Lecture 5 Accessory Motor Systems Basal Ganglia Flashcards
(35 cards)
What are the lateral pathways of the spinal cord responsible for?
Skilled voluntary movement
What are the medial pathways of the spinal cord responsible for?
Posture, Balance, and Stance
What is the Basal Ganglia responsible for?
- An upstream motor loop
- Premotor and motor cortex of THE SAME HEMISPHERE
- Initiates and terminates voluntary motor movement
What structures make up the Basal Ganglia?
- Caudate Nucleus — input nucleus
- Lentiform (Lenticular) Nucleus
Putamen — input nucleus
Globus Pallidus — output nucleus - Subthalamic Nucleus
- Substantia Nigra
- Nucleus Accumbens — input nucleus
What is the function of the Caudate Nucleus?
- Lines the outside of the lateral ventricles
- Cognitive processes controlled by the Basal Ganglia
- INPUT Nucleus of basal ganglia
Where is the Lentiform located? What is the Lentiform Nucleus composed of?
- Located anterior and lateral to the thalamus
- Putamen (lateral)
- Globus Pallidus (Medial)
What is the function of the Putamen?
- Input nucleus of Basal ganglia
- receives cortical input for motor function
What is the function of the Globus Pallidus?
- Output nucleus of the basal ganglia
- Output to cortex is relayed by the Thalamus
What is the function of the Subthalamic Nucleus and where is it located?
- Part of the “stop pathway” for voluntary movement (preventing movement)
- Located lower diencephalon/midbrain
Where is the Substantia Nigra located and what is its function
- Located in the midbrain (upper brainstem region)
- Neurons contain black pigment (melanin)
- enhances activity of “go pathway”
- Promotes motor movement and inhibits “stop pathway”
What stimulates the Substantia Nigra?
Reticular formation while awake
What is the function of the Nucleus Accumbens and where is it located?
- Reward Behavior, emotions
- a “Pleasure center” of the brain
- an input nucleus of the Basal Ganglia
- Receives limbic input entering basal ganglia
Cup shape piece of grey matter connecting the head of the caudate and putamen
What does the striatum consist of?
Caudate (Medial)
Putamen (lateral)
Nucleus Accumbens (Anterior to both)
What are the portions of the lenticular nucleus?
- Putamen (lateral)
- Globus Pallidus (medial)
What is the Globus Pallidus divided into?
GPe (exterior)
GPi (interior)
What do the Cerebral Peduncles contain?
Descending fibers of the internal capsule
- pass along the front of the midbrain
(externally visible above the pons)
Describe the “Stop Pathway” in the brain regarding motor movement
- Cortex sends signals to…
- the Striatum (indirect pathway)
- The striatum activates the subthalamic nucleus
- This signals to the Globus Pallidus interior
- GPi sends signals the cortex through the thalamus to prevent movement
Describe the “Go Pathway” in the Brain regarding motor movement
- Cortex sends signals to…
- The striatum (direct pathway)
- Substantia Nigra sends additional signals to the striatum to initiate movement AND inhibits subthalamic nuclear inhibititon of the GPi
- The striatum directly sends signals to the Globus Pallidus Interiror
- GPI sends signals back to the cortex via the thalamus
What is happens when the basal ganglia is lesioned?
- Lesions produce contralateral motor deficits in downstream corticospinal pathway
Lesions of the “Go pathway” will lead to…
Difficulty initiating movement
Lesions of the “Stop pathway” will lead to…
Excessive, uncontrollable movement
- (Hyperkinesia)
Lesions of the Globus Pallidus Interior (GPi) will lead to…
- Since GPi sends INHIBITORY projections to the thalamus
- Lesions = excessive movement
(Athetosis: writhing snake like movement of contralateral limb)
Lesions of the Putamen will lead to…
Symptoms vary greatly
- Akinesia: inability to initiate movement
- Dystonia: sustained, slow, twisting movements/abnormal posture
- Chorea: excessive uncontrollable movements
Lesions of the Subthalamic Nucleus will lead to…
- Ballismus: involuntary flailing movements of the contralateral limb
- affects the “stop pathway”
