homeostais and body_fluid

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