DSA Neuroanatomy of Gustation & Olfaction Flashcards
Via _______ _______ neurons, humans can recognize thousands of airborne odors, many at extremely low concentrations. This plays a role in the pleasure associated with eating and helps us recognize environments.
Olfactory receptor
The bones of the nasal cavity are very (THICK/THIN). This makes the olfactory receptor neurons very sensitive to facial trauma.
Thin
The taste system has a very limited range of sensation. The four basic tastes are…
Sweet
Salty
Sour
Bitter
Umami sensation may be important for the identification of…
Amino acids
T/F. The combinations of taste qualities are important in acceptance or rejection of foods.
True
What can recognize a wider variety of sensations?
A. Tongue
B. Nose
C. They are the same
B. Nose
How are we able to recognize different tastes other than the 4 basic ones?
A. There are thousands of types of taste receptors.
B. Few taste receptors in different combinations result in different taste sensations.
C. I have no idea.
B. Few taste receptors in different combinations result in different taste sensations.
1.5 yo male presents with a cold. Their parent reports they are completely stopped up. The parent also reports that the child put coffee beans in their mouth and did not spit it up. Why?
A. Young children put stuff in their mouth all the time.
B. The child obviously likes coffee.
C. Olfaction and taste are intimately related.
C. Olfaction and taste are intimately related.
This is a critical anatomical structure that helps humans smell. It lies in the cribriform plate of the ethmoid bone.
Olfactory Bulb
This helps transmit sensory information from the environment to the brain.
Olfactory Tract
The olfactory bulb sits here. This is the rostral end of the olfactory sulcus and the rostral portion of the anterior cranial fossa.
Cribriform Plate
These neurons are located on the roof of the nasal cavity. They are located on the inferior surface of the cribriform plate, along the nasal septum, and on the medial wall of the superior turbinate (concha).
Olfactory Receptor Neurons
The Olfactory Receptor Neuron is CN 1. It has a single _______ _______ that receives information from the environment. These receptors are found in olfactory mucosa of the superior portion of the nasal cavity.
Dendritic process
This is what keeps the nasal cavity moist.
Ducts and glands within the olfactory epithelium
Olfactory nerve bodies are surrounded by _________ cells. The dendrites and receptors of these cells will extend into the olfactory epithelium where they will have good exposure to smell molecules.
Supporting
The cilia of an Olfactory Receptor Neuron are _________ and contain _________ receptors.
Non-motile
Odorant
What type of receptors are odorant receptors?
GPCRs
An odorant receptor is activated by a ligand odor molecule binding to its specific GPCR. This causes a signal to be sent from the Olfactory Receptor Neuron to the…
Olfactory Bulb
This layer of CT holds lots of immune cells. This is important because the mucosa is directly exposed to the external environment.
Lamina Propria
These cells are just superficial to the basement membrane. These act as stem cells for Olfactory Receptor Neurons and supporting cells. They continuously turn over and as a result, most cells in the olfactory mucosa have a life span of 30-60 days.
Basal cells
The cell bodies of Olfactory Receptor Neurons lie in one layer, while their single dendrite extends to the ________ layer. The axons travel up to the olfactory bulb through the _______ _______.
Mucus
Lamina Propria
These cells offer physical and metabolic support to the surrounding cells in the olfactory mucosa.
Supporting/Sustentacular cells
These are ciliated columnar epithelial cells in olfactory mucosa.
Brush Cells
This is made and secreted by the glands and ducts in the Olfactory Epithelium.
Mucus
What are the layers of the olfactory mucosa?
Lamina Propria Basal Cells Olfactory Receptor Neurons (cell bodies) Supporting/Sustentacular cells Brush cells Cilia Mucus
Describe the process of smell.
At the back of the nasal cavity is olfactory epithelium that has olfactory receptors (GPCRs). We breathe in, and odorant molecules get trapped in mucus and bind to these receptors. This activates the neurons and send a signal through the olfactory bulb, then olfactory tract and into your brain.
***We can distinguish between odors because one odor will bind to certain olfactory receptor neurons, while another odor will bind to different neurons.
Smell molecules are transmitted into sensory information when they act as a ligand and interact with the GPCR of an Olfactory Neuron Receptor. Initially, the smell molecule will contact the ________ layer that covers the Olfactory Epithelium. There it will interact with odorant-binding proteins.
Mucus
The smell molecule acts as a ligand and binds a GPCR. This activates _______ ______ which results in an increase in _______.
Adenylyl Cyclase
cAMP
After smell molecules have lead to the increase in cAMP, cAMP binds ion channels which leads to an increase in _______ and _______ influx into the cell. This causes a depolarization and an action potential. The action potential travels up the Olfactory Receptor Neuron where it synapses with neurons in the ________ ________.
