Respiration
Organization of the Respiratory System The Airways and Blood Vessels Site of Gas Exchange The Alveoli Relation of the Lungs to the Thoracic Chest Wall Ventilation and Lung Mechanics The Stable Balance between Breaths Inspiration Expiration Lung Compliance Airway Resistance Lung Volumes and Capacities Alveolar Ventilation Exchange of Gases in Alveoli and Tissues Partial Pressures of Gases Alveolar Gas Pressures Alveolar-Blood Gas Exchange Matching of Ventilation and Blood Flow in Alveoli Gas...
Veins
Blood flows from capillaries into venules and then into veins. Some exchange of materials occurs between the interstitial fluid and the venules, just as in capillaries. Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition Indeed, permeability to macromolecules is often greater for venules than for capillaries, particularly in damaged areas. The veins are the last set of tubes through which blood flows on its way back to the heart. In the systemic circulation, the force...
Figure 718
Mechanism by which an activated receptor stimulates the enzymatically mediated breakdown of PIP2 to yield of IP3 and DAG. IP3 then causes the release of calcium ions from the endoplasmic reticulum, and DAG activates a particular protein kinase known as protein kinase C. Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition TABLE 7-6 Calcium as a Second Messenger Common mechanisms by which stimulation of a cell leads to an increase in cytosolic Ca2 concentration a....
The Receptor Potential
The transduction process in all sensory receptors involves the opening or closing of ion channels that receive either directly or through a second-messenger system information about the outside world. The ion channels occur in a specialized receptor membrane and not on ordinary plasma membranes. The gating of these ion channels allows a change in the ion fluxes across the receptor membrane, which in turn produces a change in the membrane potential there. This change in potential is a graded...
Figure 64
The increase in intracellular concentration as a substance diffuses from a constant extracellular concentration until diffusion equilibrium Q C0 is reached across the plasma membrane of a cell. The magnitude of the net flux is directly proportional to the difference in concentration across the membrane Co C , the surface area of the membrane A, and the membrane permeability constant kp The numerical value of the permeability constant kp is an experimentally determined number for a particular...
Osmosis 1
I. Water crosses membranes by 1 diffusing through the lipid bilayer, and 2 diffusing through protein channels in the membrane. II. Osmosis is the diffusion of water across a membrane from a region of higher water concentration to a region of lower water concentration. The osmolarity total solute concentration in a solution determines the water concentration The higher the osmolarity of a solution, the lower the water concentration. III. Osmosis across a membrane permeable to water but...
Essential Nutrients 1
I. Approximately 50 essential nutrients, listed in Table 4-9, are necessary for health but cannot be synthesized in adequate amounts by the body and must therefore be provided in the diet. II. A large intake of water-soluble vitamins leads to their rapid excretion in the urine, whereas large intakes of fat-soluble vitamins lead to their accumulation in adipose tissue and may produce toxic effects. electron transport chain chemiosmotic hypothesis hydrogen peroxide superoxide anion hydroxyl...
Osmosis
Water is a small, polar molecule, about 0.3 nm in diameter, that diffuses across most cell membranes very rapidly. One might expect that, because of its polar structure, water would not penetrate the nonpolar lipid regions of membranes. Artificial phospholipid bi-layers are somewhat permeable to water, indicating that this small polar molecule can diffuse, at least to some extent, through the membrane lipid layer. Most plasma membranes, however, have a permeability to water that is 10 times...
xz
PART THREE Coordinated Body Functions Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition PART THREE Coordinated Body Functions point. On the right, outflow tube 1 has been opened, as in the previous example, while tubes 2 to 4 have been simultaneously tightened. The increased resistance offered by tubes 2 to 4 compensates for the decreased resistance offered by tube 1 therefore total resistance remains unchanged, and reservoir pressure is unchanged. Total outflow...
Cerebellum 1
The cerebellum is behind the brainstem see Figure 12-2a . It influences posture and movement indirectly by means of input to brainstem nuclei and by way of the thalamus to regions of the sensorimotor cortex that give rise to pathways that descend to the motor neurons. The cerebellum receives information both from the sensorimotor cortex relayed via brainstem nuclei and from the vestibular system, eyes, ears, skin, muscles, joints, and tendons that is, from the very receptors that are affected...
