For the 12th edition of Textbook of Medical Physiology, I have the same goal as for previous editions—. However, Textbook of Medical Physiology is not a reference book that attempts to provide an overview of the latest advances in physiology.
The Heart
Contraction of skeletal muscle 71 Physiological anatomy of skeletal muscle 71 General mechanism of muscle contraction 73 Molecular mechanism of muscle contraction 74 Energetics of muscle contraction 78 Characteristics of whole muscle. Complex of excitation and contraction 83 Transmission of impulses from nerve endings to skeletal muscle fibers: neuromuscular.
The Circulation
Role of the kidney in long-term control of arterial pressure and in hypertension: the integrated system for arterial pressure.
The Body Fluids and Kidneys
Glomerular Filtration, Renal Blood Flow,
Proteins are important intracellular buffers 383 Respiratory regulation of acid-base balance 384 Renal control of acid-base balance 385 Excretion of H+ and reabsorption of HCO3−. Clinical causes of acid-base disorders 392 Treatment of acidosis or alkalosis 393 Clinical measurements and analysis of.
Blood Cells, Immunity, and Blood Coagulation
Leukocytes, Granulocytes, the Monocyte- Macrophage System, and Inflammation 423
Immunity and Allergy Innate Immunity 433 Acquired (Adaptive) Immunity 433
Respiration
Aviation, Space, and Deep-Sea Diving Physiology
The Nervous System: A. General Principles and Sensory Physiology
The Nervous System: B. The Special Senses
The Nervous System: C. Motor and Integrative Neurophysiology
Gastrointestinal Physiology CHAPTER 62
Metabolism and Temperature Regulation
Endocrinology and Reproduction CHAPTER 74
Testosterone and other male sex hormones 979 Abnormalities of male sexual function 984 Erectile dysfunction in the male pineal gland 985—its function in control. Development of organ systems 1019 Adaptations of the baby to extrauterine life 1021 Special functional problems in the neonate 1023 Special problems of prematurity 1026 Growth and development of the child 1027.
Sports Physiology CHAPTER 84
Introduction to Physiology: The Cell and General Physiology
Functional Organization of the Human Body and Control of the “Internal
The Cell and Its Functions
Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction
Unit i
Functional Organization of the Human Body and Control of the “Internal Environment”
Cells as the Living Units of the Body
Extracellular Fluid—The “Internal Environment”
The intracellular fluid differs significantly from the extracellular fluid; for example, it contains large amounts of potassium, magnesium, and phosphate ions instead of the sodium and chloride ions found in the extracellular fluid. Special mechanisms for the transport of ions across the cell membranes maintain the ion concentration differences between the extracellular and intracellular fluids.
Homeostatic” Mechanisms of the Major Functional Systems
Much of the blood pumped by the heart also passes through the walls of the gastrointestinal tract. The passage of the blood through the kidneys removes most other substances from the plasma, apart from carbon dioxide, which the cells do not need.
Control Systems of the Body
In other words, the initiating stimulus causes more of the same, which is positive feedback. Thus, one can see how complex the feedback control systems in the body can be.
Summary—Automaticity of the Body
This process continues over and over again until the nerve signal travels all the way to the end of the fiber. For example, some movements of the body occur so quickly that there is not enough time for nerve signals to travel from the peripheral parts of the body all the way to the brain and then back to the periphery to control the movement.
The Cell and Its Functions
Organization of the Cell
In fat cells, triglycerides are often responsible for as much as 95 percent of the cell mass. However, carbohydrates in the form of dissolved glucose are always present in the surrounding extracellular fluid, so they are readily available to the cell.
Physical Structure of the Cell
Most cell organelles are covered by membranes composed mainly of lipids and proteins. The formation of nuclei (and of ribosomes in the cytoplasm outside the nucleus) begins in the nucleus.
Comparison of the Animal Cell with Precellular Forms of Life
Another example of microtubules is the tubular skeletal structure in the center of each cilium that radiates upward from the cell's cytoplasm to the tip of the cilium. Correspondingly, the cell's functions and anatomical organization are also far more complex than those of the virus.
Functional Systems of the Cell
But first, let's note the specific products that are synthesized in specific parts of the endoplasmic reticulum and the Golgi apparatus. Some of the intracellular vesicles formed by the Golgi apparatus fuse with the cell membrane or with the membranes of intracellular structures such as mitochondria and even the endoplasmic reticulum.
