medical physiology

1. BIOMEDICAL - PHYSIOLOGY
COURSE CODE NHS6110
LEC: PROF KIAMA
MSCN YEAR ONE STUDENT NAME : TAWONGA JERE –
HNS6/44507/2023

2. 1. DESCRIBE BODYFLUIDS AND ELECTROLYTES.
2. EXPLAIN THE COMPARTMENT OF BODY FLUIDS
AND ELECTROLYTES
3. DISCUSS THE VARIOUS FUNCTIONS OF
ELECTROCYTES IN THE BODY
OBJECTIVES

3. • Water is the major constituent of all body fluid compartments.
• Approximately 50% to 60% of total body weight consists of water (approximately
50% in women, 60% in men, and 75% in infants).
• Roughly two thirds of total body water (TBW) is located within cells (intracellular
fluid, ICF), with the remainder located in the extracellular fluid (ECF) compartment.
Transcellular fluids include many small fluid compartments such as the peritoneal,
pleural, synovial, pericardial, and cerebrospinal fluids and the aqueous humor of the
intraocular compartment.
• The percentage of body weight that water occupies depends on the amount of adipose
tissue (fat) a person has
DESCRIPTION

4. • A lean person has a high, and an obese person a low percentage of body
weight that is water, because adipose tissue contains a low percentage of
water (about 10%), whereas most other tissues have a much higher percentage
of water. For example, a muscle is about 75% water.
• The relationship between water content and body weight is clinically
important, since changes in body weight can be used to estimate changes in
body water content.
• For example, in the absence of other explanations, a sudden weight loss of 3
kg reflects a loss of 3 kg (≈3 L) of total body water.
DESCRIPTION CONTINUED

5. • Newborns have a high percentage of body weight in form of water
because of a relatively large ECF volume and little fat.
• Adult women have relatively less water than men, because, on
average, they have more subcutaneous fat and less muscle mass.
• As people age, they tend to lose muscle and add adipose tissue; hence
water, content declines with age.
• In the average young adult male, 18% of the body weight is protein
and related substances, 7% is mineral, and 15% is fat.
•
DESCRIPTION CONT;

6. 1. Move electrolytes and oxygen into and out of cells as needed.
2. Aid in the digestion.
3. Facilitates the transportation of nutrients throughout the body and
removes waste from the body.
4. Regulate body temperature.
5. Lubricate joints and mucous membranes.
6.Moistens the tissues, muscles, body organs and skin.
7.They maintain efficient metabolism of the body.
8.Helps in maintenance of body osmolality within the narrow limits
and maintenance of ECF and blood volume at adequate level.
FUNCTIONS OF FLUIDS

7. • Total body water can be divided into two major compartments or
spaces: intracellular fluid (ICF) and extracellular fluid (ECF).
• The ICF is composed of the fluid within the trillions of cells in
our body.
• The ECF is composed of fluid outside of the cells. In a young
adult man, two thirds of the body water is in the ICF and one
third is in the ECF.
• These two fluids differ strikingly in terms of their electrolyte
composition.
• Their total solute concentrations (osmolalities), however, are
normally equal, because of the high water permeability of most
cell membranes, so that an osmotic difference between cells and
ECF rapidly disappears.
FLUID COMPARTMENT

8. • The ECF is subdivided into two major sub compartments which are separated
from each other by the endothelium of blood capillaries vessels.
• The blood plasma is the ECF found within the vascular system.
• It is the fluid portion of the blood in which blood cells and platelets are
suspended.
• The blood plasma water comprises about one fourth of the ECF, or about 3.5 L
for an average 70-kg man .
• The interstitial fluid and lymph are considered together, because they cannot be
separated easily.
FLUID COMPARTMENT CONTINUED

9. • The water of the interstitial fluid and lymph comprises three fourths of the
ECF. The interstitial fluid directly bathes most body cells, and the lymph is the
fluid within lymphatic vessels.
• The blood plasma, interstitial fluid, and lymph are nearly identical in
composition, except for the higher protein concentration in the plasma.
FLUID COMPARTMENT CONT;

10. • Transcellular fluid is small but physiologically important.
• Transcellular fluid amounts to about 1% to 2% of body weight.
• Transcellular fluids include cerebrospinal fluid, aqueous humour of the eye,
secretions of the digestive tract and associated organs (saliva, bile, and
pancreatic juice), renal tubular fluid and bladder urine, synovial fluid, and
sweat.
• The fluid is separated from the blood plasma by an epithelial cell layer in
addition to a capillary endothelium.
FLUID COMPARTMENT CONT;

