Schizophrenia Flashcards
what are positive symptoms for schizophrenia?
hallucinations - mainly auditory
thought disorders
steryotyped behaviours
what are negative symptoms for schizophrenia?
poverty of affect (more common in poorer communities)
cognitive impairment
temporal disorientation
what are causes of schizophrenia?
-genetic
-psychosocial
-brain damage
-viral infection
how are genetic risks of schizophrenia and the environmental exposure linked?
genetics can cause an increased number of risk loci for developing schizophrenia. the chance of it being developed can be potentiated by environmental insults that increase its chance of development.
what affects the psychosocial causes of schizophrenia?
-tends to have an adolesent onset.
-stress can precipitate it
-higher rate of relapse in ‘emotionally charged homes
-blunted cortisol response
what effect does schizophrenia have on the limbic system structures?
the limbic structures of the brain. decreased size of temporal lobe, increased activity during auditory hallucination.
what occurs to the dominant cerebral hemisphere in schizophrenia?
left hemisphere in specialised for verbal function in normal individuals. in Schizophrenia this is disrupted during verbal tasks.
How do viral infections affect schizophrenia
Hypotheisis that exposure of mother to virus during second trimester increases the risk of schizophrenia to the child. There is a higher incidence in patients born i late winter or spring
what is the site of action for antipsychotic drugs
Basal ganglia
What is chlorpromazine?
Antipsychotic drug. increases dopamine turnover. a Dopamine receptor antagonist. Leads to increase apperance of metabolites in the CSF (cerebrospinal fluid)
what is the dopamine hypothesis of schizophrenia
that the symptoms are due to excess dopamine neurotransmission in mesolimbic and mesocortical regions of the brain
What does clinical studies think of the dopamine hypothesis?
No evidence for increased dopamine release. confliciting litrature.
how is dopamine synthesised?
From tyrosine. gets converted to DOPA by tyrosine hydroxylase. DOPA to dopamine by DOPA carboxylase.
How is dopamine broken down?
by monoamine oxidase A (MAO A), MAO B and catechol-o-methyltransferase. (COMT)
what is the rate limiting step in dopamine production and where is its expression increased in schizophrenia?
Tyrosine hydroxylase. expression is significantly higher in the substantia nigra of schizophrenia patients compared to normal subjects.
Dysfunction in what dopamine receptor has been linked to the negative symptoms of schizophrenia?
D1. mediates dopaminergic transmission in the prefrontal cortex.
WHERE does the mesolimbic pathway project?
from the venteral tegmental area to the nucleus accumbens in the limbic system.
how does dopamine activity affect psychotic symptoms in the mesolimbic pathway?
hyperactivity of dopamine in the mesolimbic pathway leads to positive psychotic symptoms. it is also the pathway that mediates agression.
the mesolimbic pathway is the site of rewards. what do antipsychotics to that alter this pathway
block the D2 receptors. they reduce pleasure effects. leads to self pleasure hypothesis. schizophrenic patients have higher incidences of smoking as nicotine enhances dopamine release.
Where does the mesocortical pathway project?
from the VTA to the prefrontal cortex.
Has projections to the dorsolateral prefrontal cortex regulating cognition and executive functioning.
Ventromedial prefrontal cortex projections to regulate emotion an affect.
where does the nigrostriatal pathway project and what does it mediate?
projects from the dopaminergic neurons in the substantia nigra to the basal ganglia or striatum.
mediates motor moments.
What are some typical antispychotics (neuroleptics)
Phenothiazines
Thioxanthenes
Butrophenones