TouchPressure
Stimulation of the variety of mechanoreceptors in the skin see Figure 9-17 leads to a wide range of touch-pressure experiences hair bending, deep pressure, vibrations, and superficial touch, for example. These mechanoreceptors are highly specialized nerve endings encapsulated in elaborate cellular structures. The details of the mechanoreceptors vary, but generally the nerve endings are linked to collagen-fiber networks within the capsule. These networks transmit the Vander et al. Human I II....
Activation of the Postsynaptic Cell
A feature that makes postsynaptic integration possible is that in most neurons one excitatory synaptic event by itself is not enough to cause threshold to be reached in the postsynaptic neuron. For example, a single EPSP may be only 0.5 mV, whereas changes of about 15 mV Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition Neural Control Mechanisms CHAPTER EIGHT Neural Control Mechanisms CHAPTER EIGHT Intracellular recording from a postsynaptic cell during episodes when...
Control of Muscle Tension
The total tension a muscle can develop depends upon two factors 1 the amount of tension developed by each fiber, and 2 the number of fibers contracting at any time. By controlling these two factors, the nervous system controls whole-muscle tension, as well as I. Tension developed by each individual fiber a. Action-potential frequency frequency-tension relation b. Fiber length length-tension relation a. Number of fibers per motor unit b. Number of active motor units shortening velocity. The...
Twitch Contractions
The mechanical response of a single muscle fiber to a single action potential is known as a twitch. Figure 11-20a shows the main features of an isometric twitch. Following the action potential, there is an interval of a few milliseconds, known as the latent period, before the tension in the muscle fiber begins to increase. During this latent period, the processes associated with excitation-contraction coupling are occurring. The time interval from the beginning of tension development at the end...
SkeletalMuscle Energy Metabolism
As we have seen, ATP performs three functions directly related to muscle-fiber contraction and relaxation see Table 11-1 . In no other cell type does the rate of ATP breakdown increase so much from one moment to the next as in a skeletal muscle fiber 20 to several hundredfold depending on the type of muscle fiber when it goes from rest to a state of contractile activity. The small supply of preformed ATP that exists at the start of contractile activity would only support a few twitches. If a...
Genetic Engineering 1
I. With the use of bacterial restriction nucleases, segments of DNA can be cut from the DNA of one cell and inserted into the DNA of another cell transfection forming a transgenic organism. II. Transfection of human genes into bacteria provides a mechanism for producing large quantities of the expressed protein, which can be isolated and used to treat disease for example, the production of insulin . III. Analysis of the pattern of tissue DNA fragments formed by nuclease digestion is the basis...
Blood Volume and LongTerm Regulation of Arterial Pressure
The fact that the arterial baroreceptors and other baroreceptors as well adapt to prolonged changes in pressure means that the baroreceptor reflexes cannot set long-term arterial pressure. The major factor for long-term regulation is the blood volume. As described earlier, blood volume is a major determinant of arterial pressure because it influences in turn venous pressure, venous return, end-diastolic volume, stroke volume, and cardiac output. Thus, an increased blood volume increases...
Endoplasmic Reticulum
The most extensive cytoplasmic organelle is the network of membranes that forms the endoplasmic reticulum Figure 3-12 . These membranes enclose a space that is continuous throughout the network. The continuity of the endoplasmic reticulum is not obvious when examining a single electron micrograph because only a portion of the network is present in any one section. Two forms of endoplasmic reticulum can be distinguished granular rough-surfaced and agranular smooth-surfaced . As noted on the next...
Abbreviations Used In The Text
ACE angiotensin converting enzyme acetyl CoA acetyl coenzyme A ACh acetylcholine ACTH adrenocorticotropic hormone adrenocorticotropic, corticotropin ADCC antibody-dependent cellular cytotoxicity ADH antidiuretic hormone vasopressin ADP adenosine diphosphate AIDS acquired immune deficiency BM basement membrane BMI body mass index BMR basal metabolic rate C Celsius centigrade , creatine, cytosine, carbon, capillary, cervical C clearance, concentration Ca calcium Ca2 calcium ion cal calorie CAM...
