Download Ch 4 Drug Effects on the Brain

Chapter 4
Altered States of Consciousness:
Drugs and Their Effect on the Brain
and Behavior
The Limbic System
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The Limbic System is the specific area of the
brain, the reward system, that regulates
feelings of pleasure.
This region is activated by drugs of abuse.
How do drugs cause their effects on the brain
and behavior?
What do drugs actually do in that brain region?
Dopamine
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Drugs interfere with neurotransmission.
Drugs of abuse produce feelings of pleasure by
altering neurotransmission by neurons in the reward
system that release the neurotransmitter dopamine.
Drugs like alcohol, heroin, and nicotine excite the
dopamine-containing neurons so that they produce
more action potentials.
An increase in action potentials = an increase in the
amount of dopamine released = an increase in
feelings of pleasure
Adenosine
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THC (the main psychoactive ingredient in marijuana)
and morphine activate specific receptors
Caffeine, the mild stimulant found in coffee and soft
drinks, prevents a neurotransmitter called adenosine
from binding to its receptor
In normal situations, adenosine causes sedation; it is a
natural sleep-inducer
Instead of causing sedation, caffeine blocks adenosine
and leads to an increase in activity and arousal levels
Serotonin
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Serotonin, an important neurotransmitter, is
involved in a wide variety of functions,
including mood and basic survival functions
such as sleep and eating
LSD acts on some serotonin receptors while at
the same time blocking other serotonin
receptors
Removal of Neurotransmitters
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Synaptic transmission can also be altered by
removing the neurotransmitter from the
synapse
Cocaine and amphetamines work this waythey block the dopamine transporter
The result is fairly fast feeling of euphoria and
well-being
Conclusion
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Drugs of abuse share a common action: they
act on the brain’s reward system within the
system, they all (except for LSD) share the
ability to increase the levels of dopamine
This accounts for the rewarding (pleasurable)
effects of abused drugs
The dose changes the drug’s effect
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For drugs to exert an effect, a person must take
them into the body and absorb them into the
bloodstream
Some effects relate to the amount of the drug
taken
Once a drug enters the bloodstream, a response
can be measured
This point is known as the threshold
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As the amount of drug increases, so does the
response
At some point, the response to a given amount
of drug will reach a plateau, or a maximum
level
At high doses, the response to the drug
remains at the maximum level
Drugs Enter the body in Different
Ways
Routes of Administration
Inhalation
Ingestion
Injection
Snorting/Snuffing
Routes of Administration
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The dose is not the only factor that changes the
effects that a drug causes in the body
How a drug enters the body can lead to a
milder or more severe response
Inhalation
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A drug that is smoked reaches the brain very quickly
Inhaled drugs go directly from the lungs into the left
side of the heart where they enter the arterial
circulation that carries them to the brain
Marijuana and nicotine
The intensity of the effect may be slightly less
because some of the drug will be exhaled with the
rest of the smoke
Ingestion
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Drugs taken this way enter the body through the mouth
Stimulants, depressants
Drugs taken orally enter the bloodstream more slowly than by
other routes
The drugs pass through the digestive tract until they reach the
stomach and intestine where they are absorbed in to the
bloodstream
The body begins to metabolize the drugs before they can act
on the brain
Enzymes in the stomach, intestine, and liver begin breaking
down the drugs so that they can be cleared for the body
Injection
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A drug that is injected intravenously travels
quickly to the brain
The rapid passage of the drug brings a high
risk of overdose
Ex.: Heroin in the blood can reach lethal level
much faster than medical help could possibly
be obtained
Snorting or Snuffing
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Drug is taken in through the nose where it is
absorbed through the mucous membranes
lining the nasal passages
Drugs taken this way are less intense because
it takes the drug longer to get into the
bloodstream and because it does not enter the
blood as efficiently
Drug Abuse and Addiction
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Drug addiction is a complex brain disease
Reasons for using drugs:
Individuals make choices to begin using drugsperhaps to relieve a medical condition
Depressed individuals may use illicit drugs to selfmedicate
To feel pleasure
To escape the pressures of life
To alter one’s view of reality
When does drug abuse become drug
addiction?
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No one becomes addicted with the first use of
a drug
Drug abuse and drug addiction can be thought
of as points along a continuum
Any use of a mind-altering drug or the
inappropriate use of medication (prescription
or over-the-counter) is drug abuse
The point when drug abuse becomes drug
addiction is less clear
Drug Addiction
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Drug addiction is defined as the continued
compulsive use of drugs in spite of adverse health or
social consequences
Drug addicts have lost control of their drug use
Often become isolated from family or friends, have
difficulty at work or school, become involved with
crime and the criminal justice system
Their primary focus is continuing their drug habit
Drug Reactions
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Certain drugs, including opiates and alcohol,
cause a strong physical reaction in the body
when drug use stops
Heroin: a variety of physical withdrawal
symptoms- watery eyes, runny nose,
irritability, loss of appetite, diarrhea, shivering,
sweating, abdominal cramps, increased
sensitivity to pain, sleep problems
Cravings
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For most drugs, physical withdrawal
symptoms can usually be controlled effectively
with medications
However, stopping drug use is difficult
because of the changes the drugs have caused
in the brain
Once the drug stops, the abuser will have
cravings, or intense desire for the drugs
Cravings
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Arise form the brain’s need to maintain a state of
homeostasis that now includes the presence of drugs
Can occur at any stage of drug abuse or addiction,
even I the early experimentation phase of drug abuse
Have a physical basis in the brain- even seeing
images of drug paraphernalia can stimulate the
amygdala (part of the brain that controls memory) in
drug addicts
Changes in the brain
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A drug “high” lasts a short time, less than an
hour to 12 hours depending on the drug and
dose
Changes in the brain that result from continued
use can last a long time
Some changes disappear when drug use stops,
some disappear within a short time after drug
use stops, and other changes are potentially
permanent
Tolerance
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One of the first changes in the brain that
occurs in response to repeated drug use
Develops when a person needs increasing
doses of a drug to achieve the same ‘high’ or
“rush’ that previously resulted form a lower
dose of the drug
Long-term changes in the brain’s
neurons
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Alcohol, methamphetamine, and Ecstasy can
kill neurons
Unlike neurons in other parts of the body,
brain neurons cannot regenerate
Alcohol kills neurons in the parts of the brain
that helps create new memories. If those
neurons die, the capacity for learning
decreases.
High risk and drug abuse
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Functional and anatomical changes in the brain occur
with abuse- as does other health problems
Inhalant abuse= disruption of heart rhythms
Snorting cocaine= ulcerations in the mucous
membranes of the nose
Increased risk of contracting HIV or AIDS through
shared needles
Also- responsible for hepatitis B and C, tuberculosis,
motor vehicle accidents
Risk Factors for Addiction
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Weak coping skills
Early age for initial use
Genetic factors
Content in which a person uses the drug;
cancer patient may not become addicted to
morphine unlike a street addict- sick person
uses the drug not to get “high” but to ease their
pain and improve their quality of life