Anatomy & Physiology I
Unit Three
Organelles of An animal cell
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Chromatin
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Fluid Mosaic Model of the
Plasma Membrane
Fluid Mosaic Model of the
Plasma Membrane
Fluid Mosaic
Model of the
Plasma Membrane
Fluid Mosaic Model of the
Plasma Membrane
Fluid Mosaic Model of the
Plasma Membrane
Does not require energy from the cell
Substances move from an area of
high concentration to an area of low
concentration
Substances can move in both
directions, depending on the
concentration gradient
Diffusion – the movement of a
substance from an area of high
concentration to an area of low
concentration
Facilitated diffusion – same as above,
but with the help of membrane
proteins
Osmosis – the diffusion of water
Does require energy from the cell
Substances move from an area of low
concentration to an area of high
concentration
Substances can move in only one
direction, against the concentration
gradient
Sodium/Potassium pump – a membrane
protein that moves sodium out, while
moving potassium in
Endocytosis
* Phagocytosis
* Pinocytosis
Exocytosis
Osmosis
Solute – substance that is dissolved in a
medium (solvent)
Solvent – substance (usually liquid) that
dissolves a solute
Solution – mixture of solutes dissolved in
a solvent
Osmotic pressure is created by the
movement of water toward a higher
solute concentration
Osmosis
Diffusion
Semipermeable
membrane
Osmosis
Osmosis
Animal Cell Osmosis
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Lysed
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Crenated
Plant Cell Osmosis
Turgor
Osmosis
Therefore, the higher the solute
concentration, the higher the osmotic
pressure
Many body systems create high solute
concentrations so as to produce higher
osmotic pressure
Osmosis
Edema – the excess collection of
extracellular fluids due to high solute
concentration
Dehydration – the loss of extracellular
fluids due to various causes
Electrolyte Functions
The functions of electrolytes are varied and
important:
+ chemically reactive and
participate in metabolism
+ determine charge difference
across cell membranes
Electrolyte Functions
The functions of electrolytes are varied and
important:
+ powerfully affect the
osmolarity of body fluids and
the body’s water content and
distribution
+ form essential minerals
+ regulate acid/base balance
Electrolyte Concentrations
Extracellular fluids (ECF) are fluids of the body found
outside the cells
Intracellular fluids (ICF) are fluids of the body found
inside the cells (cytoplasm)
Electrolyte Concentrations
HPO43(Lo)
HPO43(Hi)
Na+
(145mEq/L)
Ca2+
Mg2+
(Lo)
Mg2+
(Hi)
(Hi)
Ca2+
(Lo)
K+
(4mEq/L)
K+
(150mEq/L)
Na+
(12mEq/L)
Electrolyte Concentrations
Cl(103mEq/L)
Cl(4mEq/L)
HCO3
(Hi)
HCO3(Lo)
OH-
-
H+
H+
OH-
ICF vs. ECF
ICF
65% of body fluids
Major electrolytes
K+
Mg2+
HPO43-
ECF
35% of body
fluids
Major electrolytes
Na+
Ca2+
Cl-
ICF vs. ECF
10L
26L
Interstitial
Fluids
3.2L
Blood
Plasma
Lymph
40L total body fluid
0.8L
Other
Movement of Water
Fluids are constantly exchanged
between these compartments
Osmosis occurs across capillary
walls and plasma membranes
Movement of Water
The movement of the water from
one compartment to the other is
determined by solute
concentrations
Movement of Water
Introducing Fluids
in the Body
As has been established, body cells must
maintained in isotonic conditions
On an average the solute concentration of body
cells is 300mosm
Introducing Fluids
in the Body
This means on an average, the ECF osmolarity
would also be 300mosm
There are exceptions to both ICF and ECF
osmolarities
Introducing Fluids
in the Body
Since a loss of fluids also means a loss of
electrolytes, fluid replacement therapy (IVs) may
be necessary to restore homeostatic concentrations
and volumes
Introducing Fluids
in the Body
Fluids introduced to the body must therefore have
the same osmolarity
> 0.9% normal saline (NS) or
physiological saline (PSS)
> D5W (dextrose 5% in water)
(5% glucose)
> Ringer’s lactate solution
Fluid
Balance
Balance of body fluids means that fluid
intake should equal fluid output
In addition, the fluid gained or lost must
be added to or taken from the right
compartment (ICF or ECF)
Fluid
Balance
Fluid
Balance
As has been seen, electrolyte
concentrations in the different
compartments must also be stringently
maintained
Electrolytes attract water through
osmosis, therefore a loss of fluids results
in the loss of electrolytes
Fluid & Electrolyte
Balance
ICF
65% of body fluids
Major electrolytes
K+
Mg2+
HPO43-
ECF
35% of body
fluids
Major electrolytes
Na+
Ca2+
Cl-
Fluid
Balance
The three structures that play the major
role in fluid and electrolyte balance are:
* brain (hypothalamus)
* kidneys
* adrenal glands
Regulation of Fluid
Intake
volume of ECF
Decreased
or
Increased
osmolarity of ECF
Increased
volume of ECF
which
decreases
osmolarity of ECF
Hypothalamus
Decrease saliva
Creates thirst
Drink fluids