Cns basal ganglia
-
Upload
physiology-lectures -
Category
Documents
-
view
2.191 -
download
1
Transcript of Cns basal ganglia
BASAL GANGLIA
Basal Ganglia (Nuclei)
• Group of deep, interrelated subcortical N
• Accessory motor system that • Functions usually not by itself but in close
association with cerebral cortex & corticospinal motor control system
• Most input signals from: cerebral cortex• Most output signals back to: cerebral cortex
Anatomy– Caudate– Putamen– Globus
pallidus– Substantia
nigra– Subthalamic
nucleus
Anatomy Overview
Anatomy
The Putamen Circuit – Executing Patterns of Motor Activity
The Putamen Circuit - Functions
• Putamen circuit + cerebral cortex• Controls complex patterns of motor activity
– Writing, Cutting paper with scissors, Hammering nails – Shooting a basketball through a hoop, passing a football,
Throwing a baseball – Most aspects of vocalization – Controlled movements of the eyes – And virtually any other skilled movements
The Putamen Circuit - Lesions
• Globus Pallidus: • Spontaneous, continuous writhing movements of a hand, an
arm, the neck, or the face – Athetosis
• Subthalamus: • Sudden flailing movements of an entire limb –
Hemiballismus
• Putamen: • Flicking movements in hands, face, & other parts of body –
Chorea
• Substantia Nigra: • Common and extremely severe disease of rigidity, akinesia,
and tremors - Parkinson’s disease
The Caudate Circuit – Cognitive Control of Sequences of
Motor Patterns
– Cognition • Most motor
actions occur as a consequence of cognition
• Caudate nucleus is pivotol
The Caudate Circuit
• Timing and Scaling of movements
BG Circuit - Neurotransmitters
?
• What was common between Yasir Arafat, Muhammad Ali & Adolph Hitler?
Parkinson’s Disease
• Degenerative disorder of basal ganglia
• Dopamine depletion results from:• Degeneration dopamine nigrostriatal system• Antipsychotic drugs that block dopamine receptors• Toxic reaction to a chemical agent
» The Northern California drug dealer!*
• Severe carbon monoxide poisoning
Parkinson’s Disease – Clinical
• Tremor (involuntary tremor)– Affects distal segments of limbs (hands and feet; head,
neck, face, lips, tongue; or jaw)– Characterized by rhythmic, alternating flexion &
contraction movements (4-6 beats/minute)– Disappears during voluntary movement– Start unilateral- spread bilateral
• Rigidity – Resistance to movement of both flexors & extensors
throughout the full range of motion– Most evident during passive joint movement
» involves jerky, cogwheel-type movements requiring considerable energy
– Start unilateral- spread bilateral
Parkinson’s Disease – Clinical• Bradykinesia (slowness of movement)
• Movements:– Are slow to initiate & perform– Difficult to stop– Are stiff & staccato in character instead of smooth
• While walking:– Walking and turning en bloc is difficult
» Freezing spells– take small, shuffling steps without swinging arms
• Posture:– Lean forward to maintain center of gravity– Loss of postural reflexes – fall (often backward)
• Masked face:– Emotional & voluntary facial movements become limited– Loss of blinking reflex – Failure to express emotion
• Throat:– Tongue, palate, and throat muscles – rigid
» Drooling common• Speech:
– slow and monotonous, without modulation and poorly articulated
Parkinson’s Disease – Clinical
• Advanced Parkinsonian features:• Dementia (similar to Alzheimer’s disease) • Falls • Fluctuations in motor function • Neuropsychiatric disorders• Sleep disorders
Parkinson’s Disease – Treatment
• Nonpharmacologic• Group support • Education• Daily exercise, adequate nutrition • Botulism toxin injections
• Pharmacologic• Antiparkinson drugs act by:
– Increasing functional ability of underactive dopaminergic system
» Increase dopamine levels (levodopa)» Augment release of dopamine (amantadine)» Function as dopamine agonists (bromocriptine)» Inhibit metabolic breakdown of dopamine (selegiline)
– Reducing excessive influence of excitatory cholinergic neurons» Anticholinergic drugs
Parkinson’s Disease – Treatment
• Surgical• Thalamotomy or pallidectomy performed using
stereotactic surgery
Overall Motor Control