Practice question

Fast electrical block depolarizes plasma membrane within one to three seconds after sperm fusion, creating immediate short barrier preventing additional fusions. By holding membrane positive, further sperm cannot undergo voltage-sensitive merger. This transient depolarization provides critical window lasting roughly sixty to one hundred twenty seconds before permanent slow block assembles. During this calcium wave triggers cortical exocytosis and progressive elevation and hardening of fertilization envelope. Voltage clamp experiments showing artificially negative holding permits supernumerary fusions confirm mechanism. Duration of fast block generally quoted as one to two minutes covering overlapping transition between blocks.