schizophrenia: bio explanation - NTs

Question 1

what is a neurotransmitter?

Answer 1

• the body’s chemical messengers
• molecules used by nervous system to transmit messages between the neurons

Question 2

what is dopamine?

Answer 2

• neurotransmitter made in your brain
• plays as a ’reward centre’/sense of pleasure

Question 3

what is it meant by hyperdopaminergia?

Answer 3

• overactive
• having too much dopamine activity

Question 4

what is hypodopaminergia?

Answer 4

• underactive
• having too little dopamine activity

Question 5

what is a dopamine agonist?

Answer 5

• drugs that activate certain types of cells in your brain

Question 6

what is the mesocortical pathway?

Answer 6

• neural connection between ventral tegmental area and the frontal cortex

Question 7

what is the mesolimbic pathway?

Answer 7

• begins in the ventral tegmental area and connects nucleus accumbens, amygdala, hippocampus and prefrontal cortex

Question 8

what is glutamate?

Answer 8

• most abundant excitatory neurotransmitter in your brain and central nervous system

Question 9

what is antagonist?

Answer 9

• chemical/medication that attaches to brain receptors and inhibits an antagonist from reacting

Question 10

what is amphetamine?

Answer 10

• stimulant drugs that speed up messages between brain and body

Question 11

what is the dopamine hypothesis?

Answer 11

• states that the brain of schizophrenic patients produces more dopamine than the brain of a “normal person
• through research, it is now thought that schizophrenics have an abnormally high number of d2 receptors

Question 12

how can dopamine be linked to schizophrenia?

Answer 12

• dopamine (or da and specifically d2 receptors), a neurotransmitter has been linked to schizophrenia
• dopamine is present in higher levels in the brain and this leads to symptoms of schizophrenia
• presence of excess number of dopamine receptors at the synapses in the brain contributes to the illness
• if there’s an increase in the mesolimbic pathway, then positive symptoms are presented and if there is a decrease in the mesocortical pathway contributes to negative symptoms
• neurons that use dopamine fire too often and transmit too many messages or too often
• certain d2 receptors are known to play a key role in guiding attention
• lowering da activity helps remove the symptoms of schizophrenia

Question 13

what are the role of drugs linked to schizophrenia?

Answer 13

• amphetamines (agonists) lead to increase in da levels
• large quantities lead to delusions and hallucinations
• if drugs are given to schizophrenic patients their symptoms get worse

Question 14

what is the glutamate hypothesis?

Answer 14

• theory that first emerged in the 1980s, but which has gained wider support, traces the origins of schizophrenia symptoms to the neurotransmitter glutamate rather than dopamine
• glutamate is the major “excitatory” neurotransmitter in the brain, which means that it helps to activate neurons and other brain cells
• theory that decreased activity of the excitatory neurotransmitter glutamate is responsible for the clinical expression of schizophrenia
• developed by overseeing symptoms induced by phencyclidine that act as antagonists at nmda receptors
• glutamate is thought to control the amount of dopamine released by the brain, and normally seems to lower levels of dopamine

Question 15

evidence for neurotransmitters as explanation: Falkai et al 1988

Answer 15

• autopsies have found people with schizophrenia have larger than usual number of dopamine receptors
• increase of da in brain structures and receptor density (left amygdala and caudate nucleus putamen)
• concluded that da production is abnormal for schizophrenia

Question 16

evidence for neurotransmitters as explanation: Lindstroem et al 1999

Answer 16

• radioactively labelled chemical called L-DOPA, used by the brain to produce dopamine
• they ** administered the l-dopa to ten untreated patients** with schizophrenia and a control group of ten people with no diagnosis
• using pet scans, they were able to trace what happened to the l-dopa
• l-dopa was taken up more quickly in patients with schizophrenia, suggesting they were producing more dopamine than the control group

Question 17

evidence for neurotransmitters as explanation: Snyder 1985

Answer 17

• found chlorpromazine acts as an antagonist at many dopamine receptors, especially. d1 and d2, and has antipsychotic effect
• haloperidol is a dopamine antagonist with a narrower range of biochemical effects yet is more effective in reducing schizophrenic symptoms
• findings suggest that excess activity on specific but not all dopamine receptors is implicated in the development of symptoms

Question 18

evidence for neurotransmitters as explanation: haloperidol

Answer 18

• dopamine antagonists that bond to d2 receptors such as haloperidol, can successfully reduce positive symptoms

Question 19

evidence for neurotransmitters as explanation: Tenn et al 2003

Answer 19

• found that rats given 9 amohetamine injections over 3 weeks showed various schizophrenia like symptoms
• dopamine antagonists (drugs that dopamine d1 receptors) were successful in reversing these effects

Question 20

strengths: supporting evidence

Answer 20

• Lindstroem et al 1999 found **schizophrenics used L-DOPA faster than the control group, suggesting they were producing more dopamine at a quicker rate, and the **excess dopamine can explain how schizophrenia is caused

Question 21

weaknesses: opposing evidence

Answer 21

• PET scans show that blocking receptors does not always remove symptoms. PET scans have suggested that drugs that block dopamine do not reduce the symptoms of schizophrenia, in particular those who had schizophrenia for 10 years
• Depatie + Lal 2001 found that giving people drugs that increase production of dopamine does not create symptoms of schizophrenia as would be expected if excess dopamine caused it, so it is **not the only explanation of the causes of schizophrenia (can be different things as well)

Question 22

weaknesses: different things

Answer 22

• anti-psychotic drugs block dopamine receptors very quickly but it takes a few days for the symptoms of schizophrenia to be reduced so there may be other factors involved in developing schizophrenia, not just neurotransmitters so it does not fully explain the development of schizophrenia
• Wim Veling et al 2008 shows that Moroccan immigrants were more likely to be diagnosed with schizophrenia than Turkish immigrants. This correlated to the amount of actual and perceived discrimination faced by each group. this suggests that environmental factors such as social stress may interact with internal neurochemistry making some people more prone to psychosis
• neurotransmitter explanation of schizophrenia can be said to be incomplete as it ignores other possible causes of schizophrenia such as early childhood experiences or cognitive processes, and it is not the only explanation. researchers at Liverpool University in 2012 found that childhood trauma makes you three times more likely to develop schizophrenia, suggesting that there is strong relationship between the environment and the development of schizophrenia, and it is not just due to neurotransmitters

Question 23

strengths: other things

Answer 23

• amphetamines produce symptoms similar to those of excess dopamine. this psychosis is called ’amphetamine psychosis’ and the symptoms are similar to those positive symptoms of schizophrenia

Question 24

weaknesses: other things

Answer 24

• using pet scanning to obtain evidence about neurotransmitter functioning could affect validity. when undergoing scanning humans might feel under pressure and are likely to respond differently from normal. this means that any findings gathered might not be accurate