Calcium levels in Mr. Gallariani's blood are dropping to dangerously low levels. The hormone PTH is released and soon blood calcium levels begin to rise. Shortly after, PTH release slows. Is this an example of a positive or negative feedback mechanism? What is the initial stimulus? What is the result?

Verified step by step guidance

1. Identify the key components of the feedback mechanism: stimulus, response, and feedback.
2. Recognize that the initial stimulus is the drop in calcium levels in Mr. Gallariani's blood.
3. Understand that the response to the stimulus is the release of parathyroid hormone (PTH), which increases blood calcium levels.
4. Determine that the slowing of PTH release after calcium levels rise indicates a feedback mechanism.
5. Conclude that this is a negative feedback mechanism, as the response (PTH release) counteracts the initial stimulus (low calcium levels) to restore balance.

Key Concepts

Negative Feedback Mechanism

A negative feedback mechanism is a process that counteracts a change in a physiological variable, helping to maintain homeostasis. In this case, the release of parathyroid hormone (PTH) in response to low calcium levels is a classic example, as it works to increase calcium levels back to a normal range, thus reducing further PTH release.

Initial Stimulus

The initial stimulus refers to the condition or change that triggers a physiological response. In Mr. Gallariani's case, the dangerously low levels of calcium in the blood serve as the initial stimulus that prompts the release of PTH to restore calcium levels.

Physiological Result

The physiological result is the outcome of the body's response to the initial stimulus. Here, the result of PTH release is an increase in blood calcium levels, which alleviates the low calcium condition and ultimately leads to a decrease in PTH secretion, illustrating the body's regulatory mechanisms.