Which statement best describes the central principle of physiology related to homeostasis?

• A. The internal environment is primarily regulated by voluntary skeletal muscle activity.
• B. The body keeps all physiological variables constant with no fluctuation.
• C. Organ systems function independently with minimal coordination to preserve energy.
• D. The body maintains a relatively stable internal environment despite changes in the external environment.

Answer: (D)

Verified step by step guidance

1. Understand the concept of homeostasis: it refers to the body's ability to maintain a stable internal environment despite external changes.
2. Recognize that homeostasis involves regulation of physiological variables such as temperature, pH, and electrolyte balance within a narrow range.
3. Note that homeostasis is primarily controlled by involuntary mechanisms, including feedback systems involving the nervous and endocrine systems, rather than voluntary skeletal muscle activity.
4. Acknowledge that physiological variables do fluctuate within a normal range; the body does not keep them absolutely constant but maintains them relatively stable.
5. Realize that organ systems work in a coordinated manner to maintain homeostasis, rather than functioning independently with minimal coordination.