13 - Basal Ganglia Disorders Flashcards
Where does the basal ganglia project to? What gives it input?
Projects only to the motor cortex, and it’s output to the cortex is inhibitory.
Input all from the cortex, either through the direct or the indirect pathway.
What is the function of the basal ganglia?
Pacemaker of the body; harmonizes state of mind and body.
The cortex projects to the _________ which projects to the ___________. These project to the thalamus and then back to the cortex.
Caudate and putamen, which project to the globus pallidus externus and internus.
What two subloops are located in the loop between the basal ganglia and the cortex?
The caudate and putamen have a subloop to and from the substantia nigra.
The globus pallidus externus and internus have a subloop to and from the subthalamic nucleus.
The indirect pathway is the ______, while the direct pathway is the ________.
Indirect is the breaks and functions to inhibit movement.
Direct pathway is the acceleration and functions to facilitate movement.
What is the path of the direct pathway? What is the ultimate result?
Cortex excites the striatum (caudate and putamen), which inhibit the globus pallidus internus and substantia nigra (inhibition of inhibition).
This inhbition of inhibition results in an excitatory effect on the thalamus and motor cortex that results in movement.
What is the path of the indirect pathway? What is the ultimate result?
Cortex excites the striatum (caudate and putamen), which inhibits the subthalamic nucleus (inhibition of inhibition), causing excitation of the globus pallidus internus and substantia nigra (excitation of inhibition).
This excitation of inhibition is a reinforcement of inhibition that causes inhibition through the thalamus and to the cortex that inhibits movement.
What are the different classifications of movement disorders?
Hypokinetic: parkinsons, multiple system atrophy, progressive supranuclear palsy, and vascular parkinson’s.
Hyperkinetic: huntington’s, tic disorders (tourette’s), and hemiballism.
What defect occurs with parkinsons disease?
Loss of dopaminergic neurons in the substantia nigra that effects the excitatory pathway more.
Result is unbalanced innhibition to the thalamus causing hypokinetic movement.
What are cardinal features of parkinson’s disease?
- Resting tremor (“pill-rolling”)
- Rigidity
- Bradykinesia
- Postural instability (falls easily, commonly backwards)
Injury to the basal ganglia results in rapid alternating movements that are ______ and ______.
Small and fast
What are three treatment options for peopel with parkinsons and how does each work?
L - dopa (dopamine agonist): allows substantia nigra to function better
Anticholinerics: by blocking Ach you decrease the activity on the inhibitory side to balance the two sides out.
Deep brain stimulaton: of the subthalamic nucleus or globus pallidus internus
What is the function of deep brain stimulation?
It works to inhibit the subthalamic nucleus or the globus pallidus internus in order to improve symptoms of those suffering from parkinsons.
What is the cause of a factitious tremor?
Loss of funciton in the auto-agency region of the brain, the region that tells you “I am doing this movement”
Funcitonal disorder that’s not well understood at the moment.
What is huntington’s disease?
An autosomal dominant neurodegenerative disorder caused by CAG repeat expansion.
Loss of neurons in the caudate occurs.
Pts exhibit hyperkinetic movement and chorea (“dancing” movements).
What occurs to the direct and indirect pathways in huntington’s disease?
Lesion of the caudate effects the indirect pathway and reduces the inhibition that normally occurs on that side.
This results in an increase in excitation and an increased stimulus for initiating movements.
What movements are characteristic of hemiballism? What can cause this?
Breif, high amplitude, irregular movements of a limb.
Seen with lesions of the contralateral subthalamic nucleus (stroke).
