2-Minute Neuroscience: Direct Pathway of the Basal Ganglia

Summary

The basal ganglia are a group of brain structures involved in movement regulation, including the striatum, globus pallidus, subthalamic nucleus, and substantia nigra. The direct pathway in the basal ganglia plays a key role in facilitating movement by modulating the thalamus. The striatum, activated by glutamate from the cortex, inhibits the globus pallidus and substantia nigra, reducing inhibitory signals to the thalamus, thereby allowing movement. The substantia nigra pars compacta releases dopamine, enhancing the direct pathway and aiding motor control. This intricate network helps prevent unwanted movements and facilitates intentional ones.

Takeaways

• 😀 The basal ganglia are a group of structures in the brain that include the caudate, putamen (collectively known as the striatum), globus pallidus, subthalamic nucleus, and substantia nigra.
• 😀 The globus pallidus is divided into internal and external segments, while the substantia nigra has two parts: pars compacta and pars reticulata.
• 😀 The direct pathway in the basal ganglia is involved in the facilitation of movement.
• 😀 Glutamate neurons from the thalamus to the motor cortex play a role in stimulating movement via the direct pathway.
• 😀 Neurons in the globus pallidus internal and substantia nigra pars reticulata release GABA, inhibiting thalamic neurons to prevent unwanted movements.
• 😀 The corticostriatal pathway sends movement-related information from the cortex to the striatum, initiating movement.
• 😀 When the cortex sends signals to the striatum, striatal neurons release GABA, which inhibits the globus pallidus internal and substantia nigra pars reticulata.
• 😀 This inhibition of the globus pallidus internal and substantia nigra pars reticulata allows thalamic neurons to be disinhibited, facilitating movement.
• 😀 The substantia nigra pars compacta modulates the activity of the direct pathway through the release of dopamine.
• 😀 Dopamine released from the substantia nigra pars compacta into the striatum helps facilitate the activity of the direct pathway, promoting movement.

Q & A

What are the key structures in the basal ganglia?

The basal ganglia include the caudate, putamen (collectively known as the striatum), globus pallidus, subthalamic nucleus, and substantia nigra.

How is the globus pallidus divided?

The globus pallidus is divided into internal and external segments.

What are the two parts of the substantia nigra?

The substantia nigra is divided into the substantia nigra pars compacta and substantia nigra pars reticulata.

What is the function of the direct pathway in the basal ganglia?

The direct pathway is thought to be involved in facilitating movement by stimulating motor regions of the cerebral cortex through excitatory projections from the thalamus.

How do neurons in the globus pallidus internal and substantia nigra pars reticulata influence movement?

These neurons project to the thalamus and release GABA, inhibiting the thalamic neurons, which suppresses movement to prevent unwanted movements.

How does the corticostriatal pathway contribute to movement?

In the corticostriatal pathway, glutamate neurons from the cortex excite neurons in the striatum, which in turn release GABA in the globus pallidus internal and substantia nigra pars reticulata, inhibiting their activity and allowing movement to occur.

What role does the substantia nigra pars compacta play in movement?

The substantia nigra pars compacta modulates the direct pathway by releasing dopamine in the striatum, which facilitates activity in the pathway and thus supports movement.

Why is the release of GABA important in the basal ganglia circuits?

The release of GABA in certain regions, such as the globus pallidus internal and substantia nigra pars reticulata, is crucial for inhibiting unwanted movements and ensuring proper motor control.

What neurotransmitters are involved in the direct pathway and how do they affect movement?

The direct pathway involves glutamate (excitatory) from the thalamus to the cortex, which facilitates movement, and GABA (inhibitory) from the striatum to the globus pallidus internal and substantia nigra pars reticulata, which suppresses inhibitory signals to the thalamus, allowing movement.

How does the thalamus contribute to movement control?

The thalamus plays a critical role by receiving inhibitory signals from the globus pallidus internal and substantia nigra pars reticulata, which suppress movement. When the inhibition is lifted, it allows for movement signals to pass through to the motor cortex.