11A Feedback Mechanisms

Homeostasis The relatively constant internal physical and chemical conditions maintained by an organism despite changes that occur inside or outside the body Aka “keeping a balance”

Roles of Internal feedback mechanisms Triggers within a system in which the result of the process controls the process itself Ex: a thermostat maintains set temperature inside a house using an internal feedback mechanism.

In the human body, the hypothalamus (a gland in the endocrine system) responds to temperature change much like a thermostat. The hypothalamus is the control center for recognition of and response to hunger, thirst, fatigue, anger, and body temperature. Sensory nerves in the skin send messages to the hypothalamus about external temperature. If the air temperature is too cold, the hypothalamus responds with messages that cause the body to conserve or produce heat, such as by shivering. When the air temperature is hot, a similar process leads to actions that cool the body, such as sweating.

Feedback Mechanisms are either positive or negative. Negative feedbacks are more common than positive feedbacks. Both are essential for proper body function.

Negative Feedback Mechanisms An increase in the product or the results causes a decrease in the response. ex: student fails test & grade drops, student then studies, goes to tutorials, retakes tests & grades improve

Positive Feedback Mechanism An increase in the product or result causes an increase in the response. Think of a positive feedback as a process of amplification—a small change leads to a much larger change. Ex: students fails test & grade drops student gives up, quits studying, & grade drops lower

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Other ways in which organisms maintain homeostasis Ex A: Blue mussels must open their shells when the tide comes in to collect food and water and close their shells when the tide goes out in order to protect themselves from drying out and predators.

Other ways in which organisms maintain homeostasis Ex B: The human body creates an enzyme that converts gaseous CO 2 into soluble substances to keep the pH level of around 7.4, even when acids and bases are added to the blood.