Figure 143
Summary of iron balance. The thickness of the arrows corresponds approximately to the amount of iron involved. In the steady state, the rate of gastrointestinal iron absorption equals the rate of iron loss via urine, skin, and menstrual flow. In the previous section, we stated that iron, folic acid, and vitamin B12 must be present for normal erythrocyte production. However, none of these substances constitutes the signal that regulates production rate. The direct control of erythrocyte...
Figure 68
Model of mediated transport. A change in the conformation of the transporter exposes the transporter binding site first to one surface of the membrane then to the other, thereby transferring the bound solute from one side of the membrane to the other. This model shows net mediated transport from the extracellular fluid to the inside of the cell. In many cases, the net transport is in the opposite direction. There are many types of transporters in membranes, each type having binding sites that...
Capillaries
As mentioned at the beginning of Section B, at any given moment, approximately 5 percent of the total circulating blood is flowing through the capillaries, and it is this 5 percent that is performing the ultimate function of the entire cardiovascular system the exchange of nutrients and metabolic end products. Some exchange also occurs in the venules, which can be viewed as extensions of capillaries. The capillaries permeate almost every tissue of the body. Since most cells are no more than 0.1...
Exercise
During exercise, cardiac output may increase from a resting value of 5 L min to a maximal value of 35 L min in trained athletes. The distribution of this cardiac output during strenuous exercise is illustrated in Figure 14-64. As expected, most of the increase in cardiac output goes to the exercising muscles, but there are also increases in flow to skin, required for dissipation of heat, and to the heart, required for the additional work performed by the heart in pumping the increased cardiac...
Transport of Oxygen in Blood
Table 15-7 summarizes the oxygen content of systemic arterial blood we shall henceforth refer to systemic arterial blood simply as arterial blood . Each liter normally contains the number of oxygen molecules equivalent to 200 ml of pure gaseous oxygen at atmospheric pressure. The oxygen is present in two forms 1 dissolved in the plasma and erythrocyte water and 2 re-versibly combined with hemoglobin molecules in the erythrocytes. As predicted by Henry's law, the amount of oxygen dissolved in...
Figure 428
Oxidative deamination and transamination of amino acids. Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition 4. Protein Activity and Cellular Metabolism Protein Activity and Cellular Metabolism CHAPTER FOUR Protein Activity and Cellular Metabolism CHAPTER FOUR
Intercellular Chemical Messengers
Essential to reflexes and local homeostatic responses, and therefore to homeostasis, is the ability of cells to communicate with one another. In the vast majority of cases, this communication between cells intercellular communication is performed by chemical messengers. There are three categories of such messengers hormones, neurotransmitters, and paracrine agents Figure 7-5 . A hormone functions as a chemical messenger that enables the hormone-secreting cell to communicate with the cell acted...
Control of Heart Rate
Rhythmical beating of the heart at a rate of approximately 100 beats min will occur in the complete absence of any nervous or hormonal influences on the SA node. This is, as we have seen, the inherent autonomous discharge rate of the SA node. The heart rate may be much lower or higher than this, however, since the SA node is normally under the constant influence of nerves and hormones. As mentioned earlier, a large number of parasym-pathetic and sympathetic postganglionic fibers end on the SA...
The Resting Membrane Potential
All cells under resting conditions have a potential difference across their plasma membranes oriented with the inside of the cell negatively charged with respect to the outside Figure 8-7a . This potential is the resting membrane potential. a Apparatus for measuring membrane potentials. b The potential difference across a plasma membrane as measured by an intracellular microelectrode. The asterisk indicates the time the electrode entered the cell. a Apparatus for measuring membrane potentials....
Sense of Posture and Movement
The senses of posture and movement are complex. The major receptors responsible for these senses are the muscle-spindle stretch receptors, which occur in skeletal muscles and respond both to the absolute magnitude of muscle stretch and to the rate at which the stretch occurs to be described in Chapter 12 . The senses of posture and movement are also supported by vision and the vestibular organs the sense organs of balance, described later . Mechanoreceptors in the joints, tendons, ligaments,...
Local Controls
The term local controls denotes mechanisms independent of nerves or hormones by which organs and tissues alter their own arteriolar resistances, thereby self-regulating their blood flows. It does include changes caused by autocrine paracrine agents. This self-regulation includes the phenomena of active hy-peremia, flow autoregulation, reactive hyperemia, and local response to injury. Active Hyperemia Most organs and tissues manifest an increased blood flow hyperemia when their metabolic...
