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Human Physiology 2 > Week Twelve > Flashcards

Week Twelve Flashcards

1
Q

What does body fluid consist of?

A

water-based liquids

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2
Q

What’s are the body’s water based liquids?

A
  • extracellular fluid (blood plasma, interstitial fluid)
  • intracellular fluid
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3
Q

How much total body water does a typical 20-30 year old 154 lb male have? What factors affect this value?

A

60% total body water
- slightly lower in females
- declines with age

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4
Q

What are electrolytes? What are the main ones of the body?

A
  • substances that dissociate into ions when placed in water
  • Na+, K+, Cl-, Ca2+, PO43-, and Mg2+ are the main ones
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5
Q

What are the sensible water loses of the body?

A

noticeable water loss
~1500 mL (urine) and 100mL (feces)

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6
Q

What is the insensible water loss of the body?

A

unnoticeable water loss
~600mL from skin due to sweat and evaporation and 300 mL from expired air

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7
Q

What is obligatory water loss?

A

~500 mL; minimum amount of urine that must be produced per day in order to maintain healthy function and homeostasis

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8
Q

Describe the daily water gain

A

water ingested from foods: ~ 750 mL
water ingested from liquids: ~1500 mL
water formed by metabolism (catabolic reactions): ~250 mL

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9
Q

What are the two forms of stimuli that trigger thirst?

A

osmolarity of blood plasma and volume of blood plasma

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10
Q

Describe the steps in the negative feedback loop of increased plasma osmolarity

A
  1. plasma osmolarity increases above its normal range
  2. osmoreceptors in the hypothalamus detect the change in osmolarity
  3. osmoreceptors stimulate the thirst center in the hypothalamus
  4. hypothalamus triggers thirst - fluid intake increases blood
  5. receptors detect fluid intake;plasma osmolarity returns to normal; thirst is relieved
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11
Q

Describe the negative feedback loop for when plasma volume decreases below its normal range

A
  1. plasma volume decreases below its normal range
  2. if decreased volume causes a blood pressure drop > 10-15mmHg then baroreceptors detect change in blood pressure due to decreased plasma volume; JG cells in nephron detect change as well, activating the RAAS
  3. baroreceptors and angiotensin-II from RAAS stimulate the thirst center in the hypothalamus
  4. hypothalamus triggers thirst - fluid intake increase
  5. receptors detect fluid intake; plasma volume returns to normal; thirst is relieved
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12
Q

What is ADH’s role in hormonal regulation of fluid balance?

A

produced in hypothalamus → released from posterior pituitary → acts on distal tubule and collecting ducts of the nephrons → triggers insertion of water channels (aquaporins) in the plasma membrane of these kidneys cells → allow for more water to be reabsorbed from the kidneys back into the plasma by osmosis

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13
Q

What other hormones are involved in fluid balance?

A

angiotensin II, aldosterone & atrial natriuretic peptide

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14
Q

What is electrolyte homeostasis?

A

electrolyte homeostasis in the body means that the body must maintain disequilibrium of ions between intracellular and extracellular fluid

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15
Q

Describe electrolyte homeostasis of Na+

A
  • main extracellular cation
  • large concentration gradient between ICF and ECF
  • regulation of Na+ concentration is critical for fluid and electrolyte balance in the body
  • angiotensin II and aldosterone are the two main hormones that increase Na+ retention
  • ANP does the opposite: decreases Na+ and water reabsorption
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16
Q

Describe the negative feedback loop for when Na+ levels decrease

A
  1. Na+ level in the ECF decreases below its normal range
  2. receptors in the macula densa in nephrons detect the change, activating the RAAS
  3. JG cells in the kidney release renin, which leads to the production of angiotensin II which stimulates aldosterone
    release from adrenal cortex
  4. angiotensin II leads to increased Na+ reabsorption in the proximal tubule of the nephron; aldosterone release from the adrenal cortex leads to increased Na+ reabsorption from the distal tubule of the nephron
  5. Na+ level returns to normal; angiotensin II and aldosterone secretion decreases
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17
Q

What is Na+ concentration determined by?

A

by the Na+ content & the water content

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18
Q

When does Na+ imbalances occur?

A

occurs with any event that increases/decreases Na+ and/or H2O

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19
Q

What is hypernatremia?

A

high plasma Na+ concentration
(>145 mEq/l)

20
Q

What is hyponatremia?

A

low plasma Na+ concentration
(<135 mEq/l)

21
Q

Describe K+ homeostasis

A
  • K+ is the main intracellular cation
  • large concentration gradient between ICF and ECF
  • K+ balance is essential for normal cell function and electrical function of excitable cells → K+ is the main ion responsible for generating a negative resting membrane potential
22
Q

How is K+ homeostasis regulated

A

regulated by the kidneys - excess K+ is secreted into the nephron for excretion

23
Q

What causes an imbalance in K+

A

excess K+ taken in or lost
water imbalances (not as noticeable as with Na+)

24
Q

What is hyperkalemia? What does it cause

A

high plasma K+ concentration (>4.5 mEq/l) → makes the resting membrane potential of excitable cells more positive

25
Q

What is hypokalemia? What does it cause?

