Homeostasis What is homeostasis According to MerriamWebster homeostasis

Homeostasis

What is homeostasis? According to Merriam-Webster homeostasis is “the maintenance of relatively stable internal physiological conditions (as body temperature or the p. H of blood) in higher animals under fluctuating environmental conditions; also : the process of maintaining a stable psychological state in the individual under varying psychological pressures or stable social conditions in a group under varying social, environmental, or political factors” Whew. . . that is a lot of words instead let's. . break the word down: – homeo: – stasis: similar to/same equilibrium/unchanging

Homeostasis… To put it simply “homeostasis is a biological balance between an organism and it’s environment” Key word: Balance To function properly an organism (and its cells) must maintain internal conditions in a specific range in spite of environmental changes. An inability to maintain conditions in this range (balance) will cause the organism (or its cells) to not function properly (which usually means disease or death).

You can see examples of this balance at the organismal level. What does your body do to warm up when the temperature is too low? Shiver, hair stands on end What does your body do to cool down when the temperature is too high? sweat What does your body do when you do not have enough fuel (food)? Stomach sends warning signals (hunger pangs), store extra as fat, use up fat stores, conserve energy (you are weak) What does your body do when you deprive it of oxygen? (hold your breath) But why? How does your body know what to do? To understand how this happens we need to remember that the basic unit of life is the …. .

How does your body know what to do? The basic unit of life is the cell. This means that this balance is being maintained at a cellular level and the cells in your body communicate with each other. Each cell in your body has a function and they rely on each other to obtain the substances needed to function and help remove waste products.

How do your cells take in and remove substances? The cells use a variety of ways to bring in and remove substances depending on the situation. To understand the processes we need to define a few more words.

Terms that refers to internal and external conditions. Concentration is the amount of solute dissolved in a given amount of solvent. – Or how much stuff is in something.

Concentration Gradient A concentration gradient is a condition that exists when there is a difference in the concentration of a substance across a space. (higher and lower areas of concentration) – One side has more stuff in it than the other side.

Equilibrium is a condition that exists when there is an equal concentration of a substance across a space. – Each side has the same amount of stuff.

Semi-permeable membrane In a cell this “space” is usually a semi-permeable membrane that allows some things to pass through and blocks others. – Kind of like a guard. Only lets in the right stuff.

Hypotonic Environment Hypo-tonic refers to an environment where the concentration of solute is lower outside the cell than inside the cell. – There is more stuff inside the cell than outside the cell.

Hypertonic environment Hyper-tonic refers to an environment where the concentration of solute is higher outside the cell than inside the cell. – There is more stuff outside the cell than inside the cell.

Isotonic environment Isotonic refers to an environment where there is an equal concentration of solute inside and outside the cell. – There is the same amount of stuff inside and outside the cell.

Cell environements

Methods of bringing in and removing substances with no energy. Passive transport is the movement of substances into or out of the cell from an area of higher concentration to a lower concentration without the use of energy. – If there is more stuff outside the cell than inside, some of the stuff moves into the cell. It is easy, doesn't need any energy.

Methods of bringing in and removing substances with no energy: Diffusion is a type of passive transport where particles move from an area of higher concentration to an area of lower concentration. – Stuff moves from where it is crowded to where there is more room.

Methods of bringing in and removing substances with no energy: Osmosis is the diffusion of water (a solvent) from an area of lower solute concentration to an area of higher solute concentration through a semipermeable membrane. – Water (not stuff) moves from where there is less stuff to where there is more stuff.

Methods of bringing in and removing substances with no energy: Facilitated diffusion is the movement of larger particles from an area of higher concentration to an area of lower concentration with the use of carrier molecules (proteins that help a substance across a membrane). – Stuff that is too big to get through the normal goes through a special door that has to be held open by a special guard. It is still moving from where there is more stuff to where there is less stuff.

Methods of bringing in and removing substances with energy. Active transport is the movement of substances into or out of the cell which requires the use of energy. – Stuff gets in to (or out of) the cell but the cells needs to use energy to do this.

Methods of bringing in and removing substances with energy: Endocytosis is an active transport process by which large particles are engulfed into the cell. – The cell wraps itself around the stuff and closes around it.

Methods of bringing in and removing substances with energy: Exocytosis is an active transport process by which large particles are removed from a cell. – The cell sends the stuff to the membrane and opens up to get rid of it.

Now what? As a group you are going to put an example and a diagram on each of your vocabulary cards. Then you are going to work together, using your vocabulary cards, as a cell to maintain homeostasis during several environmental scenarios.

Image credits can be found in the Notes section of each slide.