Answer :
The parasympathetic nervous system causes bronchoconstriction and increases mucus secretion in the respiratory system, leading to decreased ventilation, rather than increased ventilation or bronchodilation. So the correct option is b Mucus secretion.
The effects of the parasympathetic nervous system on the respiratory system include the promotion of bronchoconstriction and stimulation of mucus secretion. The parasympathetic nervous system is responsible for the body's rest and digestion response, thus it works to constrict the bronchi, which can lead to reduced airflow through the respiratory system. In contrast, the sympathetic nervous system causes bronchodilation, increasing airflow during times of stress or increased physical activity. Therefore, of the options provided, (a) Bronchodilation is incorrect since it is an effect of the sympathetic nervous system; (b) Mucus secretion is correct as it is stimulated by the parasympathetic nervous system; (c) Increased ventilation is incorrect because the parasympathetic system decreases activity; and (d) Decreased ventilation is correct as a result of bronchoconstriction. So the correct option is b Mucus secretion.
