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Anatomy and Physiology 2 > Chapter 26- Fluid balance > Flashcards

Chapter 26- Fluid balance Flashcards

1
Q

Body fluid compartments (2)

A
  1. Intracellular fluid (ICF)- 66% of total body water found here
  2. Extracellular fluid (ECF)- 33% of remaining body water found here
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2
Q

Sub compartments of ECF (2)

A
  1. Plasma

2. Interstitial fluid (IF)- lymph, cerebrospinal fluid, humors, serous fluid, synovial fluid

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3
Q

Electrolytes

A

Anything that dissociate into ions in water (+ or - charge). These are the most abundant solutes. More responsible for fluid/shifts/movement of water, since each molecule dissociates into more than one ion- creates greater osmotic gradient. Ex- inorganic salts, acids and bases, some proteins

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4
Q

Nonelectrolytes

A

Do not dissociate in water, and have no charge. Make up the bulk of the mass of body fluids. Ex- glucose, urea, lipids, etc

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5
Q

Fluid movement

A

Water moves freely, solutes do not. Changing the osmolality of one compartment will lead to net water flow

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6
Q

What factors does optimal body water content depend on? (4)

A
  1. Age- infants and children have more water- promotes growth
  2. Sex- men have higher body water content than women
  3. Body fat %- fat is the least hydrated of all body tissues
  4. Body mass
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7
Q

Sources of water intake (2)

A
  1. Ingested food and liquid

2. Metabolic water

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8
Q

Sources of water output (2)

A
  1. Insensible water loss- lungs, skin

2. Sensible water loss- sweat, urine, feces

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9
Q

Why is proper hydration important?

A

When properly hydrated, water intake= water output. Importance- allows body to maintain osmolality of 200 mOsm

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10
Q

Which area of the brain controls the thirst mechanism?

A

Hypothalamic thirst center

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11
Q

The thirst mechanism is activated by (3)

A
  1. Osmoreceptors- detect changing ECF osmolality (measure solute concentration in extracellular fluid)
  2. Dry mouth- salivary glands cannot draw water from blood to produce saliva
  3. Decreasing blood volume/pressure- 5-10% drop initiates thirst mechanism
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12
Q

When do feelings of thirst stop?

A

Feelings of thirst stop almost as soon as we drink water. Prevents us from taking in large amounts of fluid that would over hydrate us

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13
Q

Obligatory water loss

A

The body will always lose water, even if we never drink water. Why- Insensible water loss, kidneys never stop functioning

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14
Q

Urine output depends on

A

Fluid intake, diet, other source of water loss. Excess water is eliminated in urine

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15
Q

What is the role of ADH in water balance?

A

Remember- ADH causes aquaporins to be inserted in collecting ducts. Osmoreceptors of hypothalamus monitor osmolality of ECF to inhibit or stimulate ADH release. Baroreceptors monitor blood pressure to inhibit or stimulate ADH release

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16
Q

Central diabetes insipidus

A

Decrease in ADH produced by hypothalamus or released by posterior pituitary. Symptoms- polyuria (polydipsia), very dilute urine, fatigue, eventual dehydration. Not the same thing as diabetes mellitus

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17
Q

Nephrogenic diabetes insipidus

A

ADH is produced and released in normal amounts, but the kidneys are unresponsive to it. Symptoms similar to overhydration and central diabetes insipidus

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18
Q

Why is electrolyte balance important?

A

Importance- influence water movement in body, essential for excitability, membrane permeability

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19
Q

Where does salt intake/loss come from?

A

Salt intake comes mostly from diet, with a small amount coming from metabolic processes. Salt loss- urine and feces, sweat, vomit. Renal processes help the body retain what is needed

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20
Q

How much salt accounts for ECF solute?

A

NaHCO3 and NaCl account for ~280 mOsm of total ECF solute

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21
Q

Why is sodium important in maintaining ECF volume? (2)

A
  1. Most important in establishing osmotic gradient- water flows with Na+
  2. Plasma membranes are impermeable to Na+- almost always kept out of cells and in the ECF
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22
Q

Where is most sodium absorbed?

