2. Basal Ganglia Flashcards
basal ganglia
- group of structures affecting motor control, cognitive function, and affective function
- motor: normal function is to control level of excitatory drive to cortex, level changes during movement and may be permanently altered from disease
basal ganglia in the brain
- striatum: caudate and putamen
- globus pallidus
- associated structures:
- diencephalon: motor thalamus, subthalamic nucleus
- midbrain (mesencephalon):
- substantia nigra (black substance; neurons are dopaminergic)
movement diseases/disorders involving basal ganglia
+ too much excitation: involuntary movements
- too little excitation: slowness (bradykinesia) or absence (akinesia) of voluntary movement
ex: parkinson’s, tourette’s, restless leg syndrome, tardive dyskinesia, tardive dystonia, dystonias (abnormal tone and posture), huntington’s disease (involuntary movement)
parkinson’s disease
- usually but not always in elderly
- neurodegenerative disease
- age of onset: 60+
- 55 men/45 women
- slow progressive disease
- can have substantia nigra
substantia nigra in PD
- degeneration (death) of neurons of SN, loss of dopaminergic neurons –> loss of dopaminergic input to the caudate and putamen
- cause unknown (possibly genetic, environmental, postinfectious PD)
PD symptoms
- motor, affective (depression), cognitive (dementia)
motor: - tremor (at rest, hands, mouth; disappears when movement is initiated)
- bradykinesia (slowness of movement)
- akinesia (absence of movement, esp self-initiated movement and “associated movements”; swinging arms when walking, loss of facial expression)
PD treatments
- medical: I-dopa (precursor of dopamine to help with symptoms temporarily)
- surgical: lesion in pathway (destroy axons to alleviate symptoms)
- DBS: deep brain stimulation (electrodes implanted in brain, subthalamic nucleus, pacemaker-like device); eliminates abnormal signals to cortex
- experimental: tissue/stem cell implants
MPTP
- drug that was synthesized by mistake trying to imitate heroin
- causes substantia nigra degeneration and Parkinson’s symptoms
- used to induce PD in animals and test treatments
true or false: dopamine is only found in substantia nigra
false: several other cell groups synthesize and release dopamine
- it is a transmitter in multiple structures and functional systems (ex: reward system)
true or false: several disorders are attributed to dopamine dysfunction, either too much or too little dopaminergic activity
true (transmitter, receptors, and transporters can be affected)
dopamine acts on dopamine __, of which there are multiple types (__-__) and they have different distributions in the brain
receptors, D1-D5
dopamine in schizophrenia
- too much dopaminergic action in frontal lobes
- treatment: “neuroleptics” (dopamine receptor blockers)
- longterm use of neuroleptics can result in irreversible movement disorders (tardive dyskinesia or tardive dystonia)
atypical antipsychotics
- affect only subsets of dopamine receptors (those in cortex thought to mediate schizophrenia, NOT those for movement in striatum)
- does not cause tardive dyskinesia
- may cause other medical problems like weight gain or diabetes
tourette’s syndrome
- movement disorder (tic - brief involuntary movement)
- can suppress tics for short period of time
- age 3-9, occurs with ADHD, may be misdiagnosed as behavioral
- male 3:1
- symptoms may resolve by late adolescence
- clear hereditary component but no gene disorder
- too much dopaminergic activity in motor pathways (serotonin and norepinephrine)
- treated with dopamine receptor blockers (haldol)
restless leg syndrome (RLS)
- both sensory and motor symptoms
- uncomfortable sensations that are relieved by moving legs
- worst at night, disrupts sleep (sleep and movement disorder)
- more common in women
- cause unknown, maybe too little dopamine
- genetic contribution
- basal ganglia/dopamine disorder
- treated with dopaminergic drugs and dopamine precursors
