The spinal cord is a long, slender bundle of nerve tissue extending from the brainstem down to the lower back. It acts as a primary communication link between the brain and the rest of the body. Within this structure, the dorsal spinal cord represents the posterior (back) section. This region holds a fundamental role in sensation.
Where is the Dorsal Spinal Cord?
The dorsal spinal cord is situated within the vertebral column, a bony structure that protects this delicate nervous tissue. It occupies the posterior portion of the spinal cord, separate from the anterior (front) sections. This anatomical arrangement positions it to receive incoming sensory signals.
The spinal cord consists of both white matter and gray matter. White matter is composed of myelinated nerve fibers that transmit signals quickly. Gray matter contains neuron cell bodies, unmyelinated axons, dendrites, and glial cells. Within the gray matter, the dorsal horns are located in the posterior region and serve as the main receiving areas for sensory information.
Processing Our Senses
The dorsal spinal cord functions as the initial entry point for various sensory signals. It processes a wide array of sensations, including touch (light touch, pressure, and vibration). It also handles temperature perception, distinguishing between hot and cold. It receives pain signals.
Another important sensation processed here is proprioception, which refers to the body’s awareness of its own position and movement. This allows individuals to know where their limbs are without looking, contributing to coordination and balance. As sensory neurons enter the dorsal spinal cord, they synapse with other neurons within the dorsal horns. This synaptic connection represents the initial relay point, where incoming signals are organized and processed before continuing their journey toward the brain.
The Journey of Sensation to the Brain
After initial processing or relay within the dorsal spinal cord, sensory signals embark on specific ascending pathways to reach the brain for conscious interpretation. Two main routes facilitate this transmission: the dorsal column-medial lemniscus pathway and the spinothalamic tracts. The dorsal column-medial lemniscus pathway conveys highly discriminative sensations, including fine touch, vibration, and proprioception. These signals travel up the spinal cord in the dorsal columns, cross over in the brainstem, and then proceed through the medial lemniscus to the thalamus.
The spinothalamic tracts primarily transmit information related to pain and temperature. These signals cross over to the opposite side of the spinal cord upon entering the dorsal horn. They then ascend through the spinal cord, brainstem, and also synapse in the thalamus. From the thalamus, both pathways project to the somatosensory cortex, a region in the brain’s parietal lobe. It is within the somatosensory cortex that these raw sensory inputs are ultimately interpreted, allowing individuals to consciously perceive and understand the sensations they experience.
When the Dorsal Spinal Cord is Injured
Damage to the dorsal spinal cord can disrupt the body’s ability to process and transmit sensory information. Injuries here often lead to specific sensory deficits. Common symptoms include numbness, a loss of feeling in certain areas of the body, or tingling sensations. Individuals might also experience altered sensation, where touch or temperature feels different or distorted.
A consequence of dorsal spinal cord injury can be the loss of proprioception below the level of the injury. This impairs a person’s awareness of their body’s position and movement, making coordinated actions challenging. Such injuries can stem from various causes, including traumatic events like falls or vehicle accidents, compression from conditions like herniated discs, or certain neurological diseases that affect the spinal cord. The impairment of sensory feedback due to dorsal spinal cord damage can impact an individual’s daily activities and overall quality of life.