A

low plasma K+ concentration (<3.9 mEq/l) → makes the resting membrane potential of excitable cells more negative

26
Q

Where are Ca+ and PO4 3- found in body

A

bound together in hydroxyapatite crystals of bone

27
Q

Describe the importance of Ca2+and PO43- in electrolyte homeostasis

A
  • Ca2+ balance is essential for muscle contractions, action potentials in the heart, neuronal synaptic transmission, signaling inside all cells, blood clotting
  • PO4 is important for producing ATP molecules
  • blood Ca regulated via bone remodelling, reabsorption from kidneys, absorption from small intestine
28
Q

What is hypercalcemia? What does it cause?

A

high plasma Ca2+ concentration (>10.5 mEq/l) → makes cell less permeable to Na+ = less excitable

29
Q

What is hypocalcemia? What does it cause?

A

low plasma Ca2+ concentration → makes cells more permeable to Na+ = more excitable

30
Q

Describe the electrolyte homeostasis of chloride ions

A
  • higher concentration in the ECF
  • important in creating osmotic gradient (contributing to [solute] in the ECF), forms HCl in stomach
  • kidneys regulate reabsorption in order to maintain [Cl-]
31
Q

Describe electrolyte homeostasis of magnesium

A
  • higher concentration in the ICF
  • critical in many cellular processes in activating several enzymes, important component of bone tissue
  • kidneys regulate reabsorption in order to maintain concentration
32
Q

What is the normal pH of blood?

A

7.35-7.45

33
Q

How are acids and bases formed in the body?

A

1) formed from metabolism
- biggest source of metabolic acid: CO2
- others: lactic acid (glycolysis without O2), uric acid (nucleic acid breakdown), ketone bodies (liver FA metabolism)
2) whatever is is absorbed from the GI tract

34
Q

How are acids removed from the body?

A

co2 can be removed from the blood but the lungs and kidneys and all other acids and bases can only be removed by the kidneys

35
Q

What are the two different buffering systems of the body?

A

1) chemical buffering systems in the body
2) physiological buffering systems

36
Q

Describe the chemical buffering systems in the blood

A

e.g. Co2 + water → H2Co3 → H+ + carbonic acid

37
Q

Describe the physiological buffering systems

A

Respiratory systems: can control the amount of CO2 (fast - seconds)
Renal system: the kidneys can control the amount of all other acids and bases (slower - hours to days)

38
Q

What is acidosis?

A
  • blood pH < 7.35
  • either too much CO2 or other acid for buffer to (e.g. HCO3-) is low
  • consequence: neurons are less excitable (larger stimulus needed to initiate an action potential)
39
Q

What is alkalosis?

A
  • blood pH > 7.45
  • more base ions are added than buffers can handle, H+ concentration decreases/Co2 too low
  • consequence: neurons more excitable (action potentials are initiated when they shouldn’t be)
40
Q

What causes respiratory acidosis?

A

Decreased pH in the blood due to excess CO2
Due to hypoventilation caused by:
- suppressed ventilation due to brainstem dysfunction
- blocked air passages in lungs
- decreased gas exchange in alveoli

41
Q

What is the respiratory and/or renal compensation for respiratory acidosis?

A

respiratory:
- minimal if the problem is due to impaired ventilation in the first place
- fix the issue and pH is quickly restored as excess Co2 is expired
renal:
- increased reabsorption of HCO3- back into blood
- increased secretion of H+ in urine
-kidneys can also produce new HCO3-

42
Q

What causes metabolic acidosis

A

either too much H+ in blood OR loss of HCO3-
- due to metabolism (e.g. ketoacidosis), prolonged diarrhea (loss of HCO3-), kidney failure, ingestion of acidic drugs or poison

43
Q

What is the respiratory/renal compensation for metabolic acidosis?

A

respiratory:
- hyperventilation in order to reduce H+
renal:
- if kidneys are functioning properly: increased reabsorption of HCO3- reabsorption of HCO3- back into blood and secretion of H+ in urine

44
Q

Describe respiratory alkalosis?

A

Increased pH in the blood due to low CO2
Due to hyperventilation caused by:
- psychological response (e.g. anxiety)
- physiological response (e.g. high altitude)

45
Q

What is the respiratory/renal response to respiratory alkalosis?

A

respiratory:
hypoventilation to restore CO2 and increased H+ (decreased pH)
renal:
excrete more HCO3- into urine and reabsorbed more H+ back into blood

46
Q

What is metabolis alkalosis?

A

Increased pH in the blood due to loss of H+ or too much HCO3-
- due to prolonged vomiting or too many antacids

47
Q

Describe the respiratory/renal compensation for metabolic alkalosis

A

respiratory:
hypoventilation to restore CO2 and increase H+ (decrease pH)
renal:
increased reabsorption of H+ back into blood and secretion of HCO3- in urine

Human Physiology 2 (9 decks)

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