Water Balance Pt 2 | Physiology 2 Final

What solution in an animal has the highest value of osmolality

urine

Comparing the urine of bovine and canine, which spp. has a higher urine osmolality

canine urine

What three forms can water be found in the interstitium as

1. proteoglycan gel entrapping water

2. rivulets of free fluid

3. free fluid vesicles

True or false: localized changes in a particular transcellular fluid compartment can occur pathologically but it does not affect the fluid balance of the body

true

What type of fluid has the highest percentage of body weight of the total body weight of water

intracellular fluid (ICF) - 40%

During a lactational period of a cow, how does the cow’s water intake change compared to a dry period

lactational period, a cow drinks almost 4x amount of water increasing its overall water intake compared to a dry period

During a lactational period of a cow, how does the cow’s water loss change compared to a dry period (and what leads to the most water loss)

lactational period, a cow loses most water in milk increasing its overall water loss compared to a dry period

In water balance, how does an animal gain an increase water intake (through daily actions)

1. ingestion of food

2. drinking water

3. metabolic water - water of oxidation

In water balance, what are the main sources of water loss in an animal (through daily actions)

1. kidneys

2. skin secreting sweat as water

3. lung as exhaled water vapor

4. GI tract in feces

When there is a water homestatic imbalance, what type of fluid does the body respond to with a change of those fluids

ECF - interstitial fluid, plasma, transcellular water

Hormone-mediated responses caused by significant changes in ECF composition affects the balance between what two composition of absorption and excretion

dietary absorption and urinary excretion of water

What are the four reasons why electrolytes are crucial for water balance

1. necessary for normal cell metabolism and body structures

2. facilitate osmotic movement of water between body compartments

3. maintains hydrogen ion concentration required for acid-base balance

4. maintenance of membrane potentials and production of action potentials

What is the most abundant ion in intracellular fluid

K+

What is the most abundant cation in intracellular fluid

K+

What is the most abundant anion in extracellular fluid

Cl-

What is the most abundant cation in extracellular fluid

Na+

What are the principal ions in ECF

• Na+

• Cl-

• HCO3-

What are the principal ions in ICF

• K+

• Mg+

• PO4

True or False: intracellular and extracellular osmolalities are identical

true

True or False: osmosis eliminates any differences between osmolalities of intracellular and extracellular fluids

true

Changes in concentration of major solutes in these two fluids will have a major effect on water distribution

• plasma

• interstitial fluid

When there is water imbalance, how does that affect solute concentration

alters concentration of solutes

How does the water movement between ECF and ICF respond to osmolality changes of ECF

water will move in and out of the cells into ECF until osmotic equilibrium is restored

How does the water movement between ECF and ICF respond to an increase of osmolality of ECF (such as an animal losing water but retaining electrolytes

osmolality of ECF becomes hypertonic w respect to ICF

→ water will move out of the cell into the ECF (to restore equilibrium)

How does the water movement between ECF and ICF respond to a decrease of osmolality of ECF (such as an animal gaining water but without electrolytes)

osmolality of ECF becomes hypotonic w respect to ICF

→ water will move from ECF into the cell

→ volume of ICF will increase

(to restore equilibrium)

What are the three hormones that regulate fluid imbalances

1. ADH

2. aldosterone

3. atrial natriuretic peptide (ANP)

Where are the osmoreceptors located that secrete ADH (and where do they release ADH to)

osmoreceptors are in the anterior hypothalamus that secrete ADH into the posterior pituitary gland

The rate of ADH release from hypothalamus directly varies with ___

ECF osmolarity — higher the ECF osmolarity, the greater amount of ADH released

When there is an increase of ECF osmolality, what is activated in the hypothalamic osmoreceptors and what are the two important effects

increased ECF osmolarity detected by osmoreceptors in anteior hypothalamus → ADH release from posterior pituitary to blood:

• water reabsorption in the kidneys

• stimulation of thirst center to promote fluid intake

What secretes aldosterone and what ion concentration influences the release of aldosterone

aldosterone secreted by adrenal cortex influenced by ECF K+ levels increased

When the renin-angiotensin-aldosterone system or increased K+ level stimulate aldosterone release, what is aldosterone’s major role in water balance

determine the rate of sodium absorption

• higher the plasma aldosterone conc, higher kidneys will conserve sodium, H2O will follow salt

What are the two situations that aldosterone is released

1. activation of renin-angiotensin-aldosterone system (due to low blood vol)

2. ECF K+ levels increase

What occurs to aldosterone levels, when ECF K+ decreases

aldosterone decreases

What cation is a major electrolyte in intracellular fluid but not in extracellular fluid

K+

What anion is a major electrolyte in intracellular fluid but not in extracellular

phosphate

What cation is a major electrolyte in extracellular fluid but not in intracellular

Na+

What anion is a major electrolyte in extracellular fluid but not in intracellular

Cl-

As aldosterone is released in response to high K+ ECF levels, What are the three ways aldosterone increases K+ excretion (hyperkalemia)

1. inc Na-K/ATPase activity

2. inc Na+ reabsorption in distal nephron

3. inc permeability of luminal surface for K+

True or false: atrial natriuretic peptide effects in water balance causes hyperkalemia

false; aldosterone effects in water balance causes hyperkalemia

What releases atrial natriuretic peptides (ANP) and what are the two reasons for its release

cardiac muscle cells release ANP due to:

1. elevated BP

2. inc Blood Volume

What are the 4 effects of ANP on water balance (and what is the overall effect of ANP release in response to abnormal stretching of atrial walls)

decreases blood volume and blood pressure:

1. inc water secretion in kidneys

2. dec thirst

3. block release of ADH

4. stimulate peripheral vasodilation

If there is a high volume of water into the kidneys, what hormone inhibits ADH and increases water secretion/decreases water reabsorption in kidneys

ANP

What antagonist hormone in water balance, has opposing effects on water reabsorption of ADH and aldosterone

ANP

How does hyperkalemia by aldosterone promote water balance

inc K+ secretion, inc Na reabsorption causing H2O to be reabsorbed

What two forces control the movement of water from one body compartment to another

1. hydrostatic pressure

2. colloid osmotic pressure (oncotic pressure)

When net hydrostatic or osmotic pressures are affected, what type of fluid is affected

ECF