By A. Iomar. Wright State University.

Other types of T cells which ingest bacteria cheap toprol xl 50 mg otc, and macrophages buy toprol xl 100 mg cheap, deactivate or suppress B-lymphocyte and which ingest dead tissue. The process of other cell activity when appropriate anti- ingesting cells and foreign objects is body levels have been reached. Some T lymphocytes become memo- white blood cells fight infection through a ry cells so that if the specific organism process called acquired immunity (the abil- invades the body again, it is “remem- 234 CHAPTER 8 CONDITIONS OF THE BLOOD AND IMMUNE SYSTEM bered” and the immune response is more They are disk-shaped and contain no intense. Another type of T cell, the killer hemoglobin but are concerned with the cell or cytotoxic T cell, carries the T8 mark- clotting of blood. Killer cells, in addition to working to walls of the blood vessels contract, and rid the body of infected cells, are also platelets adhere to the site of the injury. Lymphocytes called natural causes other platelets to collect at the site; killer cells target tumor cells as well as oth- thus, they “plug” injured blood vessels to er infectious organisms. Cells carry markers (allogens) to ensure Platelets alone cannot stop the bleeding that the body recognizes its own tissue as indefinitely. Sometimes the im- tivates clotting factors (coagulation factors mune system becomes unable to recognize from the liver, plasma, and other sources) so the body’s own tissue and begins to pro- that a clot forms to control the bleeding. Vita- of autoimmune diseases are systemic lupus min K is necessary for the formation of erythematosus and rheumatoid arthritis (see some clotting factors. For example, basophils (a type of body’s immune response and leave indi- white blood cell) are thought to have viduals more susceptible to disease. Be- some role in stopping the coagulation cause it is necessary to suppress the im- process once the bleeding is under control. Individuals with certain types of cancers, The term blood dyscrasias is used to such as lymphoma and leukemia (see describe a large group of disorders that Chapter 16), may become immunodeficient affect the blood. Overuse or blood-forming organs may arise from a abuse of narcotics or steroid drugs can also number of different sources; may be man- alter the immune response.

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The avid renal reabsorption of Na observed in states of volume depletion is accompanied by a factor influencing the secretion and generic 25mg toprol xl amex, therefore purchase 100 mg toprol xl visa, the excretion parallel rise in urinary H excretion. An increase in PCO increases the [K ] influence the renal excretion of H. A fall in plasma 2 2 [K ] favors the movement of K from body cells into in- formation of H from H2CO3, leading to enhanced renal terstitial fluid (or blood plasma) and a reciprocal move- H secretion and excretion—a useful compensation for any condition in which the blood contains too much H CO. In the kidney tubule cells, these 2 3 (This will be discussed later, when we consider respiratory movements lower intracellular pH and increase H se- acidosis. K depletion also stimulates ammonia synthesis 2 and, consequently, less complete reabsorption of filtered by the kidneys. The result is the complete reabsorption HCO and a loss of base in the urine (a useful compensa- of filtered HCO3 and the enhanced generation of new 3 tion for respiratory alkalosis, also discussed later). Consequently, hypokalemia (or a decrease in body K stores) leads to increased plasma [HCO3 ] Carbonic Anhydrase Activity. Hyperkalemia (or excess K in the hydrase catalyzes two key reactions in urinary acidification: body) results in the opposite changes: an increase in in- tracellular pH, decreased H secretion, incomplete reab- sorption of filtered HCO3 , and a fall in plasma [HCO3 ] (metabolic acidosis). Aldosterone stimulates the collecting ducts to secrete H by three actions: + 1) It directly stimulates the H -ATPase in collecting Increased H plasma H+-ATPase duct -intercalated cells. This response leads to hy- Na+ reabsorption Decreased pokalemia, which increases renal H secretion. K+ K+ Hyperaldosteronism results in enhanced renal H ex- cretion and an alkaline blood pH; the opposite occurs with H+ - HCO - hypoaldosteronism. The secretion of H by the kidney tubules 2 2 2 3 Increased CA and collecting ducts is gradient-limited. The collecting Carbonic anhydrase PCO2 ducts cannot lower the urine pH below 4. If more buffer base (NH3, 2– HPO4 ) is available in the urine, more H can be secreted Factors leading to increased H secretion before the limiting gradient is reached.

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