Practice question

Hyperactivation is whiplash-like, high-amplitude flagellar beating enabling sperm to detach from oviductal epithelium, traverse viscous mucus and penetrate cumulus and zona matrix. It is initiated during capacitation in female tract by alkalinization and progesterone from cumulus cells opening CatSper, sperm-specific pH-sensitive calcium channel complex located in principal piece of flagellum. Calcium entry through CatSper raises intracellular calcium, alters dynein sliding, producing asymmetric bends. Knockout of CatSper subunits in mice abolishes hyperactivation and fertility despite normal motility, while potassium, chloride or sodium channels alone are insufficient to drive this capacitation-dependent motility switch.