Download biology - effects of drugs - C7

Chapter 7 section 4
Effects of Drugs
* Drug is a substance, natural or artificial, that alters the
function of the body.
Q: What types of substances are considered drugs?
1-prescription medications, such as antibiotics, pain medications.
2-over-the-counter substances, such as aspirin, cold medications.
3-illegal substances, such as tobacco and alcohol.
4-Caffeine, such as caffeine, soda, chocolate and tea.
Q: Why are these different substances all considered
drugs?
They all affect cells or body functions in certain ways.
Q: How Drugs Work?
Drugs that affect the nervous system work in one or more of the following ways:
• A drug can cause an increase in the amount of a neurotransmitter that is
released into a synapse.
• A drug can block a receptor site on a dendrite, preventing a neurotransmitter
from binding.
• A drug can prevent a neurotransmitter from leaving a synapse.
• A drug can imitate a neurotransmitter.
*Many drugs that affect the nervous system influence the level of a
neurotransmitter called dopamine.
*Dopamine is a neurotransmitter found in the brain.
dopa–refers to an amino acid and amine refers to a derivative of ammonia.
*The functions of Dopamine:
1-the control of body movements.
2-feelings of pleasure or reward.
Q: How the dopamine work?
1-Dopamine crosses the gap from one neuron and binds to receiver sites, or
receptors, on the membrane of another neuron.
2-Dopamine transmit the impulse from one neuron to the next neuron.
3-Dopamine normally is removed from a synapse by being reabsorbed by the
neuron that released it.
Q: How the dopamine removed from a synapse?
by being reabsorbed by the neuron that released it.
Are over-the-counter drugs safer than prescription drugs?
No. Because Any use of a drug for reasons other than legitimate medical
purposes, whether deliberate or unintentional, can be considered abuse of that
drug and both over-the-counter drugs and prescription drugs can have serious
side effects and can even result in death.
*Classes of Commonly Abused Drugs
‫العقاقير الذي يساء استخدامها بشكل شائع‬
1-Stimulants ‫المنشطات او المنبهات‬
Drugs that increase alertness and physical activity.
A-Nicotine
*Nicotine in cigarette and cigar smoke increases the amount of dopamine released
into a synapse.
*Nicotine also constricts blood vessels, raising blood pressure and causing the
heart to work harder than normal.
*Cigarette smoking has been linked to about 90 percent of all lung cancer cases.
B- Caffeine
*The most commonly stimulant used, and often abused.
*Caffeine is found in coffee, tea, some soft drinks, and even some foods such as
chocolate.
Q: How the caffeine works?
1-Caffeine works by binding to adenosine receptors on neurons in the brain.
*Adenosine slows down neural activity, causing drowsiness ‫النعاس‬.
2-When caffeine binds to these receptors, it has the opposite effect. It makes
users feel awake and alert.
*Caffeine also temporarily raises epinephrine (adrenaline) levels in the body,
giving a quick burst of energy that soon wears off ‫تتالشى‬.
2- Depressants ‫المثبطات‬
*Drugs that tend to slow down the central nervous system.
Q: What are the effects of depressants?
1-Depressants can lower blood pressure, interrupt breathing, and slow the heart
rate.
2-Depressants can relieve anxiety ‫تخفيف القلق‬, but they also can cause the noticeable
effect of sedation ‫تأثير ملحوظ من التخدير‬.
A- Alcohol ‫الكحول‬
*Is a depressant.
*It affects the central nervous system and one of the most widely abused drugs in
the world today.
*Alcohol is known to affect at least four different neurotransmitters, resulting in a
feeling of relaxation and sluggishness.
*Short-term alcohol use impairs judgment‫يضعف الحكم‬, coordination, and reaction
time.
*Long-term effects of alcohol abuse include a reduction in brain mass, liver
damage, stomach and intestinal ulcers, and high blood pressure.
*Consumption of alcohol during pregnancy is the cause of fetal alcohol syndrome,
which can result in damage to a baby’s brain and nervous system.
B-Inhalants ‫المستنشقات‬
*Inhalants are chemical fumes ‫ابخره كيميائية‬that have an influence on the nervous
system.
*Exposure to inhalants might be accidental as a result of poor ventilation.
Q: How the Inhalants work?
by acting as a depressant on the central nervous system.
*Inhalants might produce a short-term effect of intoxication ‫التسمم‬, as well as
nausea ‫ الغثيان‬and vomiting.
*Long-term exposure to inhalants can cause memory loss, hearing loss, vision
problems, peripheral nerve damage, and brain damage.
C- Other drugs (illegal drugs) ‫العقاقير غير القانونية‬
*The use of illegal drugs has short-term and long-term effects.
*The effects of illegal drugs:
1-Abuse might result in disturbances in heart rhythm, heart attacks, chest pain,
respiratory failure, strokes, seizures, headaches, abdominal pain, and nausea.
2-Abuse might result in rapid heart rate, irregular heartbeat, increased blood
pressure, and irreversible, stroke-producing damage to small blood vessels in the
brain.
3-Elevated body temperature, called hyperthermia, and convulsions can also
occur.
Tolerance and Addiction
Tolerance occurs when a person needs more and more of the same drug to get
the same effect.
why the dosage needs to increase?
because the body becomes less responsive to the drug.
*Drug tolerance can lead to addiction.
Addiction: The psychological and physiological dependence on a drug.
*Current research suggests that the neurotransmitter dopamine is involved with
most types of physiological addiction.
*A person addicted to drugs derives pleasure from increased levels of dopamine
and builds up a tolerance to the drug. As a result, the person takes more of the
drug. When people who are addicted try to quit, the levels of dopamine decrease,
making it difficult to resist going back to the drug.
*Addictions can also be psychological. An individual with a psychological
dependence on a drug has a strong desire to use the drug for emotional reasons.
*Both physiological and psychological dependence can affect emotional and
physical health. Both types are strong, making it difficult to quit a drug.
Treatment
People who are either psychologically or physiologically dependent on a drug
experience serious withdrawal symptom without it.
It is very difficult for dependent users to quit on their own. They might be able to
quit for short periods of time, but they are likely to use the drug again.
Medical supervision is necessary when people who are psychologically and
physiologically dependent on a drug try to quit.
The best way to avoid an addiction is never to use drugs in the first place, even
when pressured to use them.
Physicians, nurses, counselors, clergy, and social workers are trained to direct
people to the resources they need to get help.
Teacher: Mahmoud Owais.