Question

During the immune response the first cells to encounter a foreign invader release chemicals called cytokines that stimulate hundreds of new immune cells. These new immune cells again release cytokine signals when they run into the same foregin invader activating thousands of immune cells. Is this system an example of negative feedback or positive feedback and what evidence supports your choice and why?

Answer 1

Answer

This system is an example of positive feedback.

• Positive feedback mechanism involves a stimulus that triggers a response in order to amplify the initial stimulus.
• When cytokines are released by a cell, it stimulates the production of new immune cells.
• These immune cells identify the foreign antigen. Upon exposure, they release more cytokines to produce more immune cells.
• Production of immune cells lead to events that amplify immune cell production.
• Hence, it is a positive feedback that facilitates immune system to combat foreign antigens.

Positve feedback mechanism is also used in other physiological functions such as :

- Uterine contractions during childbirth stimulates release of oxytocin from posterior pituitary gland that cause the uterine muscles to contract more vigorouslt in order to expel the baby.