B&B Week 9 Flashcards
what two areas does the basal ganglia communicate with?
there are tracts between the basal ganglia and the thalamus, and the basal ganglia and the cortex
what is the striatum?
caudate and putamen
what is the input to the basal ganglia?
corticostriatal tracts (striatum is caudate plus putamen)
what are the reciprocal interconnections of the basal ganglia?
striato-nigral (between striatum and substantia nigra)
subthalamic nucleus (between STN and globus pallidus)
globus pallidus and striatum
where does the output from the basal ganglia go?
thalamic facsiculus (from globus pallidus to thalamus)–> lenticular fasciculus and ansa lenticularis
what is the major NT of the basal ganglia? what is the clinical correlate for this?
many of the tracts involving the basal ganglia are dopaminergic (i.e nigrostriatal) and thus have implications in psychosis, since psychosis is linked to dopaminergic dysregulation
how many cerebellar hemispheres are there?
2–> there is an ipsilateral and a contralateral side
what is the vermis of the cerebellum?
midline, with nodule as most anterior part
where is the flocculus in the cerebellum?
in the groove between the superior and inferior surfaces
where is the tonsil of the cerebellum?
on the inferior surface –> prominent bulges on hemispheres, adjacent to the vermis
**sit right above the foramen magnum–> can get tonsillar herniation
what are the 3 lobes of the cerebellum?
- flocculonodular
- anterior–> rostral to primary fissure dividing the superior surface in half (quite small compared to posterior lobe)
- posterior–> remainder of the cerebellum
what is the largest cerebellar nucleus? what does it do?
dentate nucleus
links it to the rest of the brain
other than the dentate nucleus, name three other deep cerebellar nuclei
emboliform
globose
fastigial
what neurotransmitter is linked to extra-pyramidal movement disorders?
dopamine deficiency
what are extra-pyramidal symptoms?
include movement disorders –> pseudoparkinsonism, akathisia, akinesia
linked to dopamine deficiency
do NOT involve the pyramidal tract or lateral corticospinal tract
what would lead to extra-pyramidal symptoms? (EPS)
lesions to the cerebellar loops (i.e vestibulocerebellar, spinocerebellar or cerebrocerebellar loops)
what are the two major classifications for the motor system in the brain?
- pyramidal
2. extra-pyramidal
what is the pyramidal portion of the motor system in the brain?
primary motor pathway in the brain, goes via the medullary pyramids
what symptoms does damage to the pyramidal motor system cause?
spasticity (increased tone or passive resistance; velocity and direction dependent)
weakness
paralysis (no movement)
what structures are part of the extra-pyramidal motor system?
contains the basal ganglia structures: caudate and putamen ("striatum") globus pallidus (internal and external) substantia nigra (pars reticularis and pars compacta) subthalamic nucleus
which system is implicated in most movement disorders, extrapyramidal or pyramidal?
extra pyramidal
what symptoms would arise from a lesion in the extrapyramidal pathway?
rigidity
no overt weakness
insufficient OR excessive/abnormal movements (depending on whether the lesion is in the direct or indirect pathways)
what is the direct pathway of the extrapyramidal system?
cortex–> striatum–> GPi/SNr (globus pallidus interna/substantia nigra reticulate)
promotes movement–> “accelerator pedal”
damage to this pathway causes SLOWING of movement
what is the indirect pathway of the extrapyramidal system?
cortex–> striatum–> globus pallidus externa–> subthalamic nucleus–> globus pallidus interna/substantia nigra reticularis
inhibits movement–> “Brake pedal”
damage to this pathway causes EXCESSIVE movement
what NT helps control the balance of the direct and indirect pathways?
dopamine
list common movement disorders caused by lesions in the extrapyramidal pathway (i.e the basal ganglia)
- parkinson’s disease
- huntington’s disease
- tourette’s syndrome
- ballism
what is the pathophysiology of parkinson’s disease? what symptoms are associated with it? what is the tx?
extrapyramidal/basal ganglia movement disorder
damage to the dopamine secreting neurons in the SUBSTANTIA NIGRA (pars compacta)
difficulty initiating movements, stooped posture, shuffling gate, postural instability
tx–> replace dopamine with levodopa
what is the pathophysiology of huntington’s disease? what symptoms are associated with it? what is the tx?
mostly affects the STRIATUM
chorea, dementia
tx for chorea–> dopamine DEPLETING agent (tetrabenzine)
what is the pathophysiology of tourette’s syndrome? what symptoms are associated with it? what is the tx?
