What is the Difference Between Positive and Negative Feedback Homeostasis

The main difference between positive and negative feedback homeostasis is that positive feedback homeostasis bolsters the stimulus, increasing productivity. In contrast, the negative feedback homeostasis reduces the effect of the stimulus, decreasing productivity. Common examples of positive feedback homeostasis include blood clotting and childbirth in mammals while the control of an optimal internal environment by regulating temperature, blood pH, hormone levels, etc. is an example of negative feedback homeostasis. 

In brief, positive and negative feedback homeostasis are two feedback systems that are important for the maintenance of homeostasis. Generally, they are responsible for maintaining a relatively stable environment in biological systems. 

Key Areas Covered 

1. What is Positive Feedback Homeostasis
     – Definition, Features, Examples
2. What is Negative Feedback Homeostasis
     – Definition, Features, Examples
3. What are the Similarities Between Positive and Negative Feedback Homeostasis
     – Outline of Common Features
4. What is the Difference Between Positive and Negative Feedback Homeostasis
     – Comparison of Key Differences

Key Terms 

Feedback Systems, Homeostasis, Negative Feedback Homeostasis, Positive Feedback Homeostasis, Thermoregulation

What is Positive Feedback Homeostasis 

Positive feedback homeostasis is a type of feedback mechanism in biological systems, reinforcing a particular stimulus in the body. Therefore, this type of feedback mechanism promotes the change to proceed further. Thus, the initial change amplifies until the removal of the stimulus. Childbirth is one of the most precise examples of positive feedback mechanisms. During childbirth, the pressure on the cervix due to the pushing of the child’s head downwards induces the release of oxytocin, which in turn stimulates further contractions of the cervix. Subsequently, these contractions stimulate the release of oxytocin until the baby is born.  

Figure 1: Childbirth 

Furthermore, some other examples of positive feedback loops are as follows:   

• Lactation  – Breastfeeding stimulates milk production, which causes further feeding. And, this continues until the baby stops feeding.   
• Ovulation –  The dominant follicle inside the ovary releases estrogen, which stimulates the release of FSH and LH. These hormones stimulate further growth of the follicle.   
• Blood clotting –  The release of clotting factors by the activated platelets stimulates the aggregation of more platelets at the site of injury.   
• Fruit ripening – The ripened fruits release ethylene, which stimulates the ripening of the nearby fruits.   

What is Negative Feedback Homeostasis 

Negative feedback homeostasis is the opposite feedback mechanism of positive feedback mechanisms. It is responsible for reversing the stimulus by activating the opposite responses. Thus, the productivity of the stimulus is reduced. This type of feedback mechanism stabilizes biological systems maintained under homeostatic conditions, important for a constant internal environment. Furthermore, some examples of negative feedback loops include the regulation of body temperature, blood pH, hormone levels, the oxygen/carbon dioxide balance, blood sugar levels, blood pressure, acid/base balance, water balance (osmoregulation), calcium levels, and energy balance, etc.

Figure 2: negative Feedback Homeostasis

Thermoregulation 

Generally, the normal body temperature of humans is 37 °C. When the body temperature increases, mechanisms such as sweating and vasodilation are induced to release internal heat to the external environment. Subsequently, the evaporation of sweat from body surfaces uses heat in the body. Moreover, increased blood circulation near the skin through vasodilation carries internal heat to the surface of the body. Together, both of the above mechanisms cool down the increased body temperature. However, when the temperature of the body decreases, goosebumps and vasoconstriction help in increasing the body temperature by retaining the heat inside the body.  

Similarities Between Positive and Negative Feedback Homeostasis  

• Positive and negative feedback homeostasis are two feedback systems important for the maintenance of homeostasis.  
• They are responsible for maintaining a relatively stable environment in biological systems by increasing or decreasing the effects of a  particular stimulus. 

Difference Between Positive and Negative Feedback Homeostasis 

Definition 

Positive feedback homeostasis refers to a feedback mechanism resulting in the amplification or growth of the output signal, while negative feedback loops refer to a feedback mechanism resulting in the inhibition or the slowing down of a process.   

Effect on the Stimulus 

Positive feedback homeostasis bolsters the stimulus, increasing productivity, while negative feedback homeostasis reduces the effect of the stimulus, decreasing productivity. 

Frequency of Occurrence 

Moreover, positive feedback homeostasis is a less frequent process, while negative feedback homeostasis is a more frequent process. 

Effect on the Stability of the System 

Positive feedback homeostasis is less associated with the stability of the system, while negative feedback homeostasis is more associated with the stability of the system. 

Examples 

Common examples of positive feedback homeostasis include blood clotting and childbirth in mammals, while the control of an optimal internal environment by regulating temperature, pH, hormone levels, etc. is an example of negative feedback homeostasis. 

Conclusion 

In brief, positive feedback homeostasis is one of the two types of feedback mechanisms, leading to strengthening the stimulus. However, this type of feedback mechanism is less common. Furthermore, some examples of positive feedback mechanisms include fruit ripening, blood clotting, and childbirth in mammals. In comparison, negative feedback homeostasis is the opposite type of feedback mechanism, leading to reduce the stimulus. Moreover, they commonly occur in biological systems, and some examples include the regulation of temperature, pH, hormone levels, etc. of the body. Therefore, the main difference between positive and negative feedback homeostasis is the effect on the stimulus. 

References:

1. “Homeostasis | Boundless Biology.” Lumen, Available Here.

Image Courtesy:

1. “106 Pregnancy-Positive Feedback” By OpenStax (CC BY 4.0) via Commons Wikimedia     
2. “105 Negative Feedback Loops” By OpenStax (CC BY 4.0) via Commons Wikimedia