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Inputs to
internal pool
Outputs from
internal pool
(Inside body)
Input from external
environment
(through ingestion,
inhalation, absorption
through body surface,
or artificial injection)
Metabolically
produced by body
Storage depots within
body (no function
other than storage)
Internal pool
(extracellular fluid
concentration) of a
substance
Excretion to external
environment (through
kidneys, lungs, gills,
digestive tract, or body
surface, e.g., sweat, tears,
sloughed skin)
Metabolically
consumed in body
(irretrievably altered)
Reversible incorporation
into more complex
molecular structures
(fulfills a specific function)
Fig. 13-1, p.573
Fig. 13-2, p.574
Table 13-1, p.575
Difference between ECF and ICF
• Cellular proteins
• Cellular organic osmolytes
• Unequal distribution of Na+ and K+
Fig. 13-3, p.576
Osmotic and volume balance
Osmotic problems threaten cells and animals
1. Evaporation of body water into air (eg. sweating or
breathing)
2. Osmosis into or out of environment (eg. fresh water
or saline water)
3. Freezing (locks up water in ice crystals and
concentrates ions in unfrozen water)
4. Excretion (require water for waste removal)
5. Diseases (eg. Diabetes)
Fig. 13-4a, p.577
Fig. 13-4c, p.577
Fig. 13-5, p.578
Fig. 13-6, p.579
Fig. 13-7, p.579
Table 13-2a, p.580
Table 13-2b, p.580
Table 13-2c, p.581
Fig. 13-8, p.582
Fig. 13-10, p.585
Medium <5 mOsm
Absorbs water
through gills
and skin
Body fluids ca.
300 mOsm
Obtains salts through
“chloride” cells in gills
and with food
Salts lost
via feces
Removes much water and
some salt via dilute urine
Fig. 13-11, p.586
Adaptation of Freshwater Animals
•
•
•
•
Active transport of ions
Hypotonic urine
Lower internal osmolarities
Low permeability of integument
Terrestrial animals
Dietary
H2O
NaCI
H2O retention
NaCI retention
H2O lost via
respiration
H2O
NaCI lost via
excretion
Fig. 13-12, p.587
ECF Hypertonicity
1. Insufficient water intake (eg. Drought,
desert)
2. Excessive water loss (heavy sweating,
panting, vomiting, diarrhea, diabetes,
breath in dry air, exposed to salt water)
3. Drinking hypertonic saline water
4. Alcohol inhibits vasopressin secretion
ECF Hypotonicity
1. Intake of relatively more water than
solutes
2. Retention of excess water without solute
Table 13-3, p.590
ECF volume
Relieves
Relieves
Osmolarity
+
Hypothalamic osmoreceptors
(dominant factor controlling thirst
and vasopressin secretion)
+
Arterial
blood pressure
+
Left atrial
volume receptors (important only in large changes in
plasma volume/arterial pressure)
Hypothalamic neurons
Thirst
Relieves
+
Vasopressin
Arteriolar
vasoconstriction
H2O intake
H2O permeability
of distal and collecting tubules
H2O reabsorption
Urine output
Plasma osmolarity
Plasma volume
Fig. 13-13, p.591
Table 13-4, p.592
Reliev es
Na+ load in body
Reliev es
Arterial blood pressure
a
b
GFR
Aldosterone
Na+ filtered
Na+ reabsorbed
Excretion of Na+ and
accompanying Cl2 and fluid
Conservation of NaCl and
accompanying fluid
a See Figure 12-14 for details of mechanis m.
b See Figure 12-18 for details of mechanis m.
Fig. 13-14, p.593
Fig. 13-15, p.594
Fig. 13-16, p.596
Fig. 13-17, p.596
Three pH defenders and Four pH
buffer systems
•
1.
2.
3.
Three defense against pH changes
Chemical buffer systems
Respiratory control
Excretory control
Fig. 13-19, p.599
Three pH defenders and Four pH
buffer systems
•
1.
2.
3.
4.
Four buffer systems
Carbon dioxide-bicarbonate buffer
Peptide and protein buffer
Hemoglobin buffer
Phosphate buffer
p.600
Alleviates
Plasma [H+]
(or plasma [CO2])
Buffers
H+ secretion
HCO3– conservation
H+ excretion
HCO3– excretion
Plasma [H+]
Plasma [HCO3–]
Fig. 13-20, p.603
Fig. 13-23, p.606