Activity 4
FEEDBACK MECHANISM
By GEORGETTE E. ZALDIVAR
Give other examples of disturbances in the internal environment that can act as a stimulus to a feedback mechanism.
The human body necessitates for there to be a state of equilibrium in its internal environment, which we know as homeostasis. The body’s homeostasis is interconnected with the body’s responsiveness to internal stimulation; any changes in the body’s internal environment will form a response to counter the change and return to the state of equilibrium. Therefore, there is a cycle of events called the feedback system that describes how the human body controls and maintains homeostasis (Tortora & Derrickson, 2014).
A feedback system includes a stimulus, a sensor, a control center, and an effector. How it works is a sensor, which recognizes a stimulus, sends a signal to the control center, which will, in turn, send alerts to the effectors cells to produce a response to the stimulus. Such a process is continuously repeated. A negative feedback system reverses a change in a controlled condition, while a positive feedback system solidifies or reinforces a change in a controlled body condition (Tortora & Derrickson, 2014).
One example of a positive feedback mechanism is when a wound triggers bleeding. In which case, the system sends out a response loop to form blood clots that would stop the bleeding.
Prior to the discovery of oxygen 18th century, hypoxia, or the lack of oxygen thereof, was commonly stumbled upon and is recognized to be detrimental to human life. Upon its discovery, though, oxygen was utilized as a therapeutic agent to treat the critically ill. However, Paul Bert and James Lorrain Smith were able to discover the existence of oxygen toxicity. This phenomenon is caused by oxygen’s willingness to accept electrons and form various variants of aggressive radicals that disrupt normal cell functions. The human body has managed to evolve to maintain oxygen homeostasis through various molecular systems that are activated when there is a lack of oxygen or to scavenge and transform oxygen radicals when there is an abundance (Tretter, et al., 2020). Therefore, it has been established that our body needs to maintain the blood’s oxygen saturation level between 95% to 100%. An extreme decrease or increase of such levels would be the stimulus of the feedback system, which the sensors will detect and will, therefore, send a signal to the control center. In turn, the control center will send signals to the effectors and facilitate a response: upon the glomus cells’ detection of hypoxia, they depolarize and send signals to the respiratory centers in the medulla oblongata, which causes the respiratory rate to increase. On the other hand, because no organisms would have been exposed to supraphysiological oxygen tensions during evolution, biological defenses against hyperoxia may be weaker than those against hypoxia. Although oxygen levels in the atmosphere have occasionally exceeded the current 21%, they have never been as high as what man can produce. Hyperoxia protection must thus be left to the discretion of medicine, whereas hypoxia is quickly detected, and preventive measures at the cellular level are activated (Maltepe & Saugstad, 2009).
Another example of an internal stimulus is the lack or excess of water thereof. Because evaporative cooling is the most effective method of dissipating excess body heat, maintaining body water homeostasis is essential for preventing hyperthermia. Water homeostasis is achieved via water intake and loss regulation. The former is undertaken through thirst sensations that motivate water acquisition, whilst the vasopressin’s antidiuretic action governs the latter. Vasopressin secretion and thirst are stimulated by increases in extracellular fluid osmolality and declines in blood pressure and/or blood volume, signals precipitated by water depletion concomitant with the excessive evaporative water loss required to prevent hyperthermia. They are also stimulated by increases in body temperature (Sladek & Johnson, 2013).
REFERENCES:
Maltepe, E., & Saugstad, O. D. (2009). Oxygen in Health and Disease: Regulation of Oxygen Homeostasis-Clinical Implications. Pediatric Research, 261-268.
Sladek, C. D., & Johnson, A. K. (2013). Integration of thermal and osmotic regulation of water homeostasis: the role of TRPV channels. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 305(7), R669–R678. https://doi.org/10.1152/ajpregu.00270.2013
Tortora, G. J., & Derrickson, B. (2014). 1.4 Homeostasis. In G. J. Tortora, & B. Derrickson, Principles of Anatomy and Physiology (pp. 8-12). John Wiley & Sons, Inc.
Tretter, V., Zach, M.-L., Böhme, S., Ullrich, R., Markstaller, K., & Klein, K. U. (2020). Investigating Disturbances of Oxygen Homeostasis: From Cellular Mechanisms to the Clinical Practice. Frontiers in Physiology, 7. Retrieved from https://doi.org/10.3389/fphys.2020.0094