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Anatomy & Physiology III > Water, Electrolyte, and Acid-Base Balance > Flashcards

Water, Electrolyte, and Acid-Base Balance Flashcards

1
Q

Water, Electrolyte, & Acid-Base Balance
Body Water Content

Describe:

A

Higher body fat and smaller amounts of skeletal muscles means less body water content. Total water content declines throughout life.

Infants are about 75% or more water
Healthy males are about 60% water
Healthy females are about 50% water

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2
Q

Water, Electrolyte, & Acid-Base Balance
Fluid Compartments

Describe:

A

Water occupies two main fluid compartments:

Intracellular fluid (ICF)
Extracellular fluid (ECF)
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3
Q

Water, Electrolyte, & Acid-Base Balance
Fluid Compartments

Intracellular fluid (ICF)

Describe:

A

About two-thirds by volume, contained in the cells

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4
Q

Water, Electrolyte, & Acid-Base Balance
Fluid Compartments

Extracellular fluid (ECF)

Describe:

A

Consists of two major subdivisions:

Plasma- the fluid portion of the blood
Interstitial fluid- fluid in spaces between cells

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5
Q

Water, Electrolyte, & Acid-Base Balance
Fluid Compartments

Other ECF

Describe:

A

Lymph, cerebrospinal fluid, eye humors, synovial fluid, serous fluid, and gastrointestinal secretions

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6
Q

Water, Electrolyte, & Acid-Base Balance
Composition of Body Fluid

Water

Describe:

A

Water is the universal solvent (due to its polarity); water moves according to osmotic gradients

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7
Q

Water, Electrolyte, & Acid-Base Balance
Composition of Body Fluid

Solutes

Describe:

A

Solutes are broadly classified into:

Electrolytes- inorganic salts, all acids and bases, and some proteins

Non-electrolytes- examples include glucose, lipids, creatinine, and urea

Electrolytes have greater osmotic power than non-electrolytes

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8
Q

Water, Electrolyte, & Acid-Base Balance
Important Concentration Values

Blood
Sea Water
Fresh Water
Urine

Describe:

A

Water, Electrolyte, & Acid-Base Balance
Important Concentration Values

Blood - 300 mOsm 0.9% w/v
Sea Water - 1,000- 2400 mOsm 3.5% w/v
Fresh Water - 20-40 mOsm 0.1% w/v
Urine - 1200 mOsm 3.2% w/v

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9
Q

Water, Electrolyte, & Acid-Base Balance
Extracellular and Intracellular Fluids

Distinctive Pattern of Electrolytes- Extracellular Fluid

Describe:

A

Extracellular fluids are similar, except for the high protein content of plasma

Sodium is the chief cation ( + )
Chloride is the major anion ( - )

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10
Q

Water, Electrolyte, & Acid-Base Balance
Extracellular and Intracellular Fluids

Distinctive Pattern of Electrolytes- Intracellular Fluid

Describe:

A

Intracellular fluids have low sodium and chloride

Potassium is the chief cation ( + )
Phosphate is the chief anion ( - ) (needed for ATP)

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11
Q

Water, Electrolyte, & Acid-Base Balance
Extracellular and Intracellular Fluids

Anion

Describe:

A

A negatively charged ion, which has more electrons in its electron shells than it has protons in the nuclei.

Usually where oxidation occurs.

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12
Q

Water, Electrolyte, & Acid-Base Balance
Extracellular and Intracellular Fluids

Cation

Describe:

A

A positively charged ion, which has fewer electrons than protons in the nuclei.

Usually where reduction occurs.

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13
Q

Water, Electrolyte, & Acid-Base Balance
Fluid Movement Among Compartments

Describe:

A

Compartmental exchange is regulated by osmotic and hydrostatic pressures.

Net leakage of fluid from the blood is picked up by the lymphatic vessels and returned to the bloodstream

Exchanges between interstitial and intracellular fluids are complex due to the selective permeability of the cellular membranes

Two way water flow is substantial

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14
Q

Water, Electrolyte, & Acid-Base Balance
Osmotic Pressure

Describe:

A

Requires selectively permeable membranes

Is the flow of a solvent through a semi-permeable membrane in the direction of the concentrated solution

If the concentration of dissolved particles rises then the osmotic pressure will be higher

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15
Q

Water, Electrolyte, & Acid-Base Balance
Water Balance and ECF Osmolarity

Describe:

A

To remain properly hydrates, water intake must equal water output.