Local Control of Motor Neurons
The local control systems are the relay points for instructions to the motor neurons from centers higher in the motor control hierarchy. In addition, the local control systems play a major role in adjusting motor unit activity to unexpected obstacles to movement and to harmful factors in the surrounding environment. To carry out these adjustments, the local control systems use information carried by afferent fibers from sensory receptors in the muscles, tendons, joints, and skin of the body...
Hormone Structures and Synthesis
Hormones fall into three chemical classes 1 amines, 2 peptides and proteins, and 3 steroids. The amine hormones are all derivatives of the amino acid tyrosine. They include the thyroid hormones, epinephrine and norepinephrine produced by the adrenal medulla , and dopamine produced by the hypothalamus . Thyroid Hormones The thyroid gland is located in the lower part of the neck wrapped around the front of the trachea windpipe . It is composed of many spherical structures called follicles, each...
Figure 1424
Divisions of the cardiac cycle a systole b diastole. For simplicity, only one atrium and ventricle are shown. The phases of the cycle are identical in both halves of the heart. The direction in which the pressure difference favors flow is denoted by an arrow note, however, that flow, although favored by a pressure difference, will not actually occur if a valve prevents it. PART THREE Coordinated Body Functions Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition PART...
Control of Stroke Volume
The second variable that determines cardiac output is stroke volume, the volume of blood ejected by each ventricle during each contraction. As stated earlier, the ventricles do not completely empty themselves of blood during contraction. Therefore, a more forceful contraction can produce an increase in stroke volume by causing greater emptying. Changes in the force of contraction can be produced by a variety of factors, but three are dominant under most physiological and pathophysiological...
Hypertension
Hypertension is defined as a chronically increased systemic arterial pressure. The dividing line between normal pressure and hypertension is set at approximately 140 90 mmHg. Theoretically, hypertension could result from an increase in cardiac output or in total peripheral resistance, or both. In reality, however, the major abnormality in most cases of well-established hypertension is increased total peripheral resistance caused by abnormally reduced arteriolar radius. What causes the...
Mechanisms of Hormone Action
Because they travel in the blood, hormones are able to reach virtually all tissues. Yet the body's response to a hormone is not all-inclusive, but is highly specific, involving only the target cells for that hormone. The ability to respond depends upon the presence on or in the target cells of specific receptors for those hormones. As emphasized in Chapter 7, the response of a target cell to a chemical messenger is the final event in a sequence that begins when the messenger binds to specific...
Figure 617
The addition of solute molecules to pure water lowers the water concentration in the solution. Pure water high water concentration Pure water high water concentration Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition Movement of Molecules Across Cell Membranes CHAPTER SIX For example, 1 mol of glucose in 1 L of solution decreases the water concentration to approximately the same extent as does 1 mol of an amino acid, or 1 mol of urea, or 1 mol of any other molecule...
Epithelial Transport 1
I. Molecules can cross an epithelial layer of cells by two pathways 1 through the extracellular spaces between the cells the paracellular pathway, and 2 through the cell, across both the luminal and basolateral membranes as well as the cell's cytoplasm the transcellular pathway. II. In epithelial cells, the permeability and transport characteristics of the luminal and basolateral plasma membranes differ, resulting in the ability of the cells to actively transport a substance between the fluid...
Figure 1123
Summation of isometric contractions produced by shortening the time between stimuli S2 and S3. possible for a second action potential to be initiated during the period of mechanical activity. Figure 11-23 illustrates the tension generated during isometric contractions of a muscle fiber in response to three successive stimuli. In Figure 11-23a, the isometric twitch following the first stimulus Sj lasts 150 ms. The second stimulus S2, applied to the muscle fiber 200 ms after Sj when the fiber has...
Central Nervous System Spinal Cord
The spinal cord lies within the bony vertebral column Figure 8-36 . It is a slender cylinder of soft tissue about as big around as the little finger. The central butterfly-shaped area in cross section of gray matter Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition Long neural pathways and multineuronal multisynaptic pathways and their relationship to the reticular formation. Section of the spinal cord, ventral view. The arrows indicate the direction of transmission...
