Summary
Summary Homeostasis in the human body
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The type of regulatory systems in the body and how the body uses these systems to maintain homeostasis.
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HOMEOSTASISPHYSIOLOGY
study of functions in living things
Body functions:
o Purpose of body process → meeting the needs of the body
o Mechanism → cause and effect sequences
ANATOMY
Study of structure of body
Physiological mechanisms are possible through structural design
Structure = possible functions that can occur
Change in structure → function changes
Body has levels of organisation:
Chemicals → molecules → cells → tissue → organs → organ systems → organism
BODY FLUID COMPARTMENTS
Total body mass(female)
o 45% solids
o 55% fluids
Total body mass (male)
o 40% solids
o 60% fluids
Fluids made up of:
2/3 intracellular fluid (in cells)
1/3 extracellular fluid (fluid outside of cells)
o 80% interstitial fluid (in cells)
Internal environment → refers to ECF that surrounds & is in direct
contact with body cells
o 20% plasma fluid (in blood)
There is a continuous mixing of body fluids
o Lungs take CO2 out of plasma & adds O2
o Gastrointestinal tract: nutrients absorbed put into plasma
o Organs: nutrients & O2 moves into cell & CO2 and metabolic move out of
cells
o Kidneys: nitrogenous waste, ion excesses move into kidneys & gets excreted
from body
HOMEOSTASIS
Maintenance of relatively stable physical and chemical conditions, within specific
limits, in the internal fluid environment
Dynamic steady state
Compensatory physiological changes keep the body at a steady state
Doesn’t mean that composition, temperature & other characteristics are absolutely
unchanged
, Important for survival and optimal function of cells → each cell contributes to
maintenance of a relatively stable internal environment
Factors critical for cell survival must be regulated
o Cells are however in a multicellular organism, therefore cannot exchange
nutrients or waste products with external environment
o Exchange occurs via internal environment
Regulated factors
Concentration of
o nutrient molecules
o O2 & CO2
o Waste products
o Water, salt and other electrolytes
pH
Plasma volume & blood pressure
Temperature
MOLECULAR BASIS FOR A STABLE INTERNAL ENVIRONMENT
Proteins require specific conformations(shapes) for efficient functions
o If conformation is changed → function is diminished or lost
Stable internal environment needed to maintain protein conformation
o e.g. temperature
→ too high - protein denatures (conformation completely broken) → not
reversible
→ too low - slows protein function & can change conformation
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