Schizophrenia Flashcards
What is schizophrenia
Characterised by disturbances in areas of the brain associated with thought, perception, attention, motor behaviour and emotion
What are the two classes of symptoms
Positive - hallucinations, delusions, thought disorders
Negative - Blunting of emotions, withdrawal from social contact, reluctance to perform everyday tasks
What are some causes of schizophrenia
Environmental and genetic factors
Affected by illegal drugs i.e. cocaine, opiates - all induce the positive symptoms of schizophrenia
What are the four pathways of dopamine in the body
- Nigrostriatal pathway - fine motor control
- Mesocortical and mesolimbic pathways - behavioural effects, pleasure - euphoria - reward (motivation), compulsion
- Tuberohypophyseal pathway - pituitary secretion i.e. prolactin
- Medullary chemoreceptor trigger zone - nausea and vomiting
What is the cause of schizophrenia in response to dopamine
Excessive activity of the dopamine system
How is dopamine synthesised
Derived from tyrosine
Rate limiting step - tyrosine to L-Dopa- catalysed by tyrosine hydroxylase
L-Dopa to dopamine catalysed by Dopa decarboxylase
What type of receptor are dopamine receptors
GPCRs only - D1,3,5 are excitatory
activation leads to an increase in cAMP
D2,4 are inhibitory leading to a decrease in cAMP
What is the role of D2 receptors
Control the function of the dopamine releasing neurons - involved in autoregulation
How is dopamine metabolised
By MAO and COMT
What are antipsychotic drugs
Almost all act on D2 receptors and are antagonists
What are two first generation antipsychotics
Chlorpromazine, Haloperidol
What are extrapyramidal motor disturbances due to D2 antagonism
D2 receptors found in the nigrostriatal pathway causes involuntary movements defined as extrapyramidal motor disturbances
What are atypical antipsychotics
Have a lower incidence of extrapyramidal effects - no secretion of prolactin
What can prolonged usage of antipsychotics cause
Can become neurotoxic - degeneration of aminergic neurons as a result of accumulation of reactive metabolites within the neurons themselves
What can acute use of antipsychotics cause
Euphoria and excitement - effects on mesocortical and mesolimbic pathways - presents as hyperactivity
Insomnia
Increase in stamina
Anorexia - disturbed feeding behaviour
Peripheral effects - sympathomimetics in PNS cause increased blood pressure and decreased gut motility
