Negative feedback loops
Overview
The human body uses a series of feedback systems to maintain homeostasis. These systems are constantly monitoring the internal and external conditions to see if it is deviating from the set point. If conditions are outside of optimal functioning range, the body initiates mechanisms to bring itself back towards the optimal range.
This section explores feedback mechanisms that regulate the internal environment. |
This video outlines general feedback loops in nature. This can help students understand the concept of feedback loops at large before examining the body in detail
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Negative feedback mechanisms
Negative Feedback
- The response of a system that acts to maintain equilibrium by compensating for any changes made to the system
Sensor
Integrator
Set point
Effector
- gathers information about the environment
- consists of tissues or organs that detect a change or stimulus in the environment
- factors may include: pH, temperature, concentration of hormones or molecules
- usually part of the nervous or endocrine system
Integrator
- compares existing conditions with ideal conditions (set points)
- activates the effector if the environmental condition is outside the set point
- usually part of the nervous or endocrine system
Set point
- The optimal range of values value for a given variable of a system
Effector
- Elements that act to return the system to its optimal state
- May include parts of any tissues and organs
Positive feedback systems
![Picture](/uploads/6/0/8/4/60840857/2622624_orig.gif)
Positive feedback
- increases the change in the environmental condition
- bring system away from stability, cause the system to become unstable
- usually (with some exceptions) do not result in homeostasis
Examples:
1. Adrenaline: Fight or flight mechanisms
When an animal is attacked, the body releases adrenaline and hormones to get it ready to fight or flight. The release of these chemicals stimulates further release, in a positive feedback cycle, making the organism more fit to fight the attacker or flee from the attacker.
2. Oxytocin: Childbirth
Uterine contractions during childbirth stimulate the release of oxytocin from the pituitary gland, leading to more intense contractions. This leads to a cycle of more oxytocin release and continued contractions, leading to the eventual delivery of the baby. When the baby is delivered, contractions stop, and therefore oxytocin release stops.
3. Milk production: Childcare
Mammalian young suckle milk from the mother at birth. The sensation of suckling stimulates glands in the mother to produce milk. Milk production leads to greater suckling, causing further milk production in a positive feedback cycle. When the baby stops feeding, the suckling stops, and milk production ceases.
Positive feedback mechanisms tend to operate within a larger negative feedback mechanism, ultimately bringing the body back to balance.