Part I

Maintaining an internal balance within the body is known as homeostasis. How the body goes about regulating this equilibrium is through feedback mechanisms. There are both negative and positive feedback mechanisms. A negative feedback mechanism alters a system whereas a positive feedback mechanism strengthens a system. After you complete your unit reading, conduct some additional research on either a negative or positive feedback system that the body uses. Share this information with your fellow classmates and answer the following:

• What feedback system did you choose and is it positive or negative?
• What makes this mechanism important as the body tries to maintain homeostasis?

Then, later in the week, address the following.

Part II

Two women go to their doctor with suspected thyroid disorders to get their thyroid hormone levels tested via their blood serum. The results of those tests are the following:

– Patient 1 shows a low level of Thyroxine (T4) and a high level of TSH.

– Patient 2 shows a high level of Thyroxine (T4) and a low level of TSH.

Both patients are diagnosed with thyroid disorders. Based on these lab results, answer the following:

• Briefly describe how the secretion of Thyroid hormones is controlled by a negative feedback system.
• What is the diagnosis for Patient 1? What are the symptoms of this disorder?
• What is the diagnosis for Patient 2? What are the symptoms of this disorder?