Disorders that affect the brain, spinal cord, and nerves are called neurologic disorders.
Neurologic symptoms—symptoms caused by a disorder that affects part or all of the nervous system—can vary greatly because the nervous system controls so many different body functions. Symptoms can include all forms of pain, including headache and back pain. Muscles, skin sensation, the special senses (vision, taste, smell, and hearing), and other senses depend on nerves to function normally. Thus, neurologic symptoms can include muscle weakness or lack of coordination, abnormal sensations in the skin, and disturbances of vision, taste, smell, and hearing.
Neurologic disorders can interfere with sleep, making a person anxious or excited at bedtime and thus tired and sleepy during the day.
Neurologic symptoms may be minor (such as a foot that has fallen asleep) or life threatening (such as coma due to stroke).
The characteristics and pattern of symptoms help doctors diagnose the neurologic disorder. Doctors also do a neurologic examination, which can detect disorders of the brain, spinal cord, and nerves in other parts of the body (peripheral nerves).
Peripheral nerves include
The nerves that connect the head, face, eyes, nose, muscles, and ears to the brain (cranial nerves)
The nerves that connect the spinal cord to the rest of the body: 31 pairs of spinal nerves
Nerves that run throughout the body
Some peripheral nerves (sensory nerves) carry sensory information (about such things as pain, temperature, vibration, smells, and sounds) to the spinal cord and then to the brain. Others (motor nerves) carry impulses that control muscle movement from the brain through the spinal cord to the muscles. Still others (called the autonomic nerves) carry information about the body and external environment to the internal organs, such as the blood vessels, stomach, intestine, liver, kidneys, and bladder. In response to this information, autonomic nerves stimulate or inhibit the organs they supply. These nerves work automatically (autonomously), without a person’s conscious effort.
If motor nerves are damaged, muscles may weaken or become paralyzed. If sensory nerves are damaged, abnormal sensations may be felt or sensation, sight, or another sense may be impaired or lost. If autonomic nerves are damaged, the organ they regulate may malfunction. For example, blood pressure may not increase as it normally does when a person stands, and the person may feel light-headed.