Psychiatric Disorders, Drug Action and Addiction

Question 1

How do drugs function?

Answer 1

They tend to imitate substances already present in our nervous system, especially those that affect transmission at the synapse

Question 2

Legal drugs

Answer 2

nicotine, alcohol, caffeine

Question 3

illegal drugs

Answer 3

cocaine, opiates, LSD

Question 4

Why do plants make drugs?

Answer 4

The plant produces chemicals to attract insects and to stop being eaten - our nervous systems are very similar to animals

Question 5

How do drugs work?

Answer 5

Drugs can affect transmission at the synapse in two ways: antagonist and agonist . Antagonists block the neurotransmitter, agonists increase the effects of neurotransmitters, or mimic the neurotransmitter. Some drugs can do both depending on the dose.

Question 6

When does a drug have a high affinity for a receptor?

Answer 6

If it binds to the receptor but may not activate the receptor

Question 7

When does a drug have a high efficacy for a receptor?

Answer 7

If it has a tendency to activate that receptor

Question 8

What do most drugs stimulate the release of?

Answer 8

The release of dopamine particularly in the nucleus accumbens (a small subcortical area rich in dopamine receptors) a part of the dopamine pathway

Question 9

Describe the pathway of dopamine after a drug has been taken

Answer 9

Drug => Sustained bursgs of dopamine (usually inhibitory) => inhibits GABA (inhibitory transmitter) => increases activity in nucleus accumbent

Question 10

What are stimulants - how do they work?

Answer 10

Amphetamine - stimulates dopamine synapses by increasing the release of dopamine from presynaptic terminal

Cocaine - blocks the reuptake of dopamine, thus prolonging effects

These are dopamine agonists and cause an accumulation of dopamine in the synaptic cleft

Question 11

What does it mean if there is more dopamine?

Answer 11

Widespread reduction in activity in most of the brain (apart from nucleus accumbens)

Question 12

What are opiates - how do they work?

Answer 12

Morphine and heroin increases relaxation and decreases sensitivity to pain due to mimicking endorphins . They attach to specific endorphin receptors which inhibits GABA to increase dopamine BUT opiates also block a hindbrain area that usually releases norepinephrine. A reduction in norepinephrine reduces memory storage and reduces stress.

Question 13

Why are dopamine highs followed by a crash?

Answer 13

Dopamine washes away and can’t be replaced quick enough

Question 14

What is Marijuana - how do they work?

Answer 14

Contains cannabinoids which bind to specific cannabinoid receptors which are widespread in the brain. Cannabinoids inhibits GABA release which increases perception of heightened awareness. Cannabinoid receptors are abundant in the hypothalamus which is related to feeding so we have an increased appetite.

Question 15

What is Botox - how do they work?

Answer 15

Botilinium toxins are usually found in decaying food but small doses are used to block the release of acetylcholine at neuromuscular junctions (paralysis) to reduce tremors and for cosmetic purposes.

Question 16

Is there a difference between wanting and liking?

Answer 16

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.

Question 17

How does the nucleus accumbens become more sensitised?

Answer 17

Becomes more sensitised to substances after repeated use. Increased ability to release dopamine in response to the substance which reduces sensitivity to other things

Question 18

Explain withdrawal

Answer 18

Cravings for the drug , relapse causes increased sensitivity and the user learns that the drug relieves distress associated with withdrawal and so craves it more during future withdrawal.

Question 19

How can we counter addiction?

Answer 19

Varenicline is a drug that acts as a partial nicotine receptor agonist. It binds and stimulates nicotine receptors. It has a very high affinity which means that are nicotine finds it very difficult to bind onto the receptor. So you get the effect of nicotine but if you then smoke you don’t get much more of a dopamine reward.

Question 20

What is the most common drug addiction ?

Answer 20

Alcoholism

Question 21

Define drug addiction

Answer 21

Continued use of a substance which interferes with your life

Question 22

What effect does alcohol have?

Answer 22

Inhibitory effects that relax the brain and communication - stimulates GABA activity and increases dopamine

Question 23

What is type 1 alcoholism?