Leukocytes
If appropriate dyes are added to a drop of blood, which is then examined under a microscope, the various classes of leukocytes Table 14-3 are clearly visible Figure 14-5 . They are classified according to their structure and affinity for the various dyes. The name polymorphonuclear granulocytes refers to the three classes of leukocytes that have mul-tilobed nuclei and abundant membrane-surrounded granules. The granules of one group take up the red dye eosin, thus giving the cells their name...
Forebrain
The larger component of the forebrain see Figure 8-38 , the cerebrum, consists of the right and left cerebral hemispheres as well as certain other structures on the underside of the brain. The central core of the fore-brain is formed by the diencephalon. The cerebral hemispheres Figure 8-40 consist of the cerebral cortex, an outer shell of gray matter covering myelinated fiber tracts, which form the white matter. This in turn overlies cell clusters, which are also gray matter and are...
Neural Pathways in Sensory Systems
The afferent neurons form the first link in a chain consisting of three or more neurons connected end to end by synapses. A bundle of parallel, three-neuron chains together form a sensory pathway. The chains in a given pathway run parallel to each other in the central nervous system and, with one exception, carry information to the part of the cerebral cortex responsible for conscious recognition of the information. Sensory pathways are also called ascending pathways because they go up to the...
Figure 626
Glands are composed of epithelial cells. Exocrine-gland secretions enter ducts, whereas hormones or other substances secreted by endocrine ductless glands diffuse into the blood. terial diffuses into the blood, which carries it throughout the body. The endocrine glands secrete a major class of chemical messengers, the hormones, and in practical usage the term endocrine gland has come to be synonymous with hormone-secreting gland. However, it should be noted that there are ductless glands that...
Ventilation and Lung Mechanics
An inventory of steps involved in respiration Figure 15-6 is provided for orientation before beginning the detailed descriptions of each step, beginning with ventilation. 1 Ventilation Exchange of air between atmosphere and alveoli by bulk flow 2 Exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion 3 Transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow 4 Exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues...
Receptors 1
Neural activity is initiated at the border between the nervous system and the outside world by sensory receptors. Since some receptors respond to changes in the internal environment, the outside world with regard to the sensory receptors can also mean, for example, distension of a blood vessel in our body. Information about the external world and about the body's internal environment exists in different energy forms pressure, temperature, light, sound waves, and so on. Receptors at the...
Brain Motor Centers and the Descending Pathways They Control
I. The location of the neurons in the motor cortex varies in general with the part of the body the neurons serve. II. Different areas of sensorimotor cortex have different functions, but there is much overlap in activity. III. The basal ganglia form a link in a circuit that originates in and returns to sensorimotor cortex. These subcortical nuclei facilitate some motor behaviors and inhibit others. IV. The cerebellum coordinates posture and movement and plays a role in motor learning. V. The...
Mechanism of Lymph Flow
In large part, the lymphatic vessels beyond the lymphatic capillaries propel the lymph within them by their own contractions. The smooth muscle in the wall of the lymphatics exerts a pumplike action by inherent rhythmical contractions. Since the lymphatic vessels have valves similar to those in veins, these contractions produce a one-way flow toward the points at which the lymphatics enter the circulatory system. The lymphatic-vessel smooth muscle is responsive to stretch, so when there is no...
Central Nervous System Brain
During development, the central nervous system forms from a long tube. As the anterior part of the tube, which becomes the brain, folds during its continuing formation, four different regions become apparent. These regions become the four subdivisions of the brain cerebrum, diencephalon, brainstem, and cerebellum Figure 8-38 . The cerebrum and diencephalon together constitute the forebrain. The brainstem consists of the midbrain, pons, and medulla oblongata. The brain also contains four...
Synapses
As defined earlier, a synapse is an anatomically specialized junction between two neurons, at which the electrical activity in one neuron, the presynaptic neuron, influences the electrical or metabolic activity in the second, postsynaptic neuron. Anatomically, synapses include parts of the presynaptic and postsynaptic neurons and the extracellular space between these two cells. According to the latest estimate, there are approximately 1014 100 quadrillion synapses in the CNS. When active,...