Basal Nuclei (Basal Ganglia) Function in Motor Control

Study Notes

Several masses of grey matter located deep within cerebral white matter
Important inhibitory role in motor control
Inhibiting muscle tone throughout the body
Maintaining proper muscle tone by balancing excitatory and inhibitory inputs
Selecting and maintaining purposeful motor activity
Suppressing useless or unwanted patterns of movement
Helping monitor and coordinate slow, sustained contractions (especially related to posture)

Do not directly influence the efferent motor neurons
Act by modifying ongoing activity in motor pathways
Receive and send out large volume of information, as indicated by tremendous number of fibers linking them to brain regions
One important pathway of strategic interconnections is a complex feedback loop, linking motor cortical regions, basal nuclei, and thalamus

Gradual destruction of neurons that release neurotransmitter dopamine in the basal nuclei
Characteristic motor disturbances:
- Rigidity: increased muscle tone
- Resting tremor: involuntary, useless or unwanted movements
- Slowness in initiating and carrying out different motor behaviors
Standard treatment:
- Administration of levodopa (L-dopa): precursor of dopamine, can enter brain from blood

Located deep within the brain, near the basal nuclei
A midline structure that forms the walls of the third ventricular cavity
Consists of thalamus and hypothalamus
Serves as "relay station" for preliminary processing of sensory input
Screens out insignificant signals
Routes important sensory impulses to appropriate areas of somatosensory cortex and other brain regions
Helps direct attention to stimuli of interest along with brain stem and cortical association areas

Collection of specific nuclei and associated fibers, that lie beneath the thalamus
Important link between the autonomic nervous system and the endocrine system
Integrating center for many important homeostatic functions
Regulates the internal environment
Functions:
- Controls body temperature (thermostat)
- Controls thirst and urine output
- Controls food intake
- Controls anterior pituitary hormone secretion
- Produces posterior pituitary hormones
- Controls uterine contractions and milk ejection
- Serves as major ANS coordinating center, affecting all smooth muscles, cardiac muscles, and exocrine glands
- Plays role in emotional and behavioral patterns
- Participates in the sleep-wake cycle

Functional system (not separate structure), consists of ring of forebrain structures surrounding brain stem and interconnected by intricate neuron pathways
Includes portions of each of the following:
- Lobes of cerebral cortex (esp: limbic association cortex)
- The basal nuclei
- Hippocampus
- Thalamus
- Hypothalamus
- Amygdala
Associated with:
- Emotions
- Behavior
- Motivation