Fluid, pH, and electrolyte bakance

Blood pH maintenance

Avg: 7.35-7.45

Determined by ratio of HCO3- to CO2

Maintained by buffers, lungs, kidneys

Metabolic alkalosis

H+ loss

elevated bicarbonate ions in blood plasma

increase pH

CAUSE: prolonged vomiting, diuretics (excess aldosterone)

Respiratory alkalosis

Excess CO2 loss(hyperventilation→ washes out CO2 in blood→ increases pH)

CAUSE: Anxiety, altitude, brain tumor or damage to respiratory centers

Metabolic Acidosis

Excess acid

Decrease pH

Decreased bicarbonate

producing large quantities of metabolic acids

CAUSE: Diarrhea, renal failure

Respiratory acidosis

Increased PCO2

Decrease pH

CAUSE: blockage in lungs, decrease gas exchange in alveoli, decreased ventilation from brainstem dysfunction

Main chemical buffer of extracellular fluid?

Carbonic-acid-bicarbonate ion buffer system

Extracellular fluid

All fluid outside cells (interstitial fluid and plasma)

has high concentrations of Sodium, calcium, and bicarbonate

Intracellular fluid

fluid INSIDE cells

63% of total body water

has concentrations of potassium, magnesium, phosphate, and sulfate ions

Functions of potassium

Maintains resting membrane potential of neurons and cardiac cells

most abundant in ICF

most potent stimulus for the thirst mechanism?

Increased osmolarity of the ECF

what is the effect when the extracellular fluid is hypertonic compared to a cell’s cytoplasm?

Water moves out of cells, cells shrink (crenate)

the physiological buffer system will compensate for metabolic alkalosis by:

Kidneys reabsorb more hydrogen ions, respiration rate decreases (hypoventilation)

Atrial natriuretic peptide (ANP)

Lowers extracellular fluid volume (and PP) by promoting sodium and water secretion by kidneys

Chemical buffer system equation

CO2+H2O  ↔  H2CO3  ↔  H^++HCO3−

Hydrostatic pressure

outward force causes fluid to leave plasma and enter interstitial fluid

inward force draws fluid back into capillaries

Colloid osmotic pressure

fluid returns to plasma

what fluid has the greatest concentration of potassium ions?

cytosol

how is pH affected when fewer hydrogen ions are secreted into the filtrate?

Blood pH decreases

chlorine ions are involved in the production of:

stomach acids

increase in ADH has what effect of ECF volume?

ECF increases

Digoxin is a drug that increases K+ ion concentration in interstitial fluid. what condition results from digoxin toxicity?

hyperkalemia

what hormones are K+ regulated by?

Aldosterone, Insulin, Epi, and serum pH

most abundant intracellular cation?

K+

How much urine is lost through obligatory water loss each day?

500 ml

How much water does the average person lose per day

2.5 L

what triggers the release of PTH

decrease calcium ion concentration of the blood

Most abundant extracellular cation?

Sodium ion

Role of the urinary system in regulation of hydrogen ion concentration:

Kidneys secrete H+ ions into filtrate for excretion in urine when pH of the blood fails

what happens to ECF during dehydration

it becomes hyperosmotic→ cells lose water and shrink (crenate)

what electrolyte imbalance comes from loop diuretics?

low potassium due to increased urine output= hypokalemia

effects of hyperparathyroidism

increases PTH release causes hypercalcemia

how do physiological buffers compensate for metabolic alkalosis?

respiratory comp: Hypoventilation

Urinary comp: excrete bicarbonate, retention of H+

how do physiological buffers compensate for metabolic acidosis?

respiratory comp: hyperventilation

urinary comp: retention of bicarbonate, kidneys excrete H+

how do physiological buffers compensate for resparatory alkalosis

respiratory comp: hypoventilation

urinary comp: excretion bicarbonate, retention of H+

how do physiological buffers compensate for respiratory acidosis

Respiratory comp: hyperventilation to remove CO2

Urinary comp: retention of bicarbonate, excretion of H+

Acute respiratory acidosis

Most common challenge to acid-base equilibrium, due to hypoventilation and increased CO2 concentrations

Frequent causes of metabolic acidosis

Poorly controlled diabetes mellitus and severe kidney damage

ADH

Stimulates water conservation at the kidneys, and stimulates the thirst center

Atrial and Brain natriuretic hormone

Reduces thirst, lowers BP and plasma volume

Aldosterone

Conservation of sodium and increased sensitivity to salty tastes

Symptoms of hypokalemia

Muscle weakness, Paralysis

All homeostatic mechanisms respond to changes in the:

ECF (changes directly affect BP, osmolarity, and overall homeostasis)

The most frequent cause of respiratory acidosis is:

Chronic pulmonary disorders

Sodium balance in the body is maintained by:

the same hormones and receptors that regulate blood volume

Which of the following hormones play(s) a major role in mediating fluid and electrolyte balance?

ADH, ANP, aldosterone

The major anion in the extracellular fluid compartment is __________, while the major intracellular anion is __________.

Chloride, phosphate

When large amounts of pure water are consumed

osmolarities of the two compartments are slightly lower.

Approximately __________ of peritoneal fluid is produced and reabsorbed each day.

7 L

ANP

Reduces thirst, blocked aldosterone release, blocks ADH

The buffering system in the ICF is made up of ____________________.

Protein and Phosphate buffers

Buffer systems

Protein buffers (ICF, plasma)

Phosphate buffers (ICF, renal tubules)

Carbonic acid- bicarbonate (ECF)

Respiratory regulation

Hypoventilation: Increase CO2→ respiratory acidosis

Hyperventilation: Decrease CO2→ respiratory alkalosis