Physiology - Volumes & Compositions of Body Fluids

Homeostasis

Steady internal, physical, chemical, and social conditions are maintained by living systems (optimal functioning)

Homeostasis Examples

Body temperature and fluid balance being kept within certain pre-set limits

Physical or External Insults

High body temperature due to weather or exercise, lack of oxygen due to high altitude hiking

Changes to internal enviornment

Drop in blood glucose due to lack of food

Physiological stress

Demands of work or school

Negative feedback system

Reverses a change in controlled condition (Too high/reduce, too low/increase) maintaining normal condition

Positive Feedback

Strengthen the change in a controlled condition, moving the system further away from its initial state. Drives processes to completion, often involving rapid, self-perpetuating cycle

Positive Feedback Examples

Blood clotting, cytokine storm, normal child birth (uterus muscle contraction)

Negative Feedback Systems

BP, blood glucose, temp.

Study of failure to maintain homeostasis

Pathophysiology

Equilibrium

refers to a state of balance within a biological system, where opposing forces or processes are balanced, resulting in a stable condition.

Equilibrium Example

Osmotic pressure inside of cells is in equilibrium with outside of cell

Chemical Disequilibrium

More K+ intracellular, more Na+, Cl- extracellular

Electrical Disequilibrum

-70 mV intracellular

Body fluids

Liquids within body of organism

Intracellular Fluid

2/3 of total body water vol

Extracellular Fluid

1/3 of total body water vol

Types of Extracellular Fluid

Interstitial fluid, blood plasma, and lymph

Interstitial Fluid

Lies between circulatory system and the cells

Blood Plasma

Liquid matrix of blood

Components of Body Fluids

Water (solvent) and molecules dissolved in H2O (solute)

Solutes

Electrolytes, Protons, Metabolites, Proteins, and Gas

Electrolytes

Minerals in blood and other body fluids can carry an electric charge, positive or negative charged ions: Na+, K+,

Proton

H+

Metabolites

Urea, Glucose, ATP, Nucleotides, Amino Acids

Proteins

Albumin, hormones, antibodies

Gas

O2, CO2

Water Weight

50% of the body

Functional Significance of H2O

The environment for all biochemical reactions acts as a solvent, regulating internal body temperature. through sweating and respiration, transports carbohydrates and proteins, flushing waste through urination, forms saliva, lubricates joints

H2O Content with Increasing Age

Decreases due to increased fats

H2O Content for Males

Increases due to less hypodermis

Proteins in Body Fluid

High in intracellular and plasma but low in interstitial fluid

Proteins High in Intracellular

Proteins made in cell and impermeable to cell membrane

Plasma Proteins

Synthesized in the liver by B lymphocytes. Bone marrow (degenerating blood cells), spleen, and endocrine organs.

Interstitial Fluid Proteins

Low because the cell membrane blocks the movement of proteins from inside cells to outside of cells. Capillary wall limits movement of proteins from plasma outside of blood vessels

Na+ and Cl- in Body Fluid

High in extracellular fluid and low in intracellular

K+ in Body Fluid

High intracellular fluid and low in extracellular

Reason for Na+ and Cl- Concentrations in Body Fluids

Ions from food (enter the blood first) and capillary walls allow for the free movement of ions between the plasma and the interstitial fluid

Reason for K+ Concentrations in Body Fluids

Intracellular fluid marked differently than extracellular fluids due to active transport for cells to manage concentration of particular ions (membrane potential and cell excitability)

Na+ Concentration (mEq/L)

Extracellular (140), Intracellular (14)

K+ Concentration (mEq/L)

Extracellular (4), Intracellular (120)

Ca2+ Concentration (mEq/L)

Extracellular (2.5^b), Intracellular (1 × 10^-4) - 10k times larger extracellular

Cl- Concentration (mEq/L)

Extracellular (105), Intracellular (10)

pH

Extracellular (7.4), Intracellular (7.1)

Osmolarity (mOsm/L)

Extracellular (290), Intracellular (290)

Regulation of body fluid volume

Involves control of water and sodium excretion in urine and water and NaCl consumption motivated by thirst and salt appetite

Osmotic Pressure

Pressure exerted by the flow of water through a semi-permeable membrane separating two solutions with different concentrations. of solute

Hydrostatic Pressure

Pressure exerted by fluid at rest due to the force of gravity

Filtration

H2O from capillary to interstitial through capillary hydrostatic pressure

Absorption

H2O from interstitial to capillary through osmotic pressure of plasma

Osmotic Pressure

Moves body fluids (H2O) between ICF and interstitial fluid. Forces water to move from low to high concentration

Osmosis

Diffusion of solvent (H2O) from high to low solvent concentration

Hypoosmotic

Low osmole

Hyperosmotic

High osmole

Water Crossing Cellular Membrane

Aquaporins (H2O channels), which are passive conduits for transport. Can also diffuse across membrane.

Molarity (M)

Number of moles of solute per liter of solution

Osmolarity (Osm/L)

Total concentration of all solute particles in solution contributing to osmotic pressure