Transport of Oxygen in Blood

Oxygen Transport Steps

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...

Organization of the Respiratory System

Intrapleural Sac Alveoli

There are two lungs, the right and left, each divided into several lobes. Pulmonary is the adjective referring to lungs. The lungs consist mainly of tiny air-containing sacs called alveoli singular, alveolus , which number approximately 300 million in the adult. The alveoli are the sites of gas exchange with the blood. The airways are all the tubes through which air flows between the external environment and the alveoli. Inspiration inhalation is the movement of air from the external...

Hormone Metabolism and Excretion

Hormone Metabolism

A hormone's concentration in the plasma depends not only upon its rate of secretion by the endocrine gland but also upon its rate of removal from the blood, either by excretion or by metabolic transformation. The liver and the kidneys are the major organs that excrete or metabolize hormones. The liver and kidneys, however, are not the only routes for eliminating hormones. Sometimes the hormone is metabolized by the cells upon which it acts. Very importantly, in the case of peptide hormones,...

The Internal Environment and Homeostasis

Extracellular Fluid Plasma

An amoeba and a human liver cell both obtain their energy by breaking down certain organic nutrients. The chemical reactions involved in this intracellular process are remarkably similar in the two types of cells and involve the utilization of oxygen and the production of carbon dioxide. The amoeba picks up oxygen directly from the fluid surrounding it its external environment and eliminates carbon dioxide into the same fluid. But how can the liver cell and all other internal parts of the body...

Hormone Transport in the Blood

Peptide and catecholamine hormones are water-soluble. Therefore, with the exception of a few peptides, these hormones are transported simply dissolved in plasma Table 10-2 . In contrast, the steroid hormones and the thyroid hormones circulate in the blood largely bound to plasma proteins. Even though the steroid and thyroid hormones exist in plasma mainly bound to large proteins, small concentrations of these hormones do exist dissolved in the plasma. The dissolved, or free, hormone is in...

Refractory Period of the Heart

Muscle Contraction Refractory Period

Ventricular muscle, unlike skeletal muscle, is incapable of any significant degree of summation of contractions, and this is a very good thing. Imagine that cardiac muscle were able to undergo a prolonged tetanic contraction. During this period, no ventricular filling could occur since filling can occur only when the ventricular muscle is relaxed, and the heart would therefore cease to function as a pump. The inability of the heart to generate tetanic contractions is the result of the long...

Maintenance of Upright Posture and Balance

Brain Controls Erect Posture

The skeleton supporting the body is a system of long bones and a many-jointed spine that cannot stand erect against the forces of gravity without the support given by coordinated muscle activity. The muscles that maintain upright posture that is, support the body's weight against gravity are controlled by the brain and by reflex mechanisms that are wired into the neural networks of the brainstem and spinal cord. Many of the reflex pathways previously introduced for example, the stretch and...

Control Systems Involving the Hypothalamus and Pituitary

Hypothalamus And Pituitary Gland

The pituitary gland, or hypophysis, lies in a pocket the sella turcica of the sphenoid bone at the base of the brain Figure 10-12 , just below the brain area called the hypothalamus. The pituitary is connected to the hypothalamus by the infundibulum, a stalk containing nerve fibers and small blood vessels. In adult human beings, the pituitary gland is composed of two adjacent lobes the anterior pituitary toward the front of the head and the posterior pituitary toward the back of the head each...

Transport of Carbon Dioxide in Blood

Retention Carbon Dioxide

In a resting person, metabolism generates about 200 ml of carbon dioxide per minute. When arterial blood flows through tissue capillaries, this volume of carbon dioxide diffuses from the tissues into the blood Figure 15-27 . Carbon dioxide is much more soluble in water than is oxygen, and so more dissolved carbon dioxide than dissolved oxygen is carried in blood. Even so, only a relatively small amount of blood carbon dioxide is transported in this way only 10 percent of the carbon dioxide...

