Deamination: removal of an amino group from an organic compound.

Dendrites: projections of cytoplasm that carry impulses toward the cell body

Depolarization: diffusion of sodium ions into the nerve cell resulting in a charge reversal

Distal tubule: conducts urine from the loop of Henle to the collecting duct.

Dynamic equilibrium: condition that remains stable within fluctuating limits.

Efferent arterioles: small branches that carry blood away from the glomerulus to a capillary net.

Endocrine hormones: chemicals secreted by endocrine glands directly into the blood

Endorphins: natural painkillers belonging to a group of chemicals called neuropeptides; contain between 16 to 31 amino acids

Enkephalins: natural painkillers belonging to a group of chemicals called neuropeptides; contain 5 amino acids and are produced by the splitting of larger endorphin chains

Estrogen: female sex hormone that activates the development of female secondary sex characteristics, including development of the breasts and body hair, and increased thickening of the endometrium

Filtration: process by which blood or body fluids pass through a selectively permeable membrane

Flow phase: phase of the menstrual cycle marked by shedding of the endometrium

Follicles: structures in the ovary that contain the egg and secrete estrogen

Follicle-stimulating hormone (FSH): in females, a gonadotropin that promotes the development of the follicles in the ovary; in males, hormone that increases sperm production

Follicular phase: phase marked by development of ovarian follicles before ovulation