Iris sphincter muscle Iris sphincter muscle The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil. It is found in vertebrates and some cephalopods. Initially, all the myocytes are of the smooth muscle type but, later in life, most cells are of the striated muscle type. Its dimensions are about 0.75 mm wide by 0.15 mm thick. In humans, it functions to constrict the pupil in bright light (pupillary light
Muscle reading located by feedback of "hot" or "cold". June Downey had studied the practice of muscle reading from a psychological perspective. She has been described as an expert on the subject of muscle reading. The technique relies on the assertion that the subject will subconsciously reveal their thoughts through very slight involuntary physical reactions, also known as ideomotor responses. The performer can determine what the subject is thinking by recognising and interpreting those responses. Muscle reading may be billed by some entertainers as a psychic phenomenon, where the audience will be told that by creating physical contact with the subject, a