in the bronchioles are stimulated to release histamine and heparin that
induce the contraction of smooth bronchiolar muscle [bronchoconstriction,
(answers b and c)] and edema in the wall. If the bronchoconstriction is
chronic, the long-term result is thickening of the bronchiolar musculature.
There are no cilia in the alveoli (answer a)alveolar macrophages (dust cells)
ingest particulate matter that enters the alveoli. Hypersecretion of viscous
mucus from goblet cells in the bronchi (not bronchioles) can obstruct the air-
way(answer d).Eosinophils, neutrophils, lymphocytes and macrophages
signal to each other through a complex cytokine network using a variety of
mediators: bradykinin, leukotrienes, and prostaglandins, which enhance
bronchoconstriction, vascular congestion, and edema. The airway epithe-
lium responds to those mediators. Eosinophils (answer c)release proteins
that destroy the airway epithelium (releasing Creola bodies). T lymphocytes
are also present in more severe “attacks” and, along with B lymphocytes, may
play a role in the initiation of allergic asthma. T lymphocytes also release
cytokines that activate cell-mediated immunity pathways.
189.The answer is d.(Alberts, pp 866–867, 1268.)The region shown on
the MRI is the olfactory area lined by the olfactory epithelium. The response
of rod cells to light causes hyperpolarization, whereas olfactory stimuli result
in depolarization. The olfactory epithelium and rod cells are two examples of
signal transduction that bypass a protein kinase system. In the case of the
olfactory epithelium, an odorant molecule binds to an odor-specific trans-
membrane receptor found on the modified cilia at the apical surface. The
binding activates an odorant-specific G protein, Golf, which binds GTP.
(For summary of 6 proteins, see table page 106). The resulting dissociation
of the α-subunit stimulates adenylate cyclase to produce cyclic AMP (cAMP).
cAMP directly stimulates the opening of the cation channels on the mem-
brane of the bipolar olfactory receptor cells, leading to Na+influx. The result-
ing membrane depolarization is transmitted from the modified cilia to the
olfactory vesicle through the neuron to the basal axon. Axonal processes tra-
verse the lamina propria as the olfactory nerve and pass through the cribri-
form plate of the ethmoid to terminate in the olfactory bulb. In the case of the
rod, the cyclic nucleotide involved is cGMP.
190.The answer is a. (Junqueira, pp 349–353, 357.)Oxygen moving from
the alveolar air to the capillary blood and carbon dioxide diffusing in the
opposite direction pass through a three-component blood-air barrier. This
298 Anatomy, Histology, and Cell Biology