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.
Myoglobin, an iron-containing protein in muscle, receives oxygen from the red blood cells and transports it to the mitochondria of muscle cells, where the oxygen is used in cellular respiration to produce energy. Each myoglobin molecule has one heme prosthetic group located in the hydrophobic cleft in the protein.