Chapter02 - Chapter 2 Heredity, Environment, Psychoactive...

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Chapter 2 Heredity, Environment, Psychoactive Drugs CHAPTER OVERVIEW HOW PSYCHOACTIVE DRUGS AFFECT PEOPLE This chapter first examines how drugs get to the brain and the ways in which they affect brain chemistry. Drugs can be inhaled, injected, absorbed through mucous membranes, swallowed, or absorbed through the skin. Drugs are then distributed through the circulatory system until they reach the brain where they will have their greatest effect. The drugs are then metabolized, principally by the liver, and then excreted from the body in the urine, through exhaled breath, or through sweat. The nervous system consists of the peripheral nervous system (autonomic and somatic) and the central nervous system (the brain and spinal cord). Using evolutionary terminology, psychoactive drugs affect both the old (primitive) brain and the new brain (mostly the prefrontal cortex). The key circuit of the brain that drugs affect is the reward/reinforcement pathway, especially the nucleus accumbens and the amygdala. Drugs cause their effects by mimicking or modifying neurotransmitters (e.g., dopamine, serotonin, norepinephrine, GABA). Problems occur because the stop switch that shuts off the craving becomes dysfunctional. Drugs affect the nervous system at the cellular level, particularly the synaptic gap. An individual’s drug tolerance, tissue dependence, withdrawal, and metabolism determine additional effects. New research indicates “stay-stopped” switches in the brain that leads to slips and relapses making it difficult for many to remain in continuous abstinence from addictive substances. FROM EXPERIMENTATION TO ADDICTION Besides the desired effects of drugs, such as getting high, self- medicating, creating energy, relieving pain, zoning out, or altering consciousness, undesirable side effects occur, some of them minor, some major, and some fatal. The level of drug use abstinence, experimentation, social/recreational use, habituation, abuse, and addiction depends not only on the amount, frequency, and duration of drug use but on a person’s susceptibility to addiction as determined by heredity and environment. Compulsive behaviors, such as gambling and compulsive eating, also affect brain chemistry. All these factors cause alterations in brain chemistry that can affect a person for a few hours, a few days, or even a lifetime. Many of these alterations can be seen with the assistance of new imaging
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techniques such as SPECT, CAT, MRI, fMRI, and PET brain scans. Animal experiments show that they react to the same drugs in much the same way as human beings. Compulsion curves that illustrate the contributions of heredity, environment, and the use of psychoactive drugs or the practice of compulsive behaviors to addiction are useful when trying to design methods of treatment that will lead to recovery.
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Chapter 2 Heredity, Environment, Psychoactive Drugs OUTLINE HOW PSYCHOACTIVE DRUGS AFFECT US I. INTRODUCTION II. HOW DRUGS GET TO THE BRAIN A. ROUTES OF ADMINISTRATION & DRUG ABSORPTION
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This note was uploaded on 12/26/2011 for the course SCI HTW318 taught by Professor Bergen-cico during the Fall '11 term at Syracuse.

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Chapter02 - Chapter 2 Heredity, Environment, Psychoactive...

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