) back to the olfactory bulb, helping regulate olfactory sensitivity and adaptation.
Anterior Olfactory Nucleus (AON)
Anterior Olfactory Nucleus (AON)
This nucleus is a collection of neurons located along the olfactory tract. It receives input from collaterals of second-order olfactory fibers and plays a role in comparing smells between the two sides of the nose.
Lateral Olfactory Stria
Lateral Olfactory Stria
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Medial Olfactory Stria
Medial Olfactory Stria
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Anterior Commissure
Anterior Commissure
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Anterior Perforated Substance
Anterior Perforated Substance
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Amygdaloid Nucleus
Amygdaloid Nucleus
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Olfactory system
Olfactory system
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Olfactory Receptors (ORs)
Olfactory Receptors (ORs)
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Olfactory Receptor Neurons (ORNs)
Olfactory Receptor Neurons (ORNs)
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Olfactory Bulb
Olfactory Bulb
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Olfactory Stalk (Tract)
Olfactory Stalk (Tract)
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Orbitofrontal Cortex
Orbitofrontal Cortex
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Orbitofrontal Cortex & Limbic System
Orbitofrontal Cortex & Limbic System
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ORNs and Gene Expression
ORNs and Gene Expression
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Olfactory Tract Split
Olfactory Tract Split
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Primary Olfactory Cortex
Primary Olfactory Cortex
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Olfactory Pathway
Olfactory Pathway
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Olfaction and Flavor
Olfaction and Flavor
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Taste Innervation - Anterior Tongue
Taste Innervation - Anterior Tongue
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Taste Innervation - Posterior Tongue
Taste Innervation - Posterior Tongue
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General Sensation - Anterior Tongue
General Sensation - Anterior Tongue
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Epiglottis and Valleculae Sensation
Epiglottis and Valleculae Sensation
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Ventral Posteromedial (VPM) Nucleus
Ventral Posteromedial (VPM) Nucleus
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Solitariothalamic Tract
Solitariothalamic Tract
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Solitary Tract
Solitary Tract
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Primary Gustatory Cortex
Primary Gustatory Cortex
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Gustatory Association Cortex
Gustatory Association Cortex
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Olfaction
Olfaction
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Gustation
Gustation
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Odorants
Odorants
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Tastants
Tastants
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Combinatorial Encoding
Combinatorial Encoding
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Labeled-Line Encoding
Labeled-Line Encoding
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Hyposmia
Hyposmia
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Anosmia
Anosmia
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Circumvallate Papillae
Circumvallate Papillae
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Foliate Papillae
Foliate Papillae
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Fungiform Papillae
Fungiform Papillae
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Bitter Taste
Bitter Taste
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Sweet Taste
Sweet Taste
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Salty Taste
Salty Taste
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Sour Taste
Sour Taste
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Umami Taste
Umami Taste
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Chemoreceptors
Chemoreceptors
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Taste Receptor Cells
Taste Receptor Cells
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Taste Perception
Taste Perception
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Anterior Olfactory Nucleus
Anterior Olfactory Nucleus
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ORN Adaptation
ORN Adaptation
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Olfaction & Flavor
Olfaction & Flavor
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Epiglottis & Valleculae Sensation
Epiglottis & Valleculae Sensation
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Papillae
Papillae
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Trigeminal Nerve and Irritants
Trigeminal Nerve and Irritants
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Polymodal Nociceptors
Polymodal Nociceptors
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TRPV1 and Spicy Sensation
TRPV1 and Spicy Sensation
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Smell and Taste Receptor Neurons
Smell and Taste Receptor Neurons
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Taste Receptor Cells (TRCs)
Taste Receptor Cells (TRCs)
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Gustatory Pathway
Gustatory Pathway
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Taste Information Transmission
Taste Information Transmission
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Gustatory Cortex and Taste Perception
Gustatory Cortex and Taste Perception
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Olfactory Epithelium
Olfactory Epithelium
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Fila Olfactoria
Fila Olfactoria
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Cribriform Plate
Cribriform Plate
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ORNs Project to Specific Glomeruli
ORNs Project to Specific Glomeruli
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ORNs Express Only One Receptor
ORNs Express Only One Receptor
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What is the olfactory bulb and what does it do?
