True/False questions on taste and smell


In the olfactory system

a. The olfactory receptor cell makes synaptic contact with a primary afferent nerve [F] It is a neuroepithelial cell and has an axon
b. Olfactory neurones regenerate [T] Yes, one of the very few examples of a regenerating neuron
c. Olfactory neurones are unable to fire action potentials [F] It is a neuronal (neuroepithelial) cell
d. Olfactory neurones contains 8-20 cilia each [T]
e. The cilia of olfactory neurones are motile [F]


In the gustatory (taste) system

a. The filiform papillae on the tongue are non-gustatory (not taste sensitive) [T] They may have a mechanical function
b. Fungiform papillae are sensitive to sour and bitter tastes [F] Salt and sweet
c. Foliate and circumvallate papillae are raised structures on the tongue [F] Sunken pits
d. A taste bud is a large papillae [F] Papillae contain several taste buds
e. Serous glands secrete acid to break down the taste [F] They secrete a fluid that washes away the taste


In the olfactory system, the olfactory receptor neuron

a. Expresses many different odorant receptor molecules [F] Only one, or a few, at most
b. Regenerates every 3-4 weeks [T]
c. Synapses first in the olfactory bulb [T]
d. Contains cyclic nucleotide gated cation channels [T] Channels open in response to cAMP and this causes depolarization
e. Is only sensitive to molecules with a molecular mass of up to around 300daltons [T] Higher m.wt. compounds tend to have a low vapour pressure


The taste receptor cell

a. Possesses non-motile cilia [F] They have microvilli
b. Has TTX-sensitive Na+ channels on its apical membrane [F] Amiloride-sensitive Na+ channels
c. Synapses with a primary afferent neurone [T]
d. Is capable of firing action potentials [F] It generates receptor potentials not action potentials
e. Is sensitive to specific tastes [F] They mostly have a broad sensitivity to different tastes

In the olfactory system

a. Pigment in the olfactory epithelium contributes towards smell [T] Vit A (a component of pigment) deficient patients lose their sense of smell
b. Most odorant molecules have infra red vibrations [T] This fact has inspired many theories of olfaction
c. There are only 7 classes of smell corresponding to 7 different classes of odorant receptors [F] This was a subjective theory of Amoore's in the '60s
d. An odorant must first be adsorbed by the olfactory epithelium before being detected [T] It has to get through the olfactory mucous to reach the receptors on the cilia
e. Odorant strength is frequency coded [T] Which means that odorant "quality" cannot be frequency coded



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