Fast block to polyspermy occurs due to - (1) Influx of calcium ions ca...
Fast block to polyspermy occurs due to - (1) Influx of calcium ions ca...
Fast block to polyspermy
In order to prevent polyspermy, a fast block mechanism is activated immediately after the fertilization of an egg by a sperm. This fast block to polyspermy occurs due to the following process:
Influx of calcium ions causing release of cortical granules
- Upon fusion of the sperm with the egg, there is a rapid influx of calcium ions into the egg cell.
- This increase in calcium ions triggers the release of cortical granules located just beneath the egg cell membrane.
- The release of cortical granules leads to the formation of a fertilization envelope, which acts as a physical barrier to prevent other sperm from fertilizing the egg.
Opening of sodium ion channels to depolarize ovum membrane
- The influx of calcium ions also leads to the opening of sodium ion channels in the egg cell membrane.
- This results in depolarization of the ovum membrane, making it refractory to the entry of any other sperm.
Formation of new membrane of ovum
- The release of cortical granules and the depolarization of the ovum membrane together contribute to the formation of a new membrane around the egg, preventing additional sperm from fertilizing it.
Loss of cone of membrane of ovum
- As part of the fast block mechanism, the cone of membrane present in the egg is lost, further inhibiting polyspermy.
In conclusion, the fast block to polyspermy is a rapid and effective mechanism that prevents multiple sperm from fertilizing the same egg. Through the influx of calcium ions, release of cortical granules, depolarization of the ovum membrane, formation of a new membrane, and loss of the cone of membrane, the egg is protected from polyspermy.
To make sure you are not studying endlessly, EduRev has designed NEET study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in NEET.