Contraction of the cremaster muscle occurs because of

In human males, the cremaster muscle is a thin layer of striated and smooth muscle found in the inguinal canal and scrotum between the external and internal layers of spermatic fascia, surrounding the testis and spermatic cord. It lowers and raises the testis in order to control its temperature. Contraction of this muscle can also occur during arousal which can prevent injury to the testicles during sex.