BASAL GANGLIA | Anatomy2Medicine
BASAL GANGLIA,Stroke

BASAL GANGLIA

The basal ganglia

    • lia are the deep nuclei of the telencephalon:
      • caudate nucleus
      • putamen,
      • globus pallidus
      • amygdala.
    • There also are associated nuclei, including the (MCQ)
      • ventral anterior and ventral lateral nuclei of the thalamus
      • subthalamic nucleus of the diencephalon
      • substantia nigra of the midbrain.

 

  • Basal ganglia –functions (MCQ)

 

      • The main function is to influence the motor cortex via pathways through the thalamus.
      • aid in planning and execution of smooth movements
      • contribute to affective and cognitive functions.

 

  • Indirect pathway vs Direct Pathway

 

      • Almost all areas of the cerebral cortex project topographically onto the striatum, including a critical input from the motor cortex.
      • The striatum then communicates with the thalamus and then back to the cortex via two different pathways.
      • Indirect pathway(MCQ)
        • striatum has inhibitory input to the external segment of the globus pallidus
        • external segment of the globus pallidus has inhibitory input to the subthalamic nuclei.
        • subthalamic nuclei project excitatory input to the internal segment of the globus pallidus and the pars reticulata of the substantia nigra

 

  • internal segment of the globus pallidus and the pars reticulata of the substantia nigra send inhibitory input to the thalamus.

 

        • The thalamus then sends excitatory input back to the motor cortex.

 

  • In this pathway, the inhibitory neurotransmitter is GABA, and the excitatory neurotransmitter is glutamate. (MCQ)

 

      • The overall output of the indirect pathway is inhibitory(MCQ)
    • Direct pathway(MCQ)
      • the striatum sends inhibitory input to the internal segment of the globus pallidus and the pars reticulata of the substantia nigra
      • internal segment of the globus pallidus and the pars reticulata of the substantia nigra send inhibitory input to the thalamus.
      • As in the indirect pathway, the thalamus sends excitatory input back to the motor cortex.
      • The overall output of the direct pathway is excitatory(MCQ)
    • Additional pathway between striatum and the pars compacta of the substantia nigra
      • The neurotransmitter for the connection back to the striatum is dopamine.
      • dopamine will be (MCQ)
        • inhibitory (via D2 receptors) in the indirect pathway
        • excitatory (via D1 receptors) in the direct pathway.

 

  • Diseases of the Basal Ganglia
  • Parkinson’s disease(MCQ)
    • cells of the pars compacta of the substantia nigra degenerate
      • reduce inhibition via the indirect pathway
      • reduce excitation via the direct pathway.
  • Huntington’s disease is caused by destruction of (MCQ)
  • striatal and cortical cholinergic neurons
    • inhibitory GABAergic neurons.