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Chapter 15

PSYC 370 Chapter Notes - Chapter 15: Tachycardia, Morphine, Insomnia

Course Code
PSYC 370

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Psyc370 Chapter 15: Drug Addiction and the Brain’s Reward Circuits
15.1 Basic Principles of Drug Action
Psychoactive Drugs: drugs that influence subjective experience and behaviour by
acting on the nervous system
Drug Administration and Absorption
oThe route of administration influences the rate and degree to which the
drug reaches its sites of action in the body
oOral Ingestion
Stomach  intestine  bloodstream
Some pass through stomach wall to bloodstream (alcohol)
Advantage: ease, safety
Disadvantage: unpredictability (influenced by food in stomach)
Intravenous, subcutaneous, or intramuscular injections
Advantage: strong effect, fast
Often prefer to inject intravenously (directly into vein)  delivered
straight to brain. Fast but no way to counteract effects of overdose,
allergic reaction, etc.
Lungs  bloodstream
Disadvantage: difficult to regulate dose, lung damage
oAbsorption Through Mucous Membranes
Mucous membranes of nose, mouth, or rectum. Damage occurs.
Ex. cocaine
Drug Penetration of the Central Nervous System
oBloodstream  CNS. Blood-brain barrier makes it difficult for many
dangerous chemicals to pass from CNS to neurons
Mechanisms of Drug Addiction
oDifferent mechanisms. Some act diffusely on neural membranes in CNS
(alcohol) while others bind to particular synaptic receptors, influencing
Drug Metabolism and Elimination
oDrug Metabolism: the conversion of a drug from its active form to a non-
active form  done by the liver
Eliminates drug’s ability to pass through blood-brain barrier. Drug
then passes through body in form of urine, sweat, feces, breath,
and mother’s milk
Drug Tolerance: a state of decreased sensitivity to a drug that develops as a result
of exposure to the drug
oCross Tolerance: tolerance to the effects of one drug that develops as the
result of exposure to another drug that acts by the same mechanism
oDrug Sensitization: an increase in the sensitivity to a drug effect that
develops as the result of exposure to a drug

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oDrug tolerance often develops to some effects of a drug but not others (ex.
tolerance to nausea but not other aspects)
oNo single mechanism responsible for drug tolerance
oTwo categories of change underlie drug tolerance:
Metabolic Tolerance: tolerance that results from a reduction in the
amount of a drug getting to its sites of action
Functional Tolerance: tolerance resulting from a reduction in the
reactivity of the nervous system (or other sites of action) to a drug
Most common effect for psychoactive drugs
Reduces number of receptors for drug, decreases efficiency
with which it binds to existing receptors, or diminishes the
impact of receptor binding on the activity of the cell
Drug Withdrawal Effects and Physical Dependence
oWithdrawal Syndrome: the illness brought on by the elimination from
the body of a drug on which the person is physically dependent
Effects of withdrawal often opposite to initial effects of drug
oPhysically Dependent: being in a state in which the discontinuation of
drug taking will induce withdrawal reactions
oWithdrawal effects may be produced by the same neural changes that
produce drug tolerance
Addiction: What is it?
oAddicts: habitual drug users who continue to use drugs despite its adverse
effects on health and social life, and despite repeated efforts to stop
15.2 Role of Learning in Drug Tolerance
Contingent Drug Tolerance: drug tolerance that develops as a reaction to the
experience of the effects of drugs rather than to drug exposure alone
oGrow tolerant to drug’s effects, but not drug exposure
oRats that received alcohol injections before convulsive stimulations
became tolerant. Rats that received alcohol injections after convulsions
(didn’t experience the anti-convulsive properties of alcohol) did not
become tolerant
Conditioned Drug Tolerance : tolerance effects that are maximally expressed
only when a drug is administered in the situation in which it has previously been
oConditioned Compensatory Responses: physiological responses
opposite to the effects of a drug that are thought to be elicited by stimuli
that are regularly associated with experiencing the drug effects
oExteroceptive Stimuli: external, public stimuli
oInteroceptive Stimuli: internal, private stimuli  just thinking about a
drug can invoke conditioned compensatory responses
oBoth equally strong in conditioned drug tolerance
oDrug sensitization can also be situationally specific
15.3 Five Commonly Abused Drugs

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oNicotine: the major psychoactive ingredient of tobacco
Acts on nicotinic cholinergic receptors in the brain
oTar- 4,000 other chemicals in cigarettes
oGreatest addiction in the U.S
oEffects experienced by smokers & nonsmokers different  smokers feel
relaxed, nonsmokers feel nauseated, dizzy, vomit, etc.
oNicotine addiction has a high genetic component  heritability 65%
oSmoker’s Syndrome: the chest pain, labored breathing, wheezing,
coughing, and heightened susceptibility to infections of the respiratory
tract commonly observed in tobacco smokers
oSmokers highly susceptible to lung diseases & disorders. Also increases
risk of cancer all over the body & cardiovascular diseases
oSmokers more likely than non-smokers to experience panic attacks
oBuerger’s Disease: a condition in which blood vessels, especially those
supplying the legs, are constricted whenever nicotine enters the
bloodstream, the ultimate result being gangrene and amputation
oAffects people around smokers & unborn children
oTeratogen: a drug or other chemical that causes birth defects
oAlcohol molecules small & water + fat soluble  invade & attack all parts
of the body
oDepressant: a drug that depresses neural firing
At low doses however it can actually stimulate neural firing 
increases sociability
oAlcoholism has a strong genetic component  55% + genes associated with
oModerate dose  cognitive, perceptual, verbal & motor impairment
oHigh dose  unconsciousness, and risk of death via respiratory depression
if blood levels 0.5%
oIntoxication dilates blood vessels, increasing amount of heat lost from the
blood to the air (through surface of the skin – why skin turns red) and
leads to a decrease in body temperature
oDiuretic  increases production of urine by the kidneys
oHangovers are actually alcohol withdrawal
oFull-blown alcohol withdrawal goes through 3 stages  tremors, vomiting,
abdominal cramps. Phase 2  convulsive activity. Phase 3  Delirium
Tremens: hallucinations, delusions, agitation, confusion, hyperthermia,
rapid heart beat (tachycardia)
oKorsakoff’s Syndrome: a neuropsychological disorder that is common in
alcoholics (produces thiamine deficiency) and whose primary symptom is
severe memory loss
oBesides thiamine deficiency, also reduces flow of Ca+ ions into neurons,
interferes with second messengers inside neurons, disrupts GABAergic &
glutaminergic transmission, and triggers apoptosis
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