Fluid and Electrolyte Balance - Mod. 2 Flashcards
What percent of the body is made up of fluids?
55-60 percent.
What organ is primarily responsible for regulating fluid balance?
The kidney.
What are the two main categories of body fluids?
- Intracellular fluid (ICF) - inside cells
- Extracellular fluid (ECF) - outside cells
What substances are found in body fluids?
Ions, nutrients, gases, and waste products.
What percentage of the male body is composed of fluid?
60%
What percentage of the female body is composed of fluid?
55%
What is intracellular fluid (ICF)?
The fluid found inside cells, making up about 2/3 of total body fluids.
What is extracellular fluid (ECF)?
Fluid found outside of cells, making up about 1/3 of total body fluids.
What are the two subtypes of extracellular fluid?
- Blood plasma - found inside blood vessels
- Interstitial fluid - bathes the cells of the body.
What percent of extracellular fluid is blood plasma?
20% of ECF (6.6% of total body fluids)
What percent of extracellular fluid is interstitial fluid?
80% of ECF (26.6% of total body fluids.
What fluid transports white blood cells and lipids?
Lymph
What fluid surrounds the brain and spinal cord?
Cererospinal fluid (CSF)
What fluid is found inside joint capsules to provide lubrication?
Synovial fluid
What fluid helps maintain ocular pressure in the eye?
Aqueous humor
What fluid helps maintain the shape of the eye and prevents collapse?
Vitreous humor
What fluid fills the inner ears membranous labyrinth and helps detect motion?
Endolymph
What fluid cushions the membranous labyrinth inside the bony labyrinth of the inner ear?
Perilymph
What fluid prevents friction between the lungs and ribs?
Plural fluid
What fluid surrounds the heart?
Pericardial fluid
What are the two main barriers between fluid compartments?
The plasma membrane and blood vessel walls.
What does the plasma membrane separate?
It separates intracellular fluid from interstitial fluid.
What is the permeability of the plasma membrane?
It is selectively permeable, so that some substances may pass through easily, while others cannot.
What do the blood vessel walls separate?
They separate blood plasma from interstitial fluid.
Where does fluid exchange between blood and interstitial fluid occur?
Only in the capillaries, where the walls are thin enough to allow the movement of water and solutes.
What must happen for the bodys water balance to remain constant?
Water intake must equal water output.
Why is water balance important?
It is essential for maintaining homeostasis.
What is the main mechanism that regulates water intake?
The perception of thirst.
How does the thirst mechanism help maintain water balance?
It triggers voluntary drinking behavior, increasing water intake.
What organ plays a fundamental role in regulating water output?
The kidneys, by adjusting the amount of water excreted in urine.
What are the three main stimuli that trigger the bodys response to dehydration?
- Decreased blood volume and blood pressure
- Increased blood osmolarity (higher solute concentration
- Decreased salivation
What kidney cells detect dehydration and what do they release?
Juxtaglomerular cells in the kidney detect dehydration and release renin.
What hormonal system is activated by renin?
The renin-angiotensin-aldosterone system (RAAS).
What happens when renin is secreted?
It leads to increased production of angiotensin ll via a signaling cascade.
Where is angiotensin ll primarily produced?
In the capillaries of the lungs and then transported in the blood.
What hypothalamic receptors detect increased blood osmolarity?
Osmoreceptors in the hypothalamus.
What sensory receptors detect dryness in the mouth and throat?
Sensory receptors in the mouth and pharynx.
Where do signals from angiotensin ll and sensory receptors converge?
They converge on the thirst center within the hypothalamus.
What does the thirst center of the hypothalamus do?
It sends nerve impulses to the cortex, creating a conscious perception of thirst.
What is the effect of increased thirst perception?
It leads to the behavioral activity of drinking water.
How does drinking water restore homeostasis?
It increases blood volume, decreases blood osmolarity, and increases hydration levels in the oral mucous membranes.
What happens once normal water balance is restored?
The stimulus (dehydration) decreases, reducing the thirst response, completing a negative feedback loop.
How is water loss from the body controlled?
By the movement of solutes, as water moves passively by osmosis from areas of low osmolarity to areas of high osmolarity.
What are the most abundant solutes in urine and extracellular fluid?
Sodium (Na+) and chloride (Cl-).
What is the main determinant of body fluid volume?
