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Chapter 9. Smell & Taste

A young boy was diagnosed with congenital anosmia, a rare disorder in which an individual is born without the ability to smell. Which parts of the nervous system might be defective in an individual with congenital anosmia to account for the inability to detect odors?

A. Glossopharyngeal nerve, olfactory bulb, ventral posterior medial nucleus of the thalamus, and anterior insula-frontal operculum

B. Olfactory sensory neurons, olfactory glomeruli, nucleus of the tractus solitarius, and ventral posterior lateral nucleus of the thalamus

C. Olfactory nerve, olfactory bulb, medial olfactory tract, and anterior insula-frontal operculum

D. Olfactory sensory neuron, 1st cranial nerve, olfactory glomeruli, and frontal cortex

E. Trigeminal nerve, olfactory glomeruli, lateral olfactory tubercle, and entorhinal cortex

While working in a laboratory studying the olfactory system, a medical student was intrigued by the fact that a simple sense organ like the human olfactory epithelium can discriminate perhaps more than 1 million distinct odors. What factors may contribute to this phenomenon?

A. There are 500 types of odorant receptors and over 1000 types of odorant-binding proteins that sequester odorants to enhance sensory discrimination.

B. Each olfactory sensory neuron expresses a single odorant receptor gene and projects to a particular subset of mitral cells that connect to distinct parts of the olfactory cortex.

C. Odorants bind to a mixture of GPCR and ion channel receptors on olfactory sensory neurons and the axons of these sensory neurons form anatomically discrete synaptic units called olfactory glomeruli.

D. Lateral inhibition within olfactory glomeruli sharpen and focus olfactory signals and granule cells within the olfactory glomerulus make specific projections to the postcentral gyrus in the somatosensory cortex.

E. There are about 5000 types of odorant receptors and each odorant binds to only one of these.

As part of a research experience, a medical student was reviewing reports on the effects of exposure to various neurotoxins on odor detection in humans. Which cells in the olfactory system are responsible for the ability to retain the sense of smell despite the fact that toxins can damage elements of the nasal mucosa?

A. Basal cells in the olfactory bulb undergo mitosis to generate new olfactory sensory neurons.

B. Surviving olfactory sensory neurons undergo neuroplasticity and make connections with the mitral and tufted cells that were originally connected to the destroyed sensory neurons.


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