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BIOL 1191 > Ch. 27 - Homeostasis > Flashcards

Ch. 27 - Homeostasis Flashcards

1
Q

What are the 2 places that exchange between body fluids can occur?

A
  1. plasma membrane (b/t intracellular and IS fluid)

2. BV/capillary walls (b/t IS fluid and blood plasma)

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2
Q

How does the body gain water?

A

ingestion and metabolic synthesis

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3
Q

How does the body lose water?

A
  • excreted by kidneys as urine
  • eliminated by GI tract in feces
  • evaporation as sweat/insensible perspiration
  • exhaled from lungs as water vapour
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4
Q

What are 4 things that stimulate the thirst center in hypothalamus?

A
  • increased blood osmolarity
  • decreased blood vol
  • decreased BP
  • dry mouth
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5
Q

Which hormonal responses are triggered in response to thirst?

A
  1. RAA pathway to decrease blood osmolarity and increase BP/blood vol
  2. ADH to reabsorb more water
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6
Q

What are 3 hormones that regulate renal excretion of Na+ and Cl- ?

A

aldosterone, angiotensin II, ANP

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7
Q

How does the RAA pathway conserve water?

A
  • angiotensin II increases Na+ reabsorption in PCT
  • aldosterone increases Na+ reabsorption/K+ secretion in DCT/cd
  • increased Na+/water reabsorption leads to increased BP/blood vol
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8
Q

How does the ANP pathway function in fluid regulation?

A
  • ANP decreases Na+ reabsorption in PCT/CD, results in increased Na+ excretion
  • increased urine/Na+/H2O secretion
  • decreased BP/blood vol
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9
Q

If IS fluid increases in osmolarity…

A

…fluid will leave ICF and cells will shrink

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10
Q

If IS fluid decreases in osmolarity…

A

…fluid will move into ICF and cells will swell

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11
Q

What causes water intoxication? (decreased osmolarity of IS fluid)

A
  • when water consumption is faster than kidney can excrete it
  • hypersecretion of ADH
  • dilutes [Na+] in plasma/IS fluid –> water moves into cells –> water causes cell swelling
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12
Q

How can you treat a patient with water intoxication?

A

saline solution

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13
Q

What are 4 functions of electrolytes in body fluids?

A
  1. control osmosis of water bt body compartments
  2. maintain acid-base balance
  3. carry electrical current, allowing for APs
  4. cofactors required for optimal activity of some enzymes
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14
Q

What is the major cation and anion in ECF?

A

Na+ ; Cl-

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15
Q

What is the major cation and anion in ICF?

A

K+; HPO4 (-2)

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16
Q

What does sodium retention lead to?

A

water retention; edema (abnormal accumulation of is fluid)

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17
Q

What can cause sodium retention?

A
  • renal failure (cannot excrete Na+)

- hyperaldosteronism (excessive reabsorption of Na+)

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18
Q

What can cause excessive loss of sodium? (hypovolemia = low blood vol)

A
  • inadequate secretion of aldosterone

- excessive intake of certain diuretics

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19
Q

What regulates Cl- levels?

A
  • reabsorption indirectly due to Na+/Cl- symporters

- indirectly regulated by aldosterone

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20
Q

How is K+ regulated?

A

mainly by aldosterone through Na+/K+/Cl- pumps

- as Na+/Cl- are reabsorbed, K+ is being secreted (levels decrease)

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21
Q

Describe levels of bicarbonate ion in plasma acid-base buffer system

A
  • increased levels in systemic capillaries due to increased CO2
  • decreased levels in pulmonary capillaries as CO2 is exhaled
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22
Q

How are bicarbonate ion levels regulated?

A

by kidneys

  • form more HCO3- if blood levels are too low
  • excrete excess in urine if blood levels are too high
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23
Q

How are Ca2+ levels regulated?

A
  • by PTH when blood Ca2+ levels are low (increases production of calcitriol!)
  • by calcitonin when blood Ca2+ levels are high
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24
Q

What is the function of phosphate in body fluids?

A
  • buffer of H+ in body fluids/urine

- buffers in blood

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25
Q

How are phosphate levels regulated?

A
  • resorption of bone releases phosphate
  • PTH: increases phosphate elimination in kidneys
  • calcitriol: increases GI absorption of phosphate
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26
Q

How are magnesium levels regulated?

A

excreted by kidneys in urine in response to several stimuli

27
Q

What is the normal range for plasma pH?

A

7.35-7.45

28
Q

What are 3 major mechanisms to regulate pH?

A
  1. buffer systems in body fluids
  2. exhalation of CO2 (resp system)
  3. kidney excretion of H+ (urinary system)
29
Q

What do most buffer systems consist of?

