Chapter 4 Physiological Feedback Loops

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Feedback loop: when a stimulus or change in the environment is present, feedback loops respond to keep systems functioning near a set point, or ideal level.

Homeostasis is keeping that steady state to function at optimal levels regardless of external change. This is predominantly regulated by negative feedback loops.

Hormesis: conditioning or priming effects of a mild level of a stressor results in the organism being better able to cope with exposure to higher levels of the stressor when encountered on subsequent occasions.

Positive feedback loop:

pos

Negative feedback loop:

negat

Example in homeostasis:

home

Environmental Physiology (Willmer et al): Chapter 2.5.4: Feedback systems and metabolic control

Content from Environmental Physiology of Animals: Willmer et al. lab copy (only accessible to putnam lab members) here.

feedbackloop

Examples in corals:

Negative feedback
1. Temperature increases in the water, therefore increasing the coral’s body temperature.
2. Temperature increases activity of mitochondria and thus production of ROS. Also, TRP channel subunits detect thermal stimuli. See Signal-Transduction for full pathway that can also enduce thermo-regulated processes.
3. Coral increases antioxidant function to reduce ROS.

Positive feedback loops

Symbiosis?

1. Endosymbiont exchange of nutrients
   
2. Coral receiving excess nitrogen
   
3. Keeps endosymbiont within cells to then continue the exchange of nutrients