Advanced Placement (AP) Biology Practice Exam

What is a primary function of the endocrine system?

1. Regulates body temperature directly.

2. Secretes hormones into the blood from ductless glands.

3. Provides immediate responses to stimuli.

4. Controls voluntary muscle movements.

The correct answer is: Secretes hormones into the blood from ductless glands.

The primary function of the endocrine system is accurately captured by the choice mentioning the secretion of hormones into the blood from ductless glands. The endocrine system is responsible for regulating various physiological processes through chemical signals known as hormones. These hormones are released directly into the bloodstream by endocrine glands, such as the pituitary, thyroid, and adrenal glands. Once in the bloodstream, hormones can travel to target organs or tissues, where they elicit specific responses that help maintain homeostasis, regulate metabolism, growth, mood, and reproductive processes. Unlike systems that provide immediate responses, such as the nervous system, the effects of the endocrine system can be longer-lasting and more generalized, acting over a longer period. The other options do not capture the primary regulatory role of the endocrine system, highlighting its function in hormonal signaling rather than immediate responses or physical control of muscles.