HUMAN PHYSIOLOGYBIOLOGY 012
John Paul L. Oliveros, MD, DPPS
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
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
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
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)
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
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
Internal Environment
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
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)
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
Body Fluid Compartments
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