The nervous system has three main functions: sensation, integration, and motor output. Sensory functions detect and process stimuli from external and internal environments. This information is collected by specialized receptors located throughout the body and transmitted to the central nervous system or CNS for processing. Integrative functions process and interpret sensory information received by the CNS, which is used to make decisions and generate the appropriate responses. Motor functions transmit signals from the CNS to muscles and glands. These signals result in voluntary or involuntary responses, such as controlling movements, maintaining posture, and regulating the body's internal environment. For example, when a person writes with a pen, mechanoreceptors in their fingers sense the pen. Next, the CNS integrates tactile sensations with visual information about the paper and the intended size and shape of letters. Then the brain sends motor signals to muscles in the hand and arm to move the pen, enabling legible writing.