Homeostasis

By the end of the lesson you should be able to: Define Homeostasis Explain why homeostasis is necessary How homeostasis needs to be maintained in humans

HOMEOSTASIS Your body and its individual cells need just the right conditions to perform at their best. temperature, pH, solute, concentration etc .

Simple aquatic organisms (like Amoeba) obtain their food, water and oxygen directly from the water that surrounds them.

More complex organisms carry their own internal sea inside them (the tissue fluid), which is in contact with all the living cells of the body. Tissue Fluid

even when conditions in their external environment are changing!!!!! Homeostasis is the maintenance of a constant internal environment within the body. even when conditions in their external environment are changing!!!!! Many organisms can control conditions of temperature, fluid balance and chemistry within themselves (their ‘internal environment’)

Homeostasis is necessary if an organism is to be independent of its surroundings, and if its metabolism is to function efficiently.

Exchange systems A way to gets the things that we need into our cells and that we don’t need out of our cells

Difficulty with diffusion Large organisms have problems with diffusion because the gases cannot travel long distances very quickly.

Difficulties with diffusion Can be overcome by: the body may be flattened, thus reducing the distance between the two surfaces example: the leaves of plants

Difficulties with diffusion Can be overcome by: 2. Increasing the surface area for exchange to happen e.g. alveoli in the respiratory system

Difficulties with diffusion Can be overcome by: 3. the body developing systems where the material to be exchanged is brought to the body surface e.g. by respiratory and excretory systems

Gas exchange

The need for a circulatory system Large active animals need rapid exchange of materials in their cells! They require a circulatory system to help in the transport of gaseous materials and toxic materials.

Homeostasis Homeostasis means “controlling internal conditions”: Waste products need to be removed --- how ? CO2 Produced by respiration, removed via lungs Urea Produced by liver breaking down amino acids, removed by kidneys and transferred to bladder Internal conditions need controlling --- how ? Temperature Increased by shivering, lost by sweating Ion content Increased by eating, lost by sweating + urine Water content Increased by drinking, lost by sweating + urine Blood glucose Increased and decreased by hormones

Explain why homeostasis is necessary Learning check... Define Homeostasis Explain why homeostasis is necessary How homeostasis needs to be maintained in humans