Ravela Da Cruz

Feedback Study Guide

Cell communication or cell feedback is the way cells communicate and send information through signals to one another.


Hormones usually alter conditions inside the cells in response to stimuli. In this way, they are activated at certain specific times. Hence, they must be turned on and turned off in a loop manner. Every hormone controls the cells, and they are very important in the process of homeostasis. These hormones are, in turn, regulated by feedback mechanisms.

Feedback Mechanism

The mechanism of our human body to maintain regular levels of hormones in the desired quantity is termed a feedback mechanism. The main function of hormones in our body is to control our internal body temperature. So, even the slightest increase or decrease in the level of these hormones triggers the feedback mechanism, and they help to regulate biochemical pathways.

Types of feedback loops Source

There are two types of feedback mechanisms:

1. Negative Feedback Mechanism – It usually occurs when the effect of the stimulus slows down and normalizes things when they start becoming too extreme. Example: The thyroid gland. It is regulated by a negative feedback mechanism, during which the hormone secreted by the hypothalamus stimulates the pituitary gland to release the TSH (Thyroid Stimulating Hormone). The TSH triggers the thyroid gland to release its hormones.

When the level of thyroid increases in the thyroid gland, the hormones inhibit the secretion of TRH by the hypothalamus and secretion of TSH by the pituitary gland with the help of this mechanism. Hormones secreted by the thyroid gland are inhibited without stimulation of the TSH, and the level of thyroid hormone thus falls to a very low level.

A most common example of a negative feedback mechanism is regulation of our body temperature in a human being with the help of certain endotherms. Due to sudden changes in the external environment, our body temperature generally rises, as a result of which heat is released from our body in the form of sweat. This happens when the brain sends signals to our various organs. This causes the temperature to go down, and the negative feedback mechanisms fail to operate and are shut down immediately. This also happens when the body temperature rises beyond a particular limit.

Negative Feedback Source

2. Positive Feedback Mechanism – This occurs when the effect of the stimulus is to be enhanced. Example: The milk secretion from a mother’s mammary glands is one of the most common forms of a positive feedback mechanism. When an infant sucks milk out from the nipple, the nerve sends signals from the nipple to stimulate prolactin release from the pituitary gland. As a result, the prolactin also triggers the mammary glands to secrete milk required for the infant’s nourishment.

Positive feedback Source

Positive Feedback System

A positive feedback system involves a self-reinforcing or a positive response to external or internal outputs. It changes the body’s physiological state and enhances the product formation for maintaining body stability by regulating a stimulus. This feedback system is mainly known to amplify the change, and the effect of this change leads to a response of a widely amplified output. So, all responses are enhanced to a higher level in this system.

What is a Positive Feedback Loop?

A positive feedback loop is a physiological system that involves or enforces a change and promotes to intensify this change. Originally, the variation of this change is perceived by a receptor, and the effector provides the outcome of the change. The effector is mainly required to provide an identical outcome. The entire process keeps repeating itself, and the change continues to amplify until the stimulus is taken out.

The loop intends to play a very important role in maintaining homeostasis. Homeostasis is a process through which a stable body temperature is maintained by the living organisms. It aims to protect our bodies from harmful external threats and sudden changes in the environment. The factors responsible for homeostasis are the type of organism and its habitat. Warm-blooded animals usually preserve higher body temperatures to maintain internal stability, whereas cold-blooded animals have lower body temperatures. The positive feedback loop is made up of four processes required to maintain homeostasis, and they are:

  1. Stimulus
  2. Receptor
  3. Control Centre
  4. Effector

Other Examples of Positive Feedback Mechanisms

  • Clotting of blood causes the release of clotting factors that cover up the wound.
  • Childbirth causes dilation of the uterus walls, which causes contraction that leads to further stretching until the baby is delivered.
  • Ripening of fruit causes the release of ethylene, which enhances the ripening process of fruits.
  • The menstrual cycle causes the release of estrogen, which promotes the secretion of other hormones that help in ovulation in females.


  • Feedback Mechanisms play a vital role in maintaining perfect body temperatures, and it brings the body to a stable state.
  • It occurs in the form of loops and is immediately activated as soon as the body experiences a change.
  • It is a dynamic process and causes continuous changes in our living systems.


1. What is feedback in cell communication?

The property of a system to control any change in the body, amplify the change, and use its output as an input is called feedback in cell communication.

2. What is cell-cell communication?

Cell-cell communication is a direct interaction between the cell surfaces that plays a vital role in organisms’ development and functional activities.

3. What is used by cells to interact with other cells?

Cell junctions are used by cells to interact with other cells.

4. How are feedback loops related to cell communication?

Feedback loops are processes that change to maintain the homeostasis of multi-cellular organisms during a cell cycle.

5. What is positive feedback used for?

Positive feedback amplifies and promotes to intensify a change.

6. Is negative inhibition the same as feedback inhibition?

Yes, negative inhibition may also be used for promoting a certain process.

7. How does cell signaling relate to the cell cycle?

The signaling pathways control the cell growth, which directly impacts the cell cycle.

8. What is the difference between positive and negative feedback?

Positive feedback enhances or amplifies changes; and tends to move a system away from its equilibrium state. Negative feedbacks buffer changes and thus hold the system in an equilibrium state (more stable).

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  1. Feedback mechanism of hormones https://byjus.com/biology/feedback-mechanism-of-hormones/ Accessed 30 Dec, 2021.
  2. Cell cycles https://microbenotes.com/cell-cycle/ Accessed 30 Dec, 2021.
  3. Feedback https://apcentral.collegeboard.org/pdf/ap-biology-course-and-exam-description-0.pdf?course=ap-biology Accessed 30 Dec, 2021.