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

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.

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.

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.

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

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

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

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

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

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

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

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

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

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

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.

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.

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.

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

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.

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