Terms about osmosis and homeostasis

 

Term

Definition

Homeostasis

keeping variables like the body's water, temperature, etc. stable

Receptor or sensor

Part of the body that measures the variable and notices a change in the internal situation

Set Point

The normal range for the variable.

Control (integrating) center

This is the part of the body that knows what level the variable should be at (the SET POINT). The sensor tells the integrating center what the variable's level is, and the integrating center compares that level to the set point and tells the effector what it should do to bring the variable back to set point.

Effector

Part of the body that reacts to correct the change in the variable

Negative feedback

When the response to a stimulus caused by a change in the body corrects that change and makes the stimulus go away

Positive feedback

When the response to a stimulus caused by a change in the body makes that change greater and makes the stimulus stronger

Osmosis

Movement of water across a semipermeable membrane

Solutes

Molecules dissolved in a solvent (water)

Osmolarity or osmotic pressure

The total concentration of all the solutes dissolved in a solution

Isosmolar

Two solutions that have the same osmolarity

Hyperosmolar

A solution that has more solutes

Hypoosmolar

A solution that has fewer solutes

Tonicity

Refers to whether a solution will cause water to diffuse into or out of living cells

Isotonic

A solution with the same tonicity as cells - it won't make them swell or shrink

Hypotonic

A solution with a low concentration of molecules that won't enter cells. There are more solutes in the cells than in this solution, so water will enter the cells and they will swell

Hypertonic

A solution with a high concentration of solute molecules that cannot enter the cells. There are more solutes in this solution than in the cells, so water will leave the cells and they will shrink