You just experienced homeostasis. Your body was trying to keep you upright by maintaining your balance. Homeostasis is regulated by the nervous system. Stand up and balance on one foot for 3 minutes. After the timer goes off, sit back down in your seat. Discuss the following questions with your table partners: 1.What did you notice during this activity? 2.Did it get more difficult to balance as time went on? 3.What did you want to do?

Organisms respond to changes in their environment in order to maintain balance. We call this balance homeostasis. Example: The stimulus is being struck with the hammer. Example: The response is the knee jerk reflex.

StimulusResponseHomeostasis Balance Hunger Thirst Excess body heat Low body temperature Increased Exercise Spoiled food Bacteria or virus Predator

Organisms have an internal warning system to alert them of hunger, thirst, and temperature extremes to maintain homeostasis.

Hunger is an example of homeostasis because food is something we need to keep our bodies balanced and healthy. When you are hungry a nerve sends a signal to your brain telling it that you need food.

StimulusResponse Homeostasis (Balance) Hunger EatingHunger pains are gone

StimulusResponse Homeostasis (Balance) Thirst Drinking water/ fluids Body Fluid Balance

Sweating helps maintain a stable body temperature of about 98.6°F. When we "heat up" we sweat. The evaporation of sweat returns the body to its original temperature. Muscles shiver to create heat. Muscle movement causes heat to build up (friction) and warm the body.

StimulusResponse Homeostasis (Balance) Excess Body Heat Low Body Temp. Sweating Shivering Stable body temperature

Increased Exercise Increase in heart rate and respiratory rate

StimulusResponse Homeostasis (Balance) Increased Exercise Increase in heart rate and respiratory rate. Normal O 2 Levels in the blood

Fever or vomiting in animals allows them to maintain balance. Food

StimulusResponse Homeostasis (Balance) Spoiled Food VomitingWellness

bacteria or viruses Fever Fever or vomiting in animals allows them to maintain balance.

StimulusResponse Homeostasis (Balance) Bacteria or Virus FeverWellness

If an organism feels threatened by an external stimulus, such as a predator, it responds by fighting or running away.

StimulusResponse Homeostasis (Balance) Predator Fight or Flight Threat Eliminated

StimulusResponse Homeostasis (Balance) 1. Hunger 2. Thirst 3. Excess body heat 4. Low body temperature 5. Increased Exercise 6. Spoiled Food 7. Bacteria or Virus 8. Predator

StimulusResponse Homeostasis (Balance) Excess water in the body Excreted as urine. Balanced water levels NightmareFight or Flight Threat eliminated, Sleep restored Wilting plant Roots take up water from the soil and pass it up through the rest of the plant. Turgor pressure is restored

L1 1. Describe a situation where an organism responds to an external stimulus in order to maintain a state of balance, or homeostasis. 2. Describe a situation where an organism responds to an internal stimulus in order to maintain a state of balance, or homeostasis.

L2 Organisms respond to changes in the environment in order to maintain balance. We call this balance (1)____________. The change in the environment is called a (2)________, and the reaction of the organism is called a (3)_______. Homeostasis is regulated by the (4)________ system. StimulusResponse 5. Spoiled Food 6. Bacteria or Virus 7. Hunger Directions: Fill in the blanks and complete the table below.