PSL201Y1 Lecture : Introduction2.docx
Document Summary
Body fluid compartments: cell membranes and epithelial tissues are selectively permeable or semipermeable, total body water (tbw): total volume of fluid enclosed within the outer epithelial layer. Intra. fluid contains many proteins and is relatively rich in potassium. Extra. fluid contains few proteins and is relatively rich in sodium: 20% of the extracellular fluid is in blood and the remainder is outside the blood. Plasma is the portion of the blood (relatively rich in proteins). Capillaries are not permeable to proteins hence no proteins in isf. Homeostasis: maintenance of constant condition in the internal environment. The internal environment is regulated to remain constant means that the composition, temperature, and volume of extracellular fluid do not change significantly under normal conditions. Regulated variable: body temperature regulated to stay within relatively narrow limits. Plasma concentrations of k, na, and ca are regulated variables because they are kept constant by homeostatic regulatory mechanisms or the organ systems.