Positive and Negative Feedback Mechanisms – Endocrine System Example

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"Positive and Negative Feedback Mechanisms" is a wonderful example of a paper on the endocrine system. The presence of positive or negative feedback strongly suggests that a significant change in the homeostatic balance of the human body has just occurred. Unlike positive feedback, it is more common for the human body to receive a negative feedback mechanism each time the body undergoes a homeostatic imbalance (Marieb, 2004, pp. 10– 11).                       In the study of endocrinology, negative feedback occurs each time a person experiences a sudden increase or decrease in the level of hormones.

For example, given that there is a sudden decrease in the calcium homeostasis in the blood (< 9-11mg/100ml), the parathyroid gland will secrete parathyroid hormone (PTH) to regulate the calcium ion (CA2+) in the blood. Basically, the PTH is responsible for the development of osteoclasts (a. k.a. the process of destructing the bone cells to release more calcium in the blood). On the other hand, given that there is excessive calcium in the blood (> 9-11mg/100ml), the parathyroid gland will secrete calcitonin hormone to stimulate the calcium salt deposit in the bone (Marieb, 2004, p.

290). Thus, maintaining the balance of calcium levels in the blood.                       The process of accelerating blood clots is considered a positive feedback mechanism (Martini, 2007, p. 10; Marieb, 2004, p. 10). Based on scientific explanation, the process of blood clotting evolves in three major phases known as platelet plug formation, vascular spasms, and coagulation. As soon as the platelet plug forms, the platelet releases some chemicals to attract more platelets to pile up in the wounded area. Before a vascular spasm takes place, the platelet will release serotonin to make the vessels constrict.

Eventually, coagulation takes place when the injured tissue releases thromboplastin (responsible for blood clotting) and PF3 (interacts with thromboplastin and other blood protein clotting factors to form clotting cascade) (Marieb, 2004, p. 316).  


Marieb, E. N. (2004). Essentials of Human Anatomy & Physiology. 7th Edition. Pearson Education South Asia PTE. Ltd.

Martini, F. (2007). Anatomy and Physiology 2007 Edition. Jurong: Peason Education South Asia Pte. Ltd.

Thapar, K., Kovacs, K., Scheithauer, B., & Lloyd, R. (2001). Diagnosis and Management of Pituitary Tumors. NJ: Humana Press Inc.

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