What controls most hormone concentrations?Multiple ChoiceNegative feedbackPositive feedbackExposure to sunMuscle contraction

1. Break Down the Problem

The question requires identifying what mechanism controls most hormone concentrations. The options provided include:

• Negative feedback
• Positive feedback
• Exposure to sun
• Muscle contraction

2. Relevant Concepts

To address hormone regulation, it's essential to understand:

• Negative Feedback: A process where the output of a system inhibits its own production, helping to maintain homeostasis.
• Positive Feedback: A process where the output enhances or increases the production of a substance.
• Other options like exposure to sun and muscle contraction are not primary controls over hormone levels.

3. Analysis and Detail

• Negative Feedback: Commonly regulates hormones such as insulin, cortisol, and thyroid hormones. For example, when blood glucose levels rise, insulin is secreted to lower glucose levels, which in turn reduces insulin secretion.
• Positive Feedback: Less common and typically occurs during specific processes, such as childbirth where oxytocin increases contractions, leading to more release of oxytocin.

4. Verify and Summarize

Negative feedback is the predominant mechanism in hormone regulation. Most hormones are maintained at optimal levels through this means, whereas positive feedback is less common.

Final Answer

The correct answer is Negative feedback, as it controls most hormone concentrations by maintaining homeostasis in the body.