Maintaining Dynamic Maintaining Dynamic EquilibriumEquilibrium

Unit 4 Homeostasis

Nervous SystemEndocrine

System

Equilibrium 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?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 poolExample: Chlorine in a pool

Rate of DiffusionRate of DiffusionAll 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 (300 C) *most diffusedB room temperature (200C)C refrigertor (30C) *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 PressureIn 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 EquilibriumAny 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

TonicityTonicityIdeally, 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 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 cell

MetabolismMetabolism is the sum of all chemical reactions is the sum of all chemical reactions within a cell, or the sum of all cellular within a cell, or the sum of all cellular

activities in an organismactivities in an organism

Special conditions are necessary (ideal) for metabolic chemical

reactionsBut 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…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 Assignment 1. Read page 117

2. Read page 222-2273. Answer questions 1-6 on page 2284. Copy the flow chart from page 225

(fig.10.3) and page 229 (fig.10.10). Compare these.