Mydriasis iris sphincter, composed of circularly arranged muscle fibers, and the iris dilator, composed of radially arranged muscle fibers. The sphincter is innervated by (signaled by nerves of) the parasympathetic nervous system, and the dilator by the sympathetic nervous system. Sympathetic stimulation of the adrenergic receptors causes the contraction of the radial muscle and subsequent dilation of the pupil. Conversely, parasympathetic stimulation causes contraction of the circular muscle and constriction of the pupil. The mechanism of mydriasis depends on the agent being used. It usually involves either a disruption of the parasympathetic nerve supply to the eye (which normally constricts the
What a Man My Man Is What a Man My Man Is "What a Man My Man Is" is the name of a No. 1 U.S. country music hit by Lynn Anderson, from 1974. This was Anderson's last No. 1 country hit, staying at the top for one week and spending a total of nine weeks on the chart. It was also her last pop entry on the Hot 100, reaching number 93. For the next few years, Anderson would place hits in the Country top 15 and 20, but wouldn't reach the top 10 again until 1979 with "Isn't it Always Love". The song has