n and the cerebellum) and the spinal cord to other parts of the central nervous system.
However, the function of the cerebral peduncles is not limited to “passing on” information. They also play a role in “refining” the instructions passed on from the cerebral cortex.
Once the higher regions of the brain decide on the best course of action, the information moves into the cerebral peduncles. Here, the peduncles “adjust” the instructions to fit the situation.
I.e., nerve impulses emitted by the cortex fail to factor in certain aspects, like where the limbs are, how the body is already moving, etc. The cerebral peduncles receive this information from the other brain regions and adjust the nerve impulses accordingly.
If the instructions were not tailored to fit the need, our responses would be exaggerated, insufficient, and ungainly.
The cerebral peduncles also assist in learning new motor skills and maintaining balance and posture through interpreting proprioceptive stimuli.
The cerebral peduncles are a product of their various components. Each component is responsible for different functions and information processing; some of these include:
The Crus Cerebri Purpose, Function, And Structure
The two horns of the cerebral peduncles (located in the midbrain’s anterolateral regions) are separated from the tegmentum by the substantia nigra.
The crus cerebri contains four fiber tracts:
- Frontopontine fibers. These fibers, located most medially, originate in the frontal lobe and terminate at the pontine nuclei.
- Corticospinal fibers. These motor fibers originate in the primary motor cortex. This region is the bridge between the upper and lower motor neurons. The upper fibers connect the brain and spinal cord, while the lower fibers connect the spinal cord to the muscles.
- Corticobulbar tracts. The fibers here are also motor fibers from the primary motor cortex and originate in the precentral gyrus (the origin of several motor pathways). This tract innervates the cranial nerves linked to the head and face.
- Temporopontine fibers. These fibers originate in the cerebral cortex (within the temporal lobe) and run posterolateral. From the sublenticular limb of the internal capsule, these fibers join the crus cerebri and terminate in the pons.
The crus cerebri connects the cerebral hemispheres to the cerebellum through a network of neurons. These neurons are mostly the white matter (axons covered in myelin sheaths) of motor neurons.
The crus cerebri is critical for transporting nerve impulses from the brain, down the spinal cord, and eventually to the relevant muscles.
The Substantia Nigra Purpose, Function, And Structure
Together the anterior pars reticulata and the posterior pars compacta from the substantia nigra, a collection of pigmented nuclei. The substantia nigra separates the crus cerebri from the tegmentum.
- Due to the presence of melanin, the pars compacta provides the region with dark pigmentation. The cells in this area produce/synthesize dopamine.
These cells mediate movement and motor coordination (usually inhibiting neurons, particularly those in the caudate nucleus and putamen).
- Cells in the pars reticulata receive impulses from the pars compacta and push the impulses along to the thalamus. This region is important for eye movements, thinking, and learning.
These cells also have an inhibitory action through the gamma-aminobutyric acid present in their cells.
This inhibitory effect prevents/blocks impulses from your brain from reaching the muscles.
The pars compacta and reticulata (together with the globus pallidus) create the striatum.
The substantia nigra plays a fundamental role in assisting with movement, facilitating connections in the brain (as part of the basal ganglia), and controlling various chemical components (e.g., dopamine).
The Tegmentum Purpose, Function, And Structure
Separated from the crus cerebri by the substantia nigra and located in the posterior region of the midbrain (but still anterior to the tectum), the tegmentum continues down through the pons and up through the midline.
The tegmentum c