damage to the thalamus, basal ganglia and frontal cortex
multiple tics, childhood onset, persistent for more than 1 year, coprolalia
tx–> dopamine DEPLETING agents (tetrabenzine)
what is the pathophysiology of ballism? what symptoms are associated with it? what is the tx?
damage to the SUBTHALAMIC NUCLEUS
hemiballism is often associated with stroke
can develop into chorea
tx–> sedation, tetrabenzine it develops into chorea
name the first generation typical antipsychotics
- haloperidol
- loxapine
- chlorpromazine
- fluphenazine
which of the first generation typical antipsychotics has a low affinity for D2 receptors? high affinity?
low affinity–> chlorpromazine (need higher dosage)
high affinity–> haloperidol, dimozide, perphenazine (need lower dosage)
what are the receptor effects of first generation antipsychotics that have low affinity for the D2 receptor, like chlorpromazine?
related to H1, alpha-1 and M2 receptor antagonism at high intakes
what are the receptor effects of first generation antipsychotics that have high affinity for the D2 receptor, like haloperidol, dimozide, perphenazine?
related to D2 receptor antagonism (very strong D2 receptor blockers)
what are side effects of chlorpromazine (low affinity for D2 receptor)?
sedation
weight gain
orthostatic hypotension
urinary retention
what are side effects of haloperidol, dimozide, perphenazine (high affinity for D2 receptor)?
extrapyramidal symptoms–> dystonia, and pseudoparkinsonism
what is the MOA of first generation typical antipsychotics?
dopamine antagonist in the brain
goal is to antagonize the dopamine receptors in the mesolimbic system in the brain
specifically, the mesolimbic system is responsible for positive symptoms, therefore blocking DA receptors will reduce positive symptoms
side effects arise from dopamine antagonism in other pathways in the brain, and effects on other receptors
in addition to the mesolimbic pathway (memory and emotional behaviors), what other pathways in the brain use dopamine as a major NT (and thus can be affected by first generation typical antipsychotics)?
mesocortical pathway
tuberoinfundibular pathway
nigrostriatal pathway
what is the function of the mesolimbic pathway?
associated with memory and emotional behaviors
what is the function of the mesocortical pathway?
associated with cognition and motivation
what is the function of the nigrostriatal pathway?
controls motor movement and extrapyramidal signs
what is the function of the tuberoinfundibular pathway?
controls prolactin secretion
what side effects result from typical antipsychotics due to the following action:
dopamine antagonist in the mesocortical pathway?
neuroleptic induced deficit syndrome–> makes negative symptoms worse
i.e alogia (inability to speak), affective flattening, avolition (lack of motivation, drive)
what side effects result from typical antipsychotics due to the following action:
dopamine antagonism in the nigrostriatal pathway?
extrapyramidal symptoms
i.e dyskinesias (repetitive, involuntary and purposeless movements), akathisia (extreme internal or external restlessness), dystonia (very strong uncontrollable muscle contractions)
what side effects result from typical antipsychotics due to the following action:
dopamine antagonism in the tuberoinfundibular pathway?
hyperprolactinemia
what side effects result from typical antipsychotics due to the following action:
H1 antagonism?
sedation, weight gain
what side effects result from typical antipsychotics due to the following action:
alpha-1 antagonism?
decreased BP, dizziness, drowsiness
what side effects result from typical antipsychotics due to the following action:
M1 antagonism?
dry mouth
urinary retention
blurred vision
constipation
how does the MOA of typical and atypical antipsychotics differ?
typical–> D2 antagonsim
atypical–> D2 and 5HT2a receptor antagonism
how do the side effect profiles of typical and atypical antopsychotics differ?
typical–> neuroleptic induced deficit syndrome, extrapyramidal signs, increase in prolactin
atypical–> reduced neuroleptic induced deficit syndrome (better), reduced EPS (better), reduced prolactin liability (better) BUT have metabolic side effects
is there a clear and consistent difference between typical and atypical antipsychotics when it comes to positive symptoms treatment?
no
***exception!!–> CLOZAPINE
clozapine works in resistant patients
*atypical agents have better treatment response to negative symptoms (i.e do not induce negative symptoms)
what antipsychotic is known to work in resistant patients?
clozapine (atypical)
what are the metabolic side effects associated with atypical antipsychotics?
weight gain
T2D
dyslipidemia
metabolic syndrome
name 4 atypical antipsychotics
clozapine
olanzapine
quetianine
risperidone
what is the MOA of atypical antipsychotics?
