Ibook: Neuroanatomy of Gustation and Olfaction Flashcards
What can recognize a wider variety of sensations, the tongue or nose?
Nose
What allows us to recognize different tastes other than the 4 basic ones?
Few taste receptors in different combinations result in different taste sensations
Where are olfactory receptor neurons found?
Olfactory mucosa of the superior portion of the nasal cavity
What type of receptors are odorant receptors?
GPCRs
When an odorant receptor is activated where does it send its signal?
Olfactory receptor neuron to olfactory bulb
What layer of CT holds lots of immune cells and is important because the mucosa is directly exposed to the external environment?
Lamina propria
What cells are superficial to the basement membrane, act as stem cells for olfactory receptor neurons, and have a life span 30-60 days?
Basal cells
What has a single dendrite that extends to the mucus layer and its axons travel up to the olfactory bulb through the lamina propria?
Olfactory receptor neurons
What cells are ciliated columnar epithelial cells?
Brush cells
What is an important characteristic of the cilia of olfactory epithelium?
They are non-motile
What is made and secreted by the glands and ducts in the olfactory epithelium?
Mucus
When the smell molecule ligands bind to a GPCR it results in the activation of?
Adenyl cyclase which results in the increase in cAMP
The increase in cAMP binds ion channels which leads to?
Increase in Ca2+ and Na+ influx into the cell (depolarization and AP)
What are the 5 layers of the olfactory bulb?
1) Granule cell layer
2) Mitral cell layer
3) External plexiform layer
4) Glomerular layer
5) Olfactory epithelium
GRow My EGO
Where do olfactory receptor neurons pass through in order to synapse with the olfactory bulb?
Cribriform plate
How does the olfactory bulb connect to the rest of the brain?
Olfactory tract
What reach the olfactory bulb via the anterior commissure?
Centrifugal fibers
Afferent projections from olfactory receptor neurons synapse with?
Mitral and Tufted cells in the olfactory glomerulus
The axons of an olfactory receptor neuron only synapse in ______, however, _______ has a large number of?
The axons of an olfactory receptor neuron only synapse in one glomerulus, however, a single glomerulus has a large number of olfactory receptor neurons synapses within it
Centrifugal fibers have what type of effect on granule cells?
Positive
The granule cell has what type of effect on Mitral and Tufted cells?
Negative
Increasing Centrifugal fiber activity will indirectly do what?
Decrease Mitral and tufted cell activity
Olfactory receptor neurons upregulate the activity of?
Mitral/Tufted cells and Periglomerular cells
Periglomerular cells antagonize the activity of?
Mitral and olfactory receptor neuron cells
The periglomerular cells have an important role in?
Getting used to smells
As olfactory receptor neurons continue to be active, the periglomerular cells respond to?
Shut down mitral and tufted cells effectively inhibiting the transmission of info from the environment to the brain
What cell type carries afferent info from olfactory bulb to the brain?
Tufted cells
Which cell type carries efferent info form the brain to the olfactory bulb?
Centrifugal Fibers
A student walks into the room of a patient and notices it smells like garlic. Later the physician check the oral cavity of the patient and they wince under the odor. The student realized they forgot to warn the attending. Why did the student forget?
The negative feedback of the granular cells inhibited the propagation of info of the mitral and tufted cells
What NT is released by granular cells in the olfactory bulb and has an inhibitory effect?
Gamma aminobutyric acid (GABA)
Constant stimulation of Mitral and Tufted cells have what type of effect on Granular cells?
Positive
Activated Granular cells have what type of effect on mitral and tufted cells?
Negative
The olfactory bulb carries info to the olfactory cortex via?
Lateral olfactory tract
The cells that are sending their axons to the olfactory cortex through the lateral olfactory tract are?
Mitral and Tufted cells
Afferent projections from the olfactory bulb go where first?
Where can it go second?
1) Olfactory cortex
2) Dorsomedial thalamic nucleus
If info is directed from the olfactory cortex to the lateral hypothalamus then?
The body responds with appropriate feeding behavior
Ex) A person smells warm bread causing them to salivate and become hungry
If info is directed from the olfactory cortex to the hippocampus then?
The input is linked to learning and behavior
Ex) I smell bad body odor all day no matter where i go. It must be me. I smell. I will shower later.
The Neocortex helps with?
Discriminating and identifying odors
Ex) This drink smells like coffee, if I drink this it will help me stay awake
What helps integrate smell and taste to help humans experience flavors and enjoy food?
Orbitofrontal cortex
Before the brain can react to and respond to smell, how many neurons took part in the transmission of info?
Two
Patient presents to clinic complaining that when they smell metal they become anxious and suddenly scared. You ask if the smell of KC BBQ makes them hungry to which they respond it always does. Where is the lesion?
Part of olfactory cortex is damaged such as the Paleocortex
What happens if the left orbitofrontal cortex has a lesion?
Unable to differentiate between smells
What is the second neuron involved in olfaction?
Mitral or Tufted cells
What innervates fungiform papillae and anterior foliate papillae on the anterior 2/3 of the tongue?
Chorda Tympani
Taste buds on the soft palate are innervated by?
Greater superficial petrosal nerve
Soluble chemical from food diffuse through a taste pore and bind to receptors on?
Apical microvilli of taste cells
Afferent fibers of the facial nerve carrying taste sensory info enter the brain stem where?
Pontomedullary junction
Where are sensory fiber cell bodies of the CN VII located?
These fibers carry taste sensation to?
1) Geniculate ganglia
2) Rostral solitary nucleus (AKA Gustatory nucleus)
What innervates taste buds in the vallate papillae and posterior foliate papillae?
CN IX
What innervates taste buds of the epiglottis and espohagus?
CN X
After synapsing in the solitary nucleus sensory info from the taste buds travels through 2nd order neurons and travel via?
Ipsilateral central tegmental tract
The central tegmental tract is the highway for?
Where does the gustatory sensory info travel next?
1) 2nd order neurons to travel
2) Parvicellular ventral posteromedial nucleus (VPMpc)
What happens in the VPMpc?
2nd order neurons synapse with 3rd order neurons
Where does the gustatory sensory info shuttle to next after VPMpc?
By what route?
1) Frontal operculum and anterior insular cortex
2) Ipsilateral posterior limb of the internal capsule
What is the specific areas of the frontal operculum and anterior insular cortex that gustatory info arrives at?
Brodmann area 3b in post central gyrus
The pathway that gustatory sensory info travels is responsible for?
Discriminating taste
A patient has a negative gag reflex. Where would you expect the patient to have diminished taste sensation?
Vallate papillae
The gustatory ganglia synapse in what nucleus of the brain stem?
Solitary nucleus
If a patient has a middle ear infection along with the sense of taste lost what might be lesioned?
Chorda tympani
What is the term for the decreased sensitivity to odorants?
Hyposomia aka Olfactory Hypesthesia
What can cause Hyposomia aka Olfactory Hypesthesia ?
Nasal polyps
What is the term for the loss of smell?
Anosmia
What is the term for the complete loss of taste?
Ageusia
What is the term for the decreased taste sensitivity?
Hypogeusia
What is the term for the perception of taste altered and is commonly due to drug use?
Paraguesi/ Dysgeusia
A tumor in the internal auditory meatus (vestibular schwannoma) can cause?
Lesion of CN VII
In terms of taste, lesion of CN VII can result in?
Loss of taste in anterior 2/3 of tongue on ipsilateral side
Damage to distal geniculate ganglion can result in?
Ipsilateral facial paralysis
