muscles tighten, and elimination and digestive function are put on hold. The second stage of stress is resistance, which involves the secretion of regulating hormones that allow the body to continue carrying out the emergency strategy beyond the initial moment of alarm. If there is no relief of the stress or risk (that is, if the stimulus or stress is not interrupted or relief is not possible), the final stage is one of exhaustion. Exhaustion begins when the body is no longer able to tolerate the stress or danger. In this stage, if stress is not alleviated, the body releases cortisol. Long-term exposure to stress can result in physical wear and tear, including the development of cardiovascular, upper respiratory and digestive difficulties. Massage can slow autonomic arousal and the tension that builds daily from our adrenaline responses. Massage stimulates the nervous system though the sensory receptors, disrupting the existing pattern in the central nervous system, and results in shifting impulses that affect the peripheral nervous system, restoring homeostasis. Limbic system The autonomic nervous system is controlled by areas in the cerebral cortex, the medulla oblongata and primarily, the hypothalamus, which receives impulses from sensory fibers in the organs, muscles and joints. The hypothalamus is part of the limbic system, which also includes the hippocampus and the amygdala, along with other areas of the brain. The hypothalamus is responsible for homeostasis or self-regulation. It sends instruction to the body through the autonomic nervous system, controlling blood pressure, heart rate and perspiration, as well as through the pituitary gland, regulating the body’s metabolism and growth. The limbic system is largely responsible for and closely associated with emotions and the creation of memories. Known as the pain and pleasure center , it is also associated with changes in mood and emotional states. The limbic system receives input regarding the fullness or emptiness of the stomach and the skin’s temperature, and also manages feelings of hunger, thirst, pleasure, pain, sexual response and aggression. ● Pharmacokinetics : The way the drug is absorbed, distributed, metabolized and excreted from the body. ● Medical pharmacology : The study of substances used to prevent, diagnose and treat disease. Nearly all of the thousands of existing drugs can be classified into about 70 different groups, and many of the drugs within each group share similar pharmacodynamic and pharmacokinetic properties. In most of these groups, it is possible to identify a small number of prototype drugs that are associated with significant characteristics that typify that group of drugs. travel from the site of administration to the site of action during the time period in which it is effective, avoiding excretion or inactivation before its mission is complete. The vast majority of drugs range from a molecular weight of 100 to 1,000. Drugs within this range are large enough to allow selectivity of action (sufficiently unique in fit and charge to prevent binding to other receptors), and small enough to allow movement throughout the different compartments of the body. Very large drugs that will not diffuse through body compartments must be administered directly into the target area.
The following table reviews a number of the changes associated with sympathetic and parasympathetic nervous system function. Autonomic Nervous System Organ Sympathetic Arousal Parasympathetic Arousal Heart Heartbeat accelerates. Heartbeat decelerates.
Majority of blood vessels (Skeletal muscle blood vessels)
Vasoconstriction (Vasodilation).
None.
Iris
Dilation of pupil.
Bladder
Inhibits bladder (relaxes). Opens bronchial tubes.
Stimulates bladder (contracts). Constricts bronchial tubes.
Lungs
Intestines
Decreases peristalsis.
Increases peristalsis.
Digestive gland
Inhibits digestive juices.
Increases digestive juices.
Stress and sympathetic arousal Stress-related illnesses are associated with exaggerated sympathetic effects, which may include headaches, digestive problems, feelings of anxiety, high blood pressure and a variety of aches and pains. Long-term activation of the sympathetic nervous system typically results in what we have come to call “stress,” which can take its toll on the body. The flight-or-fight response is the body’s first reaction to stress or risk. During activation of the sympathetic nervous system, the adrenal glands release adrenaline (epinephrine). In a response that lasts up to a half hour, the blood pressure increases, skeletal
INTRODUCTION TO PHARMACOLOGY
Pharmacology is the study of substances that interact with living systems through chemical processes, especially by binding to regulatory molecules and activating or inhibiting normal body processes (Katzung, 2017). More simply, it is the study of the interaction of chemicals with living things. This section introduces the following concepts of pharmacology: ● Drugs : Chemicals that act on living things at the molecular (chemical) level. ● Pharmacodynamics : The action of a drug on the body, i.e., the way the drug produces effects on the body, encompassing mechanisms of therapeutic vs. toxic actions, receptor interactions and dose-response phenomena. Nature and composition of drugs A drug is a substance that causes a change in biological processes through chemical actions. Hormones are drugs made within the body. In general, a drug molecule interacts with a particular molecule of the living thing that regulates some aspect of the biological system. This molecule in the biological system is called a receptor . In order to interact chemically with a receptor, the drug molecule must match the specific size and shape of the receptor, as well as the appropriate electrical charge and atomic composition. Additionally, as most drugs are administered far from the target action site (a pill is taken by mouth and must travel to its needed location in the body), the drug must have the ability to Drug administration Drugs are commonly administered through the following routes. Each method has different pharmacokinetic implications: ● Oral (swallowed).
● Intravenous. ● Sublingual (under the tongue). ● Rectal (suppository).
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