What is the slow block to polyspermy due to?

The slow block to polyspermy in the sea urchin embryo consists of a physical barrier to further sperm penetration into the egg. Cortical granule exocytosis results in the formation of the fertilization envelope (often called the fertilization “membrane”, even though the structure is not a true membrane).

How is polyspermy in mammals prevented?

To prevent polyspermy, the zona pellucida, a structure that surrounds mammalian eggs, becomes impermeable upon fertilization, preventing the entry of further sperm. The structural changes in the zona upon fertilization are driven by the exocytosis of cortical granules.

Do mammals have fast block to polyspermy?

a) Enzymes in the cortical vesicles digest away adhesion molecules on the oocyte surface, that are needed for sperm to stick to eggs. Mammals have only this kind of slow block to polyspermy; it is called “the zona reaction”.

Where does the block to polyspermy occur?

The fast block to polyspermy. The fast block to poly-spermy is achieved by changing the electric potential of the egg plasma membrane. This membrane provides a selective barrier between the egg cytoplasm and the outside environment, and the ionic concentration of the egg differs greatly from that of its surroundings.

What is Fast block and slow block polyspermy?

1) FAST BLOCK = electrical barrier, preventing fusion of sperm p.m. and egg p.m.; Slow Block is mechanical block to polyspermy, i.e. the fertilization membrane., which hardens and is impervious to further sperm.

What causes the slow block to polyspermy quizlet?

Fast block to polyspermy occurs early in the acrosomal reaction and involves depolarization of the egg cell membrane during the sperm/egg cell membrane fusion. Slow block to polyspermy occurs later in the cortical reaction and involves receptor clipping.

What is the difference between fast and slow block to polyspermy?

Keep your answer brief. 1) FAST BLOCK = electrical barrier, preventing fusion of sperm p.m. and egg p.m.; Slow Block is mechanical block to polyspermy, i.e. the fertilization membrane., which hardens and is impervious to further sperm.

How does the ovum help in preventing polyspermy?

How does zona pellucida of ovum help in preventing polyspermy? Answer: When a sperm penetrates ovum, it induces changes in the membrane that make the zona pellucida layer impenetrable to additional sperms. Thus, it ensures that only one sperm can fertilize an ovum and stops polyspermy.

How fast do blocks stop polyspermy?

The fast block to polyspermy, which has been best studied in sea urchins, consists of a rapid electrical depolarization of the plasma membrane of the egg. The resting membrane potential of the egg changes from about − 70 to + 10 mV within 2–3 s after fusion of the spermatozoon with the egg.

What is fast and slow block to polyspermy?

What is the first block to polyspermy?

In humans, block to polyspermy is attributed to “oocyte membrane block,” also known as “fast block,” which primarily involves depolarization of the oocyte membrane after binding of the first spermatozoa and transiently prevents any subsequent sperm binding to the oocyte.

Why is the fertilization envelope considered a slow block to polyspermy?

Why is the fertilization envelope considered a slow block to polyspermy? Sperm binding activates a signal transduction pathway in which calcium ions are released from the endoplasmic reticulum.

What is the slow block to polyspermy?

What is the slow block to Polyspermy? The slow block to polyspermy in the sea urchin embryo consists of a physical barrier to further sperm penetration into the egg. Cortical granule exocytosis results in the formation of the fertilization envelope (often called the fertilization “membrane”, even though the structure is not a true membrane).

What is the slow block to polyspermy in the sea urchin embryo?

The slow block to polyspermy in the sea urchin embryo consists of a physical barrier to further sperm penetration into the egg. Cortical granule exocytosis results in the formation of the fertilization envelope (often called the fertilization “membrane”, even though the structure is not a true membrane). Click to see full answer.

What is the fast block to polyspermy in marine invertebrates?

Fast block to polyspermy: In marine invertebrates, including the sea urchin, a fast block to polyspermy occurs within a tenth of a second of fusion. The fast block to polyspermy involves the opening of Na+ channels in the egg plasma membrane.

What are the Egg’s Blocks to polyspermy?

The egg’s blocks to polyspermy (fertilization of an egg by more than one sperm) were originally identified in marine and aquatic species with external fertilization, but polyspermy matters in mammalian reproduction too. Embryonic triploidy is a noteworthy event associated with pregnancy complication …