11. • The epithelial layer modifies the electrolyte composition of the fluid, so that
Transcellular fluids are not plasma ultrafiltrates (as are interstitial fluid and
lymph).
• They have a distinct ionic composition.
• There is a constant turnover of Transcellular fluids; they are continuously
formed and absorbed or removed.
•
FLUID COMPARTMENT CONT;

12. FLUID COMPARTMENT CONT;

13. FLUID COMPARTMENT CONT;

14. CALCULATION OF TOTAL BODY WATER

15. • About 90% (≈2500 mol) of our fluids come from ingested
substances, such as food and drink.
• These substances break down into water.
• Fluids can also come from IV substances, blood, blood
products, and the accumulation from metabolic oxidation
SOURCES OF BODY FLUIDS

16. • The usual fluid intake per day in a healthy adult :
ingested fluids 1300 mol
water in foods 1000 mol
metabolism 300 mol
Total 2600 mol
• Acceptable fluid intake and loss on a daily basis for a healthy
adult is 1500 to 3000 mol
SOURCES OF FLUIDS CONTINUED

17. • Fluid loss is by 2 ways:
sensible and insensible.
1. Sensible loss:
• Refers to loss that is SEEN and
i. Includes urine (1400mL), and faeces (100mL)..
ii. The kidneys excrete 800 to 1500 mol/day of fluid depending on
the individual’s intake.
HOW HUMANS LOSS FLUID

18. 2. Insensible fluid loss:
• loss that is NOT SEEN.
i. Occurs through the kidneys, intestinal tract, lungs, and
skin.
ii. Includes water evaporation from the skin (350mL).
iii.Exhalation from the lungs accounts for approximately 350
mol/day fluid loss.
• Approximately 100 to 200 mol/day is lost through
gastrointestinal output

19. • Abnormal fluid loss results from a physiologic imbalance.
• Examples include
i. Fever or an increased room temperature, which escalates fluid loss
through the lungs and skin.
ii. Severe burns, which cause increased fluid loss (skin can’t hold fluid
in if it’s damaged).
iii. Haemorrhage where the vascular volume decreases at an accelerated
rate (for example, bleeding during surgery, trauma, or a ruptured
aneurysm).
ABNORMAL FLUID LOSS

20. • Body fluids contain many uncharged molecules e.g. glucose
and urea.
• Electrolytes contribute most to the total solute concentration
(or osmolality) of body fluids.
• Electrolytes are ionised substances
COMPOSTION OF BODY FLUIDS

21. Interstitial fluid - is an ultra filtrate of plasma.
• It contains all of small electrolytes essentially the same
concentration as in plasma, but little protein.
• The proteins are largely confined to the plasma because
of their large molecular size.
• Cations (such as Na+) are lower in interstitial fluid than
in plasma and the concentrations of diffusible anions
(such as Cl-) are higher in interstitial fluid than in
plasma.
INTERSTITIAL FLUIDS

22. • Plasma proteins bind Ca2+ and Mg2+ (about 40% and
20%, respectively), and only the free (unbound) ions can
diffuse through capillary walls.
• The total (bound plus free) plasma Ca2+ and Mg2+
concentrations are higher than in interstitial fluid.
INTERSTITIAL FLUID CONTINUED

23. • ICF composition is different from ECF composition.
• The cells have higher K+, Mg2+, and protein concentrations
than in the surrounding interstitial fluid.
• The intracellular Na+, Ca2+, Cl-, and HCO3
- levels are lower
than outside the cell.
• The anions in skeletal muscle cells labelled as others are
mainly organic phosphate compounds important in cell energy
metabolism, such as creatine phosphate, adenosine
triphosphate (ATP), and adenosine diphosphate (ADP).
INTERSTTITIAL FLUID CONT

24. • The high intracellular [K+] and low intracellular [Na+] are
a consequence of plasma membrane Na+/K+-ATPase
activity; this enzyme extrudes Na+ from the cell and takes
up K+.
• The low intracellular [Cl-] and [HCO3
-] in skeletal muscle
cells is primarily a consequence of the inside negative
membrane potential (-90 mV), which favors the outward
movement of these small negatively charged ions.
• The intracellular [Mg2+] is high; most is not free but is
bound to cell proteins. Intracellular [Ca2+] is low; the
cytosolic [Ca2+] in resting cells is about 10-7 M (0.0002
mEq/L).

