Topic 6- Principles of homeostasis and negative feedback

Question 1

what is homeostasis?

Answer 1

-The maintenance of an internal environment within restricted limits in organisms
-By physiological control systems

Question 2

what does homeostasis ensure?

Answer 2

Ensures that cells of the body are in an environment that meets their requirements
-> allows them to function despite external changes

Question 3

What are there in organisms and what does homeostasis have the ability to do?

Answer 3

-there are continuous fluctuations brought about variations in internal + external conditions
-these changes however occur around an optimum point
-homeostasis-> ability to return to that optimum point and so maintain organisms in a balanced equilibrium

Question 4

Explain the importance in maintaining stable core temperature

Answer 4

-if temperature is too high:
-hydrogen bonds in tertiary structure of enzymes break
-enzymes denature; active site changes shape and substrates can’t bind
-so fewer enzyme- substrate complexes

-if temperature is too low:
-not enough KE so fewer enzyme substrate complexes

Question 5

Explain the importance of maintaining a stable blood pH

Answer 5

-above or below optimal pH, ionic/ hydrogen bonds in tertiary structures break
-enzymes denature; active sites change shapes and substrates can’t bind
-so fewer enzyme substrate complexes form

Question 6

Explain the importance in maintaining stable blood glucose concentration

Answer 6

Too low (hypoglycaemia
-not enough glucose (respiratory substrate) for respiration
-so less ATP produced
-active transport cannot happen-> cell death

Too high (hyperglycaemia)
-water potential decreases
water lost from tissue to blood via osmosis
-kidneys can’t absorb all glucose -> more water lost in urine causing dehydration

Question 7

what is hypoglycaemia

Answer 7

blood glucose concentration too low

Question 8

what is hyperglycaemia

Answer 8

blood glucose concentration is too high

Question 9

what can happens if pH and temperature fluctuates?

Answer 9

-enzymes and other proteins are sensitive to changes in pH and temperature
-any change to these factors reduce the rate of reaction of enzymes or could denature them (cannot work at all)
-small fluctuations in temp and pH can impair the ability of enzymes to carry out their roles effectively
-maintaining constant internal environment-> reactions take place at a suitable rate

Question 10

what can happened due to changes to water potential of the blood and tissue fluid?

Answer 10

-may cause cells to shrink and expand
-as a result of water leaving or entering them by osmosis
-the maintenance of constant blood glucose concentration is essential in ensuring water potential
-constant blood glucose level also ensures a reliable source of glucose for respiration by cells

Question 11

what is the advantage that organisms that can maintain a constant internal environment have?

Answer 11

-they are more independent of change in the external environment
-they have a wider geographical range-> have greater chance of finding food/ shelter

Question 12

Control mechanisms:
What is the optimum point?

Answer 12

point at which the system operates best art

Question 13

Control mechanisms:

what is the optimum point monitored by?

Answer 13

• receptor
  |> which detects any deviation from the optimum point (ie stimulus)

Question 14

Control mechanisms:

what does the receptor inform?

Answer 14

-informs the coordinator
|>the coordinator coordinates information from the receptors

Question 15

Control mechanisms:

Coordinates send
instructions to an appropriate…

Answer 15

-effector
|> often a muscle or gland-> brings about changes to return system to optimum point

Question 16

Control mechanisms:

what does the return to the optimum point by the effector create?

Answer 16

-a feedback mechanism
|> receptor responds to a stimulus created by the change to the system brought about by the effector

Question 17

Describe the role of negative feedback in homeostasis

Answer 17

1.Receptord detect change from the optimum
2.Effectors respond to counteract change
3.Returning levels to optimum

Question 18

Examples of negative feedback

Answer 18

-control of blood glucose conc, blood pH, core temperature and blood water potential

Question 19

Explain the importance of conditions being controlled by separate mechanisms involving negative feedback

Answer 19

-departures in different directions from the original state can all be controlled/ reversed
-giving a greater degree of control (over changes in the internal environment)

Question 20

Describe positive feedback

Answer 20

-receptors detect change from the optimum
-effectors respond to amplify change
-producing greater deviation from the set point/ normal

Question 21

what is positive feedback not involved in?

Answer 21

Homeostasis