Extracellular Osmolarity and Cell Volume

Cell Volume Hypotonic Solution

We can now apply the principles learned about osmosis to cells, which meet all the criteria necessary to produce an osmotic flow of water across a membrane. Both the intracellular and extracellular fluids contain water, and cells are surrounded by a membrane that is very permeable to water but impermeable to many substances nonpenetrating solutes . About 85 percent of the extracellular solute particles are sodium and chloride ions, which can diffuse into the cell through protein channels in the...

Velocity of Capillary Blood Flow

Blood Flow Velocity Capillaries

Figure 14-44 illustrates a simple mechanical model of a series of 1-cm-diameter balls being pushed down a single tube that branches into narrower tubes. Although each tributary tube has a smaller cross section than the wide tube, the sum of the tributary cross sections is three times greater than that of the wide tube. Let us assume that in the wide tube each ball moves 3 cm min. If the balls are 1 cm in diameter and they move two abreast, six balls leave the wide tube per minute and enter the...

Autonomic Nervous System

Mesenteric Nervous System

The efferent innervation of all tissues other than skeletal muscle is by way of the autonomic nervous system. A special case occurs in the gastrointestinal tract, where autonomic neurons innervate a nerve network in the wall of the intestinal tract. This network, termed the enteric nervous system, will be described in Chapter 17. In the autonomic nervous system, parallel chains, each with two neurons, connect the central nervous system and the effector cells Figure 8-43 . This is in contrast to...

Types of Endocrine Disorders

Defects And Hormone

Most endocrine disorders fall into one of four categories 1 too little hormone hyposecretion 2 too much hormone hypersecretion 3 reduced response of the target cells hyporesponsiveness and 4 increased response of the target cells hyperresponsive-ness . In the first two categories, the phrases too little hormone and too much hormone here mean too little or too much for any given physiological situation. For example, as we shall see, insulin secretion decreases during fasting, and this decrease...

Types of Skeletal Muscle Fibers

Myoglobin Muscle Fibers

All skeletal-muscle fibers do not have the same mechanical and metabolic characteristics. Different types of fibers can be identified on the basis of 1 their maximal velocities of shortening fast and slow fibers and 2 the major pathway used to form ATP oxida-tive and glycolytic fibers. Fast and slow fibers contain myosin isozymes that differ in the maximal rates at which they split ATP, which in turn determine the maximal rate of cross-bridge cycling and hence the fibers' maximal shortening...

Feedforward Regulation

Another type of regulatory process frequently used in conjunction with negative-feedback systems is feedforward. Let us give an example of feedforward and then define it. The temperature-sensitive nerve cells that trigger negative-feedback regulation of body temperature when body temperature begins to fall are located inside the body. In addition, there are temperature-sensitive nerve cells in the skin, and these cells, in effect, monitor outside temperature. When outside temperature falls, as...

Sequence of Excitation

Heart Sequence Excitation

To reiterate, the SA node is the normal pacemaker for the entire heart. Its depolarization normally generates the current that leads to depolarization of all other cardiac muscle cells, and so its discharge rate determines the heart rate, the number of times the heart contracts per minute. The action potential initiated in the SA node spreads throughout the myocardium, passing from cell to cell by way of gap junctions. The spread Vander et al. Human Physiology The Mechanism of Body Function,...

Exchange of Gases in Alveoli and Tissues

Po2 Length Capillary

We have now completed our discussion of the lung mechanics that produce alveolar ventilation, but this is only the first step in the respiratory process. Oxygen must move across the alveolar membranes into the pulmonary capillaries, be transported by the blood to the tissues, leave the tissue capillaries and enter the extracellular fluid, and finally cross plasma membranes to gain entry into cells. Carbon dioxide must follow a similar path in reverse. In the steady state, the volume of oxygen...

Motor Control Hierarchy

Hierarchy Motor Control

Throughout the central nervous system, the neurons involved in controlling the motor neurons to skeletal muscles can be thought of as being organized in a hierarchical fashion, each level of the hierarchy having a certain task in motor control Figure 12-1 . To begin a movement, a general intention such as pick up sweater or write signature or answer telephone is generated at the highest level of the motor control hierarchy. This highest level encompasses many regions of the brain, including...