25. Osmotic Equilibrium
• Despite the different compositions of ICF and ECF, the total
solute concentration (osmolality) of these two fluid
compartments is normally the same.
• ICF and ECF are in osmotic equilibrium because of the high
water permeability of cell membranes, which does not permit
an osmolality difference to be sustained.
• If the osmolality changes in one compartment, water moves
so as to restore a new osmotic equilibrium.
INTERSTITIAL FLUID CONT;

26. Type Example ECF Volume effect ICF Volume effect Osmolality effect Haematocrit effect t
Plasma [protein]
effect
Isosmotic volume
contraction
Diarrhea; burn ↓ N.C. N.C. ↑ ↑
Hyper osmotic
volume contraction
Sweating; fever;
diabetes insipidus
↓ ↓ ↑ N.C. ↑
Hyposmotic volume
contraction
Adrenal insufficiency ↓ ↑ ↓ ↑ ↑
Isosmotic volume
expansion
Infusion of isotonic ↑ N.C. N.C. ↓ ↓
NaCl
Hyper osmotic
volume expansion
High NaCl intake ↑ ↓ ↑ ↓ ↓

27. What are electrolytes?
• Electrolytes are elements that, when dissolved in water, acquire an
electrical charge — positive or negative.
• Body fluid is mainly a mixture of water and electrolytes.
• If either water or electrolytes get out of the normal in the body —
causing lack of homeostasis — then clients may encounter potentially
life-threatening problems.
ELECTROLYTES

28. • Because of the net charge on water molecules, electrolytes
tend not to reassociate in water.
• It is important to note that electrolytes and other charged
compounds e.g. proteins are unevenly distributed in the
body fluids.
ELECTROLYTES CONTINUED;

29. I. Sodium (Na+)
II. Potassium (K+)
III. Calcium (Ca2+)
IV. Magnesium (Mg2+)
V. Chloride (Cl−)
VI. Phosphate (HPO4
2-)
VII.Bicarbonate (HCO3
-)
VITAL ELECTROLYTES IN THE BODY

30. • There are 3 measurement units used to count
the number of electrolytes in the serum .
• Referred to as plasma and vascular space.
• The unit of measurement varies from
laboratory to laboratory and they include.
MEASURING ELECTROLYTES

31. I. 1. mg/100 mol (milligrams/100 mol): Measures the weight
of the particle in a certain amount of volume. This is the
same as mg/dL (decilitre).
II. 2. mEq/L: Milliequivalent is one-thousandth of an
equivalent—the amount of a substance that will react with
a certain number of hydrogen ions. This is measured per
litre of fluid. Simply put, this is atomic weight.
III. 3. mol/L (millimoles/litre): Millimole is one-thousandth of
a mole per litre of fluid. Basically, this measurement offers
an in-depth analysis of the electrolyte being evaluated.
MEASURING ELECTROLYTES CONTINUED

32. 1. Potassium: found inside the cell; most
plentiful electrolyte in the intracellular
compartment.
2. Magnesium: found inside the cell; second
most plentiful electrolyte in the body.
3. Sodium: Found outside the cell. Most
plentiful electrolyte in the extracellular fluid
4.Phosphorus: found inside the cell and in the
bones.
5. Calcium: found mainly in bones and teeth;
some floats around in the blood as well.
6. Chloride: found inside the cell, the blood, and
the fluid between cells.
ELECTROLYTES FOUND IN THE BODY

33. • Hormones help keep electrolytes within normal range.
• Here are a few examples:
I. Parathyroid hormone (PTH): moves calcium from the bone into the blood
when serum calcium levels are low. This causes the serum calcium to
increase.
II. Calcitonin: moves calcium into the bones as needed. When the serum
calcium is too high, calcitonin kicks in and moves calcium from the blood
into the bone. This causes serum calcium to decrease.
III. Vitamin D: Is a fat soluble. Helps the body to absorb and retain calcium
and phosphorus. Lab studies show that it can reduce cancer cell growth and
helps control infections.
HORMONES

34. • Na+ is the most abundant cation in the ECF and, along with its
accompanying anions Cl- and HCO3.
• The amount of Na+ in ECF determines the ECF volume, which in turn
determines plasma volume, blood volume, and blood pressure.
SODIUM

