Biological Explanations - Biochemical Factors Flashcards
How do genetic factors operate?
Through brain mechanisms, and either biochemistry or neuroanatomy could provide vehicles for genetic transmission.
The brain is composed of millions of neurone which make up the main anatomical structures of the brain.
What are neurotransmitters?
Chemical messengers that transmit impulses across the synapse between neurones.
The most promising line of research in neurotransmitters has focussed on dopamine.
What is the dopamine hypothesis?
Schizophrenia results from an excess of dopamine activity at certain synaptic sites.
This could be caused by the release of excess dopamine, an excess of dopamine receptors or over-sensitivity of dopamine receptors.
Phenothiazines to support dopamine hypothesis:
(Drugs that act by blocking dopamine at the synapse)
Are effective in alleviating some of the major symptoms of schizophrenia.
Clozapine drug as a support for the dopamine hypothesis:
- a drug that is one of the most clinically effective treatments for schizophrenia
- has been shown via PET scans to occupy dopamine receptor sites to the same extent as other neuroleptic drugs (used mainly to treat patients with psychotic conditions)
L-dopa drug to support dopamine hypothesis:
(A drug used to treat Parkinson’s disease)
Acts by increasing dopamine levels and it can produce symptoms of schizophrenia in previously unaffected individuals.
Amphetamine drug as support for the dopamine hypothesis:
Amphetamines can produce psychotic symptoms like those seen in schizophrenia and a drug that reduced these symptoms, reserpine, is know to reduce the activity of dopamine.
So researchers realised if amphetamines induce psychosis by increasing dopamine activity and antipsychotic medication reduces dopamine activity, then an increase in dopamine must be responsible for the psychotic symptoms in schizophrenia.
What have dopamine receptors in the brain shown us about schizophrenia?
- when dopamine is released it needs a specific receptor on the receiving neurone for it to have an effect.
- it was found that in the prefrontal cortex there were only D1 receptors so it cannot only be D2 receptors involved in schizophrenia, as initially thought
What is the activity of dopamine like in the prefrontal cortex?
- activity of dopamine in this region is low rather than high.
- this suggests that reduced dopamine in frontal parts of the brain might be causing the negative symptoms whilst increased dopamine in other regions are causing the positive symptoms.
What have post-mortems shown us?
-that people with schizophrenia have an increased level of dopamine RECEPTORS in parts of the brain (Seeman found an increase in dopamine receptors density of between 60 and 110% compared to controls)
Evaluation of post-mortems:
- examinations have usually been on people who have taken neuroleptic drugs for years, which makes it difficult to tell whether increased dopamine levels are the result of drug therapy rather than the cause of schizophrenia
- it is likely that dopamine is implicated in causing schizophrenia but it’s an oversimplification on its own
Findings on glutamate as a neurotransmitter:
- if glutamate activity is reduced it paves the way for the increase in dopamine levels
- this link between glutamate receptor malfunction and schizophrenia can also account for the timing of the onset of schizophrenia
- there are many developmental changes to the brain during adolescence and it’s shown that disruption to normal glutamate functioning leads to many deficits seen in schizophrenia.
AO3 phenothiazines:
Do not work for everyone and they tend only to alleviate the positive symptoms and not the negative symptoms.
AO3 L-dopa:
Does not worsen all cases
