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 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.
The sympathetic nervous system is primarily responsible for preparing the body for activities related to the “flight or fight” response – either running or fighting – while the parasympathetic nervous system, rooted in the brain stem and the spinal cord of the lower back, is responsible for the “relaxation” response and restoring the body to normalcy. When we physically or emotionally tire, parasympathetic functions return us to a peaceful, calm state. Depression may be associated with parasympathetic dysfunction. The sympathetic autonomic system governs functions that expend energy in an emergency situation, while the parasympathetic part restores the body to a more normal, non-emergency state. Activation of the sympathetic nervous system is associated with a number of effects in the viscera or organs. 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
Constriction of pupil
Bladder
Inhibits bladder (relaxes)
Stimulates bladder (contracts)
Lungs
Opens bronchial tubes
Constricts bronchial tubes
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
INTRODUCTION TO PHARMACOLOGY
toxic actions, receptor interactions and dose-response phenomena. ● 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.
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. 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 .
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