Psychiatric Disorders, Drug Action and Addiction Flashcards
What are drugs?
Tend to imitate substances already present in our nervous system, particularly those that affect transmission at the synapse
Why do drugs tend to imitate substances already present in our nervous system
- Mainly from plants (e.g. nicotine - tobacco plant)
- The plant produces these chemicals to attract insects, to stop being eaten etc., or for own processes
Name the 2 ways that drugs affect transmission at the synapsy
- Antagonist
- Agonist
Describe an Antagonistic drug
- Inhibit transmission at the synapse
- Block neurotransmitter
Describe an Agonistic drug
- Facilitate transmission at the synapse
- Increase effects of neurotransmitter, or mimic the neurotransmitter
How much affinity do drugs have?
Drug has a high affinity for a receptor if it binds to that receptor
How much efficacy do drugs have?
Drug has a high efficacy if it has a tendency to activate that receptor
What do most drugs stimulate?
Most drugs stimulate the release of dopamine
Particularly in the nucleus accumbens
Define the nucleus accumbens
small subcortical area rich in dopamine receptors
How do drugs work?
(diagram)
Name 2 stimulants?
> Amphetamine (Speed)
> Cocaine
What does Speed do?
Stimulates dopamine synapses by increasing the release of dopamine from presynaptic terminal
What does Cocaine do?
Blocks the reuptake of dopamine, thus prolonging effects
Why are stimulants followed by a crash?
Dopamine washes away, can’t be replaced quick enough
Name 2 Opiates
> Morphine
> Heroine
How do Opiates work?
- Inhibits GABA, so increases dopamine
- Also blocks a hindbrain area that usually releases norepinepherine
What does Marijuana consist of
> Contains cannabinoids
> Bind to specific cannabinoid receptors (widespread in the brain)
What does marijuana do to the brain?
- Inhibit GABA release (increase in dopamine release in nucleus accumbens) = perception of heightened awareness
- Cannabinoid receptors abundant in hypothalamus (feeding!) = increased appetite
How do the functioning of drugs relate to addiction?
- Many addictive substances increase activity at dopamine synapses
- Particularly in the nucleus accumbens
What is the difference between liking and wanting drugs?
Drugs increase ‘need’ for the substance even if the experience is not pleasant
- Mice with increased dopamine production showed no more pleasure in food, but made more effort to get it
- Mice with decreased dopamine production made less effort to get food, but ate just as much.
(Kalat)
How does the sensitization of the nucleus accumbens relate to drugs?
– Becomes more sensitive to substances after repeated use
– Increased ability to release dopamine in response to the substance
– Reduced sensitivity to other things
How does the withdrawal symptoms of drugs relate to addiction
– Cravings for the drug
– Relapse causes increased sensitivity
– User learns that the drug relieves distress associated with withdrawal, and so craves it more during future withdrawal
Name something that can counter addiction
Varenicline (CHAMPIX), treatment for smoking
What is the functio of valenicline
Partial nicotine receptor agonist.
Stimulates and binds the nicotine agonist
How does alcohol affect the brain?
Alcohol acts on many areas of the brain – mainly inhibitory effects
State the 2 types of alcoholism
Type 1 and 2
Describe Type 1 alcoholism
Late onset (after 25)
Gradual onset
Equal men and women
Less severe
Describe Type 2 alcoholism
Early onset (before 25)
Rapid onset
More men than women
Severe
Can Genes influence alcoholism?
Genes might influence alcoholism in many ways (not as simple as ‘a gene for alcoholism’
Give an example of how genes may influence alcoholism
- 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 predispositions to alcoholism?
- Show less than average intoxication – tolerance to alcohol
- Show greater decrease of stress when drinking
- Slightly smaller amygdala (therefore increased risk taking?)
Define Clinical/Major Depression
Feelings of extreme sadness and helplessness
Severe enough to interfere with daily life, and can last for weeks or months rather than days
Can Serotonin be a cause of depression?
low serotonin turnover associated with aggression AND depression
So genes controlling serotonin have been implicated
What study supports the suggestion that serotonin might be a cause of depression
Caspi et al. (2003)
What did Caspi et al. (2003) find?
- gene controlling the serotonin transporter protein
- this protein controls the ability of an axon to reabsorb serotonin (recycling)
What types of depression genes are there, and how do they affect a person’s depression
Short and long types
If you have two short forms of the gene = more likely to have depression in response to stressful events
Define Postnatal Depression (postpartum)
Depression after giving birth
Define Unipolar Disorder
Varying between normality and depression
Define Bipolar Disorder
Varying between mania and depression (formally manic depression)
How is Bipolar disorder treated?
Treated with lithium salts - Block synthesis of arachidonic acid (associated with brain inflammation)
What does SAD stand for?
Seasonal Affective Disorder (SAD)
What is Seasonal Affective Disorder?
- depression associated with one season (usually winter)
- common near the poles where the nights are long (circadian rhythms!)
- less severe than major depression
- light therapy as treatment (affects biological clock)
Define Schizophrenia
‘Split Mind’
the SPLIT refers to a division between emotional and intellectual experiences and behaviour
What are the symptoms of schizophrenia
Some patients show inappropriate emotional expression that seems detached from current circumstances
Hallucinations, delusions, thought disorder, movement disorder
Can be acute or chronic
Name the types of symptoms in schizophrenia
> Positive Symptoms (additions)
> Negative Symptoms (absences)
Name the two types of positive symptoms in schizophrenia
Psychotic - delusions and halucinations
Disorganised - odd emotional and thought disorder
Name the 3 types of negative symptoms of schizophrenia
> Poor social interaction
> Poor speech
> absent facial expression
Name the problem with schizophrenia
Not all patients exhibit all symptoms
- difficult to diagnose, often confused with other conditions
- difficult to pinpoint a specific brain area
What demographic data is there about schizophrenia
More common in men Earlier onset in men
Present in 1% of the population
Equal proportions in all cultures/populations
What did Kalat find?
It is more likely to develop in closely related individuals (i.e. MZ twins or a child of two schizophrenic parents)
What did Kalat’s findings suggest?
May not be one gene, but instead a combination of genes interacting with the environment
Name 2 ways which are theorised to be the cause of development of schizophrenia?
Neurodevelopmental hypothesis
Brain abnormalities
Define Neurodevelopmental hypothesis
abnormalities in the development of the nervous system before birth (prenatal) and in the newborn
Explain the Neurodevelopmental hypothesis
- Infections, poor nutrition, complicated delivery BUT, only increases chance of schizophrenia slightly
- Some slight brain abnormalities in patients, suggesting subtle changes during development
Name Brain Abnormalities of Schizophrenic
- Ventricles larger, so less space for brain cells
- Prefrontal cortex damaged
- Cell bodies are smaller in the hippocampus and prefrontal cortex
- Less lateralisation than most people
