Hormones Trigger Sperm Power Kick (IMAGE) University of California - Berkeley Caption Hormones surrounding the egg trigger hyperactivation in sperm cells. The whip-like motion of the sperm's tail provides the power kick it needs to penetrate and fertilize the egg. Credit UC Berkeley graphic by Carin Cain. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.