What type of receptors are involved with the internal urethral sphincter?

The internal urethral sphincter is primarily controlled by sympathetic receptors. Specifically, the sympathetic nervous system plays a significant role in the storage phase of the bladder filling process, where it activates the internal urethral sphincter to maintain continence. The activation of these sympathetic receptors leads to the contraction of the sphincter muscle, which helps prevent urination during times when the bladder is filling.

While other types of receptors and systems are involved in micturition, such as the parasympathetic system that facilitates bladder contraction during urination, the direct control of the internal urethral sphincter during the storage phase is primarily mediated by sympathetic signals. Somatic receptors are also involved in micturition but are more associated with the external urethral sphincter and voluntary control. Therefore, sympathetic receptors are the correct choice as they directly relate to the functioning of the internal urethral sphincter.