The rate of urinary excretion of Na+ and Cl-
What three key hormones regulate fluid volume homeostasis?
- Renin-angiotensin-aldosterone system (RAAS) - increases Na+, Cl-, and water reabsorption.
- Antidiuretic hormone (ADH) - increases water reabsorption directly.
- Atrial natriuretic peptide (ANP) - increases Na+ and Cl- loss, promoting water loss.
What triggers activation of the renin-angiotensin-aldosterone system (RAAS)?
A decrease in blood volume or blood pressure.
What enzyme is released when renin-angiotensin-aldosterone system is activated?
Renin is released.
What is the function of angiotensin ll?
It increases water retention in the kidneys and stimulates the secretion of aldosterone from cells in the adrenal cortex.
What does aldosterone do?
It increases Na+ and Cl- reabsorption, and increases water reabsorption, preserving blood volume.
What is the main function of antidiuretic hormone (ADH)?
It increases water retention by making kidney cells more permeabale to water, and it helps the body regulate water and salt levels, blood pressure, and urine production.
Where is antidiuretic hormone (ADH) produced and released?
It is produced in the hypothalamus and it is released by the pituitary gland into the blood.
What happens to urine concentration when antidiuretic hormone (ADH) levels are high?
Less urine is produced, and it bocomes more concentrated.
When are antidiuretic hormone (ADH) levels naturally higher?
At night, to prevent urination during sleep.
How does atrial natriuretic peptide (ANP) regulate water balance?
It increases water loss by blocking Na+ and Cl- reabsorption.
Where is atrial natriuretic peptide (ANP) secreted from?
From the right atrium of the heart in response to high blood pressure.
Why do fluid compartments maintain different electrolyte concentrations?
Because of selective permeability of capillary walls and plasma membranes.
What type of blood sample is often used for electrolyte testing?
Blood serum
Why is blood serum used instead of whole blood for testing electrolytes?
Because cells and clotting proteins are removed, preventing interference with the test results.
How can proteins in blood affect electrolyte measurements?
Proteins can bind (sequester) ions, altering their measured concentration.
What is the second most common extracellular anion?
Bicarbonate (HCO3-), with high levels in the interstitial fluid and blood plasma.
What is the primary function of bicarbonate ions (HCO3-)?
Helps to prevent large fluctuations in pH within both extracellular and intracellular compartments.
Where is the majority of calcium (Ca2+) stored?
In the skeleton and teeth.
What are the three main functions of calcium?
Blood clotting, neurotransmitter release, and muscle activity.
What hormone regulates blood calcium levels?
Parathyroid hormone (PTH).
What happens when calcium (Ca2+) levels decrease?
Parathyroid hormone (PTH) is released, promoting the release of Ca2+ from the bones into the blood.
What hormone lowers blood calcium levels?
Calcitonin
How does calcitonin reduce blood calcium?
It inhibits calcium release from bones.
Where is chloride (Cl-) predominantly found?
Extracellular fluid
What are the two main functions of chloride (Cl-)?
- Balance the level of anions in different fluid compartments
- Aids digestion by forming hydrochloric acid in the stomach.
What is the main function of magnesium (Mg2+)?
Acts as a cofactor for enzymes.
What organ regulates magnesium levels?
The concentration of magnesium is regulated by the kidneys.
Where is the majority of phosphate stored?
85% is stored in the skeleton and teeth.
What are the two main functions of phosphate?
It is combined with calcium, forming a mineral lattice, helping to strengthen the skeleton and act as an important pH buffer.
What is the most abundant form of phosphate in the body?
HPO42- (hydrogen phosphate).
What three hormones regulate phosphate levels?
- Parathyroid hormone (PTH)
- Calcitriol
- Calcitonin
What is the most abundant extracellular cation?
Sodium (Na+), it makes up 90% of extracellular cations.
What is the primary function of sodium (Na+)?
Regulates fluid and electrolyte balance
What three hormones regulate sodium levels?
- Renin-angiotensin-aldosterone system (RAAS)
- Antidiuretic hormone (ADH)
- Atrial natriuretic peptide (ANP)
Where is sulfate concentration higher?
Much higher in the intracellular compartment than the extracellular compartment.
What does pH measure?
The concentration of hydrogen ions and hydroxyl ions in a solution.
What does pH indicate about a substance?
