Homeostasis: principles of homeostasis and negative feedback

What is homeostasis

Internal environment is maintained within set limits around an optimum

Why is it important that core temperature remains stable

1. Maintain stable rate of enzyme-controlled reactions and prevent damage to membranes

2. Temperature too low= enzyme and substrate molecules have insufficient kinetic energy

3. Temperature too high= enzymes denature

Why is it important that blood pH remains stable

• Maintains stable rate of enzyme-controlled reactions (and optimum conditions for other proteins)

• Acidic pH= H+ ions interact with H bonds and ionic bonds in tertiary structure of enzymes- shape of active site changes, no ES complexes formed

Why is it important that blood glucose concentration remains stable

• Maintain constant blood water potential: prevents osmotic lysis

• Maintain constant concentration of respiratory substrate: organism maintain constant level of activity regardless of environmental condit

Define negative and positive feedback

• Negative feedback: self-regulatory mechanisms return internal environment to optimum when there is a fluctuation

• Positive feedback: a fluctuation triggers changes that result in an even greater deviation from the normal level

Outline the general stages involved in negative feedback

Receptors detect deviation- coordinator - corrective mechanism by effector - receptors detect that conditions have returned to normal

Suggest why separate negative feedback mechanisms control fluctuations in different directions

Probed more control , especially in case of overcorrection which would lead to a deviation in the opposite direction from the original one

Suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors

• Receptors may send conflicting information

• Optimum response may require multiple types of effector

Why is there a time lag between hormone production and response by an effector

• Takes time to:

• produce hormone

• Transport hormone in the blood

• Cause required change to the target protein