35. 1. Chief electrolyte in ECF.
2. Assists with generation and transmission of nerve impulses.
3. An essential electrolyte of the sodium–potassium pump in the cell membrane.
4. Food sources include: bacon, ham, sausage, catsup, mustard, relishes,
processed cheese, canned vegetables, bread, cereals, and snack foods.
5. Excess sodium is excreted by kidneys and this helps to retain potassium.
6. Normal adult sodium level is 135 to 145 mEq/L.
7. Helps maintain the volume of body fluids.
FUNCTIONS OF SODIUM

36. • The kidneys are primarily involved in the regulation of Na+ balance.
• If Na+ excretion is less than Na+ intake, then the person is in positive Na+ balance.
• In this case, extra Na+ is retained in the body, primarily in the ECF. When the Na+
content of ECF is increased, there is increased ECF volume or ECF volume
expansion; blood volume and arterial pressure also increase, and there may be
oedema.
FUNCTIONS OF SODIUM CONTINUED

37. • Conversely, if Na+ excretion is greater than Na+ intake, then a person is
in negative Na+ balance.
• When excess Na+ is lost from the body, there is a decreased Na+ content
of ECF, decreased ECF volume or ECF volume contraction, and
decreased blood volume and arterial pressure.
FUNCTIONS CONT;

38. • An important distinction should be made between Na+ content of the body
(which determines ECF volume) and Na+ concentration.
• Na+ concentration is determined not only by the amount of Na+ present but
also by the volume of water. For example, a person can have an increased Na+
content but a normal Na+ concentration (if water content is increased
proportionately). Or, a person can have an increased Na+ concentration with a
normal Na+ content (if water content is decreased).
• In nearly all cases, changes in Na+ concentration are caused by changes in
body water content rather than Na+ content.
FUNCTIONS CONT;

39. • Hyponatremia is serum sodium less than 135 mEq/L.
• Hypernatremia
Hypernatremia is serum sodium greater than 145 mEq/L
SODIUM CONT;

40. • K+ is the major osmotically active solute in cells, the amount of cellular K+ is the
major determinant of the amount of water in (and therefore the volume of) the ICF
compartment, in the same way that extracellular Na+ is a major determinant of ECF
volume.
• When cells lose K+ (and accompanying anions), they also lose water and shrink; the
converse is also true. The distribution of K+ across cell membranes, that is, the ratio of
intracellular to extracellular K+
•
• concentrations, is the major determinant of the resting membrane potential of cells
and hence their excitability.
POTASSIUM

41. 1. Makes skeletal and cardiac muscle work correctly.
2. Major electrolyte in the intracellular fluid.
3. Potassium and sodium are inversely related (when one is up, the other is
down).
4. Plays a vital role in the transmission of electrical impulses.
5. Food sources: peaches, bananas, figs, dates, apricots, oranges, melons, raisins,
prunes, broccoli, potatoes, meat, and dairy products.
6. Excreted by the kidneys.
7. Stomach contains large amount of potassium.
8. Normal potassium level: 3.5 mEq/L to 5.5 mEq/L
FUNCTIONS OF POTASSIUM

42. • Most of the total body K+ is located in the ICF: 98% of the total K+ content is in
the intracellular compartment and 2% is in the extracellular compartment.
• Hypokalemia:
Hypokalemia is serum potassium below 3.5 mEq/L.
• Hypercalcemia
Hypercalcemia is serum potassium greater than 5.0 mEq/L
POTASSIUM CONTINUED

43. • Most of the body's calcium (Ca2+) is contained in bone (99%). The remaining
1% is present in ICF (mostly in bound form) and in ECF.
• The total Ca2+ concentration in plasma is 5 mEq/L or 10 mg/dL. Of the total
plasma Ca2+, 40% is bound to plasma proteins, 10% is bound to other anions
such as phosphate and citrate, and 50% is in the free, ionized form.
• The plasma Ca2+ concentration is regulated by Parathyroid hormone (PTH),
involving a complex interaction of bone, the gastrointestinal tract, and the
kidneys.
CALCIUM

44. • Ca2+ regulates a very large number of physiologic processes that are
as diverse as proliferation, neural signaling, learning, contraction,
secretion, and fertilization.
• Regulation of intracellular Ca2+ is of great importance.
CALCIUM CONTINUED

