And the anus consists of two muscles of two sphincter muscles. One of those sphincter muscles known as the internal sphincter muscle is under involuntary control and that means the autonomic nervous system is responsible for opening and closing that internal sphincter muscle. Now the second sphincter muscle known as the external sphincter muscle is actually controlled voluntary. So we are capable of controlling the external sphincter muscle. And that means it is controlled by our or somatic nervous system. So the internal sphincter is controlled by the autonomic, but the external is controlled by the somatic nervous system.