Basal Ganglia +Visceral Motor System Flashcards
SA:Summarize the role of the basal ganglia in movement
The basal ganglia connect various brain regions and regulate the start and end of movement sequences, essential for controlling voluntary movements.
SA: Which structures are the major components of the basal ganglia? List the primary receiving and output areas of the basal ganglia.
The basal ganglia consist of the striatum (caudate and putamen) and the pallidum (globus pallidus and substantia nigra pars reticulata).
- Input is received at the striatum
- The pallidum receives input from the medium spiny neurons of the striatum and is known as the output area, due to its projections to other parts of the brain
SA: Define and describe the corpus striatum
The corpus striatum, meaning “striped body,” historically included the caudate, putamen, and globus pallidus, but recent research distinguishes the pallidum from the striatum (caudate and putamen nuclei) based on neurochemical, anatomical, and physiological differences.
What is the largest source of neural input to the basal ganglia?
The basal ganglia receive the largest neural input from the cerebral cortex, with almost all regions projecting to the striatum through the corticostriatal pathway.
Would putamen neurons fire as a person is reaching for a doughnut, or in anticipation of the
reach? Would the firing correspond with the position of the doughnut or with the starting
position of the arm? What does this suggest about the role of the putamen?
Putamen neurons fire in anticipation of reaching for the doughnut, corresponding to the doughnut’s position rather than the arm’s. This indicates that the putamen is involved in deciding to move toward a goal, rather than the movement itself.
What is disinhibition? Briefly describe how inhibition and disinhibition operate in the control
of saccades
Disinhibition happens when one inhibitory signal blocks another, freeing up downstream targets. In saccades, cortical signals inhibit caudate neurons, which normally inhibit the substantia nigra. When this inhibition is lifted, the superior colliculus can trigger a saccade.
In Parkinson’s disease, which neurons degenerate? Explain the hypokinetic symptoms of this
disease in terms of the circuitry of the basal ganglia.
-Dopaminergic neurons from the substantia nigra degenerate in Parkinson’s disease, reducing dopamine release onto the caudate and putamen.
-This reduces their inhibitory output, leading to increased inhibition of the VA/VL complex of the thalamus, causing decreased input to the frontal cortex and hypokinetic symptoms.
What types of treatments have been used to alleviate Parkinson’s symptoms?
- Deep brain stimulation of the globus pallidus and subthalamic nucleus
Others: Gene therapy, stem cell grafts, and medications such as Levodopa to boost dopamine levels in the basal ganglia.
Parallel loops involving the basal ganglia each handle information from different cortical
areas. Diagram the motor loop, indicating whether each of the pathways is excitatory or
inhibitory. What are the other loops involving the basal ganglia
Other non-motor loops that use the basal ganglia include the dorsolateral prefrontal loop and the limbic loop.
SA:List five consequences of activating the sympathetic nervous system, and explain how each
prepares the animal for “fight or flight.”
- Pupillary Dilation: Enhances visual perception.
- Vasoconstriction in Skin and Gut: Redirects blood to muscles.
- Piloerection (Hair Standing Up): Increases perceived size.
- Bronchial Dilation: Improves oxygen intake.
- Increased Heart Rate and Stroke Volume: Maximizes blood flow to muscles and brain.
SA: List four consequences of activating the parasympathetic nervous system, and explain how each effect serves the “rest and digest” function
1.Pupillary Constriction:
- Reduces light to retina; supports relaxation.
2. Decreased Heart Rate:
- Promotes rest; conserves energy.
3. Increased Peristalsis and Secretion:
- Aids digestion; enhances nutrient absorption.
4. Bladder Wall Contraction:
- Facilitates urinary voiding; promotes elimination during relaxation.
Why do many investigators consider the enteric nervous system to be separate from the
autonomic nervous system?
The enteric nervous system can function without input from the autonomic nervous system, as seen when gut movements like peristalsis occur even in isolated tissue outside the body.
Is there a sensory component to the visceral motor system? Explain
Yes, sensory signals from the internal organs inform reflex circuits locally and higher brain centers, regulating both organ function and broader responses like hormones and behavior.
What are the two main cortical regions that regulate the autonomic nervous system?
The posterior insular cortex and the medial prefrontal cortex
