Olfaction And Taste Flashcards
Sensation of odors that results from the detection of odorous substances aerosolized in the environment
Olfaction
Sensation evoked by stimulation of taste receptors located in the oropharyngeal cavity
Taste
Contributes to the experience of flavor by detecting irritating components in smells like ammonia or the “hot” in spicy food like peppers
Somatosensory system
What is responsible for thermal and textural perceptions in food
Somatosensory system
Appetite
Orexia
Lack of appetite
Anorexia
Lack of smell
Anosmia
What is smell most important in humans for
Learning and smelling poison
Plays a role in pleasures associated with eating and with the many scents that make up our world
Olfactory system
What ar the taste sensations
Sweet, salty, sour, bitter, and more recently umami (amino acids)
_____ which originates from receptors in the oropharyngeal cavity, is important to determine the acceptance or rejection of foods. This info is relayed by neural pathways that underlie various ingestive and digestive functions
Taste
What is the sensation of taste though smell
Retrosnasal smell, from food
What part of the nervous system is the olfactory bulb
CNS
Where does the olfactory bulb lie
Cribiform plate
What bone is the cribiform plate on
Ethmoid bone
Olfactory bulb in relation to the frontal lobe
Inferior to the medial aspect of the frontal lobe
Where do the olfactory fibers pass through
Cribiform plate
Receptors responsible for transduction of odor molecules are found in the
Olfactory mucosa
Where is the olfactory nasal mucosa
Roof of the nasal cavity on the inferior surface of the cribiform plate and along the nasal septum and medial wall of the superior turbinate
How is the olfactory mucosa different than the respiratory epithelium
The olfactory mucosa is yellowish in color and has greater thickness
What does the olfactory epithelium contain
- olfactory receptor neurons
- supporting cells
- basal cells
- ducts of small glands (Bowmans) that secrete mucous
Where are the olfactory receptors found
Bodies of bipolar olfactory receptor neurons are found in the basal two thirds of the epithelium
Makeup of olfactory receptor
-each has a single thin apical dendrite and a nasally located unmyelinated axon
The apical dendrite of the olfactory receptor
Extends to the surface of epithelium where it terminates in a knob like olfactory vesicles from which 10 to 30 nonmotile cilia arise
The unmyelinated axons of an olfactory receptor neuron pass through the lamina proprioceptive and group together into bundles called _______, whihc collectively make up the olfactory nerve (CN1)
Olfactory fila
Where do the olfactory film pass through
The cribiform plate and terminate in the olfactory bulb
Where is the olfactory bulb
Located on the ventral surface of the frontal lobe in the olfactory sulcus and is attached to the rest of the brain by the olfactory tract
Where do the olfactory fila synapse?
Olfactory bulb
What type of odorants are more likely to cross the mucus
Hydrophobic such as musk
How do hydrophobic molecules cross the mucus in olfactory transduction
By interacting with small proteins called odorant binding proteins
After crossing the mucus, what do hydrophobic odorants do
Bind to odorants receptors on the cilia of the olfactory receptor neurons, which causes depolarization of the dendrite of the olfactory receptor neuron
What do the axons of the olfactory receptor neuron do
Communicate with the second order neurons in the olfactory tract (in bulb) called mitral cells, which emerge from the caudal portion of he olfactor bulb to form the lateral olfactory tract
What is the only system to bypass the thalamus
Olfactory
How do the axons of the olfactory tract course
Caudally to terminate in areas on the ventral surface of the frontal lobe, which are broadly defined as the olfactory cortex
What are the principal areas making up the olfactory cortex
- anterior olfactory nucleus
- olfactory tubercle
- piriform cortex
- periamygdaloid cortex
- entorhinal cortex
What is unique about the olfactory system
The bulb projects directly to the cortex
Where does the olfactory cortex send projections
To the orbitofrtonal cortex and insula (also receive taste input)
In addition to neocortical projections, the olfactory cortex also sends fibers directly to the
Lateral hypothalamus and hipposcampus
Projections from the olfactory cortex to the lateral hypothalamus
Important for feeding behavior and sense of hunger
The olfactory cortex projections to the hippocampus
Links olfactory input to centers concerned with learning and behavior (smells bringing back memories)
Conductive olfactory deficits
Caused by nasal polyps, septal deviation, and inflammation (blockage)
Sensorineural olfactory deficits
Triggered by processes that damage the olfactory receptor neurons or parts of the olfactory CNS (head injuries, neurodegerneative diseases, severe upper respiratory infection)
What is considered the primary olfactory cortex in humans
Piriform cortex
Affect on smell of seizures originating in the vicinity of the uncut
May begin with an illusion of smell or taste, most often an unpleasant one. May go on to include chewing movements or smacking of lips
Seizures that affect the piriform complex that result in illusions of smell and or taste and are accompanied by chewing movements or smacking of the lips
Uncinate seizures
The loss of smell (anosmia) or decreased smell can be associated with
Nasal polyps
What can nasal polyps result from
Inflamed mucous membranes or allergic reactions and can obstruct the nasal cavities or extend into the nose
What are some causes of disrupted sense of smell
Nasal polyps Rhinitis or sinusitis Head trauma Features along anterior base of skull Tumors Cocaine Smoking
What can cause CSF to leak through nose
Fractures along the anteiror base of the skull may cause drainage of CSF into the paranasal sinuses and through the nose (CSF rhinorrhea)
What is specific anosmia
Healthy person who is unable to perceive the odor of a particular compound. May be inherited
Psychiatric disorders and smell
Patients may experience parosmia, a distortion in a smell or the perception of a smell when no odoer is present
Chief complaint of most patients with chemosensory disturbances
Loss or alteration of taste. People confuse taste with flavor
Detection of odorous substance
Indicates the integrity of the peripheral nerve and its pathway
Identification of the odor
Reveals intact cortical functions
If the patient is aware of a smell but cannot recall the name of the scent
The disorder is likely to reside at higher levels of the sensory system (initial symptoms of Alzheimer’s)
Are olfactory losses unilateral or bilateral?
