3.6.4.1 - HOMEOSTASIS + NEGATIVE FEEDBACK

Question 1

in this investigation, the higher the concentration of sucrose in a rat’s mouth, the
higher the frequency of nerve impulses from each taste receptor to the brain.

if rats are given very high concentrations of sucrose solution to drink, the refractory
period makes it impossible for information about the differences in concentration to
reach the brain.

explain why (2)

Answer 1

1. refractory period leads discrete/separate nerve impulses OR refractory period limits number of impulses per second
2. when maximum frequency reached, no further increase in information

Question 2

in humans, when the stomach starts to become full of food, receptors in the wall of
the stomach are stimulated. this leads to negative feedback on the desire to eat.

suggest why this negative feedback is important (3)

Answer 2

1. negative feedback stops desire to eat
2. this limits the amount thats eaten/stops eating
3. which prevents/reduces risk of obesity

Question 3

diabetic people who do not control their blood glucose concentration may become unconscious and go into a coma. a doctor may inject a diabetic person who is in a coma with glucagon.

explain how the glucagon would affect the person’s blood glucose concentration (2)

Answer 3

1. glycogenolysis
2. gluconeogenesis

Question 4

describe what is meant by negative feedback (1)

Answer 4

where a change triggers a response which reduces the effect of a change

Question 5

what is meant by homeostasis? (1)

Answer 5

maintaining a constant internal environment

Question 6

giving one example, explain why homeostasis is important in mammals (2)

Answer 6

ANY PAIR:

1.