Basal ganglia Flashcards
What is parkinson disease caused by?
Degeneration of the dopaminergic fibers in substantia nigra.
What structures make up the basal ganglia?
Stratium
- Caudate
- Accumbens
- Putamen
Lenticular Nucleus
- putamen
- Globus pallidus (External & internal)
Sub-thalamic nucleus
Substania Nigra
- Compact
- Reticular
_______ coincides with the Insula.
Putamen
Globus pallidus has extensive BG outputs to _______.
Thalamus
What are the Basal ganglia related movement disorders?
Involuntary movement, hyperkinetic disorders
- Chorea, atheosis, ballismus
Difficulty initiating movement
Perturbed muscle tone
- Increase in flexor and extensor tone = rigidity
- Twisted posture
- tone can be decreased as well.
What are the two main parts of the Substantia Nigra?
Compact = densely packed, pigmented neurons. Reticular = closer to cerebral peduncle, non pigmented neurons.
Which part of the Substantia Nigra is a basal output Nucleus?
Reticular part
What are the 3 main functions of the basal ganglia?
- Motor control mediates by interactions with motor cortex and other structures.
- Involved in most other cortical functions as well
- Circuit includes multiple, parallel loops that modulate cortical output.
What are the major inputs and outputs of the basal ganglia?
Input = Cortical afferents to striatum (and sub thalamus)
Output: globus pallidus interna (GPi) substantia Nigra reticular (SNr)
What do Excitatory connections to the basal ganglia use?
Glutamate
- Corticostriate, thalamocortical
What do inhibitory connections to the basal ganglia use?
GABA
- GPi & SNr
True or false, the basal ganglia influences the motor cortex directly.
False! its role in motor function is to influence by affecting activity in cortical motor areas.
What us the basic Basal ganglia motor loop?
Somatosensory cortex & Motor cortex –> Striatum (Mostly with putamen) —–>GPi —-> VA/VL in thalamus —–> motor cortex & somatosensory cortex
Describe the direct pathway of the Basal ganglia motor loop…5 steps
- excitatory corticostirate fibers from cortex activate inhibitory neurons in striatum.
- Striatum inhibits GPi
- Thalmaus is disinhibited (B/c GPi was inhibited and it usually inhibits)
- Thalmus activates cortex
- Increased cortical output
What is Huntington’s disease (Chorea)?
Degeneration of striatum (Caudate & putamen)
- Chorea, rigidity and cognitive disturbances.
- Autosomal dominate, trinucleotide repeat.
- Age of onset is variable, most at about 50 yrs though.
- Rapid and continous movement of face and limbs.
Describe the Indirect pathway of the basal ganglia motor loop…
- Coritical input to striatum
- Striatal output to GPe decreases GPe output
- increase in thalamic inhibiton
- decrease in cortical output
What is Hemiballismus?
Dramatic movement disorder
- Flailing, rotary limbs
- due to cerebrovascular accident (stroke) branch of posterior cerebral artery.
Lewey bodies in compact substantia nigra are indicative of what disease?
parkinsons
Parkinsons diseases needs 2 of 3 features, what are they?
Bradykinesia
Resting tremor
rigidity
What is used to treat parkinson disease?
levodopa is used to replace dopamine lost to degeneration. (Helpful but response can fluctuate over time and can induce involuntary movement.
What are the surgical options to treat parkinson disease?
Pallidotomy = destruction of globus pallidus
Deep brain stimulation with electrodes in thalamus.
Stem cell therapy is being considered
