16.2 Feedback mechanisms

Question 1

What is an optimum point

Answer 1

The desired level at which the system operates

Question 2

What is a receptor

Answer 2

Detects the stimulus of any deviation from the norm

Question 3

What does coordinator do

Answer 3

Coordinates information from different sources

Question 4

What does effector do

Answer 4

Brings about corrective measures needed to return system back to optimum point

Question 5

When does negative feedback occur

Answer 5

• When the stimulus causes the corrective measures to be turned off
• In doing so this tends to correct the system to its original level

Question 6

Describe negative feedback for blood glucose level if it is too low

Answer 6

. When it is too low, this stimulus is detected by receptors on the cell surface membrane of alpha cells (coordinator) in the pancreas
. These secrete hormone glucagon into the blood which causes liver cells to convert glycogen to glucose
. This blood with a higher level of glucose circulates back to pancreas and there is reduced stimulation of alpha cells so they secrete less glucagon

Question 7

Describe negative feedback if blood glucose level is too high

Answer 7

• The stimulus is detected by receptors on cell surface membrane of beta cells in pancreas which secrete the hormone insulin
• This increases uptake of glucose by cells and more of it is converted to glycogen and fats
• So this fall in glucose makes the levels return to optimum