Spinal Cord Anatomy: 3 Functions of the Spinal Cord

The spinal cord is a long chain of nerve cells from the brainstem to the cauda equina, a bundle of nerve roots near the second lumbar vertebra. The spinal cord, along with the brain, forms the central nervous system and controls the movements and functions of the body. The spinal cord contains of 62 spinal nerves, blood vessels, and cerebrospinal fluid.

The spinal canal runs the length of the vertebral column (or backbone) and contains four sections from top to bottom: the cervical curve, the thoracic curve, the lumbar curve, and the sacral curve. At all points along this canal, bundles of nerves branch out to communicate with the body's peripheral nervous system. For example, nerve cells in the lumbar region connect with the digestive system, while nerve cells in the sacral region connect with the legs and feet.

There are 31 pairs of spinal nerves that span the human spinal cord. Each is made up of nerve fibers attached to posterior roots and anterior roots. Posterior nerve roots, also called sensory roots or afferent roots, send information from the body to the brain. Anterior nerve roots, also called motor roots or efferent roots, carry information from the brain to the body.

Each bundle of spinal nerves connects to a pair of dorsal root ganglia, made up of cell bodies of sensory neurons that extend outside of the spinal canal and connect to the peripheral nervous system. Spinal nerve cells are protected by cerebrospinal fluid and three layers of meninges: the pia mater, the dura mater, and the arachnoid mater.

The spinal cord is responsible for sensory, motor, and autonomic functions:

1. 1. Sensory functions: The spinal cord transmits the sensations of touch, temperature, pressure, and pain back to the brain via sensory neurons. Sensations emanating from the eyes, ears, mouth, and nose transmit directly through the cranium and do not require the spinal cord.
2. 2. Motor functions: The spinal cord communicates all messages from the brain to various parts of the body, including arms, legs, chest, and pelvis. Muscle and ligament contractions are controlled by motor neurons.
3. 3. Autonomic functions: The spinal cord also serves as the main conduit for the autonomic nervous system, which controls all parts of the body that are not governed by conscious thought. The smooth muscle in a digestive tract, the cardiac muscle that controls blood pressure and heart rate, and all the body's internal organs are controlled by the brain via the spinal cord.

The spinal cord works by sending nerve impulses up and down the spinal canal via electrical charges. Information is sent along the spinal column via nerve impulses also known as action potentials. Electrical charges allow an action potential to travel along the axon of a nerve cell. The cell then transmits its message to another nerve cell via a synapse, or a microscopic gap between neurons. Neurotransmitters leap between the axon of one cell and bind with the receptors on the dendrite (or extension) of an adjacent neuron. Through an endless stream of nerve impulses, vital information spreads throughout the entire central nervous system and peripheral nervous system.

Spinal nerves consist of gray and white matter. The gray matter, which runs through the center of the spinal column, is responsible for processing neural stimuli, while the white matter that surrounds it is responsible for sending and receiving the information.

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