The Primary Neurotransmitters of the ANS Are Acetylcholine and Norepinephrine

Paravertebral Nerve Block Anatomy

In the somatic nervous system, neurotransmitter is released from specialized nerve endings that make intimate contact with the target structure. The mammalian motor endplate, with one nerve terminal to one skeletal muscle fiber, illustrates this principle. This arrangement contrasts with the ANS, where postganglionic axons terminate in varicosities, swellings enriched in synaptic vesicles, which release the transmitter into the extracellular space surrounding the effector cells see Fig. 6.1 ....

Body Temperatures And Heat Transfer In The Body

Temperature Body Shell

The body is divided into a warm internal core and a cooler outer shell Fig. 29.2 . Because the temperature of the shell is strongly influenced by the environment, its temperature is not regulated within narrow limits as the internal body temperature is, even though thermoregulatory responses strongly affect the temperature of the shell, especially its outermost layer, the skin. The thickness of the shell depends on the environment and the body's need to conserve heat. In a warm environment, the...

Memory and Learning Require the Cerebral Cortex and Limbic System

Septal Nucleus Basal Forebrain

Memory and learning are inextricably linked because part of the learning process involves the assimilation of new information and its commitment to memory. The most likely sites of learning in the human brain are the large association areas of the cerebral cortex, in coordination with subcortical structures deep in the temporal lobe, including the hippocampus and amygdala. The association areas draw on sensory information received from the primary visual, auditory, somatic sensory, and...

Skeletal Muscle Action Potential

Action Potential Skeletal Muscle

Brane potential to change after a stimulus is applied is called the time constant or t, and its relationship to capacitance C and resistance R is defined by the following equation In the absence of an action potential, a stimulus applied to the neuronal membrane results in a local potential change that decreases with distance away from the point of stimulation. The voltage change at any point is a function of current and resistance as defined by Ohm's law. If a lig-and-gated channel opens...

Increased Blood Glucose Stimulates the Secretion of Insulin

Chemoreceptors That Detect Blood Acidity

A variety of factors, including other pancreatic hormones, are known to influence insulin secretion. The primary physiological regulator of insulin secretion, however, is the blood glucose concentration. Proinsulin Synthesis. The gene for insulin is located on the short arm of chromosome 11 in humans. Like other hormones and secretory proteins, insulin is first synthesized by ribosomes of the rough ER as a larger precursor peptide that is then converted to the mature hormone prior to secretion...

Endothelial Cells Can Release Chemicals That Cause Relaxation or Constriction of Arterioles

An important contributor to local vascular regulation is released by endothelial cells. This substance, endothelium-derived relaxing factor EDRF , is released from all arteries, microvessels, veins, and lymphatic endothelial cells. EDRF is nitric oxide NO , which is formed by the action of nitric oxide synthase on the amino acid arginine. NO causes the relaxation of vascular smooth muscle by inducing an increase in cyclic guanosine monophosphate cGMP . When cGMP is increased, the smooth muscle...

Lung Volumes Affect Pulmonary Vascular Resistance

Lung Volume Laparoscopic

Pulmonary vascular resistance is also significantly affected by lung volume. Because pulmonary capillaries have little , Measuring pulmonary wedge pressure. A catheter is threaded through a peripheral vein in the systemic circulation, through the right heart, and into the pulmonary artery. The wedged catheter temporarily occludes blood flow in a part of the vascular bed. The wedge pressure is a measure of downstream pressure, which is pulmonary venous pressure. Pulmonary venous pressure...

Hypogonadism Can Result From Defects at Several Levels

Male hypogonadism may result from defects in spermato-genesis, steroidogenesis, or both. It may be a primary defect in the testes or secondary to hypothalamic-pituitary dysfunction, and determining whether the onset of gonadal failure occurred before or after puberty is important in establishing the cause. However, several factors must be considered. First, normal spermatogenesis almost never occurs with defective steroidogenesis, but normal steroidogenesis can be present with defective...

