- The spinal cord is a long, cylindrical structure made of nervous tissue that extends from the brainstem (specifically the medulla oblongata) down through the vertebral canal, terminating around the level of the first or second lumbar vertebra in adults.
- It serves as the primary communication pathway between the brain and the rest of the body, transmitting sensory input to the brain and conveying motor commands from the brain to the peripheral body. In addition to serving as a conduit, the spinal cord also plays a direct role in reflex activity, acting independently of the brain in some cases to produce immediate responses to stimuli.
- Structurally, the spinal cord is protected by three meninges: the dura mater (outermost), arachnoid mater (middle), and pia mater (innermost), which surround the cord and enclose the cerebrospinal fluid (CSF) that cushions and nourishes the tissue. The cord is housed within the vertebral column, and its integrity is essential for the proper functioning of both the central and peripheral nervous systems. It is divided into 31 segments, each giving rise to a pair of spinal nerves that exit through openings between the vertebrae to innervate specific regions of the body, forming a key part of the somatic and autonomic nervous systems.
- The spinal cord has a distinctive H-shaped core of gray matter surrounded by white matter. The gray matter contains neuronal cell bodies, interneurons, and motor neurons, and is involved in processing incoming and outgoing information. The dorsal (posterior) horns receive sensory information from afferent nerves, while the ventral (anterior) horns contain motor neurons that send signals to skeletal muscles. The white matter, composed mainly of myelinated axons, is arranged into ascending tracts (carrying sensory information to the brain) and descending tracts (carrying motor commands from the brain).
- A remarkable function of the spinal cord is its role in reflex arcs, which are automatic, rapid responses to stimuli that occur without direct involvement of the brain. For example, the patellar reflex (knee-jerk response) is mediated solely by the spinal cord. These reflexes are vital for survival, enabling quick reactions to potentially harmful stimuli and helping to maintain posture and balance.
- Damage to the spinal cord can have severe and often irreversible consequences, depending on the level and extent of injury. Spinal cord injuries may result in paralysis, loss of sensation, or autonomic dysfunction below the site of injury. Conditions such as multiple sclerosis, amyotrophic lateral sclerosis (ALS), spinal tumors, and herniated discs can also compromise spinal cord function. Modern medical imaging, neurorehabilitation, and experimental treatments like stem cell therapy and neuroprosthetics are areas of ongoing research aimed at improving outcomes for individuals with spinal cord disorders.