Locomotion of Cells
Each cilium is an outgrowth of a structure that lies just below the cell membrane called the cilium basal body. As a result, the fluid is constantly propelled in the direction of rapid forward motion.
Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction
Genes in the Cell Nucleus
The arrangement of nucleotides to form two loosely linked strands of DNA. The internal molecules connecting the two strands of the helix are purine and pyrimidine bases; these determine.
The DNA Code in the Cell Nucleus Is Transferred to an RNA Code in the Cell
This is located approximately in the center of the tRNA molecule (at the bottom of the cloverleaf configuration shown in Figure 3-9). The third type of RNA in the cell is ribosomal RNA; it makes up about 60 percent of the ribosome.
Synthesis of Other Substances in the Cell
In this chemical reaction, a hydroxyl radical (OH−) is removed from the COOH part of the first amino acid and a hydrogen (H+) from the NH2 part of the other amino acid is removed. This combines to form water, and the two reactive sites left on the two consecutive amino acids bond with each other, resulting in a single molecule.
Control of Gene Function and Biochemical Activity in Cells
They can also be located either upstream or downstream of the gene they regulate. Variations in the basic mechanism of promoter control have been discovered rapidly in the last 2 decades.
The DNA-Genetic System Also Controls Cell Reproduction
During metaphase (see Figure 3-14E), the two asters of the mitotic apparatus are pushed further apart. This membrane is formed from portions of the endoplasmic reticulum that are already present in the cytoplasm.
Cell Differentiation
During this stage (see Figure 3-14D), the growing microtubular spines of the aster tear apart the nuclear envelope. We know little about the mechanisms that maintain the correct number of different types of cells in the body.
Apoptosis—Programmed Cell Death
It differentiates into a mesodermal spindle containing segmentally arranged somites and, as a result of inductions in the surrounding tissues, gives rise to the formation of the core of all body organs. Therefore, a large part of the embryo develops as a result of such inductions, one part of the body affects another part, and this part affects still other parts.
Cancer
In the case of DNA viruses, the DNA strand of the virus can insert itself directly into one of the chromosomes and thereby cause a mutation that leads to cancer. Hahn S: Structure and mechanism of the RNA polymerase II transcription machinery, Nat Struct Mol Biol.
Membrane Physiology, Nerve, and Muscle
Transport of Substances Through Cell Membranes
Membrane Potentials and Action Potentials
Contraction of Skeletal Muscle 7. Excitation of Skeletal Muscle
Unit ii
Transport of Substances Through Cell Membranes
The Lipid Barrier of the Cell Membrane, and Cell Membrane Transport Proteins
Although there are many variations of these basic mechanisms, diffusion means the random molecular movement of substances molecule by molecule, either through intermolecular spaces in the membrane or in combination with a carrier protein. The following is a more detailed explanation of the basic physics and physical chemistry of these two processes.
Diffusion
Therefore, substances can move by simple diffusion directly along these pores and channels from one side of the membrane to the other. Suction is then applied inside the pipette to pull the membrane towards the tip of the pipette.
Active Transport” of Substances Through Membranes
All these molecules and ions then cause osmosis of water to the interior of the cell. One is in the cell membrane and pumps calcium to the outside of the cell.
Membrane Potentials and Action Potentials
Basic Physics of Membrane Potentials Membrane Potentials Caused by Diffusion
The magnitude of this Nernst potential is determined by the ratio of the concentrations of that specific ion on the two sides of the membrane. Third, a positive ion concentration gradient from inside the membrane to outside causes electronegativity within the membrane.
Measuring the Membrane Potential
The sign of the potential is also positive (+) if the ion diffusing from the inside out is a negative ion, and it is negative (-) if the ion is positive. The concentration gradient of each of these ions across the membrane helps determine the tension of the membrane potential.
Resting Membrane Potential of Nerves
In the normal nerve fiber, the permeability of the membrane to potassium is about 100 times greater than its permeability to sodium. 4 millivolts contributes to the membrane potential of the continuously acting electrogenic Na+-K+ pump, giving a net membrane potential of -90 millivolts.
Nerve Action Potential
Conversely, tetraethylammonium ion blocks potassium channels when applied to the interior of a nerve fiber. Note the sudden opening of sodium channels (activation rate) in a small fraction of a millisecond after the membrane potential is raised to a positive value.