Answer 23

Late onset (after 25), gradual onset, equal men and women and is less severe. Fewer relatives with alcoholism

Question 24

What is type 2 alcoholism?

Answer 24

Early onset (before 25), rapid onset, more men than women, severe and has more relatives with alcoholism.

Question 25

How might genes influence alcoholism?

Answer 25

1. coding for an increase in risk taking behaviour 2. coding for an increased stress response = more likely to relapse after quitting

Question 26

Do sons of alcoholic fathers show predispositions to alcoholism?

Answer 26

1. Show less than average intoxication - tolerance to alcohol 2. Show greater decrease of stress when drinking 3. Slightly smaller amygdala so maybe increased risk taking

Question 27

How prevalent is depression?

Answer 27

Twice as common in women than men , 5% adults have clinically significant depression

Question 28

Depression symptoms

Answer 28

Feelings of extreme sadness and helplessness, severe enough to interfere with daily life , and can last for weeks or months , feelings of absent happiness

Question 29

What causes depression?

Answer 29

There is a moderate degree of heritability to depression - but this is not specific to depression , relatives are more likely to suffer from anxiety, substance abuse, bulimia etc. Depression is more common along relatives of women with early onset of depression (before 30)

Question 30

Describe serotonin's role in depression

Answer 30

Low serotonin turnover associated with aggression and depression . So genes controlling serotonin have been implicated. In 2003, a particular gene that controlled the transportation of serotonin protein was discovered. There is a short version or a long version of the gene. If you have two short forms of the gene you are more likely to have depression in response to stressful events.

Question 31

What is postnatal depression? How prevalent is it ?

Answer 31

Depression after giving birth. 20% of women experience it but only 0.1% have long lasting. Evidence suggests that it runs in families but it also seems to be universal - perhaps a normal reaction to childbirth.

Question 32

What is unipolar disorder?

Answer 32

Varying between normality and depression

Question 33

What is bipolar disorder?

Answer 33

Varying between mania and depression

Question 34

What is SAD and some symptoms?

Answer 34

Seasonal Affective Disorder - Depression associated with one season . it is common near the poles where the nights are long and is less severe than major depression. Light therapy is used as treatment

Question 35

How do lithium salts treat bipolar?

Answer 35

The salts block the synthesis of arachinodonic acid which is associated with brain inflammation.

Question 36

What is schizophrenia ?

Answer 36

There is a division of emotional and intellectual experiences and behaviour. Some patients show inappropriate emotional expression that seems detached from current circumstances. Other symptoms include hallucinations, delusions and movement disorder.

Question 37

negative symptoms of SZ (absences)

Answer 37

poor social interaction , poor speech, absent facial expression

Question 38

positive symptoms of SZ (additions)

Answer 38

psychotic = delusions , hallucinations disorganised = odd emotional displays , thought disorder

Question 39

What is an issue with schizophrenia diagnosis

Answer 39

Not all patients exhibit all symptoms , difficult to pinpoint a specific brain area. But PET scans have found activation in thalamus , hippocampus and auditory cortex during hallucinations

Question 40

What demographics are affected by sz?

Answer 40

More common in men Earlier onset in men Present in 1% of the population Equal proportions in all cultures/ populations

Question 41

What is the neurodevelopmental hypothesis of SZ?

Answer 41

abnormalities in the development of the nervous system before birth and in the newborn . Could be caused by infections, poor nutrition or a complicated delivery. Could also be due to some slight brain abnormalities in parents.

Question 42

List brain abnormalities associated with schizophrenia

Answer 42

1. larger ventricles so less space for brain cells 2. Damaged prefrontal cortex (working memory) 3. Cell bodies are smaller in the hippocampus and prefrontal cortex (memory consolidation and working memory) 4. Less lateralisation than most people

Question 43

What is the dopamine hypothesis of sz

Answer 43

Excess activity of dopamine synapses - sz patients have twice as many dopamine receptors than other people however normals levels of dopamines are found when measured directly.

Question 44

What is the glutamate hypothesis of sz?

Answer 44

Deficient activity at glutamate synapses