The cervical spine is composed of 7 vertebrae. These vertebrae allow bending and turning of the head, as well as flexion and extension of the neck. Each vertebrae articulates forms a joint) with the vertebrae above and below it. Cervical vertebrae are numbered C1-C7.

The thoracic spine attaches to the ribs in the chest, and is composed of 12 vertebrae. The spinal canal is smaller in the thoracic spine, making it more vulnerable to injury than the spinal canals in the cervical and lumbar regions. The thoracic spine allows you to rotate your trunk. Ribs prevent much sideways movement. There is a small amount of movement of the thoracic spine when you bend forwards and backwards. Thoracic vertebrae are numbered T1-T12.

The lumbosacral vertebrae are thicker and wider than vertebrae of the other regions. The lumbosacral spine is composed of 10 vertebrae. These vertebrae allow you to bend at the waist and also allow some backward movement. Some movement to the side also occurs. Lumbar vertebrae are numbered L1-L5, while sacral vertebrae are numbered S1-S5. The bones of the sacrum are fused.

The spinal cord is connected to the brain and is approximately the diameter of one of your fingers. The spinal cord travels down from the brain through the vertebral column, which surrounds and protects it. Cerebral spinal fluid (CSF) bathes the spinal cord and acts as a cushion to protect delicate nerves against injury from striking up against the inside of the bony vertebrae.

The spinal cord consists of millions of nerve fibers. These fibers transmit impulses, or electrical information, to and from the limbs, trunk, and organs of the body. Impulses travel back and forth between the brain and these structures. Ascending tracts of nerves within the spinal cord carry information from the body upwards to the brain, while descending tracts of nerves carry information from the brain downwards to the body to control body functions and movement.

Spinal nerves, or nerve roots, branch off the spinal cord and exit the vertebrae through a hole in each of the vertebrae called the foramen. They carry information to and from the brain to the rest of the body:

Cervical nerves supply movement and feeling to the arms, neck, and upper trunk.

Thoracic nerves supply the trunk and abdomen.

Lumber and sacral nerves supply the legs, bladder, bowel, and sex organs.

It is important to note that spinal cord segments do not correlate exactly to the level of the vertebral bodies. This can cause confusion in describing and classifying injuries, even among physicians.

Sensory pathways carry sensations from the skin and other parts of the body relating to temperature, pain, and touch to the brain, where sensations are “felt”. Different types of sensations are sent to the brain in different pathways, called tracts.

Autonomic nerves are divided into two types, sympathetic and parasympathetic nerves. The primary role of the autonomic nervous system is to regulate internal environment of the body. It controls the digestive, respiratory, and cardiovascular systems, regulating such things as heart rate, blood pressure, and dilation and constriction of blood vessels. Control is voluntary; that is, not generally under conscious control. Sympathetic and parasympathetic nerves act in opposition to each other. For example, activation of the sympathetic nervous system causes increased heart rate, increased blood pressure, and constriction of blood vessels. The parasympathetic nervous system has the opposite effect: decrease in blood pressure and heart rate and dilation of blood vessels. The two systems generally balance each other well. Damage to nerves of this system can cause problems in regulating this system.