Propagation of the Action Potential
A major function of voltage-gated calcium ion channels is to contribute to the depolarization phase of the action potential in some cells. First, as long as the nerve fiber membrane remains undisturbed, no action potential occurs in the normal nerve.
Re-establishing Sodium and Potassium Ionic Gradients After Action Potentials
Once an action potential occurs at any point on the membrane of a normal filament, the depolarization process travels across the entire membrane if the conditions are right, or does not travel at all if the conditions are not right. Occasionally, the action potential reaches a point in the membrane at which it does not generate enough voltage to stimulate the other area of the membrane.
Plateau in Some Action Potentials
Rhythmicity of Some Excitable Tissues—
Repetitive Discharge
The central core of the fiber is the axon, and the axon membrane is the membrane that actually conducts the action potential. In fact, most of the large nerve fiber action potential complex takes place in less than 1/1000 of a second.
Contraction of Skeletal Muscle
Physiologic Anatomy of Skeletal Muscle Skeletal Muscle Fiber
These springy titin molecules act as a framework that holds the myosin and actin filaments in place so that the contractile machinery of the sarcomere will work. The titin molecule itself also appears to act as a template for the initial formation of parts of the contractile filaments of the sarcomere, especially the myosin filaments.
General Mechanism of Muscle Contraction
Each titin molecule has a molecular weight of about 3 million, making it one of the largest protein molecules in the body. Thousands of myosin cross-bridges and the interaction of cross-bridge heads with adjacent actin filaments are also shown.
Molecular Mechanism of Muscle Contraction
One of the subunits (troponin I) has a strong affinity for actin, another (troponin T) for tropomyosin, and a third (troponin C) for calcium ions. Consequently, the sites cannot attach to the heads of the myosin filaments to cause contraction.
Energetics of Muscle Contraction Work Output During Muscle Contraction
This causes the addition of new sarcomeres at the ends of muscle fibers, where they attach to tendons. In the final stage of denervation atrophy, most muscle fibers are destroyed and replaced by fibrous and fatty tissue.
Excitation of Skeletal Muscle
Neuromuscular Transmission and Excitation-Contraction Coupling
Transmission of Impulses from Nerve
Note the proximity of the release sites on the nerve membrane to the acetylcholine receptors on the muscle membrane, at the mouths of the subneural clefts. Then the rapid removal of acetylcholine prevents continued muscle re-excitation after the muscle fiber has recovered from its initial action potential.
Muscle Action Potential
During repolarization (lower panel) the conformational change in the DHP receptor closes Ca++ release channels and Ca++ is transported from the sarcoplasm to the sarcoplasmic reticulum by an ATP-dependent calcium pump.
Excitation-Contraction Coupling Transverse Tubule–Sarcoplasmic
The total duration of this calcium. "pulse" in a normal skeletal muscle fiber lasts about 1/20th of a second, although it may last several times longer in some fibers and several times less in others. In cardiac muscle, the calcium pulse lasts about one-third of a second because of the long duration of the cardiac action potential.).
Excitation and Contraction of Smooth Muscle
Despite the relatively few myosin filaments in smooth muscle and despite the slow cycling time of the cross-bridges, the maximal contractile force of smooth muscle is often greater than that of skeletal muscle—as great as 4 to 6 kg/. This large force of contraction of smooth muscle is due to the prolonged period of attachment of the myosin cross-bridges to the actin filaments.
Nervous and Hormonal Control of Smooth Muscle Contraction
Therefore, sodium plays little part in the generation of the action potential in most smooth muscle. Instead, it is a local property of the smooth muscle fibers that make up muscle mass.
III UNIT
The Heart
Cardiac Muscle; The Heart as a Pump and Function of the Heart Valves
Electrocardiographic Interpretation of Cardiac Muscle and Coronary Blood
U NIT III
Cardiac Muscle; The Heart as a Pump and Function of the Heart Valves
Physiology of Cardiac Muscle
As with skeletal muscle, when an action potential travels across the myocardial membrane, the action potential spreads into the interior of the myocardial fiber along the membranes of the transverse (T) tubules. The T-tubule action potentials in turn act on the membranes of the longitudinal sarcoplasmic tubules and cause the release of calcium ions into the muscle sarcoplasm from the sarcoplasmic reticulum.
