The nervous system consists of the body’s neurons, which together form the nerves and ganglia which in turn form the brain and related structures. The brain is the organ of thought, emotion, memory, and sensory processing, it serves many aspects of communication and controls various systems and functions. The special senses consist of vision, hearing, taste and smell. The eyes, ears, tongue, and nose gather information about the body’s environment.
From a structural perspective, the nervous system is typically subdivided into two component parts: the central nervous system (CNS), composed of the brain and the spinal cord; and the peripheral nervous system (PNS), composed of the nerves and ganglia outside the brain and spinal cord. The CNS is mostly responsible for organizing motions, processing sensory information, thought, memory, cognition and other such functions. It remains a matter of some debate whether the CNS directly gives rise to consciousness. The peripheral nervous system (PNS) is mostly responsible for gathering information with sensory neurons and directing body movements with motor neuron.
From a functional perspective, the nervous system is again typically divided into two component parts: the somatic nervous system (SNS) and the autonomic nervous sytem (ANS). The SNS is involved in voluntary functions like speaking and sensory processes. The ANS is involved in involuntary processes, such as digestion and regulating blood pressure.
The nervous system is subject to many different diseases. In epilepsy, abnormal electrical activity in the brain can cause seizures. In multiple sclerosis, the immune system attacks the nerve linings, damaging the nerves’ ability to transmit signals. Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is a motor neuron disease which gradually reduces movement in patients. There are also many other diseases of the nervous system.