D3.3.5 Thermoregulation as an example of negative feedback control Notes

Thermoregulation Maintains a Stable Body Temperature

1. Imagine stepping into a freezing room.
2. Almost immediately, your body starts to shiver, and you feel goosebumps on your skin.
3. These are not just random reactions, they are part of a sophisticated system called thermoregulation, which keeps your body temperature stable despite external changes.

What is Thermoregulation?

1. This stability is crucial because many biological processes, such as enzyme activity, are highly sensitive to temperature changes.

How Does Negative Feedback Work in Thermoregulation?

1. Negative feedback is the mechanism that controls thermoregulation by counteracting deviations from the set point.
2. This involves three main components:
   1. Sensors: Detect changes in body temperature.
   2. Integrating Center: Processes the information and decides on a response.
   3. Effectors: Carry out actions to restore the set point.

The Hypothalamus Is The Body's Thermostat

1. The hypothalamus is a small but critical part of the brain that acts as the integrating center for thermoregulation.
2. It receives input from thermoreceptors and initiates appropriate responses to maintain the set point.

How the Hypothalamus Regulates Temperature

1. When the hypothalamus detects a deviation from the set point:
   1. If the body is too cold: It triggers heat-generating and heat-conserving mechanisms.
   2. If the body is too hot: It activates heat-dissipating processes.

Heat Generation and Conservation

1. The body does several things to generate and conserve heat:
   1. Shivering: Skeletal muscles contract to generate heat.
   2. Vasoconstriction: Blood vessels narrow, reducing heat loss through the skin.
   3. Metabolic Rate Increase: The hypothalamus stimulates the thyroid gland to produce thyroxin, which raises cellular metabolism.

The Hormonal Cascade Increases Heat Production

1. In increasing the metabolic rate, more heat is produced. This works by the hypothalamus first releasing thyrotropin-releasing hormone (TRH).
2. TRH then stimulates the pituitary gland to secrete thyroid-stimulating hormone (TSH).
3. TSH ultimately prompts the thyroid gland to produce thyroxin, increasing heat production.

Why is Thermoregulation Important?

1. Maintaining a stable body temperature is vital for survival.
2. Extreme deviations can lead to:
   1. Hypothermia: Dangerous drop in body temperature, impairing cellular function.
   2. Hyperthermia: Excessive heat, leading to enzyme denaturation and organ failure.