Physiology of taste and smell Flashcards
What kind of receptors are the receptors for taste and smell?
Chemoreceptors
What does stimulation of taste and smell receptors induce?
A pleasurable or objectionable sensation
What does taste and smell provide?
A checkpoint for quality control
What does taste and smell influence?
The flow of digestive juice
What infleunces taste perception?
Information from smell receptors
What is gustation?
Taste
How are sensory receptor cells of taste mainly packaged?
In taste buds
What are the sense organs of taste?
Taste buds
What does a taste bud consist of?
Sensory receptor cells and support cells
How are taste bud cells arranged?
Like slices of orange
What is the life span of taste receptor cells?
10 days
What replaces basal cells within the taste buds?
Taste receptor cells
What do taste receptor cells synapse with?
Afferent nerve fibres
Where are taste buds mainly present?
Tongue
Palate
Epiglottis
Pharynx
Where do the majority of taste buds sit in the tongue?
In the papillae
What are papillae?
Finger-like structures which give rise tot the rough appearance of the dorsum of the tongue
How many types of papillae are there?
4
What are the 4 types of papillae?
Filliform
Fungiform
Vallate
Foliate
Which 3 papillae contain taste buds?
Fungiform
Vallate
Foliate
What does the binding of tastant (taste provoking chemicals) do the the cell?
Alters cell ionic channels and produces depolarising receptor potential
What does the receptor potential initiate?
Action potentials in afferent nerve fibres which synapse with receptor cells
How are signals conveyed?
By cranial nerves via brainstem and thalamus to cortcal gustatory areas
How do afferent taste fibres reach the brain stem?
VIIth - anterior 2/3rds of tongue
IXth - Posterior third of tongue
Xth - Epiglottis and pharynx
What are the 5 primary tastes?
Salty Sour Sweet Bitter Unami
What stimulates salty taste?
NaCL
What stimulated sour taste?
Acids containing free hydrogen ions
What stimulated sweet taste?
Glucose
What stimulates bitter taste?
Diverse group of tastants
What triggers unami flavour?
Amino acids
Especially glutamate
What is ageusia?
Loss of taste function
What can cause ageusia?
Nerve damage
Local inflammation
Some endocrine disorders
What is hypogeusia?
Reduced taste function
What causes hypogeusia?
Chemotherapy
Medications
What is Dysgeusia?
Distortion of taste function
What can cause dysgeusia?
Glossitis Gum infections Tooth decay Reflux URTI Chemotherapy Medications Zinc deficiencies
What is olfaction?
Act of smelling
Where is olfactory mucosa found?
Patch of mucosa in the ceiling of the nasal cavity
What are the 3 cell types in the olfactory mucosa?
Olfactory receptor cells
Supporting cells
Basal cells
What are olfactory receptors?
Specialised endings of renewable afferent neurons
What are the characteristics of each neuron?
Thick short dendrite
Expanded end called an olfactory rod
What project from the olfactory rods to the olfactory mucosa?
Cilia
What are odorants?
Molecules that can be smelled
What do odorants bind to?
Cilia
What is the lifespan of an olfacotry receptor?
2 months
What acts as precursors for new olfactory receptor cells?
Basal cells
What forms afferent fibres of olfactory nerve?
Axons of olfactory receptors
What transmits smell information to the brain?
Olfactory bulbs
What is the path of the olfactory bulb neurons?
Along the olfactory tract to reach the temporal lobe and olfactory areas
What does the act of sniffing enhance?
Smelling by drawing air currents upwards within the nasal cavity
What must a substance be in order to be smelled?
Sufficiently volatile
Sufficiently water soluble
What is anosmia?
Inability to smell
Can anosmia be temporary?
yes
What are some causes of anosmia?
Viral infections
Allergy
Nasal polyps
Head injury
What is hyposmia?
Reduced ability to smell
What may hyposmia be an early sign of?
Parkinsons disease
What is dysosmia?
Altered sense of smell
What are some examples of dysosomia?
Differently interpreting some odours
Hallucinations of smell
