describe how drugs that interact with receptors for acetylcholine and
adrenaline can be used in the treatment of respiratory diseases such as
asthma. this should highlight how receptor selectivity and specificity
is important in order to avoid adverse effects.

Albuterol can treat asthma because it stimulates beta-2 adronergic
receptors present in smooth muscle lining the walls of bronchioles in
the lungs.  This stimulation causes relaxation in these muscles, thus
allowing an asthmatic to breath.  Albuterol also stimulates beta1
receptors in the heart and thus causes tachycardia as a side effect. 
Nonspecific beta blockers like propanolol can interfere with both of
these effects, which is good for the hypertensive patient, but bad for
the asthmatic.  Muscarinic cholinergic receptors in lung smooth muscle
cause bronchial constriction, so I would imagine blocking them would
seem to be of use to asthmatics, but the side effects of muscarinic
blockers are too severe.  Atropine is a muscarinic receptor blocker,
and also the main agent in deadly nightshade and jimsonweed, causing
tachycardia, constipation, dry mouth, and a host of others.  Also,
atropine inhibits secretions in the lungs and consequently indeuces
bronchial constriction--counter productive to asthmatics.