Physiology Flashcards
What type of receptors cause taste and smell
Chemoreceptors
Stimulated by binding to particular chemicals
Taste receptors influence smell - true or false
False
other way around
How does our sense of taste and smell protect us
Acts as a quality control for what we eat
e.g. most poisons are bitter and gone off food is sour/acidic
Where in the body is the sensation of taste received
Sensory receptor cells are packaged into the taste buds
They are present in the tongue, palate, epiglottis and pharynx
Describe the lifespan of a taste receptor cell
Life span of around 10 days
They are replaced by basal cells in the taste buds continuously
How does the sensation of taste reach the brain
Binding of chemicals causes depolarising receptor potential
The receptor cells synapse with afferent nerve fibres which carry AP’s
Signals are sent by cranial nerves via brainstem and thalamus to the cortical gustatory area
Where are most of the taste buds found
In the papillae in the tongue
In the fungiform, vallate and foliate types
Which afferent nerve fibres (specifically) transmit taste to the brain
Chorda tympani of facial nerve - anterior tongue
Glossopharyngeal nerve - posterior tongue
Vagus nerve - areas outwith tongue
What are the 5 primary tastes
Salty - stimulated by NaCl Sweet - glucose Bitter - diverse group Sour - H+ ions (acid) Umami - meat or savoury triggered by amino acids
What is ageusia
Loss of taste function
What can cause loss of taste
Nerve damage
Local inflammation
Some endocrine disorders
What is hypogeusia
Decreased sense of taste
What can cause reduced sense of taste
Chemotherapy
Certain medications
What is dysgeusia
Distortion of taste
Many causes
What cell types are found in the olfactory mucosa
Olfactory receptor cells
Supporting cells
Basal cells
Describe how smell is sensed
Odorants bind to cilia on the surface of the olfactory mucosa
This stimuli passes up to the olfactory rods (thickened dendrite)
These rods come together to form the afferent fibres of the olfactory nerve
The nerve pierces the cribiform plate of ethmoid bone and enter the olfactory bulbs in the brain
The bulb passes info along the olfactory tract to the temporal lobe and olfactory areas of the brain
How long do olfactory receptor cells live
Around 2 months
What properties must a substance have in order to be smelled
Must be sufficiently volatile - some particles must enter the nose with air
Must be sufficiently water soluble - can dissolve in mucus
How does sniffing enhance smell
Draws air upwards in the nasal cavity which helps it reach the olfactory mucosa
What is anosmia and what can cause it
The inability to smell
Viral infection, allergy, polyps and head injury can cause it
What is hyposmia and what can cause it
Reduced ability to smell
Similar causes to anosmia (injury, infection)
May be early sign of Parkingson’s