45. • Much of the intracellular Ca2+ is bound by the endoplasmic
reticulum and other organelles.
• These organelles provide a store from which Ca2+ can be mobilized
via ligand-gated channels to increase the concentration of free Ca2+
in the cytoplasm.
• Increased cytoplasmic Ca2+ binds to and activates calcium-binding
proteins, and these in turn activate a number of protein kinases.
CALCIUM CONT;

46. 1. Acts like a sedative on muscles.
2. Most abundant electrolyte in the body.
3. Has an inverse relationship to phosphorus.
4. Necessary for nerve impulse transmission,
blood clotting, muscle contraction, and
relaxation.
5. Needed for vitamin B12 absorption.
6. Promotes strong bones and teeth.
7. Who needs extra calcium? Children,
pregnant women, lactating women.
FUNCTIONS OF CALCIUM
8.Food sources: milk, cheese, dried beans.
9. Must have vitamin D present to utilize
calcium.
10. If blood levels of calcium decrease, the body
takes calcium from the bones and teeth. (to build
the blood level back up)
11. Parathyroid hormone (PTH) increases serum
calcium by pulling it from the bones and putting
it in the blood.
12. Calcitonin decreases serum calcium by
driving the blood calcium back into the bones.
13. Normal calcium: 9.0 to 10.5 mg/dL (or
between 2.1 mmol/L and 2.6 mmol/L)

47. Hypocalcaemia
• Hypocalcaemia occurs when the serum calcium level drops below 9.0
mg/dL.
Hypercalcemia
• Hypercalcemia is a serum calcium level that exceeds 10.5 mg/dL
CALCIUM CONT;

48. • An adult body contains about 2,000 mEq of Mg2+, of which about 60% is present
in bone, 39% is in cells, and 1% is in the ECF.
• Mg2+ is the second most abundant cation in cells, after K+.
• The bulk of intracellular Mg2+ is not free but is bound to a variety of organic
compounds such as adenosine triphosphate (ATP).
• Mg2+ is present in the plasma at a concentration of about 1 mmol/L (2 mEq/L).
About 20% of plasma Mg2+ is bound to plasma proteins, 20% is complexed with
various anions, and 60% is free or ionized.
MAGNESIUM

49. • An abnormally low plasma [Mg2+] is characterized by neuromuscular and
central nervous system (CNS) hyperirritability and cardiac arrhythmias.
• Abnormally high plasma Mg2+ levels have a sedative effect and may cause
cardiac arrest.
• Dietary intake of Mg2+ is usually 20 to 50 mEq/day; two thirds is excreted in
the faeces and one third in the urine.
• The kidneys are mainly responsible for regulating the plasma [Mg2+].
MAGNESIUM

50. 1. Present in heart, bone, nerves, and muscle tissues.
2. Second most important intracellular ion.
3. Assists with metabolism of carbohydrates and proteins.
4. Helps maintain electrical activity in nerves and muscle.
5. Also acts like a sedative on muscle.
6. Food sources: vegetables, nuts, fish, whole grains, peas, beans.
7. Magnesium levels are controlled by the kidneys (excreted by
kidneys).
8. Normal magnesium: 1.3 to 2.1 mEq/L.
9. Can cause vasodilatation.
FUNCTIONS OF MAGNESIUM

51. Hypomagnesaemia
• Hypomagnesaemia is a serum magnesium level below 1.3
mEq/L.
Hypermagnesemia
• Hypermagnesemia is a serum magnesium level above 2.1
mEq/L.

52. Bicarbonate ions (HCO3
-) are the second most prevalent
extracellular anions.
Normal blood plasma HCO3- concentration is 22–28 mEq/litre
in systemic arterial blood and 23–27 mEq/litre in systemic
venous blood.
HCO3
- concentration increases as blood flows through systemic
capillaries because the carbon dioxide released by metabolically
active cells combines with water to form carbonic acid; the
carbonic acid then dissociates into H+ and HCO3
-.
BICARBONATE

53. • As blood flows through pulmonary capillaries, the concentration of HCO3
-
decreases again as carbon dioxide is exhaled.
• Intracellular fluid also contains a small amount of HCO3
-.
• The exchange of Cl- for HCO3
- helps maintain the correct balance of anions
in extracellular fluid and intracellular fluid.
BICARBONATE CONT;

54. • The kidneys are the main regulators of blood HCO3
-
concentration.
• The intercalated cells of the renal tubule can either form
HCO3- and release it into the blood when the blood level is
low or excrete excess HCO3
- in the urine when the level in
blood is too high.
• Changes in the blood level of HCO3
- are considered later in
this chapter in the section on acid–base balance.
•
BICARBONATE CONT;