Calcium
Sodium
Olfactory Bulb
Different regions of the Olfactory Epithelium line up with and carry information to specific areas of the ________ _______. This “receptor map” is the initial step for olfactory discrimination.
Olfactory Bulb
Odors are encoded by activating several different _________ at varying magnitudes. These are preferentially distributed within the olfactory epithelium.
Receptors
The Olfactory Bulb has 5 layers, which are what from deep to superficial (inferior to superior)?
Granule cell layer Mitral cell layer External Plexiform layer Glomerular layer Olfactory Nerve layer
***Mnemonic is GRow My EGO
These reach the Olfactory Bulb via the Anterior Commissure. Their main job is to help regulate feedback loops.
Centrifugal Fibers
What are the components of the Olfactory Tract?
Lateral Olfactory Tract
Cells of Anterior Olfactory Nucleus
Fibers of the Anterior Limb of the Anterior Commissure
Centrifugal fibers have a (POSITIVE/NEGATIVE) effect on Granule cells. The Granule cells have a (POSITIVE/NEGATIVE) effect on Mitral and Tufted cells. Therefore, increasing Centrifugal fiber activity will indirectly (INCREASE/DECREASE) Mitral and Tufted cell activity.
Positive
Negative
Decrease
Olfactory Receptor Neurons upregulate the activity of Mitral/Tufted cells and __________ cells. These cells antagonize the activity of Mitral and Olfactory Receptor Neuron cells, and likely have an important roll in getting used to smells, like when you’re in the anatomy lab and the smell “goes away”.
Periglomerular
As Olfactory Receptor Neurons continue to be active, the __________ cells respond to shut down Mitral and Tufted cells, effectively inhibiting the transmission of information from the environment to the brain.
Periglomerular
Afferent projections from Olfactory Receptor Neurons synapse with _______ and _______ cells in the olfactory glomerulus.
Mitral
Tufted
The axons of a Olfactory Receptor Neuron only synapses in one _________, however, a single _________ has a large number of Olfactory Receptor Neurons synapsing within it.
Glomerulus
Glomerulus
The glomerulus actually receives axons from all the Olfactory Receptor Neurons expressing the same odor molecule specific receptor. This suggest that a single glomerulus will receive input from only one type of ________.
GPCR
Activity in the glomerulus is regulated by…
Periglomerular cells Olfactory Neuron Receptors Mitral cells Tufted cells Centrifugal Fibers
Which cell type carries afferent information from the olfactory bulb to the brain?
A. Olfactory Receptor Neurons
B. Tufted cells
C. Granule cells
D. Periglomerular cells
B. Tufted cells
Which cell type carries efferent information from the brain to the olfactory bulb?
A. Mitral cells
B. Periglomerular cells
C. Centrifugal Fibers
D. Olfactory Receptor Neurons
C. Centrifugal Fibers
Certain cells in the olfactory bulb have inhibitor effects on others. What neurotransmitter is responsible for this action?
A. cAMP B. Serotonin C. Dopamine D. GABA E. ACh F. Norepinephrine
D. GABA
The olfactory bulb projects information to other regions of the brain. The information is carried from the olfactory bulb to the olfactory cortex via the ________ ________ ________. The cells carrying information are the _______ and _______ cells.
Lateral Olfactory Tract
Mitral
Tufted
***Olfactory projections go directly to the olfactory cortex, they DO NOT have to pass through the relay center (thalamus).
The olfactory epithelium has zones that corresponded with zones in the olfactory bulbs (depending on smell type). The zones of the olfactory bulb DO NOT have a similar projection pattern on the _______ _______. This means that information from the different zones of the olfactory bulb can go to any region of the _______ _______.
Olfactory Cortex
Olfactory Cortex
Smells are often associated with memory. This long-term processing occurs because of secondary projections of the Olfactory Cortex to the…
Hippocampus
Smell is a primitive sense. Smell can help an organism recognize danger and fear. In humans, projection to the ________ helps this process occur.
Amygdala
Afferent projections from the Olfactory Bulb go to several areas of the Olfactory Cortex FIRST. Then certain areas may send information to the thalamus, specifically the _______ _______ _______, for further processing. This is a SECONDARY projection.
Dorsomedial Thalamic Nucleus
***Remember, smell is a primitive sense. It does NOT have to go to the thalamus for initial processing.
After reaching information from the Lateral Olfactory Tract, the Olfactory Cortex (specifically the ________ _______ ________) sends information back to the Olfactory Bulb.
