8.1.2 biological explanation of addiction Flashcards
what is the assumption of the biological explanation of addiction?
the biological approach assumes addictive behaviours occur because of physiological changes when a substance is taken, a mode of action.
e.g. an increase in dopamine in the mesolimbic pathway
the effect of recreational drugs on the transmission process in the CNS
Drugs act by changing the way neurotransmitters operate in the brain, this is known as the mode of action. Most work on the dopamine system.
The brain contains a ‘reward pathway’ which when activated causes us to experience a pleasant and rewarding feelings, encouraging us to repeat the behaviour that activated the pathway and is a key component in learning- if we do something that is rewarded we are likely to do it again.
Being rewarded for specific behaviours has an adaptive function eg. enjoyment when eating high calorie foods ensures we store enough fat in our bodies, useful for survival in periods of food shortage.
Drugs hijack the reward system, producing pleasurable feelings without an adaptive function.
reward pathway in the brain
the brain contains a ‘reward pathway’ which when activated causes us to experience a pleasant and rewarding feelings, encouraging us to repeat the behaviour that activated the pathway and is a key component in learning- if we do something that is rewarded we are likely to do it again.
describe the mode of action of heroin
- heroin hydrolyses into morphine which binds to opioid receptors in the reward pathway (nucleus accumbens) and the pain pathway.
- this reduces GABA activity (which inhibits dopamine) leading to overactivity of dopaminergic neurotransmission in the reward pathways of the brain.
- this gives the same effect as having lots of endorphins released making the person feel euphoric and free from pain
behaviour is affected: euphoria, pain relief
describe the mode of action of nicotine
- stimulates acetylcholine receptors which are associated with thinking, learning and alertness.
- binds to acetylcholine receptors causing the neuron to fire more frequently.
- indirectly affects the dopamine pathway increasing the amount of and speed of transmission of dopamine by blocking the enzyme which breaks it down.
- beh. affected: alertness, quicker reaction times, inhibited appetite
describe the mode of action of alcohol
- depressant effect on the nervous system and social control areas of the brain.
- Inhibits neural transmission by increasing the action of GABA (an inhibitory neurotransmitter slows down messages such as noradrenaline which causes slower fight or flight responses) and reducing serotonin (associated with emotions = low mood).
- beh affected: relaxed, confident but can develop into extreme behaviour such as aggression, slowed speech, less control of motor skills, dehydration, low mood.
what are issues around drug use?
- tolerance
- withdrawal
- physical dependence
- psychological dependence
what is heroine?
Heroin is an opiate, which acts as a depressant and a pain killer in the CNS. It is produced from morphine, which comes from the opium poppy.
It is in powder form, often white, and is usually injected, sometimes smoked or snorted. There are many health risks associated with using needles to inject.
what is nicotine?
Nicotine comes from dried leaves and stems of the tobacco plant. It is a toxin and is extremely poisonous - it is also an insecticide
Cigarettes contain varying amounts of nicotine, from 15-25 mg per cigarette, so smoking doesn’t result in nicotine poisoning in its fullest form.
what is alcohol?
A drug consumed in liquid form
The type of alcohol in alcoholic drinks is called ethanol and is made from plant material: Grains, fruits or vegetables are processed and allowed to ferment for differing amounts of time, which affects the % of ethanol in the drink
bio exp of add - supporting evidence for the reward pathway
- Olds & Milner (1954) observed when the septal area in the reward pathway is stimulated with electricity it creates a rewarding effect, leading the repetition of behaviour (rats kept pressing the lever which stimulated their brain)
- T - Providing scientific, observable evidence for biological cause.
bio exp of add - supporting evidence for reward pathway - 2
- Bossert (2007) Rats will keep pressing a lever to receive heroin that goes directly to the nucleus accumbens (NA) in the mesolimbic dopa reward pathway through a needle. If the needle is placed near the NA rather than directly into it, the rat doesn’t self-administer the heroin.
- T - Providing scientific, observable evidence for the reward pathway.
bio exp of add - effective treatment
P: biological explanation has lead to effective treatments
- Methadone - opioid agonist binds to opioid receptors, reduces GABA, increases dopamine, resulting in a medically controlled high, removes the need to use heroin,
- Naltrexone for alcohol (reduces ‘buzz’) and
- Nicotine replacement therapy (‘clean’ nicotine) are also successful treatments (BUT DOESN’T WORK FOR ALL so may be a combination)
T - effective treatments suggest explanation is valid.
bio exp of add - contradicting evidence- environment plays a role
P - contradicting evidence shows that environment plays a role
E - Siegal (1982) rats overdosed on heroin when given doses in a new environment to the one they had been conditioned in. Shows cues in the environment can ‘prepare’ the body for substance and reduce overdose.
T - Shows addiction is classically conditioned, not just biological.
bio exp of add - contradicting theories explain different stages of addiction better than biological
- SLT explains how people start using, first experience of smoking can be unpleasant (nausea) but people imitate they see role models enjoying it (vicarious reinforcement)
- Operant conditioning can explain why people continue to take drugs despite knowing it is physically detrimental to their health (negative reinforcement - avoiding withdrawal symptoms).
T: Bio isn’t a full explanation on it’s own