55. • Chloride ions (Cl-) are the most prevalent anions in
extracellular fluid.
• The normal blood plasma Cl- concentration is 95–105 mEq/
litre. Cl- moves relatively easily between the extracellular and
intracellular compartments because most plasma membranes
contain many Cl- leakage channels and antiporters.
• For this reason Cl- can help balance the level of anions in
different fluid compartments.
CHLORIDE

56. • One example is the chloride shift that occurs between red blood
cells and blood plasma as the blood level of carbon dioxide either
increases or decreases.
• In this case, the antiporter exchange of Cl- for HCO3
- maintains the
correct balance of anions between ECF and ICF.
• Chloride ions also are part of the hydrochloric acid secreted into
gastric juice.
CHLORIDE CONT;

57. • Antidiuretic Hormone (ADH) helps regulate Cl- balance in
body fluids because it governs the extent of water loss in urine.
“”Processes that increase or decrease renal reabsorption of
sodium ions also affect reabsorption of chloride ions. (NOTE:
Reabsorption of Na+ and Cl- occurs by means of Na+–Cl-
symporters).
CHLORIDE CONT;

58. • Phosphate plays a critical role in the body as a constituent of
bone and as a urinary buffer for H+. Phosphate is localized
primarily in bone matrix (85%), and the remainder of the body
phosphate is divided between ICF (15%) and ECF (<0.5%).
• In ICF, phosphate is a component of nucleotides (DNA and
RNA), high-energy molecules (e.g., ATP), and metabolic
intermediates.
• In ECF, phosphate is present in its inorganic form and serves as
a buffer for H+. About 10% of the phosphate in plasma is
protein-bound.
PHOSPHATE

59. 1. Promotes the function of muscle, red blood cells (RBCs), and the
nervous system.
2. Assists with carbohydrate, protein, and fat metabolism.
3. Food sources: beef, pork, dried peas/beans, instant pudding.
4. PH as an inverse relationship with calcium.
5. Regulated by the parathyroid hormone.
6. Normal phosphorus is 3.0 to 4.5 mg/dL.
7.
FUNCTIONS OF PHOSPHATE

60. • Hypophosphatemia is serum phosphate that is below 3.0
mg/dl .
• Hyperphosphatemia is a serum phosphate level that is above
4.5 mg/dL.

61. • By comparison with children and younger adults, older adults often have an
impaired ability to maintain fluid, electrolyte, and acid–base balance.
• With increasing age, many people have a decreased volume of intracellular
fluid and decreased total body K+ due to declining skeletal muscle mass and
increasing mass of adipose tissue (which contains very little water).
• Age-related decreases in respiratory and renal functioning may compromise
acid–base balance by slowing the exhalation of CO2 and the excretion of
excess acids in urine
AGING AND FLUID AND ELECTROLYTE BALANCE

62. • Other kidney changes, such as decreased blood flow, decreased
glomerular filtration rate, and reduced sensitivity to antidiuretic
hormone, have an adverse effect on the ability to maintain fluid
and electrolyte balance.
• Due to a decrease in the number and efficiency of sweat glands,
water loss from the skin declines with age.
• Because of these age-related changes, older adults are
susceptible to several fluid and electrolyte disorders:
AGING AND FLUID AND ELECTROLYTE BALANCE

63. 1. Dehydration and hypernatremia often occur due to inadequate fluid intake or
loss of more water than Na+ in vomit, faeces, or urine.
2. Hyponatremia may occur due to inadequate intake of Na+; elevated loss of Na+
in urine, vomit, or diarrhoea; or impaired ability of the kidneys to produce
dilute urine.
3. Hypokalemia often occurs in older adults who chronically use laxatives to
relieve constipation or who take K+-depleting diuretic drugs for treatment of
hypertension or heart disease.
4. Acidosis may occur due to impaired ability of the lungs and kidneys to
compensate for acid–base imbalances. One cause of acidosis is decreased
production of ammonia (NH3) by renal tubule cells, which then is not available
to combine with H+ and be excreted in urine as NH4+; another cause is reduced
exhalation of CO2.
AGING AND FLUID AND ELECTROLYTE BALANCE

64. REFERENCES
 J Gordon Betts Johnson , Dean H Kruse , Kelly A . Young , Anatomy and
Physiology, 2013
 Ganong’s Review of Medical Physiology 24th Edition