Osmoregulation and Kidney Function

The final section covers how the body regulates water levels, particularly through kidney function.

Maintaining constant water levels in the blood is crucial: • If blood is too dilute, water moves into cells by osmosis • If blood is too concentrated, water moves out of cells

The body loses water through: • Exhaled air from the lungs (uncontrollable) • Sweat from the skin (partly controllable) • Urine produced by the kidneys (controllable)

Definition: Osmoregulation is the control of water and solute concentrations in the body.

Kidney function:

1. Blood enters the kidney through an artery
2. The kidney filters out excess water, urea, and ions
3. These waste products leave as urine
4. Filtered blood exits through a vein

Highlight: The kidneys play a crucial role in osmoregulation by controlling how much water is lost in urine.

This guide provides essential information on thermoregulation GCSE Biology and hormonal coordination in Biology, covering key topics for exam preparation.

Thermoregulation and Homeostasis

The thermoregulatory centre in the brain monitors and controls body temperature to maintain homeostasis. This section explains how the body responds to temperature changes.

Definition: Homeostasis is the maintenance of constant internal conditions in the body.

The normal human body temperature is 37°C. The thermoregulatory centre in the hypothalamus contains receptors sensitive to blood temperature. Temperature receptors in the skin also send signals to this centre.

When body temperature is too high: • Sweat glands release sweat onto the skin surface, which evaporates and cools the body • Vasodilation occurs - blood vessels dilate to increase blood flow to the skin surface and release heat

Vocabulary: Vasodilation is the widening of blood vessels to increase blood flow.

When body temperature is too low: • Vasoconstriction occurs - blood vessels narrow to reduce blood flow to the skin and conserve heat • Shivering generates heat through muscle contractions • Sweating stops to prevent heat loss

Highlight: The nervous system uses fast electrical signals, while the endocrine system uses slower but longer-lasting hormonal signals.