What is a hormone? multiple choice: o a chemical released from a nerve cell that affects nearby cells across a synapse o a chemical released from an endocrine gland that affects target cells without entering the bloodstream o a chemical found in the blood that catalyzes the destruction of ingested toxins and foreign substances o a chemical excreted from sweat gland that signals other individuals about the physiological status of the body o a chemical regulator secreted from an endocrine gland that travels through the bloodstream to affect target cells

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.

The cluster of developing cells from conception until birth is called an

Which prefix mean under less or below