Anterior Olfactory Nucleus
This tract is where the Mitral and Tufted cells are sending their axons to the Olfactory Cortex (afferent).
Lateral Olfactory Tract
If information is directed from the Olfactory Cortex to the _______ _______ the body responds with appropriate feeding behavior. For example, an individual smells warm bread, they salivate and become hungry.
Lateral Hypothalamus
If information is directed from the Olfactory Cortex to the _________ then the input is linked to learning and behavior. For example, I have smelled bad body odor all day no matter where I go. It must be me, I smell. I will take a shower later.
Hippocampus
The Paleocortex (primitive cortex) sends projections to other areas of the brain like the hippocampus and dorsomedial thalamic nucleus. These areas are part of the _________, which helps discriminate and identify odors. An example of how it processes – “this drink smells like coffee, if I drink this it will help me stay awake.”
Neocortex
This helps integrate olfaction, taste, and other food cues to help humans experience flavors and enjoy food.
Orbitofrontal Cortex
These are sensory organs that can perceive experiences of sweet, salty, sour, bitter, and umami.
Taste buds
Taste buds can be found throughout the _________ cavity. They are most obvious on the tongue.
Oropharyngeal
This innervates the Fungiform Papillae and anterior Foliate Papillae on the anterior 2/3 of the tongue.
Chorda Tympani
***Part of CN VII
The taste buds on the soft palate are innervated by the…
Greater Superficial Petrosal N.
***Part of CN VII
This is where afferent fibers of the Facial N. carrying taste sensory information enter the brainstem.
Pontomedullary Junction
This is where sensory fiber cell bodies of the Facial N. are located. These fibers of CN VII carry taste sensation to the Rostral Solitary Nucleus (aka Gustatory Nucleus).
Geniculate Ganglia
Sensory fibers of the Facial N. synapse in the Solitary Tract and information is then transmitted to the Solitary Nucleus and carried to the part called the ________ ________ (aka the Rostral portion of the Solitary Nucleus).
Gustatory Nucleus
Taste reception is initiated when soluble chemicals (from food) diffuse through a taste pore. The chemical then bind to receptors on apical ________ of taste cells and cause hyperpolarization or depolarization. If depolarization of cells is sufficient, an action potential in the taste cell is relayed to afferent fibers.
Microvilli
This nerve innervates taste buds in the Vallate Papillae and posterior Foliate Papillae.
Glossopharyngeal N.
This nerve innervates taste buds of the epiglottis and esophagus.
Vagus N.
What is the pathway for taste reception?
Taste bud afferents (from Geniculate Ganglia) —
Synapse in Solitary Nucleus (specifically rostral or Gustatory Nucleus) —
2nd order neurons travel via ipsilateral Central Tegmental Tract —
Central Tegmental Tract take neurons to synapse in VPMpc (parvicellular ventral posteromedial nucleus) —
2nd order neurons synapse with 3rd order neurons in VPMpc —
Gustatory information now traveling on ipsilateral Posterior Limb of Internal Capsule —
Taken to Frontal Operculum and Anterior Insular Cortex, specifically the Rostral area of Brodmann area 3b (in post central gyrus)
This region of the brain receive input from the primary taste cortex (Brodmann area 3b). It takes information and integrates it with visional and olfactory senses associated with food ingestion.
Lateral Posterior Orbitofrontal Cortex
This is the loss of smell.
Anosmia
This is decreased sensitivity to odorants. An example that causes this is nasal polyps (noncancerous growths in the nasal cavity or sinuses).
Hyposmia (aka Olfactory Hypesthesia)
This is a complete loss of taste. It is rare because many nerves carry gustatory sensory information (CN VII, IX, X).
Ageusia
This is decreased taste sensitivity.
Hypogeusia
This is when perception of taste is altered. Commonly due to drug use (prescription or recreational).
Parageusia/Dysgeusia
Lesions of CN VII can be caused by tumors in the Internal Auditory Meatus (called a Vestibular Schwannoma) because it may bump the Chorda Tympani. This results in loss of taste in the anterior 2/3 of tongue on the (CONTRALATERAL/IPSILATERAL) side. It will also manifest as (CONTRALATERAL/IPSILATERAL) facial paralysis, hearing loss (due to paralysis of Stapedius M.), impaired secretion of nasal, lacrimal, submandibular, and sublingual glands.
Ipsilateral
Ipsilateral
This is the first ganglion where the Facial N. fibers carrying taste information from the tongue synapse. If there is damage here, taste may or may not be lost but IPSILATERAL facial paralysis will be seen.
Distal Geniculate Ganglion
