The cells in health and disease I

Question 1

What is homeostasis?

Answer 1

-Homeostasis is the process by which internal variables are kept within a normal range of values

Question 2

What instigates homeostasis?

Answer 2

-When a stimulus changes one of these variables, a receptor detects this change
-A control centre compares the change against a reference value or set point and instructs effectors to make adjustments usually through negative
feedback.

Question 3

What happens if blood glucose levels rise?

Answer 3

Normally, if blood glucose rises, the beta cells within the pancreas act as the sensor and control centre
in that they detect this rise and release an effector, which is insulin.
-Insulin then binds to receptors in hepatocytes and skeletal muscle causing glucose to be taken up
by these cells and stored as glycogen, restoring blood glucose to its normal range.

Question 4

Summary of homeostasis

Answer 4

1. Homeostasis is the maintenance of a physiological state within a narrow range which is compatible with life.
2. Homeostatic systems are usually controlled by negative feedback but there are also examples of positive feedback loops.
3. The components of a homeostatic system are the same for both loops and include a stimulus, a sensor, a control centre and an effector.
4. Negative loops prevent an excessive response to a stimulus whereas positive loops intensify the response.