Hormone Structures and Synthesis

Estradiol Synthesis And Adrenal Disease

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...

Skeletal Muscle Energy Metabolism

Atp Sourcers Skeletal Muscle

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...

Mechanical Events of the Cardiac Cycle

The orderly process of depolarization described in the previous sections triggers a recurring cardiac cycle of atrial and ventricular contractions and relaxations Figure 14-24 . For orientation, we shall first merely name the parts of this cycle and their key events. Then we shall go through the cycle again, this time describing the pressure and volume changes that cause the events. The cycle is divided into two major phases, both named for events in the ventricles the period of ventricular...

Balance in the Homeostasis of Chemicals

Balance Diagram For Chemical Substance

Many homeostatic systems are concerned with the balance between the addition to and removal from the body of a chemical substance. Figure 7-8 is a generalized schema of the possible pathways involved in such balance. The pool occupies a position of central importance in the balance sheet. It is the body's readily available quantity of the particular substance and is frequently identical to the amount present in the extracellular fluid. The pool receives substances from and contributes them to...

Central Control of Afferent Information

All sensory signals are subject to extensive control at the various synapses along the ascending pathways before they reach higher levels of the central nervous system. Much of the incoming information is reduced or even abolished by inhibition from collaterals from other neurons in ascending pathways lateral inhibition, discussed earlier or by pathways descending Descending pathways may control sensory information by directly inhibiting the central terminals of the afferent neuron an example...

The Scope of Human Physiology

Stated most simply and broadly, physiology is the study of how living organisms work. As applied to human beings, its scope is extremely broad. At one end of the spectrum, it includes the study of individual molecules for example, how a particular protein's shape and electrical properties allow it to function as a channel for sodium ions to move into or out of a cell. At the other end, it is concerned with complex processes that depend on the interplay of many widely separated organs in the...

Ventilation and Lung Mechanics

Anatomical Dead Space Lungs

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...

Functional Classes of Neurons

Classes Neurons Vanders

Neurons can be divided into three functional classes afferent neurons, efferent neurons, and interneurons. Afferent neurons convey information from the tissues and organs of the body into the central nervous system, efferent neurons transmit electric signals from the central nervous system out to effector cells particularly muscle or gland cells or other neurons , and interneurons connect neurons within the central nervous system Figure 8-4 . As a rough estimate, for each afferent neuron...

Body Fluid Compartments

To repeat, the internal environment can be equated with the extracellular fluid. It was not stated earlier that extracellular fluid exists in two locations surrounding cells and inside blood vessels. Approximately 80 percent of the extracellular fluid surrounds all the body's cells except the blood cells. Because it lies between cells, this 80 percent of the extracellular Vander et al. Human Physiology The Mechanism of Body Function, Eighth Edition CHAPTER ONE A Framework for Human Physiology...

Anterolateral Pain Pathway

Anterolateral Pain Pathway

A stimulus that causes or is on the verge of causing tissue damage usually elicits a sensation of pain. Receptors for such stimuli are known as nociceptors. They respond to intense mechanical deformation, excessive heat, and many chemicals, including neuropeptide transmitters, bradykinin, histamine, cytokines, and prostaglandins, several of which are released by damaged cells. These substances act by combining with specific ligand-sensitive ion channels on the nociceptor plasma membrane. Vander...

Structure and Maintenance of Neurons

Neurons And Neuroglia

Neurons occur in a variety of sizes and shapes nevertheless, as shown in Figure 8-2, most of them contain four parts 1 a cell body, 2 dendrites, 3 an axon, and 4 axon terminals. As in other types of cells, a neuron's cell body contains the nucleus and ribosomes and thus has the genetic information and machinery necessary for protein synthesis. The dendrites form a series of highly branched outgrowths from the cell body. They and the cell body receive most of the inputs from other neurons, the...