drugs Flashcards
What is a Drug?
A drug is any substance taken into the body that modifies or affects chemical reactions in the body
Some drugs are medicinal drugs that are used to treat the symptoms or causes of a disease – for example, antibiotics
Antibiotics
Antibiotics are chemical substances made by certain fungi or bacteria that affect the working of bacterial cells, either by disrupting their structure or function or by preventing them from reproducing
Antibiotics are effective against bacteria but not against viruses
Some bacteria that cause disease have become resistant to antibiotics and this reduces the effectiveness of prescribed antibiotics when someone has a bacterial infection, as it might be caused by a type of bacteria that is resistant to that particular antibiotic
Why don’t Antibiotics Affect Viruses?
Viruses cannot be treated with antibiotics
This is because antibiotics work by disrupting cell functions such as respiration, or breaking down the structure of the cell in some way
However, viruses do not carry out any cell functions and do not have cell walls, cell membranes or any cell organelles
Therefore the action of antibiotics do not affect them
Antibiotic Resistance
Since the first antibiotic was discovered in 1928, many more have been discovered and developed
Antibiotics were and are widely overused
Commonly prescribed antibiotics are becoming less effective due to a number of reasons:
overuse and being prescribed when not really necessary
patients failing to complete the fully prescribed course by a doctor
large scale use of antibiotics in farming to prevent disease when livestock are kept in close quarters, even when animals are not actually sick
This has lead to the effectiveness of antibiotics being reduced, and the incidence of antibiotic resistance increasing
These bacteria are commonly known as superbugs and the most common is MRSA
Ways individuals can help prevent the incidence of antibiotic resistance increasing include:
only taking antibiotics when absolutely essential
when prescribed a course of antibiotics, ensure that the entire course is completed even if you feel better after a few days
Alcohol
Wines, beers and spirits contain an alcohol called ethanol
It is a depressant drug – it slows down signals in the nerves and brain
Because alcohol increases reaction times there are legal limits for drinking and driving in many countries
The liver removes alcohol from the bloodstream
It has enzymes that break down alcohol but the products of the reactions involved are toxic and, over time, the liver can be irreparably damaged
In many people, alcohol can be a very addictive drug
Heroin
Heroin is a powerful depressant drug
It reduces pain and slows down breathing
It is highly addictive and users quickly develop a tolerance for it, meaning they need larger and larger amounts in order to feel the same effects – this increases the risk of accidentally overdosing, which can cause death
This means they need more money to pay for the increased amounts of the drug they are taking; as the drug makes them less able to cope with everyday life and maintain a job, they may turn to crime in order to get the money they need
As it is so addictive, if a user stops taking heroin they suffer from significant withdrawal symptoms, such as nausea, muscle cramps, sweating, anxiety and difficulty sleeping
Heroin can be taken into the body in different ways; one of the most common is injecting with a syringe
As syringe needles cost money, heroin addicts may share needles which increases the risk of transmission of blood-borne infections such as HIV
Extended Only
How does Heroin Affect the Nervous System?
In the brain there are many different chemical neurotransmitters that transfer nerve impulses across synapses
The neurotransmitters diffuse across the synapse and fit into receptor molecules on the postsynaptic membrane
One group of neurotransmitters is called endorphins which help to reduce sensations of pain, affect mood and reduce sensations of hunger and thirst
When it enters the brain, heroin is metabolised to morphine
Morphine molecules fit into some of the endorphin receptors and this is why taking heroin makes users feel so good
Taking heroin can reduce the production of natural endorphins and other neurotransmitters, which is why repeated use leads to the need for greater and greater amounts in order to get the same feelings
Tobacco & Disease
Smoking causes chronic obstructive lung disease, coronary heart disease and increased risks of several different types of cancer, including lung cancer
Chemicals in cigarettes include:
Tar – a carcinogen (a substance that causes cancer))
Nicotine – an addictive substance which also narrows blood vessels
Carbon monoxide – reduces the oxygen-carrying capacity of the blood
Effects on the Gas Exchange System
Tar
Effects on the Gas Exchange System
Tar
Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs
It also contributes to COPD, which occurs when chronic bronchitis and emphysema, two different diseases which are frequently linked to smoking, occur together
Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus
It destroys cilia, inhibiting the cleaning of the airways, and mucus (containing dirt, bacteria and viruses) builds up, blocking the smallest bronchioles
A smoker’s cough is the attempt to move the mucus but it damages the epithelia resulting in scar tissue, which narrows the airways and makes breathing difficult
Emphysema develops as a result of frequent infection, meaning phagocytes are attracted to the lungs where they release elastase – an enzyme that breaks down the elastin in the alveoli walls, to enable them to reach the surface where the bacteria are
Without adequate elastin, the alveoli cannot stretch, so they recoil and many burst
Large air spaces appear, reducing the surface area for gas exchange and making sufferers breathe more rapidly
As it progresses, patients become breathless and wheezy – they may need a constant supply of oxygen to stay alive
Carbon monoxide
Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen
This puts more strain on the breathing system as breathing frequency and depth need to increase in order to get the same amount of oxygen into the blood
It also puts more strain on the circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes
Nicotine
Nicotine narrows blood vessels so will put more strain on the circulatory system and increase blood pressure
Narrow blood vessels are more likely to become clogged with fat, including cholesterol – if this happens in the coronary artery, this causes coronary heart disease
This means the heart muscle cells do not get sufficient oxygen and so less aerobic respiration takes place
To compensate the cells respire anaerobically, producing lactic acid which cannot be removed (due to lack of blood supply)
This creates a low pH environment in the cells causing enzymes to denature and eventually heart muscle cells will die
If enough die this can cause a heart attack
Smoking & Lung Cancer: Is There a Link?
Note that, as the general trend for the number of adult smokers decreases, so does the trend for lung cancer rates a few years later (as cancer takes some time to develop)
The trend in the rate of developing lung cancer for women has been increasing, while in men it is decreasing
This is because the numbers of female smokers – unlike men – continued to increase in the 1950s and 1960s before starting to fall
As cancer takes some years to develop, a fall in female rates of lung cancer is likely to occur later
Performance-Enhancing Drugs in Sport
Hormones produced in the body help to control the way it develops and responds to changes
Some people take additional hormones to increase these effects
This is most commonly done to improve sporting performance
Testosterone is the hormone produced in the testes that affects the development of male secondary sexual characteristics
It is one of a group of hormones known as steroids which stimulate anabolic reactions to occur in the body (meaning the synthesis of large molecules from smaller ones), so it is known as an anabolic steroid
One of the effects of testosterone is to cause more proteins to be made in muscles so that muscles become larger and stronger
Taking anabolic steroids therefore increases muscle mass, helps athletes train harder and for longer periods of time, and can increase aggression which can give an edge when competing
The use of anabolic steroids in sports is banned as it gives an unfair advantage and also has serious side effects, including:
increases risk of heart disease
increases risk of liver damage
increases risk of kidney damage
affect the menstrual cycle in women
decreases the ability of the immune system to destroy pathogens
