Correct Answer: Internal control of the body

The internal control of the body is directed by two systems: the nervous system and he endocrine system. The endocrine system is made up of a series of glands that release chemicals directly into the blood stream. On the other hand, the nervous system is responsible for the transmission of impulses and formation of responses to stimuli. Coordination is needed between these two organ systems. The hypothalamus is the portion of the brain that controls the pituitary gland. These organs are connected by nerves and blood vessels. The hypothalamus sends messages to the pituitary, which then releases its own chemicals, or stimulates other glands to release theirs.

When pathogens like parasites, fungi, bacteria, and viruses invade the body, the coordination between the nervous and endocrine systems might be interrupted, and thus the internal control  of the body is affected.