There were two major goals for this revision:

1. to improve the entire illustration program (and give the general layout of the book a "face-lift") for greater teaching effectiveness, clarity, consistency, and esthetic appeal
2. to update all material and ensure the greatest accuracy possible.

Almost all the figures have been redone to some extent, ranging from a complete redrawing of the figure to simply changing the labeling of graph axes for greater clarity.

• Figures 20.1 and 20.10 (Figure 20.9 in the seventh edition) provide examples of how a more realistic three-dimensional perspective has been added to many of the figures
• Figure 20.13 (Figure 20.12 in the seventh edition) shows how the picturing of complex events has been improved.
• Also, even when a specific part of the text has not required revision, we have added some new figures (for example, Figure 20.7) to illustrate the text, particularly in the case of material we know to be difficult.
• Of course, the extensive use of flow diagrams, which we introduced in our first edition, has been continued. Conventions, which have been expanded in this edition, are used in these diagrams throughout the book to enhance learning. Look, for example, at Figure 16. 28. The beginning and ending boxes of the flow diagram are in green, and the beginning is further clarified by the use of a "Begin" logo. Blue three-dimensional boxes are used to denote events that occur inside organs and tissues (identified by bold-faced underlined labels in the upper right of the boxes), so that the reader can easily pick out the anatomic entities that participate in the sequences of events. The participation of hormones in the sequences stand out by the placing of changes in their plasma concentrations in reddish/orange boxes. Similarly, changes in urinary excretion are shown in yellow boxes. All other boxes are purple. Thus, color is used in these diagrams for particular purposes, not just for the sake of decoration.
• Other types of color coding are also now used consistently throughout the book. Thus, to take just a few examples, there are specific colors for the extracellular fluid, the intracellular fluid, muscle, particular molecules (the two strands of DNA, for example), and the lumen of the renal tubules and GI tract. Even a quick perusal of Chapter 20 will reveal how consistent use of different colors for the different types of lymphocytes, as well as macrophages, should help learning.

Once again, we have considerably rewritten material to improve clarity of presentation. In addition, as noted above, most figures have been extensively redone, and new figures have been added (only a few of these are listed below). Finally, as a result of new research or in response to suggestions by our colleagues, many topics have either been significantly altered or added for the first time in this edition; the following is a partial list of these topics.

Chapter 1-Introductory section: "The Scope of Human Physiology"

Chapter 2--New figures: Hemoglobin molecule, DNA double helix base pairings,
purine-pyrimidine hydrogen bond pairings

Chapter 3--Cholesterol in membrane function; Procedures for studying cell organelles; Endosomes; Peroxisomes

Chapter 5--Miitochondrial DNA; Preinitiation complex; Factors altering the activity of specific cell proteins; Protein delivery and entry into mitochondria; Regulation of cell division of checkpoints of mitotic cycle

Chapter 6--Patch clamping; Primary active-transport mechanisms; Digitalis and inhibition of Na,K-ATPase; Cystic fibrosis chloride channel; Endocytosis; New figures illustrating transporter conformational changes

Chapter 7--Paracrine/autocrine agents; Melatonin and brain pacemakers; Receptors as tyrosine kinases and guanylyl cyclase; JAK kinases and receptors; Phospholipase, diacylglycerol, and inositol trisphosphate; Calcium-induced calcium release; Receptor inactivation

Chapter 8--Regeneration of neurons; Comparison of voltage-gated sodium and potassium channels; Information on neurotransmitters; Functional anatomy of the central nervous system

Chapter 9-Pain; Olfaction

Chapter 10--Diagnosis of the site of a hormone abnormality

Chapter 11--Passive elastic properties and role of titan; Factors causing fatigue; Role of nitric oxide in relaxing smooth muscle

Chapter 12--Cortical control of motor behavior; Parkinson's disease; Effect of the corticospinal pathways on local-level neurons; Walking

Chapter 13-Electroencephalogram; Sleep; Binding problem; Emotions; Schizophrenia; Serotonin-specific reuptake inhibitors (SSRIs); Learning and memory, and their neural bases

Chapter 14--Erythropoietin mechanism of action; Anti-angiogenic factors in treatment of cancer; Capillary filtration coefficient; Shock; Static exercise and blood pressure; Aging and heart rate; Drug therapy for hypertension, heart failure, and coronary artery disease; Dysfunctional endothelium in atherosclerosis; Homocysteine, folate, and vitamin E in atherosclerosis; Coronary stents; Nitric oxide and peripheral veins; Platelet receptors for fibrinogen; Therapy of stroke with t-PA

Chapter 15--Pulmonary vessels and gravitational/physical forces; Hemoglobin cooperativity; Carbon monoxide and oxygen carriage; Emphysema

Chapter 16--Mesangial cells and glomerular filtration coefficient; Channels, transporters, and genetic renal diseases; Micturition, including role of sympathetic neurons; Aquaporins; Medullary circulation and urinary concentration; Pressure natriuresis; Calcitonin; Bisphosphonates and osteoporosis

Chapter 17--Colipase and fat digestion; HCl secretion and inhibitory role of somatostatin; Intestinal fluid secretion and absorption

Chapter 18--Inhibition of glucagon secretion by insulin; Roles of HDL and LDL; IGF-I and fetal growth; IGF-II; Mechanism of calorigenic effect of thyroid hormones; Leptin effects on hypothalamus and anterior pituitary; Overweight and obesity; Fever and neural pathways from liver; Endogenous cryogens

Chapter 19--Dehydroepiandrosterone (DHEA); Viagra (mechanism of action); Therapy of prostate cancer with blockers of dihydrotestosterone formation; Mechanism of dominant follicle selection and function; Mechanism of corpus luteum regression; Estrogen effect in males; Cause of premenstrual tension, syndrome, and dysphoric disorder; Estrogen, learning, and Alzheimerís disease; Oxytocin and sperm transport; Parturition and placental corticotropin releasing hormone; Postcoital contraception; Lack of crossing-over in X and Y chromosomes; ACTH and onset of puberty; Leptin and onset of puberty; Tamoxifen and selective estrogen receptor modulators (SERMs)

Chapter 20--Carbohydrates and lipids as nonspecific markers on foreign cells; C-reactive protein and other nonspecific opsonins; Apoptosis of immune cells; Mechanism by which diversity arises in lymphocytes; Tumor necrosis factor and lymphocyte activation; Roles of acute phase proteins; Mechanisms of immune tolerance; Psychological stress and disease

Also, our coverage of pathophysiology, everyday applications of physiology, exercise physiology, and molecular biology have again been expanded.