What is physiology?
The study of HOW the body functions
q: why do i shiver when cold?
a: describe HOW processes occur in the body
What are the levels of organization in the body?
chemical->
cell->
tissue->
organ->
body system->
organism (whole body)
What are the basic functions essential for survival?
1) Obtaining food (nutrients) and oxygen from environment
2) perform chemical rxns that use nutrients & O2 to provide energy for the cells
3) Eliminating to cell's surrounding environment CO2 and other byproducts, wastes, produced during chemical rxns
4)
What are some specialized functions in multicellular organisms?
1) gland cells of digestive system secrete digestive enzymes that breakdown ingested food (enzymes specialized proteins)
2) certain kidney cells able to selectively retain substances needed by body while eliminating unwanted substances in urine; highly sp
What is a tissue?
Cells of similar structure & specialized function combined
What are the four primary types of tissue?
Muscle, nervous, epithelial and connective
What is an organ?
Two or more types of primary tissue organized to perform a particular function.
Stomach = all four primary types
Epithelial tissue
protection, secretion, absorption
Connective tissue
structural support
Muscle tissue
movement
Nervous tissue
communication, coordination, control
Groups of organs organized into...
body systems
A body system is
a collection of organs that perform related functions, interact to accomplish a common activity essential for survival of the whole body
How many systems does the body have?
11: circulatory, digestive, respiratory, urinary, skeletal, muscular, integumentary (skin), immune, nervous, endocrine & reproductive
Why can't the cells in a multicellular organism live and function w/o contributions from other body cells?
Most cells not in direct contact w/ the external environment
What is the external environment?
the surrounding environment in which an organism lives
What is the internal environment?
the fluid that surrounds the cells and through which they make life-sustaining exchanges
Intracellular fluid (ICF)
collectively contained within all body cells
Extracellular fluid (ECF)
fluid outside the cells; outside the cells but INSIDE the body
internal environment of the body, cells live in body's internal environment, you live in the external environment
What is ECF made of?
plasma (fluid portion of blood)
interstitial fluid (surrounds, bathes cells)
Body cells can live and function only when?
the ECF is compatible with their survival
Chemical composition and physical state of internal environment must be maintained within narrow limits
Homeostasis
maintenance of a relatively stable internal environment
essential for survival of each cell, and each cell thru specialized activities as part of a body system helps maintain the internal environment shared by all cells
Central theme of physiology
Homeostasis is essential for survival of each cell, and each cell, through its specialized activities as part of a body system, helps maintain the internal environment shared by all cells
Major body fluid compartments
Total body fluid 60% of body weight
ICF 40%, ECF 20% (plasma 4%, interstitial fluid 16%)
Blood vessel walls
separate plasma from interstitial fluid
Plasma membranes
separate intracellular from interstitial
highly discriminating
intracellular proteins (anions)
unequal distribution of Na+ and K+
K+ in/ Na+ in
K+ concentration greater in intracellular fluid
Na+ concentration greater in extracellular fluid
Plasma Membrane
envelopes all cells; thin flexible lipid bilayer separating cell from its surroundings (predominantly lipids and proteins, small amounts of carbohydrates)
cells must exchange materials across this membrane w/ homeostatically maintained fluid environment s
Membrane potential
slight negative charge on inside of the membrane, slight excess of positive charges on the outside
some cells alter their membrane potential upon appropriate stimulation (nerve, muscle, sensory cells)
Function of Plasma Membrane
Maintains difference in fluid composition inside & outside a cell; selectively permitting specific substances to pass between cell & its environment
controls entry of nutrient molecules & exit of secretory and waste products
maintains differences in ion c
Lipid bilayer structure
lipid bilayer is fluid, not rigid- consistency like cooking oil
phospholipids weak bonds, constantly moving, exchanging places millions of times per second - fluidity
Lipid Bilayer Function
forms basic structure of membrane
hydrophobic interior barrier to passage of water-soluble substances between ICF and ECF. Water soluble substances cannot dissolve in and pass thru lipid bilayer (cell maintains different concentrations of solutes inside a
Plasma Membrane proteins
proteins inserted within or attached to lipid bilayer
plasma membrane has 50x more lipid molecules than protein molecules; proteins larger than lipids
fluidity of lipid bilayer -> many membrane proteins to float freely in a moving sea of lipid