A

Na+ specific receptor has not yet been found. Most Na+ reabsorbed in PCT and nephron loop (85%)

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23
Q

Which hormones regulate sodium reabsorption? (4)

A
  1. Aldosterone
  2. Atrial Natriuretic peptide (ANP)
  3. Sex hormones
  4. Glucocorticoids
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24
Q

Aldosterone

A

Release causes increased reabsorption of Na+ in DCT and collecting ducts, so it can then enter the blood. Side effect of aldosterone release is an increase in ECF volume. This is because water follows Na+, and enters the blood to cause an increase in blood pressure.

25
Q

Atrial Natriuretic peptide (ANP)

A

Release causes decreased reabsorption of Na+, is diuretic and natriuretic (increases secretion of sodium in the urine).

26
Q

Sex hormones influence on urination

A

Estrogen exerts similar effect as aldosterone, progesterone is slightly diuretic

27
Q

Glucocorticoids

A

In high plasma levels, exerts very strong aldosterone like effects. Can contribute substantially to edema

28
Q

Hypernatremia

A

Na+ serum value is more than 145 mEg/L. Caused by- severe dehydration, excessive intravenous NaCl administration. Occurs in healthy people who are unable to communicate that they’re thirsty, like infants. Effect- thirst, twitching and convulsions, confusion and lethargy, if left untreated- coma and death. Can have an effect on cellular excitability

29
Q

Hyponatremia

A

Na+ serum value is less than 135 mEg/L. Caused by- overhydration, excessive solute loss (vomiting and diarrhea, like dysentery level), excessive water loss, severe burns, excessive ADH release, aldosterone deficiency (Addison’s disease), renal disease/failure. Effects- mental confusion, giddiness, muscular twitching, irritability, convulsions, coma, decreased blood volume/pressure (if water is also lost). Too much fluid in the brain, interferes with CNS function

30
Q

Why does potassium need to be regulated?

A

Heavy regulation due to affect on resting membrane potential. Hypokalemia and hyperkalemia can disrupt neuromuscular electrical conduction. Buffer- K+ moves in the opposite direction of H+ to balance pH

31
Q

What is the main way that potassium is regulated?

A

Mainly renal mechanism. Principal cells secrete K+ in the DCT and collecting ducts, can alter how much based on what needs to be. Type A intercalated cells can reabsorb K+ when levels are exceptionally low. The kidneys are very limited in reabsorption capabilities K+.

32
Q

Potassium secretion depends on (2)

A
  1. Plasma concentration

2. Aldosterone

33
Q

How does plasma concentration influence potassium secretion?

A

High ECF K+ concentrations drive excess K+ into principal cells- increased secretion and excretion of K+. Low ECF concentrations promotes reabsorption

34
Q

How does aldosterone influence potassium secretion?

A

Adrenal cortex secretes aldosterone when K+ ECF concentrations are higher, or when K+ is higher in the plasma of the blood. Aldosterone inserts a sodium channel and a potassium channel going between the principal cells and the DCT/collecting duct. Potassium goes down its concentration gradient to the urine, and sodium leaves the urine, goes down its concentration gradient to the principal cells, and is then pumped against its concentration gradient into the blood through the Na/K pump. This increases blood pressure and decreases blood potassium levels (K is important for electrolyte balance).

35
Q

What is the optimal pH of blood?

A

Optimal pH of arterial blood is 7.4. pH 7.45 or higher- alkalosis, pH 7.35 or lower- physiological acidosis

36
Q

Sources of H+ in the body (2)

A
  1. Ingested food

2. Metabolic processes- lactic acid, loading of CO2, phosphoric acid, etc

37
Q

How is pH regulated? (3)

A
  1. Chemical buffer systems
  2. Respiratory regulation of H+
  3. Renal regulation
38
Q

Chemical buffer systems

A

One or more compounds that resist changes in pH when strong acids or bases are introduced. Release H+ when pH rises, bind H+ when pH drops

39
Q

3 important chemical buffer systems

A
  1. Bicarbonate buffer system
  2. Phosphate buffer system
  3. Protein buffer system
40
Q

Bicarbonate buffer system

A

Important for ECF. In the event that pH is too low (acidic), H will increase and bicarbonate will decrease. The two molecules come together to form carbonic acid. Carbonic acid will then dissociate into water and carbon dioxide, removing the free H+ ions and increasing pH. Carbon dioxide is eliminated in the lungs. This works in reverse for high pH.

