The most abundant solutes in body fluids, which determines most of their physical & chemical reactions.
Electrolytes
T/F: Electrolytes do not constitute the bulk of dissolved solutes in the body fluids.
True (proteins & some nonelectrolytes like phospholipids, cholesterol, & triglycerides are large molecules that account for 90% of the mass of dissolved solutes in plasma, 60% in IF, & 97% in the ICF)
The continuous exchange and mixing of body fluids are regulated by
osmotic & hydrostatic pressures.
Solutes are unequally distributed in the body because of their...
size, electrical charge, or dependence on transport proteins
In general, substances must pass through both the plasma & interstitial fluid (IF) in order to reach the...
intracellular fluid
Exchanges between the outside world & the plasma occur almost continuously in what three areas?
Lungs Gastrointestinal tract Kidneys
Serves as the highway for delivering substances throughout the body.
Plasma
Exchanges between plasma and interstitial fluid (IF) occur...
across capillary membranes
Under normal circumstances, the small net leakage that remains behind in the interstitial space is picked up by ____________ & returned to the blood.
lymphatic vessels
Exchanges between IF & ICF occur across ___________ & depend on ___________.
T/F: Movements of nutrients, respiratory gases, & wastes are typically unidirectional.
True
T/F: Osmolarities of all body fluids are equal.
True
Increasing extracellular fluid (ECF) content can be expected to cause
a shift in water out of the cells
Intracellular fluid volume is determined by the
Extracellular fluid (ECF) solute concentration
T/F: For the body to remain properly hydrated, water intake must be equal to water output.
True
Most water enters the body through..
ingested liquids & solid foods.
Body water produced by cellular metabolism is called
metabolic water (or water of oxidation)
Water that vaporizes out of the lungs in expired air or diffuses directly through the skin is called
insensible water loss
A rise in plasma osmolarity triggers:
1) thirst (which prompts us to drink water) 2) release of antidiuretic hormone (ADH), which causes kidneys to conserve water & excrete concentrated urine
A decline in plasma osmolarity...
inhibits thirst & ADH release
The driving force for water intake.
The thirst mechanism
Output of certain amounts of water is unavoidable. These outputs are known as
obligatory water losses
______________ help explain why we cannot survive for long without drinking.
Obligatory water losses
Obligatory water loss includes:
insensible water losses & sensible water losses
The body's water volume is closely tied to a powerful water magnet known as
ionic sodium (Na+)
Factors that trigger ADH release by reducing blood volume include:
-prolonged fever -excessive sweating -vomiting or diarrhea -severe blood loss -traumatic burns (under these conditions ADH also acts to constrict arterioles which directly increases blood pressure; hense ADH's other name, vasopressin)
Principle abnormalities or disorders of water balance are
-Dehydration -Hypotonic hydration -Edema
When water output exceeds intake over a period of time & the body is in negative fluid balance, the result is
Left untreated, cerebral edema quickly leads to...
-disorientation -convulsions -coma -death
___________ is an atypical accumulation of fluid in the interstitial space, leading to tissue (but not cell) swelling
Edema
T/F: Edema is an increase in volume of ONLY the IF (interstitial fluid)
true
Factors that accelerate fluid loss from the blood include
increases in capillary hydrostatic pressure & permeability
Increased capillary permeability is usually due to...
an ongoing inflammatory response.
A condition of unusually low levels of plasma proteins, results in tissue edema because protein-deficient plasma has an abnormally low colloid osmotic pressure.
______________ is in which plasma proteins pass through "leaky" renal filtration membranes and are lost in urine.
glomerulonephritis
What happens when lymphatic vessels are blocked?
-The small amount of plasma proteins that seep out of the blood stream are not returned to the blood as usual -As leaked proteins accumulate in the IF, they exert an increasing colloid osmotic pressure, which draws fluid from the blood & holds it in the interstitial space
Edema can impair tissue function because
excess fluid in the interstitial space increases the distance nutrients and oxygen must diffuse between the blood & the cells
The most serious problems resulting from edema affect what system?
Cardiovascular system
The salt balance of the body is known as
electrolyte balance
What are the functions of salt in the body?
-important in controlling fluid movements -provide minerals essential for excitability, secretory activity, and membrane permeability
Salts are lost from the body in..
perspiration feces urine
Addison's disease
disorder entailing deficient mineralcorticoid hormone production by the adrenal cortex
The appetite for abnormal substancs such as chalk, clay, starch, or burnt match tips is known as
pica
____________ holds a central position in fluid and electrolyte balance and overall body homeostasis
Sodium
In normal plasma, _______ is the single most abundant cation in the ECF and the only one exerting significant osmotic pressure.
Na+ (sodium)
T/F: While sodium content of the body may change, its ECF concentration normally remains stable.
True (because of immediate movement of water into or out of the ICF and longer-term adjustments due to the ADH & thirst mechanisms)
T/F: Salt follows water.
False; water follows salt!!
Regulation of the Na+-water balance involves a variety of ________ & _________ controls.
neural & hormonal controls
What hormone "has the most to say" about renal regulation of sodium ion concentration in the ECF?
aldosterone
Aldosterone's central role
maintaining blood volume & blood pressure
T/F: Water always follows Na+
True
T/F: Aldosterone increases ECF volume
True
The most important trigger for aldosterone release from the adrenal cortex is...
the renin-angiotensin mechanism mediated by the juxtaglomerular apparatus of the renal tubules
What 3 situations make the juxtaglomerular apparatus respond by making its granular cells to release renin?
____________ catalyzes the initial step in the reactions that produce angiotensin II, which prompts aldosterone release.
Renin
____________ is an important intermediate pathway linking renin to aldosterone release.
Angiotensin II
Functions of angiontensin II
-prods adrenal cortex to release aldosterone -directly increases Na+ reabsorption by kidney tubules -a number of other actions which all raise blood pressure & blood volume
The principal effects of aldosterone are to
-diminish urinary output -increase blood volume
People with _________ lose tremendous amounts of NaCl and water to urine.
Addison's disease (hypoaldosteronism)
The influence atrial natriuretic peptide (ANP) can be summarized in one sentence:
It reduces blood pressure & blood volume by inhibiting nearly all events that promote vasoconstriction & Na+ and water retention.
___________ are chemically similar to aldosterone, and like aldosterone, enhance NaCl reabsorption by the renal tubules.
Estrogens
____________ decreases Na+ reabsorption by blocking the effect aldosterone has on the renal tubules.
Progesterone
The usual effect of glucocorticoids (such as cortisol & hydrocortisol) is to
-enhance tubular reabsorption of Na+ -promote an increased glomerular filtration rate that may mask their effects on the tubules
Most important effect of ionic calcium in the ECF
is on neuromuscular excitability
ECF calcium ion levels are closely regulation by what hormone?
PTH (parathyroid hormone)
Whenever the pH of arterial blood rises above 7.45, a person is said to have
alkalosis (or alkalemia)
A drop in arterial pH to below 7.35 results in
acidosis (acidemia)
Any arterial pH between 7.35 & 7.0 is called
physiological acidosis
The H+ concentration in blood is regulated sequentially by:
System of one or more compounds that acts to resist changes in pH when a strong acid or base is added.
Chemical buffer
Three major chemical buffer systems in the body are:
-bicarbonate buffer system -phosphate buffer system -protein buffer system
Mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3) in the same solution.
Bicarbonate buffer system
All the available HCO3- ions
alkaline reserve
Single protein molecule that can function reversibly as either an acid or base depending on the pH of its environment. Molecules with this ability are known as