homeostais and body_fluid
TRANSCRIPT
HomeostasisHomeostasis
Physiology: study the functions of living things
Body Fluid Compartments
Cells contained in watery internal environment: life-sustaining exchanges occur
Extracellular fluid (ECF): Fluid outside the cells
PlasmaInterstitial fluid
Intracellular fluid (ICF): Fluid contained within the cells
Homeostasis
Maintenance of a relatively stable internal environment Internal environment is the extracellular
fluid Essential for survival and function of
all cells
Homeostasis
Factors Homeostatically Regulated: Concentration of nutrient molecules Concentration of O2 and CO2 Concentration of waste products Concentration of water, salt, and other
electrolytes Volume and pressure pH Temperature
Homeostasis
All the systems of the body work together to maintain homeostasis: Gastrointestinal, Respiratory systems
Obtaining nutrients and O2 Circulatory system Transport Respiratory, Renal systems Removal
of waste and metabolic end products Nervous and Endocrine systems
Regulation
Homeostasis
Homeostatic Control Systems
Functionally interconnected network of body components that operate to maintain a given factor in the internal environment relatively constant around an optimal level
Homeostatic Control Systems
Components:Sensor: Detects deviation from set pointIntegrating (control) center: Compares input with set point & determines responseEffecter: Produces response
Homeostatic Control Systems
Feedforward: Term used for responses made in
anticipation of a change Feedback:
Refers to responses made after change has been detected
Types of feedback systems Negative Feedback Positive Feedback
Homeostatic Control Systems
Negative Feedback: Primary type of homeostatic
control Opposes initial change
Homeostatic Control Systems
Negative Feedback:
Homeostatic Control Systems
Positive Feedback: amplifies an initial change An output is enhanced A controlled variable moves in the
direction of an initial change
Homeostatic Control Systems
Positive Feedback: One example occurs during the birth of
a baby
Body FluidBody Fluid
Body fluid On average, body fluids constitute
60% of total body weight In the average 70 Kg adult male is
about 42 L
Body fluid Variation in water content:
Variation due to age: total body water (TBW) with increasing age, by age of 60 years it becomes 50 %
Variation between tissues: Most tissues are water-rich and contain 70-
80% water Plasma contains >90% water Fat is the driest tissue of all, having only
10% water content Variation between individuals:
TBW in a standard male is 60% of his body weight, while in female, its 55%, due to higher fat content
Obese adults have lower percentage
Body Fluid Compartments TBW represent about 60% of total
body weight: Intracellular fluid (ICF):
fluid within the cells about 2/3 of TBW (40%)
Extracellular fluid (ECF): fluid outside the cells About 1/3 of TBW (20%)
Body Fluid Compartments
Body Fluid Compartments
Body Fluid Compartments
Body Fluid Compartments
Body Fluid Compartments
Body Fluid Compartments ICF differs considerably from ECF
Body is in fluid balance
Daily intake of water: Fluid intake (1.250
mL/day) Food intake (1000
ml/day) Metabolically produced
H2O (350mL/day)
Daily loss of body water: Insensible water loss
(900ml/day) Fluid loss in sweat
(100ml/day) Water loss in feces
(100ml/day) Water loss by kidney
(1500 ml/day)Total intake (2600ml/day) Total output (2600ml/day)
Body is in fluid balance
In a steady state, the osmolarity in ECF is the same as in ICF Normally, cells neither shrink or swell
because intracellular and interstitial fluids have the same osmolarity (280 mmol/L)
Increasing osmolarity of ECF draws water out of cells and cells shrink
Decreasing osmolarity of ECF draw water inside of cells and causes cells to swell