Basal nuclei Flashcards
What is the function of the basal nuclei?
Assists in planning and organization of movements through activation of motor association cortex
What are the components of the basal nuclei?
Caudate nucleus
Putamen
Globus pallidus
The anatomical divisions of the basal nuclei include
Caudate nucleus and lentiform nucleus (globus pallidus and putamen)
The functional divisions of the basal nuclei include
Striatum (caudate nucleus and putamen)
Pallidum (globus pallidus)
What other two areas besides the striatum and pallidum are included when considering functional activity of the basal nuclei?
Subthalamic nucleus
Substantia nigra
Direct pathway of a signal through the basal nuclei
Input from cerebral cortex to striatum (corticostriate)
Connection from striatum to globus pallidus (striatopallidal)
Output from globus pallidus to ventral anterior nucleus of thalamus (pallidothalamic)
Thalamic fibers project to premotor cortex (thalamocortical)
What is the purpose of the direct pathway of the basal nuclei?
Basal nuclei takes information about body position to plan and organize body movement
The direct pathway connects to the substantia nigra through
The striatum
The direct pathway connects to the subthalamic nucleus through
Globus pallidus
What is the purpose of the direct pathway of the basal nuclei?
Excitatory, “the accelerator”
Enhances motor output related to agonist muscles
What is the purpose of the indirect pathway of the basal nuclei?
Inhibitory, “the brake”
Decreases motor output related to antagonist muscles
Includes detour through subthalamic nucleus
What is the purpose of the substantia nigra in the basal nuclei?
Dopamine input
Helps excite direct pathway
Helps inhibit indirect pathway
Dopamine enhances speed and/or force of movement
Where does the blood supply of the basal nuclei come from?
Lenticulostriate arteries of MCA supplies globus pallidus, putamen, caudate nucleus
Leaves perforation in the brain matter where the arteries go through the cerebral cortex
What does “negative” signs mean?
Actions the patient wants to perform but cannot
Also called hypokinetic signs
What are negative signs of basal nuclei disorders?
Akinesia
Bradykinesia
Abnormal postural adjustments
Dystonia
What is akinesia, bradykinesia, abnormal postural adjustments, dystonia?
Akinesia: hesitancy in starting movement
Bradykinesia: slowness of execution of movement
Abnormal postural adjustments: head and trunk flexion and inability to make appropriate adjustments when falling or tilting or standing
Dystonia: unusual fixed posture which occur spontaneously
What does “positive” signs mean?
Actions the patient does not want to perform but cannot prevent
Hyperkinetic signs
What are the two types of positive signs of basal nuclei disorders?
Dyskinesia (involuntary movements that cannot be controlled)
Rigidity (tone in all muscles acting on a joint is increased, hypertonicity)
Positive signs: different types of dyskinesia (5)
Tremors: rhythmic movements in distal limbs (resting tremor)
Chorea: rapid jerky movements in distal limbs
Athetosis: slow writhing movements of an entire limb
Ballismus: violent flinging movements of an entire limb
Tics: repetitive movements
Positive signs: different types of rigidity
Lead pipe: Increased resistance to passive movement in both flexors and extensors (tested with passive movement of limbs)
Cogwheel: ratchet-like movement at frequency resting tremors
What are the symptoms of Parkinson’s disease?
Akinesia
Bradykinesia
Resting tremor
What is the pathology that leads to Parkinson’s disease?
Loss of dopaminergic input from substantia nigra
Consequence of degenerative, vascular, or inflammatory change
Etiology of Parkinsons can be
Genetic, due to trauma, or unknown
Parkinsons affects which pathways of the basal nuclei
Direct and indirect pathways
Epediomology of Parkinsons disease
Initial symptoms start at 45 to 65 years of age
Incidence 1/500 with 50000 new cases each year
What are the symptoms of Huntington’s disease?
Chorea
Progressive dementia in the late stage
A lot of involuntary movements, balance not affected but lots of jerky movements
What is the pathology of Huntington’s disease?
Degeneration of neurons in striatum for indirect pathway (this pathway is inhibitory so there is disruption that leads to involuntary movements)
Huntingtons is an _____ disorder
Autosomal dominant genetic disorder
With Huntington’s disease, motor activity is released from
Inhibitory control of indirect pathway
