Physiology Flashcards
where are taste buds present?
tongue, palate, epiglottis, pharynx
taste receptors are replaced within which cells within the tastebuds?
basal cells
what is the lifespan of taste receptor cells?
10 days
which type of papillae don’t contain taste buds?
filliform
receptor potentials initiate ———— in —————– nerve fibres ich synapse with ————– cells
Receptor potential initiates action potentials in afferent nerve fibres which synapse with receptor cells
Binding of taste provoking chemical (tastant) to ————- alters cell ———– and produces —————–receptor potential
Binding of taste provoking chemical (tastant) to receptor cells alters cell ionic channels and produces depolarising receptor potential
Signals conveyed by ————- via ————- and ————–to ————– ————- areas
Signals conveyed by cranial nerves via brainstem and thalamus to cortical gustatory areas
afferent taste fibres reach the brainstem via which 3 nerves?
- chorda tympani - branch of the facial nerve - VIIth
- glossopharyngeal - posterior 1/3rd of the tongue - IXth
- vagus nerve - areas other than the tongue (iglottis and pharynx) - Xth
what are the five primary tastes?
Salty: stimulated by chemical salts especially sodium chloride (NaCl)
Sour: stimulated by acids which contain free hydrogen ions (H+)
Sweet: stimulated by configuration of glucose
Bitter: stimulated by diverse group of tastants, including e.g. alkaloids, poisonous substances and toxic plant derivatives
Umami (meaty or savory): triggered by amino acids especially glutamate
abnormalities of taste can be either ——-/——–?
temporary/ permanent
what is ageusia?
loss of taste function
what are the causes ageusia?
Can be caused by e.g. nerve damage; local inflammation (including e.g. glossitis, radiation, tobacco); some endocrine disorders
what is hypogeusia?
reduced taste function
what are the causes of hypogeusia?
Can be caused by e.g. chemotherapy; medications
what is dysgeusia?
distortion of taste function
what are the causes of dysgeusia?
Many causes including e.g. glossitis; gum infections; tooth decay; reflux; upper respiratory infections; medications; neoplasms; chemotherapy; zinc deficiency
what three types of cells does the olfactory mucosa contain?
Contains three cell types: olfactory receptor cells, supporting cells and basal cells (secrete mucus)
how many cillia are present per olfactory receptor neuron?
10-12
———————–specialised endings of renewable afferent neurons
Each neuron has a —————- and an expanded end called an ——————-
From the olfactory rods, ——– project to the surface of the —————————
Olfactory receptors - specialised endings of renewable afferent neurons
Each neuron has a thick short dendrite and an expanded end called an olfactory rod
From the olfactory rods, cilia project to the surface of the olfactory mucosa
odarants bind to?
the cilia
what is the lifespan of odarants?
2 months
Basal cells act as ———————- for new —————
——————-cells
Basal cells act as precursors for new olfactory receptor cells
what forms the afferent nerve fibers of the olfactory nerve?
axons of olfactory receptors
These pierce the ————- ————– of the —————
————and enter the olfactory bulbs in the————— surface of the brain
Olfactory bulbs transmit ———- information to the brain
From the olfactory bulb neurons pass along the———
——- to reach ————– ———- and ———– areas
These pierce the cribriform plate of the ethmoid bone and enter the olfactory bulbs in the inferior surface of the brain
Olfactory bulbs transmit smell information to the brain
From the olfactory bulb neurons passes along the olfactory tract to reach temporal lobe and olfactory areas
to be smelled a substance must?
To be smelled, a substance must be (1) sufficiently volatile i.e. some of its molecules can enter the nose with inspired air (2) sufficiently water soluble i.e. can dissolve in the mucus coating of olfactory mucosa
what is anosmia?
inability to smell
what are the causes of anosmia?
causes include: viral infections; allergy; nasal polyps; head injury
what is hyposmia?
reduced ability to smell
what are the causes of hyposmia?
Causes similar to those for anosmia
May be an early sign of Parkinson’s disease
what is dysomia?
altered sense of smell
what are the causes of dysomia?
Examples include: differently interpreting some odours; and hallucinations of smell
