Drugs Flashcards
What are drugs?
Tend to imitate substances already present in our nervous system particularly those that affect transmission at the synapse
What are types of drugs?
Illegal
- cocaine
- opiates
- LSD
Legal
- nicotine
- alcohol
- caffeine
How do drugs work?
Antagonist - block neurotransmitter
Agonist - increase effects of neurotransmitter, or mimic the neurotransmitter
Difference between affinity and efficacy?
Affinity
- high affinity for a receptor if it binds to that receptor
- may not activate the receptor
Efficacy
- high efficacy if it has a tendency to activate that receptor
How do drugs work?
Most stimulate the release of dopamine
- particularly in the nucleus accumbens
More dopamine = widespread reduction in activity in most of the brain (apart from nucleus accumbens)
How do stimulants work?
Amphetamine
- stimulates dopamine synapses by increasing the release of dopamine from presynaptic terminal
Cocaine
- blocks the reuptake of dopamine, thus prolonging effects
What are opiates?
Morphine
Heroin
- increase relaxation, decrease sensitivity to pain
Mimic endorphins
So opiates attach to specific endorphin receptors
Inhibits GABA so increases dopamine
Also blocks a hindbrain area that usually releases norepinepherine - reduction in this reduces memory storage and reduces stress
How does marijuana work?
Contains cannobinoids
Binds to specific cannabinoid receptors
- Inhibits GABA release (increase in dopamine release in nucleus accumbens) = perception of heightened awareness
- Cannabinoid receptors abundant in hypothalamus (feeding) = increase appetite
How does Botox work?
Deadly neurotoxin released by bacteria found in decaying food
Antagonist
Blocks the release of acetylcholine at neuromuscular junctions - paralysis
In small doses can be used to reduce muscle tremors and cosmetically
How do drugs become addictive?
Sensitisation of the nucleus accumbens
- becomes more sensitive to substances after repeated use
- increased ability to releases dopamine in response to the substance
- reduced sensitivity to other things
Withdrawal
- cravings for the drug
- relapse causes increased sensitivity
- user learns that the drug relives distress associated with withdrawal, and so craves it more during future withdrawal
Can we counter addiction?
Varenicline - treatment for smoking = partial nicotine receptor agonist
Whats addiction?
Continued use of a substance when it interferes with you life
What are the types of alcoholism?
Type 1
- late onset (after 25)
- gradual onset
- equal men and women
- less severe
- few relative with alcoholism
Type 2
- early onset (before 25)
- rapid onset
- more men that women
- Severe
- more relatives with alcoholism
Is alcoholism genetic
Coding for an increase in risk taking behaviour
Coding for an increased stress response = more likely to relapse after quitting
Do sons of alcoholic fathers show predisposition to alcoholism
- show less than average intoxication - tolerance
- show greater decrease of stress when drinking
- slightly smaller amygdala
Whats depression?
Feelings of extreme sadness and helplessness
Severe enough to interfere with daily life, and can last for works or months rather than days
Twice as common in women than men
What causes depression?
Moderate degree of heritability to depression
More common among relatives of women with early onset depression
Low serotonin associated with aggression and depression
What’s bipolar disorder?
Varying between mania and depression
- Increased metabolism during manic phases
- Possible genetic component - more common in monozygotic twins, but this seems to increase risk rather than cause
- treated with lithium salts
What’s SAD?
Seasonal affective disorder
Depression associated with one season
Less serve than major depression
Light treatment as therapy
Whats schizophrenia?
Positive symptoms - additions
- psychotic - delusions and hallucinations
- disorganised - odd emotional displays and though disorder
Negative symptoms - absences
- poor social interaction
- poor speech
- absent facial expression
Not all patients exhibit symptoms
Difficult to diagnose, often confused with other conditions
How does schizophrenia develop?
Abnormalities in the development of the NS before birth and in the newborn
Infections, poor nutrition, complicated delivery
What are some brain abnormalities in schizophrenia?
Ventricles (fluid filled spaces in the brain) larger, so less space for brain cells
Prefrontal cortex damage (working memory impaired)
Cell bodies are smaller in the hippocampus and prefrontal cortex
Less lateralisation than most people
What happens at the synapses for people with schizophrenia?
Excess activity of dopamine synapses
- They have twice as many dopamine receptors than other people - but normal levels found
Deficient activity at glutamate synapses
- dopamine inhibits glutamate release, and glutamate activates neurons that inhibits dopamine