Fluid mosai
Membrane found protein functions
water-filled pathways or channels
carrier or transport molecules
docking markers of secretory vesicles (inner surface)
enzymes (inner and outer surface)
receptors (outer surface)
CAMs (cell adhesion molecules) (inner & outer surface)
proteins & carbohydra
Glycoproteins/ Glycolipids
small amount of membrane carbohydrate located on outer surface of cells
short carbohydrate chains protrude like tiny antennas from outer membrane surface
bound primarily to membrane proteins & lipids
self identity markers
Cell-Cell Adhesions
plasma membrane participates in cell to cell adhesions
cells organized into appropriate groupings held together by three means:
extracellular matrix
CAMs
specialized cell junctions
Extracellular Matrix (ECM)
cells held together by a biological "glue", called ECM when cells within tissue not in direct physical contact
ECM intricate mesh work of fibrous proteins embedded in watery, gel-like substance composed of complex carbohydrates, usually called interstitia
Cell Adhesion Molecules (CAMs)
found in tissues where cells lie close to one another; provide tissue cohesion as they "velcro" adjacent cells together
specialized cell junctions: desmosomes, tight junctions, gap junctions
Desmosomes
like spot rivets, anchor two adjacent but NON TOUCHING cells
2 components: pair of dense, button-like cytoplasmic thickenings on inner membrane surface (plaques)
strong glycoprotein filaments containing cadherins (type of CAM)- extend across space between
Tight Junctions
adjacent cells bind firmly with each other at points of DIRECT CONTACT - seal off passageway between 2 cells
found primarily in sheets of epithelial tissue (cover surface of body, line internal cavities)
epithelial sheets highly selective
impermeable, pre
Gap Junctions
communicating junctions- small diameter permits small, water soluble particles to pass between connected cell- ions and small molecules can be directly exchanged between interacting cells through gap junctions without ever entering ECF
abundant - cardiac
Permeable
If a substance can cross the membrane, membrane is permeable to substance
Impermeable
If a substance cannot pass, the membrane is this
Membrane Transport
plasma membrane is selectively permeable; permits some particles to pass while excluding others
anything that passes between a cell and the surrounding ECT must be able to penetrate plasma membrane
What are the properties of particles influencing whether or not they can permeate the plasma membrane without assistance?
relative lipid solubility of the particle (highly lipid soluble particles can dissolve in lipid bilayer and pass thru membrane) (uncharged, nonpolar molecules O2 CO2 and fatty acids highly lipid soluble, readily permeate membrane), charged particles have
Passive Forces
do NOT require the cell to expend energy to produce movement
Active Forces
do require the cell to expend energy (ATP) in transporting a substance across the membrane
Passive Transport
all molecules and ions are in continuous random motion at temperatures above absolute zero due to thermal (heat) energy
Simple Diffusion
Brownian motion
net movement of molecules from area of high concentration to area of lower concentration
Increase concentration gradient of substance
increase rate of net diffusion
increase surface area of membrane
increase rate of net diffusion
increase lipid solubility
increase rate of net diffusion
increase molecular weight of substance
decrease rate of net diffusion
increase distance (thickness)
decrease rate of net diffusion
Ion Movement
affected by electrical charge
ions w/ like charges repeal; ions w/ opposite charges attract
Difference in charge between two adjacent areas produces an electrical gradient that promotes movement of ions toward the area of opposite charge
Passive Ion Movement
ions moving down their respective electrical or concentration gradient
when electrical gradient exists between ICF and ECF, only ions that can permeate plasma membrane move along gradient
Electrochemical gradient
net effect of simultaneous electrical and concentration gradients
H2O Movement
concentration gradient - driving force for net movement of water across membrane
adding solute to pure water DECREASES water concentration; one molecule of solute displaces one molecule of water
osmosis
net diffusion of water down its concentration gradient through a selectively permeable membrane
water moves by osmosis to the area of higher solute concentration
Hydrostatic (fluid) pressure
pressure exerted by a standing, or stationary fluid on an object
Osmotic pressure
tendency for osmotic flow of water into that solution because of its relative concentration of nonpenetrating solutes and water
Osmolarity
Measure of a solutions total solute concentration given in terms of the number of particles (molecules or ions), more direct means of expressing solute concentration
Expressed in osmoles/ L
What is the normal osmolarity of body fluids?
300 mOsm/L