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Biology · Class 10 · Chapter 11: Homeostasis

8 min

Key points

Homeostasis is the tendency of living organisms to maintain constant internal environment despite changes in external environment
Feedback mechanism consists of three components: receptor, control center, and effector
Negative feedback reduces the effect of stimulus and maintains homeostasis
Positive feedback amplifies the effect of stimulus and is less common in biological systems
Kidneys maintain water balance through osmoregulation by producing concentrated or dilute urine
Skin regulates body temperature through vasodilation, vasoconstriction, sweating, and shivering
Liver maintains blood glucose level by converting glucose to glycogen (glycogenesis) and glycogen to glucose (glycogenolysis)
Pancreas produces insulin and glucagon hormones to control blood sugar levels
Thermoregulation in mammals involves hypothalamus as the control center for body temperature

Definitions

Homeostasis: The tendency of living organisms to maintain constant internal environment despite changes in external environment
Feedback Mechanism: A control system that uses information from sensors to regulate the activities of effectors
Negative Feedback: A control mechanism that reduces the effect of a stimulus and brings conditions back to normal
Osmoregulation: The process by which organisms regulate water content and solute concentration in their body fluids
Thermoregulation: The ability of an organism to keep its body temperature within certain boundaries

Worked example

Define homeostasis. Explain how the human body maintains constant body temperature through negative feedback mechanism. (6 marks)

Homeostasis is the maintenance of constant internal environment of the body despite changes in external environment. When body temperature rises above normal (37°C), thermoreceptors in hypothalamus detect the change. The hypothalamus sends signals to activate cooling mechanisms like sweating and vasodilation. As body temperature returns to normal, the stimulus is removed and cooling mechanisms stop. This is negative feedback because the response opposes the original change.

Common mistakes

Students often confuse glycogenesis with glycogenolysis
Many students write positive feedback examples for homeostasis instead of negative feedback
Students forget to mention hypothalamus as control center in thermoregulation
Mixing up insulin and glucagon functions in glucose regulation
Not explaining the complete feedback loop with receptor, control center, and effector

Quick recap

Homeostasis maintains constant internal environment despite external changes. Negative feedback opposes changes (temperature regulation), positive feedback amplifies changes (blood clotting). Key organs: kidneys (water balance), skin (temperature), liver (glucose). Hypothalamus acts as the main control center detecting changes and coordinating responses.

Generated by AI from Sindh Textbook Board material; review state: ai_unreviewed. MCQs, past-paper references and examiner notes are held back until a teacher has checked them.