Introduction Biology 346 General Physiology Dr Tony Serino

Introduction Biology 346 General Physiology Dr. Tony Serino

Physiology • Physiology –study of body mechanisms (homeostasis)

Homeostasis • Maintenance of a constant internal environment • Uses a reflex arc to self regulate • Reflex functions to maintain a certain set point with a narrow physiological range

Homeostasis Reflex

Homeostatic Pathways

Factors Affecting Homeostasis • • Feedback –negative or positive Feed-forward regulation Acclimatization Biorhythms

Internal vs. External Environment

External Environment Atmosphere • Composition: 78% N 2, 20% O 2, 0. 3% CO 2 • Pressure at Sea Level = 101 k. Pa (760 mm Hg) • Pressure decline by half for every 5500 m increase in altitude • Partial Pressure (PP) of a gas = its fractional percent * total press. • Temperature range: -70 o. C to 50 o. C; declines 6 -10 o. C per 1000 m altitude from sea level

Aquatic Environments • Composition: salts, ions, dissolved gases • Temp. : ~0 -100 o. C • Pressure increases 1 atm per 10 m depth • Mean depth of ocean is 3800 m • Most light absorbed by 8 m depth

Terrestrial Environments • Biomes: classed by water abundance, temp. and dominant community • Subterranean environments might have lower oxygen and higher carbon dioxide levels and of course little to no light sources

Internal Environment • Composition by weight: 60 -90% water, 18% protein, 15% fat, 7% mineral • 63% H, 25% O, 9. 5% C, 1. 4% N • Minor elements (<1%) • Trace elements (<0. 01%)

Body Fluids Transcellular fluids are filtrates of the plasma

Important Ions