6.4.1 Homeostasis and negative feedback

Question 1

What is homeostasis

Answer 1

internal environment is maintained within set limits around an optimum

Question 2

why is it important that core temp remains stable

Answer 2

maintains stable rate of enzyme controlled reactions and prevent damage to membranes

temp too low - enzmyes and substrate molecules have insufficient kinetic dingy

temp too high - enzymes denature

Question 3

why is it important that blood pH remains stable

Answer 3

maintains stable rate of enzmyes- controlled reactions (and opt conditions for other proteins)

acid pH - H+ ions interact with H-bonds and ionic bonds in tertiary structure of enzmyes - shape of active site changes so no ES complexes form

Question 4

Why is it important that blood glucose concentration remains stable?

Answer 4

Maintain constant blood water potential: prevent osmotic lysis / crenation of cells.
Maintain constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions.

Question 5

Define negative feedback

Answer 5

Self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.

Question 6

Define positive feedback

Answer 6

A fluctuation triggers changes that result in an even greater deviation from the normal level.

Question 7

outline the general stages involved in negative feedback.

Answer 7

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

Question 8

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

Answer 8

Receptors may send conflicting information.
Optimum response may require multiple types of effector.

Question 9

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

Answer 9

It takes time to:

produce hormone
transport hormone in the blood
cause required change to the target protein