Taste and smell Flashcards
What are visceral chemoreceptors?
Keep track of concentrations of various substances outside of conscious awareness
What are gustatory receptors?
Mediate the sense of taste
Not neurons, but release NTs in response to different taste categories
What are olfactory receptors?
Mediate the sense of smell
What is unique about the pathway of olfaction?
No relay in thalamus
No neocortical projection area
What are the five tastes?
Sweet
Sour
Salty
bitter
Umami
What carries the sense of taste for the anterior 2/3 of the tongue?
Chorda tympani N branch of facial N
What carries the sense of taste for the posterior 1/3 of the tongue?
Glossopharyngeal N
What carries the sense of taste for the taste buds in other areas of the oral cavity?
Vagus N
Where do first order neurons for taste synapse?
Nucleus tractus solitarius in brainstem
Where do the fibers from the tractus solitarius project to for taste?
Through medial lemniscus to the medial of VPM nucleus in thalamus
Where do the fibers from the thalamus for taste project to?
Pass through posterior internal capsule to the lower part of the post central gyrus extending to the insula
What Brodmann’s areas are associated with taste sensation?
Area 3, 1, and 2
What connections are the basis for emotional and behavioral responses to taste?
Connections between tractus solitarius to amygdala and hypothalamus
What is ageusia?
Absence of taste
What is hypogeusia?
Decreased taste sensation
What is dysgeusia?
Disturbed taste sensation
Where is the olfactory membrane?
Superior part of the nasal cavity
What type of nerve cell are olfactory cells?
Bipolar neurons derived from CNS
What is the function of Bowman glands?
Secrete mucus onto surface of olfactory membrane
What part of the olfactory cell responds to odorants?
Cilia that form a dense mat in the mucus
Odorants bind to a G-protein coupled receptor to convert ATP to cAMP
Where do primary olfactory neurons project to?
Olfactory bulb
What types of cells are found in the olfactory bulb?
Mitral
Tufted
Periglomerular
Granule
What is the function of mitral and tufted cells in the olfactory bulb?
Carry olfaction from olfactory bulb to CNS
What are the function of periglomerular and granule cells in the olfactory bulb?
Interneurons that integrate and modulate afferent olfactory information
Granule cells also receive inputs from CNS to modulate olfactory afferents
What forms the lateral/primary olfactory tract?
Axons of mitral and tufted cells
Where does the lateral olfactory tract terminate for conscious appreciation of smell?
Medial temporal lobe
Basal frontal lobe
Where does the anterior olfactory nucleus project?
To the contralateral olfactory bulb via anterior commissure - believed to be inhibitory
How is smell related to the perception of flavor?
Olfactory information passes to adjacent parts of vertebral cortex to combine with taste information
What are the components of the sensation of flavor?
Direct chemical stimulation of taste buds
Stimulation of olfactory receptors by vapors from food
Stimulation of chemical-sensitive and somatosensory free nerve endings of the trigeminal and other nerves in the mucus membranes of oral and nasal cavities
What makes the olfactory pathway unique?
Area where CNS has direct contact with external environment
Does not relay on thalamus
No neocortical projection
Olfactory neurons act as receptors themselves
Olfactory neurons can be recycled from stem cells
What is anosmia?
Absence of smell
What is dysosmia?
Distorted sense of smell
What is parosmia?
Perverted or abnormal sense of smell
What are the characteristics of Kallmann’s syndrome?
Hypogonadism
Complete loss of smell
When do see an increased sensitivity for smells?
Adrenal insufficiency
What is the function of pyramidal cells in the piriform cortex in regards to smell?
Olfactory discrimination
What is the function of the hypothalamus and amygdala in regards to smell?
Motivational and emotional aspects of smell
What is the function of the entorhinal cortex in relation to smell?
Olfactory memories
What is the function of the vomeronasal organ?
Perception of odors that as pheromones
