Physiology of taste and smell Flashcards
What is the organ of taste?
Taste buds
What makes up a taste bud?
Sensory receptor cells and support cells
What is the life span of a taste receptor cell?
10 days
Where can taste buds be found?
Tongue, palate, epiglottis and pharynx
What are the 4 types of papillae?
Filiform
Fungiform
Vallate
Foliate
What papillae does not contain taste buds?
Filiform
How is taste generated?
Binding of tastant (chemical) to receptor cells alters cell ionic channels and produces depolarisation receptor potential
Signal conveyed by cranial nerves via brainstem and thalamus to the cortical gustatory areas
What cranial nerves are involved in taste?
Chorda tympani - branch of facial nerve supplies anterior 2/3rd of tongue
Glossopharyngeal supplies posterior 1/3rd of tongue
Vagus nerve supplies epiglottis and pharynx
What are the 5 primary tastes?
Salty Sour Sweet Bitter Umami
What stimulates salty gustation?
NaCl
What stimulates sour gustation?
Acids that contain H+
What stimulates sweet gustation?
Glucose
What stimulates bitter gustation?
Diverse group of tastants including alkaloids, poisonous substances and toxic plant derivatives
What stimulates umami gustation?
Amino acids, especially glutamate
What is anguesia and what can call it?
Loss of taste
Nerve damage, local inflammation (glossitis, radiation, tobacco)
Endocrine disorders
What is hypogeusia and what can cause it?
Reduced taste function
Chemo
Mediations
What is dysgeusia and what can cause it?
Distortion of taste
Glossitis, gum infections, tooth decay, reflux, URTI, medications, neoplasms, chemo, zinc deficiency
What are the 3 types of olfactory cells?
Olfactory receptor cells
Supporting cells
Basal cells (secrete mucosa)
Where can olfactory receptor cells be found?
Patch of mucosa in the ceiling (dorsal roof) of the nasal cavity
What is special about olfactory receptors?
Specialised endings or RENEWABLE afferent neurones
How is smell transmitted?
Olfactory neurones has a thick short dendrite and an olfactory rod
The cilia of olfactory rod will project into olfactory mucosa (10-12 per neurone)
Odorants bind to the cilia
Axons form afferent fibres of olfactory nerve which pierce the cribriform plate of the ethmoid bone to enter the olfactory bulb in the interior surface of the brain
Olfactory bulb passes AP along olfactory tract to the temporal lobe and olfactory areas
What is the life span of an olfactory receptor?
2 months
How are new olfactory receptors produced?
Basal cells
How do odorants reach the olfactory mucosa in quiet breathing?
Diffusion as the olfactory mucosa is above the normal path of airflow
Sniffing will enhance smell
What properties must a substance have to be smelled?
Sufficiently volatile - enter the nose with inspired air
Sufficiently water soluble - dissolve in the mucous coating of olfactory mucosa
What is anosmia and what can cause it?
Inability to smell
Viral infections, allergy, nasal polyps, head injury
What is hyposmia and what can cause it?
Reduced ability to smell
Early sign of parkinson’s disease
What is dysosmia and what can cause it?
Altered sense of smell
Differently interpreting some odors
Hallucinations of smell
