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