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Psychology 2020 Study Notes From start of course to test 1

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Western University
Psychology 2020A/B
Riley Hinson

Psychology 2020  A drug is a chemical compound that may produce psychological, behavioural and physiological effects.  Psychoactive effects refer to alteration in cognitive, behavioural and motor processes eg euphoria, distortions of time perception, hallucinations or increased libido.  Drugs are distributed throughout the body via the circulatory system  PROCESS: Administration, absorption, distribution, metabolism ad elimination are known collectively as pharmacokinetics.  Processes involved in the interaction of the drug with receptors at the site of action are known as pharmacodynamics.  Cytochrome P-450 is a term used for a very large group of enzymes, found primarily in the endoplasmic reticulum of liver cells, that are involved in the metabolism of most drugs.  Injection: Absorption is more rapid following intraperitoneal(stomach) administration than following intramuscular (muscle), which is more rapid than following subcutaneous (just below skin/ into fatty layer).  Mainling in s the term used for intravenous injections in the drug subculture.  Skin popping is the term often used to refer to subcutaneous injections of illicit drugs Drug Distribution:  Drugs that are guven by injection or via pulmonary route enter the circulation diffusinf through pores in capillary walls.  Drugs taken orally must be lipid soluble to be absorbed from the digestive system since there are no pores in the lining of the stomach or intestines. Factors which affect entry of a drug into circulation: 1) Ionization – most drugs are either weak acids or weak bases. Drugs that are weak acids readily ionize in alkaline environments and become less ionized in acidic environments. Reverse is true for week bases. Ionized molecules are not readily absorbed, therefore percentage of nonionized molecules determines the rate of absorption. Ionized particles penetrate cell membranes poorly compared to unionized particles. 2) Lipid solubility – lipid soluble compounds penetrate cell membranes more readily than non lipid soluble compounds more compounds than non-lipid soluble compounds. Compounds that are lipid soluble are also usually unionized.  The brain is protected by the blood brain barrier. It restricts the permeability characteristics of brain capillaries, by reducing the diffusion of water soluable or ionized molecules, but does not impede lipid soluable or un-ionized molecules. The concept arose from the work of Paul Ehrlich in 1882. 3) Receptor Binding – Drigs exert their effects by binding with receptors at relevant target tissue. A bind forms between charged groups in the receptor molecule and oppositely charged groups on the drug.  An agonist is a drug that mimics the effect of a neurotransmitter. This may occur because the agonist bonds to receptors, blocks reuptake or inhibits metabolic breakdown.  Antagonists are compounds which reduce the effects of a receptor agonist by biding to active receptors but producing no pharmacological action. Drug Response Curve:  Drug dosages are usually expressed as milligrams (mg), or if given on weight basis, mg/kg.  The dose-response curve (DRC) I the most commonly used graphical presentation mode of drug effects.  The ED50 is the dose of a drug that is effective in producing a response in 50% of the experimental subjects. (allows you to compare potency)  LD50 refers to the dose which kills 50% of the subjects.  Therapeutic index for a given drug effect is given by the ratio LD50/ ED50. The higher the ratio, the greater the difference btw the LD50 and ED50 and the less likelt chance that a lethal or other non- lethal effect will occure.  Margin of safety is a more conservative measure of a drugs safety and is the ratio of the LD1/ED99.  Phenomena associated with chronic drug administration, can be depicted by the DRC. Tolerance is represented by a shift to the right in the DRC. Sensitisation is depicted by a shift to the left in the DRC. Termination of Drug Action:  Drugs are eliminated by skin, lungs and kidneys.  The liver is important organ in this process because it is the major site of enzymatic breakdown of drugs.  Cytochromme P450 enzyme family is the primary agent involved in drug metabolism.  Individuals differ in the level of CYP enzyme activity, which in turn affects how rapidly drugs are metabolized.  Many drugs (eg: alcohol) induce the activity of CYP enzymes, and this results in a more rapid metabolism of not only the original drug, but other drugs.  Most often, enzymatic breakdown results in inactive molecules that are subsequently excreted via urine.  Enzymatic breakdown most often results in metabolites thate are less soluble, are lagrer, carry a greater charge, and are inactive or less active than the original compound. This is important because these molecules are less rapidly reabsorbed from the kidney to the blood.  