Nicotine acts in the brain by: Multiple Choice increasing serotonin reuptake. enhancing GABA's inhibitory effects. reducing blood flow to the cerebral cortex. first stimulating and then blocking cholinergic receptors.

Explanation:

Nicotine is a type of stimulant that is chemically alkaloid. It works as the receptor agonist at the nicotinic acetylcholine receptor. It is a type of addictive chemical that increases the blood flow, heart rate and some biochemical reactions of the body. In the brain, it has stimulation as well as blocking effect. Medically, it is used for various purposes such as quitting smoking and some other.

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.