A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery.
Acetylcholine. Acetylcholine (ACh) is the transmitter released by the preganglionic nerve terminals of both the sympathetic and the parasympathetic divisions (Fig 6.2). The synapse at those sites utilizes a nicotinic receptor similar in structure to the receptor at the neuromuscular junction.
Answers. 1  when a neuron fires, neurotransmitters are released from the axon terminal to the next neuron to propagate a signal. You could probably look up a more complex description on wikipedia, but I'll give you a basic idea - the neurotransmitters bind to ligand-channels on the neural dendrites of the receiving neurons.