Basal Ganglia Flashcards
What are the two components of the striatum?
Caudate and putamen
What are the structures within the lenticular nucleus?
putamen
globus pallidus
what are the efferent nuclei of the basal ganglia?
globus pallidus and pars reticulata of substantia nigra
What are the three nuclei of the basal ganglia proper?
- caudate
- putamen
- globus pallidus
Do the putamen and GP have similar functions?
No
the striatum recieves inputs from all areas of cortex except the (blank) pathways (2)
primary visual
primary auditory
The caudate follows the path of what structure?
lateral ventricle
The direct pathway (inc/dec) excitatory thalamic input to cortex?
INCREASES
The direct pathway turns (up/down) motor activity
UP
Under normal circumstances, list whether each neuron has excitatory or inhibitory actions in the direct pathway:
- cortex to striatum
- striatum to GPi
- GPi to VA/VL of thalamus
- VA/VL of thalamus to motor cortex
- Motor cortex to lower motor neurons
- e
- i
- i
- e
- e
Under normal circumstances when the cortex is sending info through the direct pathway, is the VA/VL activated or inhibited?
Activated
what neurotransmitter is used in inhibitory signaling?
GABA
What neurotransmitter is used in excitatory signaling?
Glutamate
Without pathway stimulation, is the VA/VL tonically active or inhibited?
Tonically inhibited; it requires the input from the cortex down the pathway to inhibit the inhibitor to allow signaling
the indirect pathway (inc./dec.) excitatory thalamic input to cortex
DECREASES
the indirect pathway turns (up/down) motor activity
turns down
Under normal circumstances, list whether each neuron has excitatory or inhibitory actions in the indirect pathway:
- cortex to striatum
- striatum to GPe
- GPe to subthalamic
- Subthalamic to GPi
- GPi to VA/VL
- VA/VL to motor cortex
- Motor cortex to LMN
- e
- i
- i
- e
- i
- e
- e
What are the two components of the substantia nigra?
pars reticulata
pars compacta
what neurotransmitter does the substantia nigra release? what system is it involved in
/
dopamine
reward
D1 receptors are found on the (direct/indirect) pathway
direct
D2 receptors are found on the (direct/indirect) pathway
indirect
Are D1 receptors excitatory or inhibitory? what is there effect on cAMP?
excitatory, stimulates cAMP
are D2 receptors excitatory or inhibitory? What is there effect on cAMP?
inhibitory, inhibits cAMP
what is the overall effect of dopamine release by the sub. nigra?
increase motor activity
Does the sub. nigra turn up or down the direct pathway? the indirect pathway?
turns UP direct
turns DOWN indirect
Does the sub. nigra inc or dec the drive to the VA/VL of the thalamus?
INCREASE
Where are the small cholinergic cells located?
in the striatum
Do the cholinergic neurons act on both the direct and inhibitory paths?
yes!
Do the striatal neurons turn up or turn down motor activity
turn down
What is the effect of the striatal interneurons (cholinergic) on the direct pathway? on the indirect? on the VA/VL drive to the cortex?
turns down the direct pathway
turns up the indirect pathway
decreases drive to the cortex
What are the symptoms of Parkinson’s disease?
hypokinetism rest tremor masked facies rigidity (cogwheel) retropulsion festinating gait shuffling gait loss of postural reflexes depression, anxiety, and dementia
Parkinson’s causes a loss of cells in what nucleus, leading to low levels of what neurotransmitter?
Substantia nigra, dopamine
Does Parkinson’s primarily affect the direct or indirect pathway?
direct
Describe the effects of Parkinson’s on the direct pathway
Decreased dopamine, less stimulation from sub. nigra to striatum, which leads to less “inhibiting the inhibitor”, so the VA/VL remains tonically inactivated
What is the effect of losing the D2 receptors in Parkinson’s?
Less inhibition of the indirect pathway
Hemiballismus results from a (contra/ipsi)lateral lesion of the subthalamic nucleus?
contralateral
Destruction of the subthalamic nuclei breaks the indirect pathway, thus (inc./dec.) motor activity
increasing
Specifically, destruction of the subthalamic nuclei breaks the indirect chain how?
There are no excitatory neurons heading towards the GPi to stimulate the direct inhibitor of the VA/VL
What are the characteristics of Huntington’s disease
Starts in 40s to 50s
starts as movement disorder, progresses to dementia and death
rapid jerky, dance-like motions
Huntington’s disease is caused by the loss of what basal ganglia?
the striatum, specifically the ACh neurons
What are the overall effects of HD on the direct and indirect pathways?
Increase the direct
decrease the indirect
What is the mechanism that causes the increase in direct pathway and decrease in the indirect path in HD?
Loss of ACh cells; no ACh in pathway 1 means Dopamine is unapposed, so more action. Loss of ACh in pathway 2 means there is no inhibition.
In lower motor neuron syndrome, explain your muscle control, tone, reflexes, and the side of the spinal cord that caused the problem
- paralysis
- atrophy
- areflexia
- ipsi deficit in cord
In Upper motor neuron syndrome, explain your muscle control, tone, reflexes, and the side of the spinal cord that caused the problem
- paresis (weakness)
- no atrophy
- hyperreflexia, hypertonia and SPASTICITY
- CONTRA deficit above decussation; IPSI below
In lesions of the basal ganglia, explain your muscle control, tone, reflexes, and the side of the spinal cord that caused the problem
- no paralysis
- no atrophy
- Parkinson’s: rigidity, resting tremor, bradykinesia
3b. Hungtington’s: chorea, hyperkinesia - Contralateral
In upper motor neuron syndrome, loss of tonic inhibition to (blank) fibers causes the spindles to have stronger contractions leading to hyperreflexia
gamma
Killing upper motor neurons leads to a loss of (phasic/graduated) activity of alpha motor neurons and loss of tonic (inhibition/activation) of gamma fibers
phasic, inhibition
UMN paralysis or weakness is due to the (blank) nerve fiber
alpha
UMN spasticity and hyperreflexia are due to (blank) nerve fibers
gamma
T/F: Parkinson’s patients have NORMAL deep tendon reflexes
yessiree bob!
