Major Functions of the Nervous System^[1]

The major functions of the nervous system are sensation, integration, and response.

Sensation

The first major function of the nervous system is sensation—receiving information about the environment to take in what is happening outside the body and also within the body. The sensory functions of the nervous system can detect a change in homeostasis or the environment, known as a stimulus. The senses we think of most are the “big five” or the major senses: taste, smell, touch, sight, and hearing, but there are actually more senses than just those. Those five are all senses that detect and allow us to consciously perceive stimuli from the outside world. Additional sensory receptors can receive information from the inside of the body (internal environment), such as temperature, blood pressure, the stretch of an organ wall, or the concentration of certain ions in the blood. Additional information about the senses is discussed in the “Senses” section.

Integration

Stimuli received by sensory structures are communicated to the nervous system where the information is analyzed in a process called integration. Stimuli are interpreted, compared with other stimuli, memories of previous stimuli, and the state of the individual at the particular time. Decisions are made whether to ignore a stimulus or whether to generate a specific response to the stimulus. For example, during a baseball game, the stimulus of a baseball pitched to a batter does not automatically cause a response of the batter swinging. The batter considers the trajectory of the ball and its speed, the current count of three balls and one strike, and the score of the game when deciding whether to swing at the ball or let it pass by in the hope of getting a walk to first base.

Response

The nervous system produces a response to a stimulus perceived by our senses. An example of a response is movement of voluntary muscles, such as moving your fingers to answer a text that you just received and read with your eyes, but there are numerous ways our body responds to sensory stimuli.

Responses can be divided into those that are under voluntary control or involuntary control. For example, the nervous system can respond by stimulating all three types of muscle tissue to contract, such as voluntary skeletal muscle being stimulated to move the skeleton, involuntary cardiac muscle being stimulated to increase heart rate during exercise, and smooth muscle being stimulated to move food through the digestive tract. Responses also include the neural control of glands in the body, such as the production and secretion of sweat by the sweat glands to decrease body temperature.