The Liver Is Important in Carbohydrate Metabolism

Carbohydrate Metabolism Liver

The liver is extremely important in maintaining an adequate supply of nutrients for cell metabolism and regulating blood glucose concentration Fig. 28.3 . After the ingestion of a meal, the blood glucose increases to a concentration of 120 to 150 mg dL, usually in 1 to 2 hours. Glucose is taken up by hepatocytes by a facilitated carrier-mediated process and is converted to glucose 6-phosphate and then UDP-glucose. UDP-glucose can be used for glycogen synthesis, or glycogenesis. It is generally...

The Liver Plays an Important Role in the Metabolism of Lipids

Lipoprotein Catabolism

The liver plays a pivotal role in lipid metabolism Fig. 28.4 . It takes up free fatty acids and lipoproteins complexes of lipid and protein from the plasma. Lipid is circulated in the plasma as lipoproteins because lipid and water are not mis- The Metabolism of Monosaccharides. Monosaccharides are first phosphorylated by a reaction catalyzed by the enzyme hexokinase. In the liver but not in the muscle , there is a specific enzyme glucokinase for the phosphorylation of glucose to form glucose...

Digestion And Absorption Of Carbohydrates

Structure Glycogen

The digestion and absorption of dietary carbohydrates takes place in the small intestine. These are extremely efficient processes, in that essentially all of the carbohydrates consumed are absorbed. Carbohydrates are an extremely important component of food intake, since they constitute about 45 to 50 of the typical Western diet and provide the greatest and least expensive source of energy. Carbohydrates must be digested to monosaccha-rides before absorption. The Diet Contains Both Digestible...

The Indicator Dilution Method Measures Fluid Compartment Size

The indicator dilution method can be used to determine the size of body fluid compartments see Chapter 14 . A known amount of a substance the indicator , which should be confined to the compartment of interest, is administered. After allowing sufficient time for uniform distribution of the indicator throughout the compartment, a plasma sample is collected. The concentration of the indicator in the plasma at equilibrium is measured, and the distribution volume is calculated from this formula...

Fluid Movement In Capillaries

Pulmonary Edema Osmotic

Hypoxia-Induced Pulmonary Hypertension Hypoxia has opposite effects on the pulmonary and systemic circulations. Hypoxia relaxes vascular smooth muscle in systemic vessels and elicits vasoconstriction in the pulmonary vasculature. Hypoxic pulmonary vasoconstriction is the major mechanism regulating the matching of regional blood flow to regional ventilation in the lungs. With regional hypoxia, the matching mechanism automatically adjusts regional pulmonary capillary blood flow in response to...

Muscle Cells Obtain ATP From Several Sources

Atp Sourcers Skeletal Muscle

Although ATP is the immediate fuel for the contraction process, its concentration in the muscle cell is never high enough to sustain a long series of contractions. Most of the immediate energy supply is held in an energy pool of the compound creatine phosphate or phosphocreatine PCr , which is in chemical equilibrium with ATP. After a molecule of ATP has been split and yielded its energy, the resulting ADP molecule is readily rephosphorylated to ATP by the high-energy phosphate group from a...

Cardiac Energy Consumption Is Required to Support External and Internal Cardiac Work

Cardiac energy consumption which is equivalent to cardiac oxygen consumption provides the energy for both external work and internal work. Most of the external work of the heart involves the ejection of blood from the ventricles into the aorta and pulmonary artery. The work of ejecting blood from the ventricles is the stroke work. Stroke work, strictly speaking, is equal to the product of the volume of blood ejected stroke volume, SV and the pressure against which the blood is ejected aortic...

Acute and Chronic Exercise Increases Insulin Sensitivity Insulin Receptor Density and Glucose Transport into Muscle

Insulin Exercise Response

Though skeletal muscle is omnivorous, its work intensity and duration, training status, inherent metabolic capacities, and substrate availability determine its energy sources. For very short-term exercise, stored phosphagens ATP and creatine phosphate are sufficient for crossbridge interaction between actin and myosin, even maximal efforts lasting 5 to 10 seconds require little or no glycolytic or oxidative energy production. When work to exhaustion is paced to be somewhat longer in duration,...