1. S.T.A.R. Tutoring Mr. Hester
Homeostasis
S.T.A.R. Tutoring
Mr. Hester

2. What is homeostasis?
Homeostasis is a characteristic of all living things.
It involves being able to maintain stable conditions inside your body despite changes in the environment.
Regulating the amounts of certain substances found in your body, and controlling factors like temperature.

3. Why is homeostasis important?
Without a way to regulate body systems, organisms will not be able to survive.
The inability to regulate by homeostasis can lead to diseases like diabetes, hypoglycemia and kidney failure.

4. Think of it like a see-saw…
Your body wants to keep it balanced, so when things change on one side, your body “adds weight” to the other side to make things even again.

5. Example: Temperature
After physical activity, the temperature in your body increases.
What things does our body do to cool down and return to a stable temperature?
Hot
Cold
Physical activity

6. Example: Temperature
What things does our body do to cool down and return to a stable temperature?
Sweating releases heat
Increased blood flow helps cool.
Hot
Cold
Sweating
Increase blood flow
Physical activity

7. Example: Temperature
But what if you are exposed to cold temperatures for a long time?
What things does our body do to warm up and return to a stable temperature?
Exposure to cold
Hot
Cold

8. Example: Temperature
What things does our body do to warm up and return to a stable temperature?
Shivering generates heat
Decreased blood flow helps warm.
Shivering
Decrease blood flow
Exposure to cold
Hot
Cold

9. Example: Blood Sugar
After eating sugary food, the level of glucose in your blood rises.
What things does our body do to reduce the amount of excess blood sugar?
High
Low
High blood glucose

10. Example: Blood Sugar
What things does our body do to reduce the amount of excess blood sugar?
An organ called the pancreas produces insulin, a hormone that causes your liver to absorb sugar.
Glucose in blood
Production of insulin
High
Low

11. Example: Blood Sugar But what if you don’t have enough sugar?
What things does our body do to increase the amount of sugar available for our body?
High
Low
Low blood glucose

12. Example: Blood Sugar
What things does our body do to reduce the amount of excess blood sugar?
The pancreas produces glucagon, a hormone that causes your liver to release sugar.
Glucagon
Low blood glucose
High
Low

13. Example: Membrane Transport
Cells are surrounded by a semi-permeable membrane that lets some things in and keeps some things out.
Substances can pass through the membrane through a number of different processes, with two major categories.
1) Passive Transport – No energy
2) Active Transport – Uses energy

14. Diffusion
Movement of any substance across a membrane from a high to a low concentration.
Occurs naturally, without any energy

15. Facilitated Diffusion
Normally, large molecules are too big to fit through the cell membrane.
Sometimes, special membrane proteins allow certain molecules to diffuse through larger holes in the membrane.

16. Osmosis
Cells cannot control the movement of water across their membranes.
Thus, cells will behave in predictable ways when placed in certain types of solutions.

17. Types of Solutions
Hypotonic: More water inside the cell than outside. Water will leave the cell.
Isotonic: Equal concentrations of water inside and outside the cell. Water levels don’t change.
Hypertonic: More water outside the cell than inside. Water will go into the cell.

18. Types of Solutions Cells stay Cells will shrink the same
Cells will swell

19. Active Transport
Movement of a substance across a membrane from low to high concentrations.
This process uses energy, in the form of ATP, to fuel membrane proteins.

20. Active Transport
Endocytosis and exocytosis are examples of active transport.
Endocytosis – the cell brings stuff in.
Exocytosis – the cell sends stuff out.