Excretion to external environment (through kidneys, lungs, gills,

digestive tract, or body surface, e.g., sweat, tears,

sloughed skin)

Metabolicallyconsumed in body

(irretrievably altered)

Internal pool(extracellular fluid

concentration) of a substance

Reversible incorporationinto more complex

molecular structures(fulfills a specific function)

Metabolicallyproduced by body

Input from external environment

(through ingestion, inhalation, absorption through body surface,or artificial injection)

Storage depots withinbody (no function

other than storage)

Outputs frominternal pool

(Inside body)

Inputs to internal pool

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 balanceOsmotic problems threaten cells and animals1. 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

Fig. 13-11, p.586

Medium <5 mOsm

Removes much water andsome salt via dilute urineSalts lost

via feces

Obtains salts through“chloride” cells in gillsand with food

Absorbs waterthrough gillsand skin

Body fluids ca.300 mOsm

Adaptation of Freshwater Animals

• Active transport of ions

• Hypotonic urine

• Lower internal osmolarities

• Low permeability of integument

Fig. 13-12, p.587

H2O lost viarespirationNaCI retention

NaCI lost via excretion

NaCI

H2O retention

Terrestrial animals

DietaryH2O

H2O

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

Relieves

Relieves

Relieves

ECF volume

OsmolarityArterial

blood pressure

Thirst Vasopressin

Hypothalamic osmoreceptors(dominant factor controlling thirst

and vasopressin secretion)

Left atrialvolume receptors (important only in large changes in

plasma volume/arterial pressure)

Hypothalamic neurons

Arteriolarvasoconstriction

H2O intakeH2O permeability

of distal and collecting tubules

H2O reabsorption

Urine output

Plasma osmolarity Plasma volume

++

+ +

Fig. 13-13, p.591

Table 13-4, p.592

Relieves

Relieves

Na+ load in body

Arterial blood pressure

AldosteroneGFR

Na+ reabsorbedNa+ filtered

Excretion of Na+ andaccompanying Cl2 and fluid

Conservation of NaCl andaccompanying fluid

a

b

See Figur e 12-14 for details of mechanism.

See Figur e 12-18 for details of mechanism.

ba

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

• Three defense against pH changes

1. Chemical buffer systems

2. Respiratory control

3. Excretory control

Fig. 13-19, p.599

Three pH defenders and Four pH buffer systems

• Four buffer systems

1. Carbon dioxide-bicarbonate buffer

2. Peptide and protein buffer

3. Hemoglobin buffer

4. Phosphate buffer

p.600

Alleviates Buffers Plasma [H+](or plasma [CO2])

H+ secretion HCO3– conservation

H+ excretion HCO3– excretion

Plasma [H+] Plasma [HCO3–]

Fig. 13-20, p.603

Fig. 13-23, p.606