Either
Unilateral olfactory losses
Typically observed subsequent to nasal cavity disease or after tumor associated compression of one olfactory bulb or tract
Bilateral olfactory losses (ansomia)
Sustained in response to head trauma or the common cold
Olfactory and age
Decline in olfactory function are common
-the loss occurs gradually and pt often fails to notice. Can affect the palatability of foods
What does the dense of taste result from
An interaction between gustatory stimuli and receptor cells located in sensory organs called taste buds
Where are taste buds
Tongue and oropharyngeal cavity
What are hte lingual tastebuds
- fungiform papillae
- foliate papillae
- circumvallate papillae
What are the extralingual taste buds
May not be for taste, but for detection of food and suppression of aspiration into trachea (protect from inhaling food)
Fungiform papillae
2-4 taste buds dorsally, anterior 2/3 tongue
Foliage papillae
2-9 clefts, taste buds in clefts, posterior margin of tongue
Circumvallate papillae
8-12 taste buds in cleft
What taste buds are on the anterior 2/3 of tongue
Fungiform
What taste buds are on the posteiror margin of the tongue
Foliage
What taste buds are in the cleft
Circumvallate papillae
Where are taste receptor cells located
Taste buds
Where are taste buds most obvious
Tongue
How many cells does each taste bud contain
40-100
What are the 4 different functionally distinct cell types within the taste buds
- type I: mainly perform supportive functions
- type II: receptor cells posses G protein-coupled receptors for bitter, sweet, and umami compounds
- type III: secrete NT
- type IV: basal cells
Apical end of taste cells
Covered with microvilli of variable lengths that extend into taste pore
What does the taste pore allow
Contact between the microvilli of the taste cell and the external milieu
What mus the substances pass through to reach the taste cell microvilli
Protein rich substance of the taste pore
Taste tranduction
Just like all the others
-chemicals react with receptors, increase intercellular Ca2+, results in a release of a chemical NT (serotonin)
The afferent fibers of first order taste neurons travel in the:
- Facial nerve
- Glossopharyngeal nerve
- Vagus nerve
What nerve is responsible for taste on anterior 2/3 of tongue
Facial nerve (chorda tympani)
What innervates the soft palate
Greater superficial petrosal nerve
What innervates the posterior 1/3 of the tongue
Glossopharyngeal
What innervates the small area around the epiglottis
Vagus nerve
General sensation to the tongue
Trigeminal nerve
-detecting temperature
The cell bodies of facial nerve fibers serving taste are located where
Geniculate nucleus
The primary afferent taste fibers enter the solitary tract and synapse on cells of the
Rostral solitary nucleus
Taste fibers in CN 9 and 10 have thei cell bodies of origin in the inferior ganglia of these CN
What is the primary taste nucleus
What is the principal visceral afferent nucleus of the brainstem
Solitary nucleus
How is the solitary nucleus divided
Rostral (gustatory) and caudal (visceral or cardiorespiratory) nucleus
Taste fibers traveling in CN7, 9, and 10 terminate primarily in the ____ portions of the solitary nucleus
Rostral
Axons arising from second order neurons in the gustatory nucleus (rostral solitary nucleus) ascend in the _____ central tegmental tract and terminate in the ________
Ipsilateral
VPM
Axons from the neuron in the VPM travel where
Through the ipsilateral posterior limb of the internal capsule to terminate in the inner portion of the anterior insular cortex and on the lateral frontal operculum of the postcentral gyrus
This pathway (solitary nucleus–VPM00cortex) is responsible for what
The discriminatory aspects of taste and is exclusively ipsilateral
The sensation ear perceive when eating or drinking is the sensation of flavor, it is the result of the combination of three different kinds of input:
- Direct chemical stimulation of taste buds
- Stimulation of olfactory receptors by vapors from food
- Stimulation of chemical sensitive and somatosensory free nerve endings of CNV (texture and temp)
Loss of taste sense, rare, would require injury to tongue or CN 7/9/10 afferent fibers
Ageusia
Decreased taste sensitivity
Hypogeusia
Distortions in taste perceptions
Parageusia/dysguesia