Cardiac Cycle
The duration of the action potential and the period of contraction (systole) are also shortened, but not by as large a percentage as the relaxation phase (diastole). Ventricular afterload is the pressure in the aorta leading from the ventricle.
Regulation of Heart Pumping
Thus, ventricular function curves are another way of expressing the Frank-Starling mechanism of the heart. Large amounts can also block conduction of the heart's impulse from the atria to the ventricles through the A-V bundle.
Unit iii
Rhythmical Excitation of the Heart
Specialized Excitatory and Conductive System of the Heart
This allows almost instantaneous transmission of the cardiac impulse throughout the rest of the ventricular muscle. The numbers represent the time interval from the origin of the impulse in the sinus node.
Control of Excitation and Conduction in the Heart
In either case, the pacemaker moves from the sinus node to the A-V node or to the excited Purkinje fibers. Another cause of the displacement of the pacemaker is the blockage of the transmission of the cardiac impulse from the sinus node to other parts of the heart.
The Normal Electrocardiogram
Characteristics of the Normal Electrocardiogram
The relationship between the monophasic ventricular muscle action potential and the QRS and T waves in the standard electrocardiogram. Ventricular contraction lasts almost from the beginning of the Q wave (or R if the Q wave is absent) to the end of the T wave.
Flow of Current Around the Heart during the Cardiac Cycle
The movement of the pen is controlled by appropriate electronic amplifiers connected to electrocardiographic electrodes on the patient. The remaining surface of the heart, which is still polarized, is shown by the positive signs.
Electrocardiographic Leads Three Bipolar Limb Leads
In limb I lead recording, the negative terminal of the electrocardiograph is connected to the right arm and the positive terminal to the left arm. To record limb II, the negative terminal of the electrocardiograph is connected to the right arm and the positive terminal to the left leg.
Principles of Vectorial Analysis of Electrocardiograms
Electrocardiographic Interpretation of Cardiac Muscle and Coronary Blood Flow
The polarities of the electrodes are indicated by the plus and minus signs in the figure. To determine the potential recorded at this moment in the electrocardiogram for each of the three stans.
Vectorial Analysis of the Normal Electrocardiogram
Depolarization of the atria begins in the sinus node and spreads in all directions throughout the atria. Second, the vector changes direction due to changes in the average direction of the electricity.
Mean Electrical Axis of the Ventricular QRS—and Its Significance
Similarly, angulation of the heart to the right causes the mean electrical axis of the ventricles to shift to the right. In other words, there is intense left axis deviation of about -50 degrees because the positive end of the vector points towards the left ventricle.
Conditions That Cause Abnormal Voltages of the QRS Complex
Prolonged and Bizarre Patterns of the QRS Complex
Therefore, if there is a complete blockade of one of the brachial bundles, the duration of the QRS complex is usu. Conditions That Cause Bizarre QRS Complexes Bizarre QRS complex patterns are most often caused by two conditions: (1) destruction of the cardiac muscle.
Current of Injury
Also, the method for drawing the damage potential axis is shown in the lowest panel. In other words, the negative end of the injury potential vector in this heart is against the anterior chest wall.
Abnormalities in the T Wave
By vector analysis, as shown in the figure, the resulting vector of the damage potential is found to be about -95 degrees, with the negative endpoint. In other words, the mean axis of the T wave is now deviated to the right, which is opposite to the mean electrical axis of the QRS complex in the same electrocardiogram.
Cardiac Arrhythmias and Their Electrocardiographic Interpretation
Abnormal Sinus Rhythms Tachycardia
Then, during deep breathing, the heart rate increased and decreased by as much as 30 percent with each respiratory cycle. The overflow signals cause alternate increases and decreases in the number of impulses transmitted to the heart by the sympathetic and vagus nerves.
Abnormal Rhythms That Result from Block of Heart Signals Within the Intracardiac
When the condition causing poor conduction in the A-V node or A-V bundle becomes severe, a complete blockage of the impulse from the atria to the ventricles occurs. Most of the same factors that can cause A-V block can also block impulse conduction in the peripheral ventricular Purkinje system.
Premature Contractions
V Nodal or V Bundle Premature Contractions Figure 13-10 shows a premature contraction that origi-
Conversely, many other PVCs result from stray impulses or reentrant signals that arise around the borders of infarcted or ischemic areas of the heart. Axis of the premature contractions are plotted in accordance with the principles of vectorial analysis explained in Chapter 12;.
