Chapter 13 - Section 13.1 - Study Guide - Assess Your Learning Outcomes - Page 504: 13

Descending tracts in the spinal cord are neural pathways that carry motor commands from the brain to the spinal cord and peripheral muscles. These tracts are responsible for initiating and controlling voluntary movements and other motor functions. Here are some of the key descending tracts of the spinal cord, along with their names and functions: 1. **Corticospinal Tract (Pyramidal Tract)**: - **Function**: The corticospinal tract is responsible for fine, skilled voluntary movements of the limbs and digits. It controls voluntary muscle movements, particularly those related to precise motor tasks. - **Pathway**: The tract originates in the primary motor cortex of the cerebral cortex. Its fibers descend through the internal capsule, the brainstem (specifically the medulla), and then into the spinal cord. In the spinal cord, the corticospinal tract decussates (crosses over) to the opposite side, and its fibers synapse with lower motor neurons in the ventral horn to control muscles. 2. **Rubrospinal Tract**: - **Function**: The rubrospinal tract plays a role in the control of muscle tone and motor coordination. It facilitates flexor muscle activity and inhibits extensor muscle activity. - **Pathway**: This tract originates in the red nucleus of the midbrain and descends into the spinal cord, primarily on the contralateral side. 3. **Vestibulospinal Tracts** (Lateral and Medial Vestibulospinal Tracts): - **Function**: These tracts are involved in maintaining posture and balance. They help control muscle tone and facilitate the maintenance of an upright position. - **Pathway**: The lateral vestibulospinal tract originates in the lateral vestibular nucleus, while the medial vestibulospinal tract originates in the medial vestibular nucleus, both located in the brainstem. These tracts descend along the spinal cord without crossing over, primarily on the ipsilateral side. 4. **Tectospinal Tract**: - **Function**: The tectospinal tract is involved in coordinating head and eye movements in response to visual and auditory stimuli, particularly in response to sudden or unexpected sensory input. - **Pathway**: It originates in the superior colliculus of the midbrain and descends to the cervical spinal cord. 5. **Reticulospinal Tracts** (Medial and Lateral Reticulospinal Tracts): - **Function**: These tracts influence muscle tone and reflex activity. The medial reticulospinal tract facilitates extensor muscle activity, while the lateral reticulospinal tract inhibits extensor muscle activity and facilitates flexor muscle activity. - **Pathway**: The tracts originate in the reticular formation of the brainstem and descend along the spinal cord. These descending tracts play essential roles in initiating and regulating voluntary movements, maintaining posture and balance, and coordinating various motor functions. The specific functions of each tract are associated with different aspects of motor control, allowing us to perform a wide range of movements and adapt to changes in our environment.

Descending tracts in the spinal cord are neural pathways that carry motor commands from the brain to the spinal cord and peripheral muscles. These tracts are responsible for initiating and controlling voluntary movements and other motor functions. Here are some of the key descending tracts of the spinal cord, along with their names and functions: 1. **Corticospinal Tract (Pyramidal Tract)**: - **Function**: The corticospinal tract is responsible for fine, skilled voluntary movements of the limbs and digits. It controls voluntary muscle movements, particularly those related to precise motor tasks. - **Pathway**: The tract originates in the primary motor cortex of the cerebral cortex. Its fibers descend through the internal capsule, the brainstem (specifically the medulla), and then into the spinal cord. In the spinal cord, the corticospinal tract decussates (crosses over) to the opposite side, and its fibers synapse with lower motor neurons in the ventral horn to control muscles. 2. **Rubrospinal Tract**: - **Function**: The rubrospinal tract plays a role in the control of muscle tone and motor coordination. It facilitates flexor muscle activity and inhibits extensor muscle activity. - **Pathway**: This tract originates in the red nucleus of the midbrain and descends into the spinal cord, primarily on the contralateral side. 3. **Vestibulospinal Tracts** (Lateral and Medial Vestibulospinal Tracts): - **Function**: These tracts are involved in maintaining posture and balance. They help control muscle tone and facilitate the maintenance of an upright position. - **Pathway**: The lateral vestibulospinal tract originates in the lateral vestibular nucleus, while the medial vestibulospinal tract originates in the medial vestibular nucleus, both located in the brainstem. These tracts descend along the spinal cord without crossing over, primarily on the ipsilateral side. 4. **Tectospinal Tract**: - **Function**: The tectospinal tract is involved in coordinating head and eye movements in response to visual and auditory stimuli, particularly in response to sudden or unexpected sensory input. - **Pathway**: It originates in the superior colliculus of the midbrain and descends to the cervical spinal cord. 5. **Reticulospinal Tracts** (Medial and Lateral Reticulospinal Tracts): - **Function**: These tracts influence muscle tone and reflex activity. The medial reticulospinal tract facilitates extensor muscle activity, while the lateral reticulospinal tract inhibits extensor muscle activity and facilitates flexor muscle activity. - **Pathway**: The tracts originate in the reticular formation of the brainstem and descend along the spinal cord. These descending tracts play essential roles in initiating and regulating voluntary movements, maintaining posture and balance, and coordinating various motor functions. The specific functions of each tract are associated with different aspects of motor control, allowing us to perform a wide range of movements and adapt to changes in our environment.