What is the olfactory bulb and what does it do?
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What are mitral cells and what is their role?
What are mitral cells and what is their role?
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What are granule cells and what do they do?
What are granule cells and what do they do?
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What are periglomerular cells and what is their function?
What are periglomerular cells and what is their function?
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What are glomeruli and what are they like?
What are glomeruli and what are they like?
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Gustatory Cortex
Gustatory Cortex
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TRPV1 Receptor
TRPV1 Receptor
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Amygdala
Amygdala
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Study Notes
Olfaction and Gustatory Sensation
- Olfaction and gustation are chemoreceptor systems
- Olfaction detects airborne molecules (smell)
- Gustation detects dissolved molecules (taste)
- Both use G-protein coupled receptors (GPCRs) for transduction
- Olfactory receptors are located in the olfactory epithelium in the nasal cavity
- Olfactory neurons (ORNs) are bipolar neurons with cilia that detect odorants
- Each ORN expresses a single type of odorant receptor
- ORNs project to glomeruli in the olfactory bulb
- Olfactory information passes through the olfactory tract to the olfactory cortex
- Gustatory receptors are located in taste buds on the tongue
- Different regions of the tongue detect different taste modalities
- Taste information is relayed through cranial nerves VII, IX, and X to the nucleus of the solitary tract
- The nucleus of the solitary tract relays this information to the thalamus
- Taste information then projects to the primary gustatory cortex located in the insular cortex and frontal operculum
- Olfactory signals are relayed to the primary olfactory cortex in medial and lateral striae and orbitofrontal cortex and other regions
- Taste signals are relayed through the solitary nucleus also to the thalamus
- Olfactory information reaches consciousness in the orbitofrontal cortex as "flavor"
- 80% of flavor is determined by smell
Learning Objectives
- Understand the molecular steps of olfactory and gustatory sensory transduction
- Describe the pathways for smell and taste information
- Predict sensory deficits from lesions in the olfactory or gustatory pathways
- List differences and similarities between olfaction and gustation
Chemoreceptors inside and out
- Chemical interoceptors monitor homeostasis, detecting compounds in blood, CSF, and mucus
- Peripheral chemoreceptors (e.g., carotid and aortic bodies)
- Central chemoreceptors (e.g., ventrolateral medulla, area postrema)
- Chemical exteroceptors detect compounds in the environment, including smell and taste
- Specialized receptor cells with high turnover rates
- Commonly employ G protein-coupled receptors (GPCRs)
- Communicate with limbic and memory systems
Olfactory Bulb and Stalk
- Olfactory and gustatory information reaches consciousness in orbitofrontal cortex
- 80% of flavor is determined by smell
Olfactory Receptors
- Receptor potentials are graded
- Olfactory receptor neurons (ORNs) spontaneously generate action potentials
- Olfactory cilia are non-motile organelles where odor receptor proteins are situated
- Each ORN expresses only one type of olfactory receptor gene
Olfactory System: ORN Tuning
- Each olfactory receptor binds multiple odors
- Olfactory receptor neurons (ORNs) exhibit a variety of responses to different odors.
- Response magnitude is generally correlated with stimulus intensity.