Paroxysmal Tachycardia
Ventricular Fibrillation
After about 0.25 second, part of this muscle begins to come out of the refractory state. This is achieved by passing intense current through large electrodes placed on two sides of the heart.
Atrial Fibrillation
After a few more seconds, the gross contractions of the ventricles disappear and the electrocardiogram changes to a new pattern of low-voltage, very irregular waves. The mechanism of atrial fibrillation is identical to that of ventricular fibrillation, except that the process occurs only in the atrial muscle mass rather than in the ventricular mass.
Atrial Flutter
For the same reasons that the ventricles do not pump blood during ventricular fibrillation, the atria also do not pump blood during atrial fibrillation. Numerous small depolarization waves spread in all directions through the atria during atrial fibrillation.
Cardiac Arrest
IV Unit
Overview of the Circulation; Biophysics of Pressure, Flow, and Resistance
Vascular Distensibility and Functions of the Arterial and Venous Systems
The Microcirculation and Lymphatic System: Capillary Fluid Exchange,
Nervous Regulation of the Circulation, and Rapid Control of Arterial Pressure
Cardiac Output, Venous Return, and Their Regulation
Muscle Blood Flow and Cardiac Output During Exercise; the Coronary Circulation
Cardiac Failure
Heart Valves and Heart Sounds; Valvular and Congenital Heart Defects
Circulatory Shock and Its Treatment
Unit iV
Overview of the Circulation; Biophysics of Pressure, Flow, and Resistance
Physical Characteristics of the Circulation
This explains the nervous system's large blood storage capacity compared to the arterial system. Note on the far right of figure 14-2 the respective pressures in the different parts of the pulmonary circulation.
Basic Principles of Circulatory Function
The rate of blood flow to each tissue of the body is almost always precisely controlled in relation to
As the blood flows through the systemic circulation, the mean pressure gradually falls to about 0 mm Hg by the time it reaches the end of the venae cavae where they empty into the right atrium of the heart. Also, the nervous control of the circulation from the central nervous system and hormones provide additional help in controlling tissue blood flow.
The cardiac output is controlled mainly by the sum of all the local tissue flows. When blood flows
Cardiac output is primarily controlled by the sum of all local tissue flows.
Arterial pressure regulation is generally indepen- dent of either local blood flow control or cardiac
Interrelationships of Pressure, Flow, and Resistance
Also, the most central part of the blood is in the center of the vessel. However, increasing the resistance of any of the blood vessels increases the total vascular resistance.
Vascular Distensibility and Functions of the Arterial and Venous Systems
Vascular Distensibility
Effect of sympathetic stimulation or sympathetic inhibition on the volume-pressure relationships of the arterial and venous systems. Even if none of the blood is removed after it is injected, the pressure begins to decrease immediately and approaches about 9 mm Hg after a few minutes.
Arterial Pressure Pulsations
In the aorta, the transmission speed of the pressure pulse is 15 or more times the blood flow speed, because. This progressive diminution of the pulsations in the periphery is called attenuation of the pressure pulses.
Veins and Their Functions
Blood from all systemic veins flows into the right atrium of the heart; hence the pressure in the right atrium is called central venous pressure. This takes up most of the slowdown in the circulatory system caused by lost blood.
The Microcirculation and Lymphatic System: Capillary Fluid Exchange, Interstitial
Structure of the Microcirculation and Capillary System
The 'pores' in the capillaries of some organs have special characteristics to meet the special needs of the organs. The gaps between the capillary endothelial cells are wide open, allowing almost all plasma solutes, including plasma proteins, to pass from the blood into the liver tissues.
Flow of Blood in the Capillaries—Vasomotion
In the brain, the junctions between capillary endothelial cells are mostly "tight" junctions, allowing only very small molecules such as water, oxygen, and carbon dioxide to pass into or out of the brain tissue. In the glomerular capillaries of the kidney, many small oval windows called fenestrae penetrate all the way to the middle of the endothelial cells, so that enormous amounts of very small molecular and ionic substances (but not large molecules of plasma proteins) can be filtered through the glomeruli without having to pass through the slits between endothelial cells.
Exchange of Water, Nutrients, and Other Substances Between the Blood and
