Functions of the Nervous System
The nervous system is the major controlling, regulatory, and communicating system in
the body. It is the center of all mental activity including thought, learning, and memory.
Together with the endocrine system, the nervous system is responsible for regulating and
maintaining homeostasis. Through its receptors, the nervous system keeps us in touch
with our environment, both external and internal.
Like other systems in the body, the nervous system is composed of organs, principally the
brain, spinal cord, nerves, and ganglia. These, in turn, consist of various tissues, including
nerve, blood, and connective tissue. Together these carry out the complex activities of the
The various activities of the nervous system can be grouped together as three general,
Millions of sensory receptors detect changes, called stimuli, which occur inside and
outside the body. They monitor such things as temperature, light, and sound from the
external environment. Inside the body, the internal environment, receptors detect
variations in pressure, pH, carbondioxide concentration, and the levels of various
electrolytes. All of this gathered information is called sensory input.
Sensory input is converted into electrical signals called nerve impulses that are
transmitted to the brain. There the signals are brought together to create sensations, to
produce thoughts, or to add to memory; Decisions are made each moment based on the
sensory input. This is integration.
Based on the sensory input and integration, the nervous system responds by sending
signals to muscles, causing them to contract, or to glands, causing them to produce
secretions. Muscles and glands are called effectors because they cause an effect in
response to directions from the nervous system. This is the motor output or motor