Human physiology is the study of how the human body works at the molecular, cellular, tissue, organ, and organ system levels. Cells are the basic units of life that differentiate and combine to form tissues and organs. The four main tissue types are muscle, nerve, epithelial and connective tissues. Organs consist of tissues arranged to perform specific functions. Organ systems work together to maintain homeostasis, or stability, of the internal environment surrounding cells through detection of changes and commanding responses. The body contains intracellular fluid within cells and extracellular fluid outside of cells, separated by semipermeable barriers that regulate passage of substances.

1. Human PhysiologyBiology 012 John Paul L. Oliveros, MD, DPPS

2. Mechanism and causality Physiology: is the study of how things work Human physiology: individual molecular processes  processes that depend on many separate organs of the body Mechanist view: “all phenomenon, no matter how complex, can be described in terms of physical and chemical laws” Vitalism: “ a vital force, beyond physics and chemistry, is required to explain life” Causality: to reduce a phenomenon to causally linked sequence of scientific events in order to explain it

3. Cell theory Cells: Simplest structural units in which a multicellular organism can be dividedand still retain funtions and characteristics of life Cell differentiation: the process of transforming an unspecialized cell into a specialized cell Cells with similar specialization migrate to adhere with other cells to form multicellular structures

4. Cells 200 different kinds of cells in the body Functional Classification Muscle cells: Generate mechanical forces that produces force and movement Nerve cells: Initiate and conduct electrical signals Epithelial cells: Selective secretions of ions and organic molecules Located on the surfaces Cover the body or organs Line the walls of tubular or hollow structures Connective Tissue cells Connecting, anchoring, and supporting the structures of the body Loose CT, fat cells, blood cells, bone cells

5. Tissues Aggregate of a single type of cell 4 classes Muscle tissue Nerve Tissue Epithelial Tissue Connective Tissue Extracellular fluid Extracellular matrix Protein and mineral mixture specific for each tissue Collagen fibers Elastin fibers Protein-carbohydratemixture Functions: Scafold for cellular attachments Transmits information between cells ( chemical messengers)

6. Organs and Organ systems Organs: Composed of the 4 kinds of tissues arranged in various proportions and patterns Functional Units: Smaller similar subunits of an organ Performs function of an organ Organ systems: A collection of organs that perform an overall function 10 organ systems

8. Internal Environment Cells in our body are not in direct contact with the external environment The overall effect of the activities of the organ systems is to create within the body an environment in which all cells can survive and function Internal environment: Fluid environment surrounding each cell AKA extracellular fluid

9. Internal Environment

10. Homeostasis Homeostasis: The relative constancy of the internal environment Changes may occur but are small and kept within narrow ranges Homeostatic control system: a collection of body components that functions to keep a physical or chemical property of the internal environment relatively constant 3 components : Detection of the changes in the magnitude of the property Relaying of information to appropriate sites Commanding particular cells to change their funtion to restore property to its original value

11. Body-Fluid Compartments Total Body Water (TBW): 60% of body weight Intracellular Fluid: 2/3 of TBW Extracellular fluid:1/3 of TBW Interstitial fluid 80% of ECF Fluid in between and surrounding cells Plasma: 20% of ECF Blood= plasma + suspended cells (blood cells)

12. Body-Fluid Compartments Compartmentalization: Important principle in physiology Achieved by barriers between compartments Barriers regulate passage of substances between compartments Cell membranes: between cells and interstial fluid Blood vessels: between plasma and interstitial fluid

13. Body Fluid Compartments