specific dopamine antagonist in the MESOLIMBIC pathway ONLY
5HT2a antagonism results in increased DA release in other brain pathways to reduce SEs–> normally, 5HT binds to 5HT2a receptors on dopamine neurons–> results in decreased dopamine release–> with atypical antipsychotics you stop this 5HT/dopamine neuron interaction and thus there is less inhibition of dopamine release and you get increased dopamine release–> for some weird reason this does not affect the positive pathway
what are side effects of atypical antipsychotics?
can be classified by on/off rates–> i.e time that drug is engaged with the receptor
rapid on/off–> clozapine, quetiapine (seconds)
- side effects related to H1, M1 receptor antagonism
- sedation, weight gain, orthostatic hypotension, urinary retention
slower on/off–> risperidone, olanzapine
- side effects related to D2 receptor antagonism
- EPS (dose related)–> due to decreased DA transmission and increased ACh transmission
- treat with anticholinergics
- *some antipsychotics have potent anticholinergic action, which provides some inherent anti-EPS mechanism
what is the “treatment guide” or progression for the use of atypical antipsychotics?
trial of atypical agent 1–> substitute for atypical agent 2–> substitute clozapine–> augmentation of clozapine with other class of drugs (lithium, anticonvulsants, antidepressants, benzos)–> combination of atypical and/or conventional agents (same class, antipsychotics)
what factors may prompt you to decide to change antipsychotics?
persistent positive symptoms more than mild
persistent negative symptoms
side effects
how do you treat EPS when it is a side effect of antipsychotic use?
anticholinergic and/or decrease dose of antipsychotic
how do you treat akathisia when it is a side effect of antipsychotic use?
beta blocker and/or decrease dose of antipsychotic–> benzodiazepine and/or decrease dose of antipsychotic
how do you treat neuroleptic malignant syndrome when it is a side effect of antipsychotic use?
discontinue antipsychotic use
agonists such as dantrolene, bromocriptine or amantadine may improve symptoms
what is neuroleptic malignant syndrome?
Neuroleptic malignant syndrome (NMS) is a rare, but life-threatening, idiosyncratic reaction to neuroleptic medications that is characterized by fever, muscular rigidity, altered mental status, and autonomic dysfunction
what are common co-existing symptoms in someone with a psychotic disorder/getting treated for a psychotic disorder (i.e either comorbid or as a result of antipsychotic tx)? how do you treat them?
- agitation/excitement–> benzos, conventional antipsychotics, olanzapine, risperidone PRN
- insomnia–> benzos, trazodone, zopiclone PRN//switch agents
- persistent symptoms of aggression/hostility and mood lability–> mood stabilizer (valproic acid, lithium, carbamazepine)
- depression (common together)–> SSRI, switch antipsychotic
can someone smoke when they are on treatment for schizophrenia?
nicotine is okay, but smoking can interfere with schizophrenia tx due to the effects of hydrocarbons on CYP 1A2 as an INDUCER
this can effect treatment by affecting medication levels
be aware that if patients are not allowed to smoke in hospital, when they leave hospital and smoke their levels of drug will decrease
what NT do the axons leaving the striatum and globus pallidus use? what effect does this have? why do we care clinically?
axons leaving the striatum and globus pallidus use GABA as their NT–> thus they make INHIBITORY synapses on their targets
the neurons from the internal globus pallidus projecting to the thalamus is TONICALLY ACTIVE and thus inhibits parts of the thalamus
this is important because modulations of basal ganglia activity are achieved via altering this output because thalamocortical connections are excitatory
are thalamocortical connections inhibitory or excitatory?
excitatory
what are the two pathways from the striatum to the internal globus pallidus? are these inhibitory or excitatory?
there are TWO pathways from the striatum (caudate and putamen) to the internal globus pallidus
- direct pathway–> theres a single INHIBITORY neuron that uses GABA when it synapses of the pallidothalamic fibre
- indirect pathway–> consists of a chain of TWO INHIBITORY neurons that synapse on an EXCITATORY neuron in the subthalamic nucleus rather than the internal globus pallidus
**the big picture here is that activation of the direct pathway leads to increased activity from the thalamus to the cortex and theremore more movement (target specific)
**activation of the indirect pathway results in decreased activity from the thalamus to the cortex and therefore decreased movement (less superfluous movement)
what pathway is stimulated by dopaminergic neurons from the substantia nigra?
dopaminergic neurons from the substantia nigra will stimulate the direct pathway (D1 receptors) and inhibit the indirect pathway (D2 receptors)
what effect does dopamine have on movement when it acts in the basal ganglia?
