Maintaining Dynamic Equilibrium Unit 4 Homeostasis Nervous System Endocrine System

Equilibrium Every natural process strives to achieve physiological balance Equilibrium is the state of balance between opposing processes, resulting in a stable condition.

How is this achieved? Diffusion The constant movement of molecules from areas of high concentration to areas of low concentration until each molecule is a maximum distance from every other similar molecule (uniform distribution) Example: Chlorine in a pool

Rate of Diffusion All chemical and physical processes move towards equilibrium at a speed determined by the amount of energy added. The rate of diffusion increases as thermal energy input increases Example: Dye in gelatin A incubator (30 0 C)*most diffused B room temperature (20 0 C) C refrigertor (3 0 C)*least diffused

Osmosis Water follows the Concentration Gradient (diffusing from an area of high water concentration to an area of low water concentration) Water moves to balance the concentration of the solutions on both sides of a membrane when the solute particles are unable to diffuse to establish equilibrium.

Turgor Pressure In plant cells, water within a cell puts pressure on the cell wall to give the cell rigidity. As a plant cell loses water Plasmolysis occurs The cytoplasm within the cell shrinks away from the cell wall and turgor pressure is reduced   the plant wilts This can be reversed by adding water  osmosis moves water into the cell, the cytoplasm swells putting pressure on the cell wall again Deplasmolysis

Dynamic Equilibrium Any system in a biosphere that remains stable within fluctuating limits Living systems are designed to maintain balance within an environment (open system) using a variety of processes  adapt to changes without disturbing balance Homeostasis is an organisms ability to maintain a constant internal environment while the external environment’s conditions are changing *This system of active balance requires constant monitoring

Homeostasis and Metabolism Cells exchange matter and energy with their surroundings through a semipermeable membrane (some substances may pass through while others may not) Example: starch vs water in dialysis tubing Starch molecules are too big to move across the membrane, so water moves in Sugar is small enough to diffuse, so it leaves the tubing

Tonicity Ideally, cells want to maintain the same concentration of solutes inside the cell as outside  Isotonic condition “iso”equal “tonic”concentration * The movement of water (osmosis) into the cell should balance the movement of water out the cell

Imbalance Hypotonic “hypo”below The concentration of dissolved molecules is lower on this side of the membrane Water will move away from this solution Hypertonic “hyper” above The concentration of dissolved molecules is greater on this side of the membrane Water will move toward this solution

Metabolism Cells cycle material in and out constantly to be used for energy conversion in the cellMetabolism is the sum of all chemical reactions within a cell, or the sum of all cellular activities in an organism

Special conditions are necessary (ideal) for metabolic chemical reactions But exterior conditions change constantly from ideal Homeostasis is a feedback system that maintains interior stability (balance/ ideal conditions) so the organism can survive regardless of external changes

In animals… The brain coordinates homeostasis. Special receptors in the body’s organs signal the brain once an organ begins to operate outside its normal limits. The brain relays the information to the appropriate regulator, which helps restore the normal balance.

Assignment Read page Read page Answer questions 1-6 on page Copy the flow chart from page 225 (fig.10.3) and page 229 (fig.10.10). Compare these.