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Ch. 13 The Peripheral Nervous System
Amerman - Human Anatomy & Physiology 2nd Edition
Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822Not the one you use?Change textbook
Chapter 13, Problem 16

Label the following components of the corticospinal tracts with numbers 1 through 6, with 1 being the origin of the tracts and 6 their destination.     
_____ Medullary pyramids where most fibers decussate.     
_____ Anterior horn of the spinal gray matter.     
_____ Midbrain and pons.      
_____ Upper motor neurons in the primary motor and premotor cortices.     
_____ Corona radiata and internal capsule.        
_____ Lateral funiculus of the spinal cord.

Verified step by step guidance
1
Understand the corticospinal tract: It is a major motor pathway that originates in the brain and travels down the spinal cord to control voluntary movements. The pathway involves upper motor neurons and lower motor neurons.
Identify the origin of the corticospinal tract: The upper motor neurons begin in the primary motor cortex and premotor cortex of the brain. This is labeled as step 1.
Trace the pathway through the brain: The corticospinal tract passes through the corona radiata and internal capsule, which are white matter structures that help transmit signals from the cortex to the brainstem. This is labeled as step 2.
Follow the pathway through the brainstem: The tract continues through the midbrain and pons, which are part of the brainstem. This is labeled as step 3. Then, it reaches the medullary pyramids in the medulla oblongata, where most fibers decussate (cross to the opposite side). This is labeled as step 4.
Track the pathway in the spinal cord: After decussation, the fibers travel down the lateral funiculus of the spinal cord. This is labeled as step 5. Finally, the fibers synapse with lower motor neurons in the anterior horn of the spinal gray matter, which is labeled as step 6.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Corticospinal Tract

The corticospinal tract is a major neural pathway that originates in the cerebral cortex and descends through the brainstem and spinal cord. It is primarily responsible for voluntary motor control of the body, particularly fine motor skills. Understanding its structure and function is crucial for identifying the components involved in motor signal transmission.
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Decussation

Decussation refers to the crossing over of nerve fibers from one side of the central nervous system to the other. In the context of the corticospinal tract, most fibers decussate at the medullary pyramids, which is essential for the contralateral control of motor functions. This concept is vital for understanding how motor commands are processed and executed on the opposite side of the body.

Upper Motor Neurons

Upper motor neurons are the neurons that originate in the motor areas of the cerebral cortex and project down to the spinal cord. They play a critical role in initiating and regulating voluntary movements. Identifying their location and pathways is essential for understanding the corticospinal tract's function and the overall motor control system.
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