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.
Neurotransmitters are chemical messengers that are released from the axon and received by effector cells. This process is critical for delivery of the message to the cells and tissues that are being controlled. The terminal, then, is the final point of stimulation in the axon before the charge is delivered.