Dtugs and the Brain Week 1 Notes
Dtugs and the Brain Week 1 Notes Bios 2060
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This 3 page Class Notes was uploaded by Jessa Snyder on Sunday August 21, 2016. The Class Notes belongs to Bios 2060 at Ohio University taught by Scott Hooper in Fall 2016. Since its upload, it has received 13 views. For similar materials see DRUGS AND THE BRAIN in Biological Sciences at Ohio University.
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Date Created: 08/21/16
Chapter 1: Pharmacology Introduction The interaction between the brain and drugs consist of parts of the brain make conscious choices and the drugs change the neural pathways of the brain. Pharmacology- The science of the actions of drugs and their effects on living organisms. Before the 20th century drugs were naturally occurring substances mostly from plants. o Ex: THC the main chemical that comes from marijuana Neuropharmacology- Study of the drug-induced changes in nervous system cell function. Psychopharmacology- Drug changes in mood, thinking, and behavior. Neuropsychopharmacology- Chemical substances that act on the nervous system to alter behavior. Drug Action- What the drug does to the neurons it affects. What specific neuron is affected when the drug is introduced to the body Drug Effect- The physiological or psychological function changes due to drug use. Marijuana=sleepiness Therapeutic Effect- The drug-receptor interaction produces desired physical or behavioral changes. Example scenario: A military solider needs to stay awake for long periods of time. o Solider takes amphetamine which makes them stay awake (Therapeutic Effect). Side Effect- All other effects from the brain. Same scenario: o The solider that takes amphetamine to stay awake also feels a side effect of loss of appetite. Specific Drug Effects- Based on physical and biochemical interactions of a drug with a target site in living tissue. A drug, like alcohol, is taken and the body's affect on the drug is the specific drug effect Non-Specific Drug Effects- Are based on certain unique characteristics of the individuals. (expectations, mood, etc.) How the individual feels after drug use. Example first-time marijuana users report not feeling high Placebo- fake drug, it is more likely to work if the patient believes it will. Pharmacologically inert compound, but can have therapeutic effects and side effects. They patients are more likely to believe the placebo is real if a middle aged man in a lab coat over a younger woman in regular clothes because the person fits their expectations. Psychosomatic illness- is an illness created by the mind, the brain chemicals change which replicates symptoms of an illness. One theory as to why the placebo effect works, because the people believe they received treatment. Double-Blind Experiment- Neither the patient or the doctor knows which group receives the placebo or the real drug. Bioavailability- amount of drug in the blood that is free to bind at target sites. Pharmacokinetic- How quickly the drug makes an effect. 1 Routes of administration 2 Absorption and distribution 3 Binding 4 Inactivation 5 Excretion Also depends on how rapidly the drug reaches its target, Frequency and history of drug use, the characteristics of the individuals and their environment. 1.Routes of Administration- How the drug enters the body. Alters rate of absorption and blood levels, each method has advantages and disadvantages. Enternal- methods use the gastrointestinal (GI) tract; generally slow and produces variable blood levels. Parenteral methods: injection, pulmonary, and topical administration First-Pass metabolism- potentially harmful chemicals are broken down by the liver before the chemical can enter through the bloodstream. Unless they take an abundance of the drug. Rectal Administration- Drugs taken through the rectum, this is only given for children or those who keep throwing up. Intravenous Injection- An IV the drug is admitted directly to the blood stream. Allows drug to reach brain instantly, risks of HIV. Heroin is taken through an IV. o Subcutaneous- just into the skin, slower injection but faster than oral or patches. o Intramuscular- Into the muscle can be slowed by oils. o Intravenous- Into the blood vessel. Inhalation- Inhale straight to the lungs, rapid o Marijuana, nicotine, inhalers, and crack cocaine. Topical- drug applied to mucous membranes, drug can be absorbed into the bloodstream. Intranasal Administration- Drug taken through the nasal passage. Transmitted through the brain without having to pass through the blood-brain barrier. o Example includes cocaine, heroin, and caffeine. Transdermal- the patches placed on the skin to administer drugs Epidural- drug administered to the spinal cord to bypass the blood-brain barrier. Infusion Pumps- Implanted under the scalp to continuously administer antibiotics to the brain by passes through the blood-brain barrier. Gene Therapy- application of DNA that encodes a specific protein. Insulin therapy, a viral vector is used to correct the genes that are "turned off" 2.Absorption and Distribution- The rate of passage of the drug through the membranes Phospholipids- Negatively charged region (hydrophilic) and two uncharged tails (hydrophobic) arranged in two layers. (the drawing represents the phospholipids). They form barriers. o Hydrophilic- loves water o Hydrophobic- hates water Cell membranes- surrounds the interior of the cell. Made of phospholipid. Proteins- allow ions to move across. Drugs bind to the proteins and changes the protein so the cell does something different. Passive Diffusion- lipid-soluble drugs can pass through cell membranes. o Movement goes from higher to lower concentration. Concentration Gradient- the larger, the faster the diffusion. Partition Coefficient- Measure of lipid solubility. The ratio of amount of drug in the oil to amount in the water. Extent of ionization determines the oil/water solubility of the drug. o Most drugs are not lipid-soluble because they are weak acids or bases that ionize in water. Ionization- depends on the pH solution. Low pH means more free hydrogen ions=more acidic. o Larger pH= Basic o pK aThe pH of the water at which 50% of the chemical has a hydrogen. o pKa of aspirin=3.5. o pH of stomach=2.0 Other factors that affect absorption: Rate the stomach empties, (the small intestines absorb much faster). Size and sex of individual. Women have a smaller aqueous compartment therefore they are more affected by drugs. Lipid-soluble drugs can easily enter brain tissue, but the blood-brain limits movement of ionized molecules. The brain is chemically fragile! Cerebrospinal fluid- fills the subarachnoid space around the brain and spinal cord. No neuron ever sees a blood cell! Blood vessels are surrounded by cerebrospinal fluid. Brain capillaries have distinct morphology Astrocytes- extensions of glial cells Some parts of the brain are not isolated Area postrema- (chemical trigger zone) located in the brainstem medulla detects toxins Median Eminence- the hypothalamus allow hormones to move to the pituitary gland. How the brain controls hormonal release to the body. The placenta is another barrier, however it is a very weak barrier. Many drugs can cross this barrier. Teratogens- induce developmental abnormalities things that harm the fetus. Drug Depots- Binding at inactive sites where no biological effect is initiated. Depot Binding- affects magnitude and duration of drug action This explains why drugs affect people differently.
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