Olfactory Epithelium
- Olfactory epithelium lines the nasal cavity
- Contains olfactory receptor cells
- Also includes supporting cells, basal cells, and Bowman's glands
Olfactory Epithelium (OE)
- Olfactory receptor neurons (ORNs) are bipolar neurons
- ORNs regenerate every 6-8 weeks
- Central processes of ORNs bundle into unmyelinated olfactory fibers
- These fibers then pass through the cribriform plate of the ethmoid bone
Cribriform Plate
- The olfactory nerves pass through perforations (foramina) in the cribriform plate
- ~20 perforations per side in the ethmoid bone
Olfactory Bulb (OB) and Tract
- Outgrowths of the telencephalon
- Not technically peripheral nerves
ORNs expressing the same receptor project to the same glomerulus
- ORNs and glomeruli have corresponding zonation
- There is no correlation found between zone, odor perception or chemical structure
Anatomical Organisation of the Olfactory Bulb
- Glomeruli receive axons from olfactory receptor neurons and contain mitral cells and periglomerular cells
- Mitral cells are the main output neurons of the olfactory bulb
Olfactory Tracts and Anterior Olfactory Nucleus
- Extinction and adaptation are due to centrifugal (efferent) fibers
- ORNs adapt about 50% in the first second, and then adapt more slowly
- Within a minute of stimulus sensation extinguishes
Medial Olfactory Stria
- Neurons in medial olfactory stria pass through the anterior commissure
- Travel to the contralateral olfactory bulb
Olfactory Trigone
- Olfactory tract splits into medial and lateral olfactory striae
Primary Olfactory Cortex
- Second-order neurons (mitral and tufted cells) project to the primary olfactory cortex, bypassing the thalamus
Olfactory Pathway
- Olfactory information is relayed to the primary olfactory cortex and other areas such as the orbitofrontal cortex.
The Other "20%"
- Component of flavor is called "sapid"
- Difference in taste between jellybeans is due to olfaction
Special Sensory Innervation of the Tongue
- Facial nerve (CN VII) Innervates Anterior 2/3 of tongue for taste
- Glossopharygeal nerve (CN IX) innervates Posterior 1/3 of tongue for taste
Lingual Papillae
- Located on the tongue, and include specialized structures for taste perception
- Different types of papillae are associated with different areas of the tongue
Taste Modalities
- Five basic tastes: sweet, salty, sour, bitter, and umami
- Chemical stimuli activate specific receptors leading to specific sensations
There is no "taste map" on the tongue
- Taste receptor cells are located throughout the tongue.
Surface Protein TRPV1 on Polymodal Nociceptors
- Activated by temperatures over 109°F and chemical irritants
Taste Receptors
- 50 -100 taste receptor cells (TRCs) per taste bud
- Each taste bud has TRCs of multiple types
- Each TRC expresses a single taste receptor
Gustatory Pathway
- Gustatory information is carried to the brain through cranial nerves
- Primarily relays to the nucleus of the solitary tract
Brainstem Nuclei
- Contains various nuclei involved in sensory processing, including the nucleus of the solitary tract
Solitary Nucleus and Tract
- Nucleus of the solitary tract relays gustatory information to the thalamus
- Gustatory information to the brain can also involve the Thalamus
Gustatory Pathway (for us)
- Axons from the solitary nucleus project to the contralateral thalamus
Primary Gustatory Cortex
- Located in the opercular regions of the parietal and frontal lobes, anterior, inferior insular cortex
From 1º Gustatory Cortex, information travels to:
- Gustatory association cortex in the insula
- Orbitofrontal gyri for coordination of conscious taste and smell
- Hypothalamus and/or Amygdalas for emotional and autonomic reflexes
What's the Difference?
- Olfactory receptors are airborne molecules, use modified neurons and have a variety of types
- Gustatory receptors are less volatile molecules and use modified epithelial cells
- Both involved in a variety of types of encoding
Smell
- Odorants activate olfactory receptors, which in turn cause a cascade of intracellular signals.
Taste
- Taste stimuli are detected in the taste buds.
Disorders
- Olfactory and gustatory disorders include hyposmia, anosmia, parosmia, phantosmia, and similar gustatory disorders.
Key Concepts
- Comprehensive list of concepts related to olfaction and gustation
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Description
Test your knowledge on the various cell types in the olfactory bulb. This quiz covers periglomerular cells, mitral cells, and their synapses, alongside their roles in olfactory processing. Ideal for students studying neurobiology or related fields.
