6.4.2 Negative Feedback

What is Negative Feedback?

• Negative feedback is a mechanism that reverses a change in internal conditions to restore them to their optimum levels.
• It ensures stability in the body by counteracting deviations from the norm.

Key Components of Negative Feedback:

1. Sensory Receptors:

• Detect changes in internal conditions, such as temperature or glucose levels.
• Examples include thermoreceptors for temperature and chemoreceptors for blood pH.

2. Control Centres:

• Process the information received from sensory receptors.
• Signals are sent via the nervous system or hormonal system to initiate a response.

3. Effectors:

• Organs or cells that act to reverse the change and restore balance.
• Examples include liver, muscles, sweat glands, or kidneys.

Examples of Negative Feedback in Action:

1. Thermoregulation (Body Temperature):

• If body temperature rises above 37°C:
• Thermoreceptors detect the increase.
• Signals are sent to the hypothalamus.
• Effectors (e.g., sweat glands) increase sweating, while blood vessels dilate (vasodilation) to release heat.
• If body temperature falls below 37°C:
• Thermoreceptors detect the decrease.
• Signals are sent to the hypothalamus.
• Effectors (e.g., skeletal muscles) initiate shivering, while blood vessels constrict (vasoconstriction) to retain heat.

2. Blood Glucose Regulation:

• If blood glucose levels fall:
• Detected by alpha cells in the pancreas.
• Release of glucagon triggers the breakdown of glycogen to glucose in the liver (glycogenolysis).
• If blood glucose levels rise:
• Detected by beta cells in the pancreas.
• Release of insulin increases glucose uptake by cells and its conversion to glycogen (glycogenesis).

Importance of Negative Feedback:

• Maintains conditions necessary for enzyme activity and cellular processes.
• Prevents extreme deviations that could harm the organism.
• Ensures stable conditions for survival in a constantly changing environment.