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16
Q

Water, Electrolyte, & Acid-Base Balance
Water Balance and ECF Osmolarity

Water Intake Sources

Describe:

A

Ingested fluid - 60%
Solid food - 30%
Metabolic water or water of oxidation - 10% (often a product of respiration)

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17
Q

Water, Electrolyte, & Acid-Base Balance
Water Balance and ECF Osmolarity

Water Output

Describe:

A

Urine - 60%
Feces - 4%
Insensible losses - 28% (normal loss, but not sweat)
Sweat - 8%

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18
Q

Water, Electrolyte, & Acid-Base Balance
Water Balance and ECF Osmolarity

Increase in osmolarity

Describe:

A

Increase in osmolarity triggers thirst and the release of antidiuretic hormone

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19
Q

Water, Electrolyte, & Acid-Base Balance
Regulation of Water Intake

Thirst

Describe:

A

The hypothalamic thirst center is stimulated by either decrease in plasma volume of 10%- 15% or increase in plasma osmolarity of 1%- 2%

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20
Q

Water, Electrolyte, & Acid-Base Balance
Regulation of Water Intake

Thirst (reaction to drinking)

Describe:

A

Thirst is quenched as soon as we begin to drink water

Feedback signals that inhibit the thirst centers include moistening of the mucosa of the mouth and throat, and activation of stomach and intestinal stretch receptors

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21
Q

Water, Electrolyte, & Acid-Base Balance
Regulation of Water Output

Obligatory Water Losses Include…

Describe:

A

Obligatory water losses include:

Insensible water losses from lungs and skin

Water that accompanies undigested food residue in feces

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22
Q

Water, Electrolyte, & Acid-Base Balance
Regulation of Water Output

Obligatory Water Loss Reflects…

Describe:

A

Obligatory water loss reflects that:

Kidneys excrete 900- 1200 mOsm of solutes to maintain blood homeostasis

Urine solutes must be flushed out of the body in water

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23
Q

Water, Electrolyte, & Acid-Base Balance
Influence and Regulation of ADH

Describe:

A

Water reabsorption in collecting ducts is proportional to ADH release.

Low levels produce dilute urine and reduced volume of body fluids

High ADH levels produce concentrated urine

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24
Q

Water, Electrolyte, & Acid-Base Balance
Influence and Regulation of ADH

Trigger of ADH

Describe:

A

Hypothalamic osmoreceptors trigger or inhibit AHD release. Factors that trigger ADH release include:

Prolonged fever
Excessive sweating
Vomiting
Diarrhea
Severe blood loss
Traumatic burns
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25
Q

Water, Electrolyte, & Acid-Base Balance
Disorders of Water Balance

Dehydration

Describe:

A

Water loss exceeds water intake and the body is in negative fluid fluid balance

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26
Q

Water, Electrolyte, & Acid-Base Balance
Disorders of Water Balance

Dehydration (Signs)

Describe:

A

Cottonmouth, thirst, dry flushed skin, and oliguria

Prolonged dehydration may lead to weight loss fever, and mental confusion

Other consequences include hypovolemic shock and loss of electrolytes

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27
Q

Water, Electrolyte, & Acid-Base Balance
Disorders of Water Balance

Hypotonic Hydration

Describe:

A

Renal insufficiency or an extraordinary amount of water ingested quickly can lead to cellular over-hydration, or water intoxication

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28
Q

Water, Electrolyte, & Acid-Base Balance
Disorders of Water Balance

Hypotonic Hydration (Effect)

Describe:

A

ECF is diluted- sodium content is normal, but excess water is present

The resulting hyponatremia promotes net osmosis into tissue cells, causing swelling

These events must be quickly reversed to prevent severe metabolic disturbances, particularly in neurons.