Weak acids are excreted more readily when tubular urine is alkaline because the weak acids become ore ionized and are “trapped” in tubular urine. Conversely weak acids are excreted more if urine is acidic.  The relation between reabsorption and pH is frequently used in treatment of drug toxicity.  Elimination half-life – time needed for half of a drug dose to be eliminated from the body – helps understand drug effects and is important when considering which drug to use for certain medical conditions.  It takes about 6 half-lives for most of a drug to be eliminated and for a person to be considered drug free.  Pot had a long half life hence naturally weens the body as it take a long time to leave.  “Steady State Concentration”- relatively steady blood concentration is required to maintain effects of the drug. Neuron and Neurotransmission  Drugs exert their actions by affecting neurotransmission.  The Neuron is the functional unit of the nervous system.  An action potential arriving at an axon terminal can cause the release from the presynaptic element of substance known as neurotransmitters.  Neurotransmitter release: neurotransmitter substances are stored in synaptic vesicles in the axon terminal the presynaptic element. The arriving action potential causes these vesicles to attach to the presynaptic membrane and open exuding the stored neurotransmitter. The exuded neurotransmitter crosses the synaptic cleft where it binds to receptor elements (transmembrane proteins) on the postsynaptic membrane.  Neurotransmitters are basic components of CNS functioning. Most drugs exert their action by affecting the synthesis, release or reuptake of neurotransmitters.  General model of the synthesis and breakdown of neurotransmitter substance: 1) Precursor substances (amino acids from diet), are the basic building blocks of neurotransmitters. 2) Synthesizing agents are needed to build neurotransmitters from the precursor 3) Once synthesized the neurotransmitter must be transported to the presynaptic terminal and stored 4) The stored, or newly synthesized neurotransmitter is released. 5) Released neurotransmitters bind to postsynaptic receptors 6) The neurotransmitter becomes unbound, at which point it can bind again to the receptor to produce additional action, attach to transporter proteins and be taken back up (reuptake) into the presynaptic element to be used again, or attach to proteins that breakdown the neurotransmitter. UP TO PAGE 9 Classical Conditioning and Tolerance:  The occurrence of tolerance may present problems in achieving effective medication since, as tolerance develops to some desired medical effect of a drug, the dose must be increased to reproduce the desired effect.  Many of the mechanisms underlying the development of tolerance to a drug also underlie physical dependence to the drug.  Withdrawal symptoms, the benchmark of physical dependence, to a drug are directly opposite to the actual drug effects.  Pavlovian or Classical conditioning was identified by Russian physiologist Ivan Pavlov. (Dog study)  “Psychic secretion” or Conditional Response – salivation (reponse) in advance or anticipation to the food (stimuli)  In Pavlovian conditions, a stimulus which does not elicit the response of interest at the beginning (conditioned stimulus CS) is paired with another stimulus that does elicit the response from the outset (unconditional stimulus UCS) and the response it elicits is the unconditional response (UCR).  If the CS is paired enough times with the UCS, the CS comes to elicit a response which Pavlov called the conditioned response (CR).  Since CRs strengthen, grow bigger and occur sooner, as the number of CS-UCS pairings increase, the degree to which the drug effect is reduced by the opposing CR should increase over the course of the drug administrations – characteristic of tolerance.  Shepard Siegel proposed that pav. Conditioning of drug-opposite CRs may play a role in tolerance.  Results: 1) Situational Specificity of Drug tolerance: morphine with cues A and saline with cues B. Tolerance is always greater when the drug is given in the context of the usual CS predrug cues, hence showing situational specificity. 2) Placebo CR test – giving a drug in the context of consistent set of CS predrug cues results in the development of a drug compensatory CR, and that the drug compensatory CR, elicited by the predrug cues, reduces the effect produced by the drug. Results show that usual CS predrug cues elicit the drug opposite CR predicted by pav conditioning model. 3) How might a drug opposite CRs be involved in withdrawal and relapse? Research has shown that these subclinical withdrawal symptoms are most likely drug compensatory CRs being elicited by the usual predrug cues. Hence people crave drug more (CR) when they experience the CS. Pav. Conditioning model provides explanation of why treated addicts may experience withdrawal symptoms that may lead to relapse, and also provides a connection btw the processes involved in the development of tolerance and the occurrence of withdrawal. 