Chapter 13 - Section 13.1 - The Spinal Cord - Before You Go On - Page 483: 5

Let's break down each of the mentioned spinal tracts, including whether they are ascending or descending, their origin and destination, and their sensory or motor functions: 1. **Gracile Fasciculus:** - **Direction:** Ascending. - **Origin:** It originates in the lower medulla oblongata of the brainstem, specifically from the gracile nucleus. - **Destination:** The gracile fasciculus ascends within the spinal cord and eventually reaches the brainstem and the thalamus. - **Function:** The gracile fasciculus carries proprioceptive (sensory information related to body position and movement), tactile, and vibratory sensations from the lower limbs and lower trunk to the brain. It helps in maintaining posture and coordinating movements. 2. **Lateral Corticospinal Tract:** - **Direction:** Descending. - **Origin:** It originates in the primary motor cortex of the cerebral cortex. - **Destination:** The lateral corticospinal tract descends through the brainstem and spinal cord, ultimately synapsing with lower motor neurons in the anterior horn of the spinal cord. - **Function:** This tract is primarily responsible for voluntary, fine motor control of skeletal muscles on the contralateral (opposite) side of the body. It plays a crucial role in precise and skilled movements. 3. **Lateral Reticulospinal Tract:** - **Direction:** Descending. - **Origin:** It originates in the lateral part of the brainstem, specifically the reticular formation. - **Destination:** The lateral reticulospinal tract descends through the spinal cord. - **Function:** This tract is involved in regulating muscle tone, balance, and posture. It can facilitate or inhibit motor neurons that control muscles involved in maintaining body posture and balance. 4. **Spinothalamic Tract:** - **Direction:** Ascending. - **Origin:** It originates in the spinal cord's dorsal horn, where sensory information from pain and temperature receptors is received. - **Destination:** The spinothalamic tract ascends through the spinal cord, brainstem, and thalamus before reaching the primary somatosensory cortex in the cerebral cortex. - **Function:** This tract carries sensory information related to pain and temperature from the body's periphery (skin and deeper tissues) to the brain. It helps in the perception of these sensory modalities. In summary, the gracile fasciculus and spinothalamic tract are ascending tracts that carry sensory information to the brain, with the gracile fasciculus serving proprioceptive and tactile functions and the spinothalamic tract carrying pain and temperature sensations. On the other hand, the lateral corticospinal and lateral reticulospinal tracts are descending tracts responsible for motor control, with the former involved in voluntary muscle control and the latter contributing to posture and balance.

Let's break down each of the mentioned spinal tracts, including whether they are ascending or descending, their origin and destination, and their sensory or motor functions: 1. **Gracile Fasciculus:** - **Direction:** Ascending. - **Origin:** It originates in the lower medulla oblongata of the brainstem, specifically from the gracile nucleus. - **Destination:** The gracile fasciculus ascends within the spinal cord and eventually reaches the brainstem and the thalamus. - **Function:** The gracile fasciculus carries proprioceptive (sensory information related to body position and movement), tactile, and vibratory sensations from the lower limbs and lower trunk to the brain. It helps in maintaining posture and coordinating movements. 2. **Lateral Corticospinal Tract:** - **Direction:** Descending. - **Origin:** It originates in the primary motor cortex of the cerebral cortex. - **Destination:** The lateral corticospinal tract descends through the brainstem and spinal cord, ultimately synapsing with lower motor neurons in the anterior horn of the spinal cord. - **Function:** This tract is primarily responsible for voluntary, fine motor control of skeletal muscles on the contralateral (opposite) side of the body. It plays a crucial role in precise and skilled movements. 3. **Lateral Reticulospinal Tract:** - **Direction:** Descending. - **Origin:** It originates in the lateral part of the brainstem, specifically the reticular formation. - **Destination:** The lateral reticulospinal tract descends through the spinal cord. - **Function:** This tract is involved in regulating muscle tone, balance, and posture. It can facilitate or inhibit motor neurons that control muscles involved in maintaining body posture and balance. 4. **Spinothalamic Tract:** - **Direction:** Ascending. - **Origin:** It originates in the spinal cord's dorsal horn, where sensory information from pain and temperature receptors is received. - **Destination:** The spinothalamic tract ascends through the spinal cord, brainstem, and thalamus before reaching the primary somatosensory cortex in the cerebral cortex. - **Function:** This tract carries sensory information related to pain and temperature from the body's periphery (skin and deeper tissues) to the brain. It helps in the perception of these sensory modalities. In summary, the gracile fasciculus and spinothalamic tract are ascending tracts that carry sensory information to the brain, with the gracile fasciculus serving proprioceptive and tactile functions and the spinothalamic tract carrying pain and temperature sensations. On the other hand, the lateral corticospinal and lateral reticulospinal tracts are descending tracts responsible for motor control, with the former involved in voluntary muscle control and the latter contributing to posture and balance.