Peripheral Nervous System

The peripheral nervous system consists of many nerves that branch from the brain and spinal cord to the periphery, or outer edges, of the body. Twelve pairs of cranial nerves branch from the brain and transmit information to and from the eyes, ears, nose, and tongue. Cranial nerves also control muscles in the face and neck. Thirty - one pairs of spinal nerves branch from the spine. Spinal nerves transmit information to and from all other parts of the body. The peripheral nervous system can be further subdivided into two main divisions, the somatic nervous system and the autonomic nervous system.

The somatic nevous system is concerned with a person's external environment. This system consists of sensory and motor neurons. Sensory neurons transmit impulses from sense organs to the central nervous system from the central nervous system to activate muscles or glands. The result is a response to a stimulus. When touching a sharp or hot object, you move your hand away within fractions of a second. Within that time frame, an impulse had traveled along sensory neurons to the central nervous system and along motor neurons to muscles in your hand.

The autonomic nervous system involves a person's internal environment. This part of the peripheral system controls involuntary actions and regulates heart rate and body temperature. The autonomic system is a two - part system. One part, the sympathetic nervous system, prepares the body for emergencies. The other part, the parasympathetic system, counterbalances the sympathetic system. This system maintains the body's normal state and restores balance after an emergency.

The brain is protected by the cranium and meninges.

The somatic and autonomic nervous systems are the two main divisions of the peripheral nervous system.