Can you help me with the Nervous System?

The nervous system is made of your brain, spinal cord, and nerves that reach to every part of your body.

The nervous system is the control center for all of your body.

There are two common ways to divide up the nervous system: The Central nervous system and Peripheral nervous system.

The central nervous system (CNS): is divided into two major parts: the brain and the spinal cord. An animal's response to a stimulus is coordinated by its central nervous system. The CNS gathers information about, and responds to, changes in the environment.

The peripheral nervous system (PNS): is made up of nerve cells that carry information to or from the CNS.

Together the nervous system:

.Senses your external and internal surroundings

.Communicates information between your brain and spinal cord and other tissues

.Coordinates voluntary movements (by the PNS)

.Coordinates and regulates involuntary functions like breathing, heart rate, blood pressure and body temperature and reflexes (controlled by the CNS)

The nervious system communicates through nerve cells.

The brain is the center of the nervous system. Your brain alone has around 100 billion nerve cells, also called neurons. Neurons gather and carry electrochemical signals to and from different areas of the nervous system as well as between the nervous system and other tissues and organs. When neurons are stimulated they transmit an electrical impulse and sends it to the appropriot part of your body, trigguring a responce.

The nervous system takes in information through our senses, processes the information and triggers reactions, such as making your muscles move or causing you to feel pain.

Your brain receives information directly from your skin, ears, eyes, nose and mouth, as well as from the rest of your body via the spinal cord. It uses this information to help you react, remember, think and plan, and then sends out the appropriate instructions to your body.

Divisions are based partly on anatomy and partly on function.

The central nervous system (CNS) consists of the brain and spinal cord. The brain has many functions such as controlling muscle contraction, hormone secretion, emotions, memories, cognitive skills, etc. The spinal cord serves as a link between the brain and spinal nerves (cf. below).

The peripheral nervous system (PNS) consists of all parts of the nervous system outside the CNS. It may be divided into cranial nerves, which arise directly from the brain, and are 12 in number. The spinal nerves arise from the spinal cord and there are 31 pairs.

The PNS may be divided in terms of function into the sensory and motor nervous system. The sensory system transmits nerve impulses from sensory receptors to the CNS. The motor nervous system sends nerve impulses from the CNS to effectors, i.e. muscles and glands.

The motor nervous system is further divided into the voluntary nervous system and the autonomic nervous system. The effectors of the voluntary nervous system are skeletal muscles, e.g. if you raise your lower arm your motor nervous system sends an impulse to make the biceps muscle contract. This is done voluntarily.

The effectors of the autonomic nervous system are cardiac and smooth muscle plus all glands. You have no voluntary control over these. It is further divided into the sympathetic and parasympathetic autonomic nervous system. These two branches are not completely switched on or off but achieve a balance between them depending on the body’s needs.

The sympathetic branch is to enable your body for activity such as the flight or fight response. It generally, in very simple terms, makes things go faster. This would be release of adrenaline, increase in blood sugar (glands); dilation of pupils, increased heart rate, increased breathing, dilation of arterioles in skin (muscles). The principal exception is digestion, which the sympathetic branch slows down. The parasympathetic branch has the opposite effects, with the rate of digestion increasing. So although your mother probably did not know why but when she told you not to exercise on a full stomach she was right.

The gastrointestinal system also has a whole branch of the autonomic nervous system that acts quite independently but as that is not normally dealt with in introducing the nervous system we will not go there.

The peripheral nervous system is subdivided into nerves, the autonomic system, and the somatic system. The autonomic nervous system is further subdivided into the parasympathetic and sympathetic nervous systems.

The enteric nervous system is an independent subsystem of the peripheral nervous system.

The central nervous system includes the brain and spinal cord and has various centers that integrate of all the information in the body. These can be subdivided into lower centers that carry out essential body functions and higher centers that control more sophisticated information processing.

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