A

weak acid and a weak base (of that acid)

30
Q

What is the function of buffer systems?

A

resist changes in pH (make [H+] constant)

- change the pH of solution but do not remove excess H+ from body

31
Q

What are the 3 main buffer systems?

A
  1. protein buffer system
  2. carbonic acid-bicarbonate buffer system
  3. phosphate buffer system
32
Q

Where are protein buffer systems found?

A

intracellular fluids, plasma

33
Q

How do amino acids act as a buffer?

A
  • contains at least 1 carboxyl group (-COOH) that acts as an acid and releases H+
  • contains at least 1 amino group (-NH2) that acts as a base and combines with H+
34
Q

How does the carbonic acid-bicarbonate buffer system work?

A
  • HCO3- acts as weak base and takes in excess H+ before dissociating into H2O and CO2
  • H2CO3 acts as a weak acid and dissociates into H+ and HCO3
35
Q

How does the phosphate buffer system work?

A
  • H2PO4- acts as a weak acid and releases H+ into a solution

- HPO4 (2-) acts as a weak base by absorbing H+

36
Q

Increased rate and depth of breathing causes…

A
  • more CO2 to be exhaled
  • [H+] decreases
  • increases blood pH (more alkaline)
37
Q

Decreased rate and depth of breathing causes…

A
  • less CO2 to be exhaled
  • {H+] increases
  • decreases blood pH (more acidic)
38
Q

How does the kidney excrete H+?

A
  • intercalated cells in CD and tubular cells in PCT play important role
  • Na+/H+ antiporters and H+ pumps secrete H+ into tubular filtrate
39
Q

How else does the kidney regulate pH?

A
  • synthesize new bicarbonate and reabsorb filtered bicarbonate to keep blood levels high
40
Q

What is acidosis?

A

blood pH below 7.35; causes depression of CNS through depression of synaptic transmission

41
Q

What is alkalosis?

A

blood pH above 7.45; causes overexcitability of CNS through facilitation of synaptic transmission

42
Q

What are disorders of blood PCO2?

A

respiratory acidosis and alkalosis

43
Q

What are disorders of bicarbonate concentration?

A

metabolic acidosis and alkalosis

44
Q

What are two methods of compensation for acid-base imbalances?

A

respiratory and renal

45
Q

What is compensation?

A

physiological response to acid-base imbalance that attempts to normalize arterial pH

46
Q

What is respiratory compensation?

A

hyperventilation or hypoventilation due to metabolic imbalance

47
Q

What is renal compensation?

A

changes in secretion/reabsorption of H+ and HCO3- due to respiratory imbalance

48
Q

What is respiratory acidosis?

A

elevation of PCO2 in arterial blood due to lack of CO2 removal

49
Q

What are possible causes for resp acidosis?

A

emphysema, pulmonary edema, airway obstruction

50
Q

What are treatment options for resp acidosis?

A
  • ventilation therapy to increase CO2 exhalation

- IV administration of bicarbonate

51
Q

How does renal compensation work in resp acidosis?

A

increases H+ secretion and bicarb reabsorption to increase blood pH

52
Q

What is respiratory alkalosis?

A

arterial blood PCO2 is too low

53
Q

What are possible causes for resp alkalosis?

A

hyperventilation due to high altitude, pulmonary disease, anxiety

54
Q

What are treatment options for resp alkalosis?

A

rebreathe into paper bag; inhale air with higher than normal [CO2]

55
Q

How does renal compensation function in resp alkalosis?

A

decrease H+ excretion and bicarb reabsorption to decrease blood pH

56
Q

What is metabolic acidosis?

A

arterial blood [bicarb ion] is too low, decreasing blood pH

57
Q

What are possible causes for metabolic acidosis?

A
  • excessive loss of HCO3- through diarrhea/kidney dysfunction
  • accumulation of acid (ketosis with dieting/diabetes)
  • kidney failing to remove H+
58
Q

How does respiratory compensation function in metabolic acidosis?

A

hyperventilation to get rid of CO2

59
Q

What is possible treatment for metabolic acidosis?

A

IV administration of sodium bicarbonate

60
Q

What is metabolic alkalosis?

A

arterial blood [bicarb ion] is too high, increasing blood pH

61
Q

What are possible causes of metabolic alkalosis?

A

vomiting, gastric suctioning, excessive intake of alkaline (antacid) drugs

62
Q

What is possible treatment for metabolic alkalosis?

A

fluid and electrolyte therapy

63
Q

How does respiratory compensation function in metabolic alkalosis?

A

hypoventilation

BIOL 1191 (16 decks)

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