What set of nerves is responsible for carrying information from the body to the CNS?

Although terminology seems to indicate otherwise, there is really only one nervous system in the body. Although each subdivision of the system is also called a "nervous system," all of these smaller systems belong to the single, highly integrated nervous system. Each subdivision has structural and functional characteristics that distinguish it from the others. The nervous system as a whole is divided into two subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS).

The Central Nervous System

The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault, and the spinal cord is in the vertebral canal of the vertebral column. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum.

The Peripheral Nervous System

The organs of the peripheral nervous system are the nerves and ganglia. Nerves are bundles of nerve fibers, much like muscles are bundles of muscle fibers. Cranial nerves and spinal nerves extend from the CNS to peripheral organs such as muscles and glands. Ganglia are collections, or small knots, of nerve cell bodies outside the CNS.

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (motor) division. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action.

Finally, the efferent or motor division is again subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system, also called the somatomotor or somatic efferent nervous system, supplies motor impulses to the skeletal muscles. Because these nerves permit conscious control of the skeletal muscles, it is sometimes called the voluntary nervous system. The autonomic nervous system, also called the visceral efferent nervous system, supplies motor impulses to cardiac muscle, to smooth muscle, and to glandular epithelium. It is further subdivided into sympathetic and parasympathetic divisions. Because the autonomic nervous system regulates involuntary or automatic functions, it is called the involuntary nervous system.

The neuromuscular system includes all the muscles in the body and the nerves serving them.

Every movement the body makes requires communication between the brain and the muscles. The nervous system provides the link between thoughts and actions by relaying messages from the brain to other parts of the body.

Nerves and muscles, working together as the neuromuscular system, make the body move as you want it to and also control functions such as breathing.

How does the neuromuscular system work?

Nerves have cells called neurons. Neurons carry messages from the brain via the spinal cord. The neurons that carry these messages to the muscles are called motor neurons.

Each motor neuron ending sits very close to a muscle fibre. Where they sit together is called a neuromuscular junction. The motor neurons release a chemical, which is picked up by the muscle fibre. This tells the muscle fibre to contract, which makes the muscles move.

Diseases involving the neuromuscular system

Many different diseases affect the neuromuscular system, and together they are known as neuromuscular diseases.

Some examples of neuromuscular diseases are:

• neuropathies (problems with the nerves), such as Charcot-Marie-Tooth disease or motor neuron disease
• myopathies (problems with the muscles), such as muscular dystrophy
• neuromuscular autoimmune conditions, such as myasthenia gravis or multiple sclerosis

In some neuromuscular diseases, the nerves are damaged, and do not carry messages from the brain as they should. In others, the muscles are damaged, and they either cannot receive messages from motor neurons, or they cannot respond as they should.

Either way, the person affected can have problems with tiredness, weakness, muscle pain, wasting and spasms. Often, the symptoms affect the arms and legs more than other parts of the body.

In severe cases, neuromuscular diseases can lead to difficulties in swallowing, speaking and breathing.

Treatments for neuromuscular diseases generally aim to ease symptoms and improve quality of life, but in many cases there are no effective medications. Unfortunately, most neuromuscular disorders cannot currently be cured.

What nerves send information to the CNS?

What carries information from the CNS to the body?