Lecture 12 - Basal Nuclei Control of Motor Function Flashcards
Basal Nuclei
•Plan and execute motor commands in concert with cerebral cortex; help cortex execute subconscious but learned pattern •Help plan multiple parallel sequential patterns •Control complex patterns of motor activity
Basal Nuclei receive most of their input from __ and return most of their output to __.
cerebral cortex and cerebral cortex
The principal role of the basal nuclei is
to work with corticospinal system to modulate thalamic output to the motor cortex to plan and execute smooth movements
Two major basal nuclei circuits
Putamen circuit (direct)
Caudate nucleus circuit (indirect)
Putamen Circuit
Direct
Function: not clear
inhibits athetosis or non-volitional movements
suppresses rigidity
•For subconscious execution of learned patterns of movement
•Overall excitatory –tends to increase motor activity
BYPASSES CAUDATE
caudate nucleus circuit
indirect
motor planning: activating muscle in sequence for motor patterns 5 seconds ahead or more
For cognitive planning of sequential and parallel motor patterns. Plays major role in cognitive control of motor activity. Overall inhibitory –tends to decrease motor activity.
Dopamine is __ on the direct pathway and __ on the indirect pathway.
excitatory (D1 receptors)
inhibitory (D2 receptors)
Dopamine’s function overall is __
excitatory
Exciting the putamen ___ the IGP/SbNigRet and allows the thalamus to send ___ signals to the motor cortex. IGP/SubNigRet is otherwise active and sends __ signals to the thalamus.
inhibits
excitatory
inhibitory
Lesions in Globus Pallidus
- Result in inability to maintain postural support.
* Result in continuous spontaneous writhing movements of a hand, arm, neck or face = athetosis
Lesions in subthalamic nuclei
- Result in the release of inhibition on the contralateral side.
- Result in sudden, flailing movements of an entire limb = hemiballismus
Lesions in striatum
- Results in the release of inhibition
- Results in flicking movements in hands, face, or elsewhere = chorea.
- Occur in patients with Huntington disease.
Lesions in substantia nigra
- Caused by destruction of dopaminergic neurons.
- Occur in patients with Parkinson’s disease.
- Results in rigidity, akinesia, and tremors.
- Since dopamine inhibits the indirect (inhibitory) pathway and excites the direct (excitatory) pathway, destruction of the dopaminergic neurons results in an overall inhibitory effect.
Neurotransmitters
Substantianigra→ caudate nucleus and putamen
Dopamine (inhibitory)
Neurotransmitters
Caudate nucleus and putamen →globuspallidus and substantianigra
GABA (inhibitory)