The correct answer is option d, that is, neurotransmitters.
A neurotransmitter refers to a chemical component, which is discharged at the terminal of a nerve fiber by the introduction of a nerve impulse, and by diffusing across the junction or synapse. It helps in the transfer of the impulse to another muscle fiber, nerve fiber, or some other composition. Acetylcholine is a kind of neurotransmitter, that is, used by neurons in the CNS and the PNS in the control of activities ranging from heart rate and muscle contraction to digestion and memory.
Answer:
The second sperm entry is blocked by the fertilized oocyte.
Explanation:
An ovum prevents polyspermy by two mechanism:
1. When the first sperm fuses with the oocyte then rapid depolarization of egg's plasma membrane takes place which prevents other sperms to fuse with the egg.
2. The fusion of sperm cause an increase in the amount of calcium ion in the cytosol of egg. This higher calcium level activates the development of egg which results in the change in the structure of the egg's outer layer. The outer layer(zona pellucida) becomes hard and prevent the entry of other sperms.
So the chromosomes from the 2nd sperm cell will not normally function in the resulting embryo because the fertilized oocyte block the entry of other sperms.
The Voluntary Sector is usually comprised of organizations whose purpose is to benefit and enrich society, often without profit as a motive and with little or no government intervention.
Unlike the private sector where the generation and return of profit to its owners is emphasized, money raised or earned by an organization in the voluntary sector is usually invested back into the community or the organization itself.