4) How is tolerance lost and what are the implications for treatment? Pavlov found that in order to get rid of a CR he had to present the CS and not follow it with the expected UCS, a procedure that he called extinction. If drug compensatory CRs are the basis of subclinical withdrawal symptoms and subsequent relapse in treated addicts, extinction procedures could be useful in reducing the likelihood of any such withdrawal and perhaps reduce the likelihood of relapse. PARADIGMS TO STUDY DRUG REINFORCEMENT:  Behaviour, such as drug self administration, in maintained by one of two processes, either positive or negative reinforcement  Positine reinforcement- situation in which the performance of some behaviour results in the experiencing of some desirable or rewarding outcome.  Negative reinforcement involves situations in which the performance of some behaviour results in the termination or avoidance of some undesirable or aversive outcome.  The most common procedure used to study positive reinforcement is call the operant self- administration paradigm. (Animals required to press lever to get reward)  Research of this type (investigation what brain regions or neurotransmitters are involved) has led to the general conclusion that an increase in dopaminergic activity in the ventral tegmental area and nucleus accumbens is very importantly involved in the positively reinforcing properties of the vast majority of drugs.  The progressive ratio procedure is a self-administration paradigm that provides info in the relative reinforcing properties of drug (ie; how far someone is willing to go/ pay for the drug). The largest number of responses that the animal will make to obtain the drug is called the break point.  Studies of the reinforcing effects of drugs comparison Self-Administration Paradigm Conditioned Place Preference (CPP)  Animals surgically prepared, put in  Based on classical conditioning skinner boxes and press lever to be  Rectangle tube with 2 boxes at either administered drug. end. Mice given drug placed in one box.  Allows for more obvious comparison of Mice then given saline, placed in other differential reinforcement effects of box. Test by placing animal in middle of drugs (progressive ratio procedure) box and allowed to move around freely,  Allows researches to examine the dependant measure is amount of time pattern of drug admin. spends in the boxes (if drug has positive  Difficult to determine adverse properties reinforced properties, it will stay in box associated with drug).  Shows adverse effects – animal will spend less time in box associated with drug. ALCOHOL:  Alcohol is ethanol or ethyl alcohol  C6H 12 6 C2H 5H + 2CO 2  One molecule glucose acted upon yeast in the presence of heat and absence of oxygen produces cellular energy and 2 molecules of ethanol and 2 molecules of carbon dioxide as waste. This process is called fermentation and occurs naturally in any item that has sugars or starches (which can be converted to sugars). Consumption in modern times:  Alcohol is the second most widely used psychoactive substance in the world. It is estimates that 90% of the people in westernized societies have consumed alcohol at some point in their lives.  In Canada and the US the average age of first drink is 12, with the average age of regular use 16.  Binge drinking is define as having 5+ drinks on one occasion.  When taken orally, 20% of alcohol is absorbed from the stomach and 80% from the small intestine.  Absorption from the gastrointestinal tract is influenced by: o Greater concentration of alcohol the more rapid it is absorbed – because higher concentration alcohol beverages tend to be more radpidly moved from the stomach to the small intestine o Other chemical in alcohol (ie: vodka and gin more pure so more rapidly absorbed) o Food in stomach slows absorption o Alcohol in carbonated beverages is more rapidly absorbed – carbonation speeds gastric emptying into small intestine o Ingested alcohol goes to liver then brain. If absorption is slow BAC will be lower since liver can metabolize more alcohol. Liver metabolises alcohol at constant rate, and if alcohol is consumed rapidly (leading to absorption) then alcohol will enter bloodstream since liver cannot keep up. o Lean bodies have more water. Alcohol is more widely distributed the higher the water content. Hence leaner person has lower BAC. o Women have about 50% less alcohol dehydrogenase than men, meaning more alcohol enters the blood stream of a female.  Alcohol is metabolised primarily in the liver by alcohol dehydrogenase Alcohol acetaldehyde acetic acid (by acetaldehyde dehydrogenase) carbon dioxide and water.  Typical measure of alcohol is the blood alcohol curve (BAC) – shows amount of alcohol in blood as a function of time since ingest
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