explain what is meant by homeostasis and the importance of homeostasis in mammals

Published by Patrick Mutisya · 14 days ago

Homeostasis in Mammals – Cambridge A‑Level Biology 9700

Homeostasis in Mammals

What is Homeostasis?

Homeostasis is the process by which living organisms maintain a relatively stable internal environment despite changes in the external environment. In mammals, this involves the coordinated action of physiological systems that monitor and adjust variables such as temperature, blood glucose, water balance, and pH.

Why is Homeostasis Important in Mammals?

Maintaining homeostasis is essential for the proper functioning of cells, tissues, and organs. Disruption of homeostatic balance can lead to impaired metabolism, organ failure, or death. The importance can be summarised as follows:

  • Enzyme Efficiency: Enzymes have optimal temperature and pH ranges; deviations reduce reaction rates.

  • Cellular Integrity: Osmotic balance prevents cell swelling or shrinkage.

  • Energy Supply: Stable blood glucose ensures a continuous supply of energy to the brain and muscles.

  • Neurological Function: Precise ion concentrations are required for nerve impulse transmission.

  • Survival: Ability to cope with environmental extremes (e.g., heat, cold, dehydration) enhances survival and reproductive success.

Key Homeostatic \cdot ariables in Mammals

VariableNormal Range (Adult Human)Primary Control MechanismConsequences of Imbalance
Body Temperature36.5–37.5 °CThermoregulatory centre in hypothalamus; sweating, shivering, vasodilation/constrictionHypothermia, hyperthermia, protein denaturation
Blood Glucose4.0–6.0 mmol L⁻¹ (fasting)Insulin and glucagon secretion from pancreasHypoglycaemia, hyperglycaemia, diabetes mellitus
Plasma Osmolality275–295 mOsm kg⁻¹Antidiuretic hormone (ADH) and thirst mechanismDehydration, oedema, electrolyte disturbances
Blood pH7.35–7.45Buffer systems (bicarbonate), respiratory CO₂ control, renal H⁺ excretionAcidosis, alkalosis, impaired enzyme activity

Typical Homeostatic Feedback Loop

A homeostatic system generally follows these steps:

  1. Stimulus: A change in the internal or external environment.

  2. Sensor (Receptor): Detects the deviation from the set point.

  3. Control Centre: Processes the information and determines the appropriate response.

  4. Effector: Carries out the response to restore the variable to its set point.

  5. Feedback: The effect is monitored; if the set point is reached, the response is reduced or stopped.

Mathematical Representation of a Simple Negative‑Feedback System

Consider a variable \$x(t)\$ that is regulated towards a set point \$x_s\$ with a proportional feedback constant \$k\$. The rate of change can be expressed as:

\$\frac{dx}{dt} = -k\,(x - x_s)\$

Solution of this differential equation shows exponential decay of the deviation \$x - x_s\$, illustrating how negative feedback restores balance.

Examples of Homeostatic Regulation in Mammals

  • Thermoregulation: In cold conditions, shivering generates heat; in hot conditions, sweating promotes evaporative cooling.

  • Glucose Regulation: After a meal, blood glucose rises, stimulating insulin release, which promotes cellular uptake of glucose and storage as glycogen.

  • Water Balance: Increased plasma osmolality triggers ADH release, increasing water reabsorption in the kidneys.

  • pH Regulation: Elevated CO₂ (acidic) stimulates increased ventilation, expelling CO₂ and raising pH.

Suggested diagram: Flowchart of a negative‑feedback loop showing stimulus, receptor, control centre, effector, and response.

Summary

Homeostasis is the cornerstone of mammalian physiology. By continuously monitoring and adjusting critical internal variables, mammals maintain the conditions necessary for cellular function, overall health, and survival. Understanding these mechanisms is essential for studying disease states where homeostatic control fails.