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29
Q

Water Intoxication (Acute Hyponatremia)

Describe:

A

From large volumes of water being retained in short periods of time (<48 hours)

30
Q

Water Intoxication (Acute Hyponatremia)

Causes

Describe:

A

Post-operative (from increased ADH secretion as part of a stress response)

Psychotic (self-induced)

Excess intake during exercise

3, 4 methylenedioxymetamphetamine (MDMA)

31
Q

Water Intoxication (Acute Hyponatremia)

Symptoms

Describe:

A

Headache, weakness, nervousness, vomiting, delirium, and ultimately convulsions and coma

May have dilated pupils and hemiparesis

32
Q

Water Intoxication (Acute Hyponatremia)

Treatment

Describe:

A

Hypertonic Saline (3%)

33
Q

Hyponatremia (Not Acute)

Describe:

A

When serum sodium levels are less than 135 mEq/L

Is considered severe when the serum level is below 125 mEq/L

Neurological symptoms most often due to very low serum sodium levels (usually <115 mEq/L), resulting in intracerebral osmotic fluid shifts and brain edema

34
Q

Disorders of Water Balance

Describe:

A

Atypical accumulation of fluid in the interstitial space, leading to tissue swelling

35
Q

Disorders of Water Balance

Causes

Describe:

A

Caused by anything that increases flow of fluids out of the bloodstream or hinders their return.

Factors that accelerate fluid loss include:
Increased blood pressure, capillary permeability
Incompetent venous valves, localized blood vessel blockage
Congestive heart failure, hypertension, high blood volume

36
Q

Disorders of Water Balance

Hypoproteinemia

Describe:

A

Low levels of plasma proteins.

Forces fluids out of capillary beds at arterial ends

Fluids fail to return at the venous ends

Results from protein malnutrition, liver disease, or glomerulonephritis

37
Q

Disorders of Water Balance

Blocked (or surgically removed lymph vessels)

Describe:

A

Cause leaked proteins to accumulate in interstitial fluid

Exert increasing colloid osmotic pressure, which draws fluid from the blood

38
Q

Edema

Describe:

A

Refers to peripheral or dependent edema; accumulation of fluid in the parts of the body most affected by gravity.

Ambulatory people = legs
Limited mobility = sacral edema

39
Q

Edema

Pitting edema

Describe:

A

Pressing down will lead to a shift in the interstitial fluid and the formation of a small pit that resolves over seconds

40
Q

Edema

Non-pitting edema

Describe:

A

May reflect lymphedema, a form of edema that develops when lymph vessels are obstructed

41
Q

Electrolyte Balance

Describe:

A

Electrolytes are salts, acids, and bases, but electrolyte balance therapeutically usually refers to only salt balance.

Salts enter the body by ingestion and are lost vis perspiration, feces, and urine

42
Q

Electrolyte Balance

Salts (Important for)

Describe:

A

Neuromuscular excitability
Secretory activity
Membrane permeability
Controlling fluid movements

43
Q

Sodium in Fluid and Electrolyte Balance

Hypernatremia

Describe:

A

A serum sodium concentration > 147 mEq/L

44
Q

Sodium in Fluid and Electrolyte Balance

Hyponatremia

Describe:

A

A serum sodium concentration of < 135 mEq/L

45
Q

Sodium in Fluid and Electrolyte Balance
Influence of Other Hormones on Sodium Balance

Estrogens

Describe:

A

Enhance NaCl reabsorption by renal tubules. May cause water retention during menstrual cycles. Are responsible for edema during pregnancy

46
Q

Sodium in Fluid and Electrolyte Balance
Influence of Other Hormones on Sodium Balance

Progesterone

Describe:

A

Decreases sodium reabsorption. Acts as a diuretic, promoting sodium and water loss

47
Q

Sodium in Fluid and Electrolyte Balance
Influence of Other Hormones on Sodium Balance

Glucocorticoids

Describe:

A

Enhances the reabsorption of sodium and promotes edema

48
Q

Regulation of Potassium Balance
Hyperkalemia

Describe:

A

A serum potassium concentration of > 5.3 mEq/L

49
Q

Regulation of Potassium Balance
Hypokalemia

Describe:

A

A serum potassium concentration of < 3.5 mEq/L

50
Q

Regulation of Potassium Balance
Hyperkalemia and Hypokalemia

Effect on body…

Describe:

A

Hyperkalemia and hypokalemia can disrupt electrical conduction in the heart and/or lead to sudden death.

51
Q

Potassium Regulatory Site: Cortical Collecting Ducts

Describe:

A

Less than 15% of filtered K+ is lost to urine regardless of need.

