10. Antigens are 11. Attenuat A) sometimes occur naturally B) can be produced in the laboratory C) have never been hums B) renal system ofygen and carbon dioxide D) circulatory system 13. Functions of the kidney include A) elimination of waste products by filtration C) secretion of important nutrients for the body D) regulation of bormones and to 8. A ligand is any molecule that can A) specifically binds to a molecule and can deliver a message B) transmit the signal inside of the cell C) be located on the inside or outside of the surface of the cell D) convert a signal to another form 9. The action potential is passed along the axon by A) saltatory conduction B) myelin sheath that serves as insulation C) depolarization and repolarization of the signal D) the nucleus of the cell 10. Antigens are A) substances introduced into the body that can stimulate the production of antibodies B) major histocompatibility complexes C) produced by plasma cells D) produced when a cell encounters a foreign antibody 11. Attenuated viruses A) sometimes occur naturally B) can be produced in the laboratory C) have never been used in humans D) destroy the DNA/RNA in the virus 12. Major methods for waste elimination include A) exchange of oxygen and carbon dioxide B) renal system C) digestive system D) circulatory system 13. Functions of the kidney include A) elimination of waste products by filtration B) reabsorbing important nutrients for the body C) secretion of hormones and toxins D) regulation of blood pressure.