bottom line is dopamine activity in the basal ganglia means increased movement
its important to note the way that dopamine neurons from the substantia nigra inhibit the indirect pathway by inhibiting an excitatory cholinergic interneuron
what effect does ACh have on movement when it acts in the basal ganglia?
decreased movement
*note that elsewhere in the body, liek in the neuromuscular junction, ACh is essential for movement–> its just in the basal ganglia it acts to decrease movement whereas dopamine increases movement (because the basal ganglia projections are inhibitory)
what is the pathophysiology of ballismus? specifically, what NT is involved? what is the tx?
ballismus is uncontrolled, big time movement/flinging of the limbs (on one side only it is called hemiballismus)
problem is in the SUBTHALAMIC nucleus, usually due to a vascular lesion (stroke)
the excitatory neurotransmitter GLUTAMATE that normally stimulates inhibition of the thalamus is gone, therefore there is uncontrolled thalamus activity to the cortex and those crazy movements
tx–> dopamine blocking drugs (i.e perphenazine, haloperidol)
what is the pathophysiology of huntington’s chorea? specifically, what NT is involved? what is the tx?
repetitive, rapid “dance like” movements of limbs and often face and tongue
problem is degeneration of the STRIATUM, specifically the CAUDATE NUCLEUS
it appears that there is increased movement because of the loss of the FIRST INHIBITORY synapse in the INDIRECT pathway resulting in increased activity in the second inhibitory neuron in the indirect pathway and therefore inhibition of the excitatory neuron from the subthalamic nucleus–> this means the inhibition from the internal globus pallidus to the thalamus is decreased and the thalamus is “set free” to be overly active–> increased movement results
ACh and GABA are implicated
tx–> supportive (tx for other types of chorea is to treat the underlying cause)
what is the pathophysiology of parkinson’s? specifically, what NT is involved? what is the tx?
difficulty moving (hypokinesis, akinesia), bradykinesia, resting tremor and rigidity
there is degeneration of the DOPAMINE-containing neurons of the SUBSTANTIA NIGRA
since dopamine always means go, loss of dopamine will result in a no go
tx–> methods of increasing or replacing dopamine and anticholinergic drugs
what is the etiology of schizophrenia?
psychotic disorders are caused by both genes and environment
the genetic differences that contribute to psychotic disorders are best referred to as “conferring susceptibility”, vulnerability or predisposition–> NOT causation
in general, psychotic disorders are NOT inherited, but one can inherit a vulnerability to it–> i.e DiGeorges Syndrome
environmental factors include: obstetric complications, drug use (esp. marijuana), winter births, immigration, urban upbringing, head injury, stress
what is DiGeorges syndrome?
22q11 deletion syndrome
a rare genetic cause of psychosis
30% of patients will have at least one incident of psychosis
what is the pathyphysiology of schizphrenia?
- enlarged ventricles and smaller brain volume occur in some, but not all, patients with schizophrenia–> changes are not specific and cannot be used to make a diagnosis
- symptoms are likely due to aberrant functional connectivity (between temporal, frontal and subcortical regions)
- white matter tracts that connect frontal, temporal and subcortical brain regions are smaller or disorganized
- electrophysiological parameters are altered
- pre-pulse inhibition (stimulus that attenuates the startle reflex) is reduced (so more startle reflex) - atrophy of neutropil (regions between cell bodies; includes axons, dendrites and other processes)
- decreased size and complexity of neuronal dendrites
- neurons are slightly smaller–> smaller cell body, therefore, smaller processes
- decreased number of dendritic spines
- decreased levels of synaptic proteins
neurotransmission is thought to be altered in schizophrenia… how is the following neurotransmitter implicated in this?
dopamine
INCREASED dopamine activity in SUBCORTICAL regions, in particular the mesolimbic pathway–> results in POSITIVE symptoms
DECREASED dopamine activity in the FRONTAL cortex, in particular the mesocortex pathway–> results in NEGATIVE symptoms and cognitive deficits
neurotransmission is thought to be altered in schizophrenia… how is the following neurotransmitter implicated in this?
serotonin
psychotic symptoms result from INCREASED 5HT transmission
LSD acts on the 5HT2a receptor
many atypical antipsychotics are 5HT2a antagonists
neurotransmission is thought to be altered in schizophrenia… how is the following neurotransmitter implicated in this?
glutamate
psychotic symptoms result from DECREASED glutamate transmission
phencyclidine (PCP) and ketamine are NMDA (glutamate) receptor antagonists–> binding of these drugs to the receptor can mimic both positive and negative symptoms of schizophrenia