K+ balance is controlled by cortical collecting ducts by changing the amount of potassium secreted into filtrate

52
Q

Influence of Plasma Potassium Concentration

Describe:

A

High K+ content of ECF favors collecting duct principal cells to secrete K+

Low K+ or accelerated K+ loss depresses its secretion by collecting ducts

53
Q

Regulation of Calcemia
Hypercalcemia

Describe:

A

A serum Ca2+ concentration > 11mg/dl

Inhibits neurons and muscle cells; may cause heart arrythmias

54
Q

Regulation of Calcemia
Hypocalcemia

Describe:

A

A serum of Ca2+ concentration < 8.5 mg/dl

Increases exciteability; causes muscle tetany

55
Q

Regulation of Calcemia
Calcium Balance is Controlled By

Describe:

A 
Parathyroid hormone (PTH)
Calcitonin
56
Q

Calcitonin Regulation of Calcium

Describe:

A

Released in response to rising blood calcium levels:

Decreasing calcium absorption by the intestines
Decreasing osteoclast activity in bones
Decreasing calcium and phosphate reabsorption by the kidney tubules

57
Q

Dialysis

Describe:

A

Principle of the diffusion of solutes along a concentration gradient across a semipermeable membrane

In all types of dialysis, blood passes on one side of a semipermeable membrane and a dialysis fluid is passed on the other side

By altering the composition of the dialysis fluid, the concentrations of undesired solutes (chiefly potassium and urea) are low and desired solutes (sodium for example) are at their natural concentration

58
Q

Acid-Base Balance
Normal pH of Body Fluids

Arterial blood
Venous blood
Intracellular fluid

Describe:

A

Acid-Base Balance
Normal pH of Body Fluids

Arterial blood - 7.4
Venous blood - 7.35
Intracellular fluid - 7.0

7.0 is considered pH neutral

59
Q

Acid-Base Balance

Compatibility with life

Describe:

A

A pH below 6.8 or above 7.8 is incompatible with life

60
Q

Acid-Base Balance

Alkalosis or alkemia

Describe:

A

Arterial blood pH rises above 7.45

61
Q

Acid-Base Balance

Acidosis or acidemia

Describe:

A

Arterial pH drops below 7.35 (physiological acidosis)

62
Q

Acid-Base Balance
Sources of Hydrogen Ions

Describe:

A

Most hydrogen ions originate from cellular metabolism

Breakdown of phosphorous containing proteins

Anaerobic respiration of glucose produces lactic acid

Fat metabolism yields organic acids and ketone bodies

Transporting carbon dioxide as bicarbonate releases hydrogen ions

63
Q

Acid-Base Balance
Hydrogen Ion Regulation

Describe:

A

Concentration of hydrogen ions if regulated sequentially by:

Chemical buffer systems - act within seconds

The respiratory center in the brain stem - act within 1-3 minutes

Renal mechanism - require hours to days to effect pH changes

64
Q

Chemical Buffer Systems
Acids

Describe:

A

Strong acids- all their H+ is dissociated completely in water

Weak acids- dissociate partially in water and are efficient as preventing pH changes

65
Q

Chemical Buffer Systems
Bases

Describe:

A

Strong bases- dissociate easily in water and quickly tie up H+

Weak bases- accept H+ more slowly (e.g. HCO3 and NH3)

66
Q

Chemical Buffer Systems

Describe:

A

One or two molecules that act to resist pH changes when strong acid or base is added

67
Q

Chemical Buffer Systems

Major Systems

Describe:

A

Bicarbonate buffer system (blood)

Phosphate buffer system (urine)

Protein buffer system (everywhere)

68
Q

Chemical Buffer Systems
Bicarbonate Buffer System

Describe:

A

A mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3) (potassium or magnesium bicarbonates work as well)

69
Q

Chemical Buffer Systems
Phosphate Buffer System

Describe:

A

Nearly identical to the bicarbonate system. This system is an effective buffer in urine and intracellular fluid

70
Q

Chemical Buffer Systems
Protein Buffer System

Describe:

A

Plasma and intracellular proteins are the body’s most powerful buffers. Amphoteric molecules are protein molecules that can function as both a weak acis and weak base (so can water)

Anatomy & Physiology III (3 decks)

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