Chapter 29 Homeostasis

Objectives – What you will need to know from this section 3.4.1 HOMEOSTASIS Objectives – What you will need to know from this section Define the term homeostasis. Explain the need for homeostasis. Explain the role of the excretory system in homeostasis -- the ability and necessity to maintain constancy of body temperature, fluid balance and chemistry.

External & Internal environments The external environment surrounds the outside of an organism. The internal environment surrounds the cells in an organism. Homeostasis in the Human Body [3D Animation] 5:08mins

Homeostasis Homeostasis is the ability of an organism to maintain a constant internal environment within the body. It is necessary to maintain constant conditions such as: Temperature 370C – enzymes pH, Blood composition - Glucose conc., CO2 levels, wastes, etc.

It is necessary to maintain the right conditions as much as possible for: organisms to function at their most efficient rate If an organism is to be independent of its surroundings. To allow cells metabolism efficiently

Organ & Organ Systems involved Homeostasis involves many organs and organ systems acting together, co-ordinated by the brain e.g. Lungs Kidneys Liver Skin

Homeostasis requires Exchange Homeostasis often requires an organism to exchange materials with its environment by diffusion (gases, nutrients, wastes etc.) Osmosis (water) Active transport

Organs of exchange Special organs of exchange are not needed in small organisms e.g. Amoeba because diffusion is adequate.

Single Celled Organisms Simple aquatic organisms e.g. Amoeba, seaweeds obtain their food, water and oxygen directly from the water that surrounds them and excretes their wastes into the surrounding water by Diffusion & Osmosis. Special organs of exchange are not needed in small organisms e.g. Amoeba because diffusion is adequate.

Methods to improve rate of exchange – multicellular organisms Large organisms require special features such as: flat structures (Leaves) a respiratory system with a large surface area (alveoli) respiratory and excretory systems, which take materials (sweat) from within the body to the body surface

HOMEOSTASIS: The Body in Balance 3mins This video uses a variety of vivid examples to show how homeostasis is essential for the survival of living things. Eye-catching graphics and computer animation clarify complex biological processes. Video first looks at negative feedback systems and ways that cold-blooded and warm-blooded animals regulate their internal temperatures. Program examines how the human excretory system maintains stable levels of water and important chemicals inside the body while getting rid of poisonous wastes. The video also describes how the pancreas secretes insulin and glucagon, which maintain levels of glucose in the blood within certain critical levels.

Homeostasis - Temperature Regulation Our normal core body temperature is maintained at 37°C Body temperature is controlled by the hypothalamus in the brain. The heat being mainly produced from the liver during its metabolism. Muscles, skin and blood all play a role in controlling body temperature.

Temperature influences the rate of enzyme-controlled reactions. Mammals and birds are endotherms (warm blooded): they have a fairly constant body temperature. They can operate in low temperature environments, as they can keep the rate of enzyme activity high.

Most animals are ectotherms (cold blooded) —their body temperature varies with the external temperature, e.g. fish, amphibians, reptiles.

The SKIN – Temperature control

Homeostasis Song

LEARNING CHECK What is homeostasis? Name some things conditions in the cells and bodies of living organisms that we have to keep steady /constant. Why is it necessary to maintain the right conditions? All organisms have the ability to maintain constant conditions in the cells and bodies by homeostasis by? The process of Homeostasis requires what?