Textbook Notes (363,078)
Canada (158,177)
Psychology (4,731)
Chapter 15

Chapter 15.pdf

3 Pages
Unlock Document

Western University
Psychology 2220A/B
Scott Mac Dougall- Shackleton

Chapter 15: Drug Addiction and the Brain’s Reward Circuits BASIC PRINCIPLES OF DRUG ACTION • Psychotic drugs - drugs that influence subjective experience and behaviour by acting on the nervous system • Drug Administration and Absorption • Drugs are usually administered in one of four ways • The route of administration influences the rate at which and the degree to which the drug reaches its sites of action in the body • Oral Ingestion •The oral route is the preferred route of administration for many drugs •Drugs that are not readily absorbed from the digestive tract or that are broken down into inactive metabolites before they can be absorbed must be taken by some other route •The two main advantages of the oral route of administration over other routes are its ease and relative safety •Disadvantage is its unpredictability • Injection •Effects of injected drugs are strong, fast, and predictable •Drug injections are typically made subcutaneously (SC), into the fatty tissue just beneath the skin, intramuscularly (IM), into the large muscles or intravenously (IV), directly into veins at points where they run just beneath the skin •The speed and directness of the intravenous route are mixed blessings; after an intravenous injection, there is little or no opportunity to counteract the effects of an overdose, an impurity, or an allergic reaction • Inhalation •Two main shortcomings of this route are that it is difficult to precisely regulate the dose of inhaled drugs, and many substances damage the lungs if they are inhaled chronically • Absorption through Mucous Membranes •Administered through the mucous membranes of the nose, mouth and rectum • Drug Penetration of the CNS • Once a drug enters the bloodstream, it is carried in the blood to the blood vessels of the CNS • A protective filter, the blood-brain barrier, makes it difficult for many potentially dangerous blood borne chemicals to pass from the blood vessels of the CNS into its neurons • Mechanisms of Drug Action • Psychotic drugs influence the nervous system in many ways • Some drugs, act diffusely on neural membranes throughout the CNS • Others act in a more specific way: by binding to particular synaptic receptors; by influencing the synthesis, transport, release, or deactivation of particular neurotransmitters; or by influencing the chain of chemical reactions elicited in postsynaptic neurons by the activation of their receptors • Drug Metabolism and Elimination • Actions of most rugs are terminated by enzymes synthesized by the liver • These liver enzymes stimulate the conversion of active drugs to nonactive forms - a process referred to as drug metabolism Chapter 15: Drug Addiction and the Brain’s Reward Circuits • In many cases, drug metabolism eliminates a drug’s ability to pass through lipid membranes of cells so that it can no longer penetrate the blood-brain barrier • Drug Tolerance • Drug tolerance is a state of decreased sensitivity to a drug that develops as a result of exposure to it • Three important points to remember about the specificity of drug tolerance •Once drug can produce tolerance to other drugs that act by the same mechanism; this is known as cross tolerance •Drug tolerance often develops to some effects of a drug but not others • Increasing sensitivity to a drug is called drug sensitization •Drug tolerance is not a unitary phenomenon, that is, there is no single mechanism that underlies all examples of it • Two categories of changes underlie drug tolerance: metabolic and functional • Drug tolerance that results from changes that reduce the amount of the drug getting to its sites of action called metabolic tolerance • Drug tolerance that results form changes that reduce the reactivity of the sites of action to the drug is called functional tolerance • Tolerance to psychoactive drugs is largely functional • Drug Withdrawal Effects and Physical
More Less

Related notes for Psychology 2220A/B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.