Wethere it is acidic, neutral, or basic (alkaline).
What is the normal pH range of extracellular fluid for life?
6.8 to 7.8
What is the pH of an acid?
Less than 7
How does acid strength relate to pH?
The stronger an acid, the more freely it dissociates into hydrogen ions.
Lower pH means stronger acid.
What is one of the strongest acids in the body?
Hydrochloric acid, found in the stomach (pH = 2).
What is the pH of a base?
Greater than 7
How do bases dissociate in water?
They break into hydroxide ions and a cation.
How does base strenght relate to pH?
Stronger bases have a higher pH.
What is the pH of a neutral solution?
pH of 7
What happens to hydrogen and hydroxide ions in a neutral solution?
They are in equal balance.
What is the range of the pH scale?
0 to 14
What is another term for hydrogen ions in water?
Hydronium ions (H3O+)
What does the body use to maintain homeostatic pH balance?
Buffer systems
What is a buffer?
Chemicals that resist changes in pH when small amounts of acid or base are added.
What is an example of an important buffer in the body?
An aqueous solution of carbonic acid and bicarbonate ions.
What happens to carbonic acid at equilibrium?
It partially dissociates to form bicarbonate ions and hydrogen ions.
What happens when a strong acid is added to a buffer solution?
It increases hydrogen ion concentration, lowering the pH.
How does the buffer system respond to strong acids?
The buffer acts to minimize the concentration of hydrogen ions, causing bicarbonate ions to bind to hydrogen ions, forming carbonic acid.
What happens when a strong base is added to a buffer solution?
It increases hydroxide ion concentration, raising the pH.
How does the buffer system respond to strong bases?
The buffer acts to minimize the concentration of hydroxide ions, causing carbonic acid to bind to hydroxide ions, forming bicarbonate ions and water.
How does the buffer system maintain pH stability despite added acids or bases?
It shifts the equilibrium between carbonic acid and bicarbonate to neutralize pH changes.
What is the most widespread buffer system in the body?
Carbon acid-bicarbonate buffer system
What is the function of the carbonic acid-bicarbonate buffer system?
It is a key buffer in the blood that helps regulate pH through compensatory mechanisms.
Where is the protein buffer system most commonly found?
In blood plasma and intracellular fluid.
What component of proteins allows them to act as buffers?
Amino acids, which act as zwitterions (molecules that can accept or donate H+).
What protein in red blood cells serves as an important buffer?
Hemoglobin
How does hemoglobin function as a buffer?
It can bind or release H+ ions depending on pH conditions in the blood.
Where is the phosphate buffer system primarily found?
In intracellular fluid.
Why is the phosphate buffer system important?
It helps regulate pH inside cells.
What ion in the phosphate buffer system bind excess H+ and acts as a weak base?
Monohydrogen phosphate
What ion in the phosphate buffer system acts as a weak acid and donates H+?
Dihydrogen phosphate
What is acidosis?
Occurs when the pH of systemic arterial blood falls below the normal range (below pH 7.35).
What is alkalosis?
Occurs when the pH rises above the normal range (above pH 7.45)
What are the two major categories of acidosis and alkalosis?
Respiratory and metabolic.
What causes respiratory acidosis?
Occurs when blood carbon dioxide levels increase and blood pH drops due to a low breathing rate.
How does the body compensate for respiratory acidosis?
By increasing heart rate to improve oxygen delivery and vasodilating blood vessels to maintain blood pressure.
What causes metabolic acidosis?
Happens when the body produces to much acid or the kidneys cant adequately remove acids from the bloodstream, causing an acidic blood pH.
What caused respiratory alkalosis?
Occurs when blood carbon dioxide levels drop and blood pH increases due to a high breathing rate.
What causes metabolic alkalosis?
Occurs when the body loses large amounts of hydrogen ions or when large quantities of bicarbonate ions build up within the body.
What is respiratory compensation?
A physiological process that helps the body maintain a normal acid-base balance by adjusting breathing rate.
What part of the brain controls respiratory compensation?
The brainstem respiratory centers.
How speed does respiratory compensation occur?
Within minutes to hours.
What is renal compensation?
A process that helps the kidneys maintain the bodys pH balance by increasing bicarbonate levels in the plasma.
What speed does renal compensation occur?
It is the slowest compensation, may take hours to days.