41
Q

Phosphate buffer system

A

Important for ICF and urine. Similar to bicarbonate buffer system, but utilizes different weak acids and bases. Salts of dihydrogen phosphate (weak acid) and monohydrogen phosphate (weak base). The end result is the same- prevents drastic pH changes

42
Q

Protein buffer system

A

Important in ICF and blood plasma (ECF). Carboxyl groups (-COOH) can release H+ when pH rises. NH2 group can bind free H+ when pH decreases

43
Q

Amphoteric molecule

A

A single protein can function as either an acid or a base. Depends on the pH of the environment

44
Q

Respiratory regulation of H+

A

Reminder- CO2 accumulation lowers pH of blood. Rising PCO2 reactivates respiratory patterns. If you don’t balance out the carbon dioxide being transported, the blood pH will change.

45
Q

Which pH adjustment mechanisms are short term?

A

Buffers and respiratory regulation are short term adjustments

46
Q

Respiratory acidosis

A

PCO2 is greater than 45 mmHg= respiratory acidosis. Respiration is shallow/slow (hypoventilation), can be due to many respiratory conditions. Rate and depth of breathing increases to get rid of carbon dioxide.

47
Q

Respiratory alkalosis

A

PCO2 is less than 35 mm Hg= respiratory alkalosis. Respiration is deep/fast (hyperventilation), caused by- stress/anxiety, pain. Rate and depth of breathing decreases

48
Q

During renal regulation, how can the amount of bicarbonate in the blood be adjusted? (3)

A
  1. Reabsorbing HCO3
  2. Generating new bicarbonate
  3. Secretion of bicarbonate
49
Q

How is HCO3 reabsorbed?

A

Kidney tubule cells cannot reabsorb bicarbonate directly from filtrate. H2CO3 in tubule cell broken down into H+ and HCO3

50
Q

How is H2CO3 in the tubule cell broken down into H+ and HCO3? (3 steps)

A
  1. H+ secreted into filtrate
  2. HCO3- generated in tubule cell is pumped into peritubular capillary
  3. The reabsorption of HCO3- depends on the secretion of H+ into filtrate. The more H+ secreted, the more bicarbonate is reabsorbed.
51
Q

How is new bicarbonate generated?

A

PCT and type A intercalated cells of collecting ducts can generate new bicarbonate ions to be pumped into plasma. Type A and B are most useful during acidosis

52
Q

How is bicarbonate secreted?

A

Type B intercalated cells in collecting ducts can secrete bicarbonate ions while reclaiming H+ from filtrate. Secretion of bicarbonate is not efficient- even in alkalosis, more bicarbonate will be reabsorbed than secreted.

53
Q

Metabolic acidosis

A

Low bicarbonate levels. Common causes- excessive alcohol intake, long term diarrhea. Alcohol increases glycolysis and releases fatty acids, but the fatty acids aren’t used and start building up.

54
Q

Metabolic alkalosis

A

High bicarbonate levels. Common causes- excessive vomiting, excessive base intake. Base intake= taking too many tums

55
Q

Effects of metabolic acidosis and alkalosis

A

Blood pH limits are 6.8 and 7.8. Below 6.8- CNS depression, results in coma and death. Above 7.8- overstimulated CNS. Muscle tetany (the bad kind- skeletal muscle tissue locks up involuntarily), restlessness/nervousness, convulsions, death

56
Q

Metabolic acidosis/alkalosis definition

A

Any acid-base imbalance that does not involve CO2, bicarbonate ion balance especially

57
Q

Which 3 mechanisms can compensate for alkalosis and acidosis?

A
  1. Kidneys or lungs can act to restore pH when one system fails
  2. Respiratory compensation
  3. Renal compensation
58
Q

How can the respiratory system compensate for alkalosis and acidosis?

A

Changes in respiratory rate and depth evident when lungs must compensate for metabolic imbalances. Metabolic acidosis (bicarbonate less than 22 mEq/L)- respiratory rate and depth increase. This blows off excess carbon dioxide to increase blood pH again

59
Q

How can the renal system compensate for alkalosis and acidosis?

A

Kidneys can compensate for acid base imbalance of respiratory origins. Respiratory acidosis- kidneys conserve more bicarbonate ions. Respiratory alkalosis- kidneys either secrete more bicarbonate ions or simply do not reabsorb it

Anatomy and Physiology 2 (20 decks)

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