1.5: Physiology of Taste and Smell Flashcards
What are the receptors for taste and smell?
Chemoreceptors
Where are the sensory receptor cells for taste found?
They are mainly found packaged in taste buds
What are the sense organs for taste?
Taste Buds
Describe the structure of taste buds?
Where are they found?
These have sensory receptors cells and support cells (arranged like the segments of an orange)
Found on the tongue, epiglottis, palate, pharynx
The majority of taste buds sit in …. of the tongue?
Papillae
Papillae are finger like projections of the tongue
Name the four types of papillae?
Which ones contain taste buds?
Filiform - most numerous
Fungiform*
Vallate*
Folliate*
* = Contains taste buds
How long is the life span of taste receptor cells?
Short lifespan of about 10 days
They are contanstly replaced by basal cells within the taste bud
Describe taste buds and nerve fibres?
The taste receptor cells (within taste buds) synapse with afferent nerve fibres
What cranial nerves are invovled in taste sensation?
7, 9, 10
- Facial
- Glossopharyngeal
- Vagus
Describe how taste signals reach the brain?
- Binding of tastant (taste provoking chemical) to receptor cell causes depolarization
- Action potential in afferent nerve fibres (which synapse with receptor taste cells)
- Signals conveyed via brain/thalamus to the cortical gustory area by the cranial nerves
Describe where the cranial nerves carry taste from?
CN VII (Facial Nerve) - anterior 2/3rds of tongue
CN IX (Glossopharyngeal) - posterior 1/3rd of tongue
CN X (Vagus) - rest of mouth eg: Epiglottis, pharynx
What are the 5 primary tastes?
Give exampels of each
Salty (Eg: NaCl)
Sweet (Eg: Glucose)
Sour (Eg: Acid)
Bitter (Eg: Toxins)
Umami (Meaty) Eg: Amino acids especially glutamate
What is Ageusia?
Loss of taste function
Can be caused by nerve damage, endocrine, loca inflammation
What is hypogeusia?
Reduced taste function
Eg: Chemotherapy, medications
What is dysguesia?
Dysfunction of taste
Eg: Inflammation/infections, reflux, medications
Describe the structure of the olfactory receptors?
Olfactory bulb is composed of afferent nerves fibres. The ending of these nerve fibres are olfactory receptor cells and cilia on the end for odorants to bind to
Axons of the olfactory receptors collectively form…?
Axons of the olfactory receptors collecting form afferent nerve fibres of the olfactory nerve
Describe how the afferent nerve fibres get to the brain?
Afferent nerve fibres of the oflactory nerve pierce the CRIBRIFORM PLATE OF THE ETHMOID BONE
to reach the olfactory bulb (in the brain)
Label this diagram?
A = Olfactory Bulb
B = Afferent Nerve fibres of the oflactory nerve
C = Basal Cell
D = Olfactory Receptor Cell
E = Supporting Cell
F = Cilia
