Lecture Exam 2 - Urinary System Study Guide Flashcards Preview

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Flashcards in Lecture Exam 2 - Urinary System Study Guide Deck (127):
1

Urinary system consists of:

2 kidneys
2 ureters
1 bladder
I urethra

2

Define: Nephrology

scientific study of the anatomy, physiology and pathology of kidneys.

3

Define: Urology

study of anatomy, physiology and pathology of male and female urinary systems and male reproductive system.

4

Know the basic seven functions of the urinary system as laid out in lecture.

1) Regulation of blood ionic composition - particularly Na+,
K+, Ca(^2+), Cl-, HPO4(^2-).

2) Regulation of blood pH - excrete H+ and conserve HCO3- in order to regulate pH.

3) Regulation of blood volume - adjust blood volume by conserving or eliminating water as necessary. Increased blood volume increases blood pressure and vice versa.

4) Regulation of blood pressure - help regulate blood pressure by secreting renin (part of reninangiotensin-aldosterone system).

5) Maintenance of blood osmolarity - by regulating loss of water and loss of solutes - maintain relatively constant blood osmolarity of 300 milliosmoles/litre (mOsm/l).

5) Production of hormones. Kidneys produce 2 hormones:
i. Calcitriol - active form of Vit D that helps regulate blood calcium homeostasis.
ii. Erythropoetin - stimulates
production of red blood cells.

6) Regulation of blood glucose level - can use the amino acid, glutamine for gluconeogenesis
(also occurs in liver). Glucose produced is released into blood.

7) Excretion of wastes and foreign substances - formation of urine to secrete wastes.

e.g. a) ammonia and urea from deamination of amino acids
b) bilirubin from catabolism of hemoglobin
c) creatine from breakdown of creatine phosphate in muscle.
d) uric acid from catabolism of nucleic acids. drugs and environmental toxins.

5

Where are the kidneys located with respect to the spinal column?

Located between T10 and L3.
Partially protected by 11th and 12th ribs.

6

Where are the kidneys located with respect to the ribs?

Partially protected by 11th and 12th ribs.

7

Which kidney is higher than the other and why?

Right kidney slightly lower than left kidney because of size of right liver lobe.

8

Approximately how long and how wide is a human kidney?

4-5 inches long 2-3 inches wide

9

What are the 3 coverings of the kidney?
What type of tissue makes up each of these coverings?

3 layers surround each kidney (from deep to superficial)

1) Renal capsule - dense irregular CT

2) Adipose capsule - protective

3) Renal fascia - another thin layer of dense irregular CT - anchors kidney to peritoneum

10

What is the pathway followed by urine when it exits the kidney?

A nephron is a functional unit of the kidney - about 1 million nephrons present in each kidney.

Urine from the nephrons drains into papillary ducts that drain into cup-like structures (calyces) and then into the renal pelvis.

Renal pelvis drains into renal sinus and into ureter.

11

Through what vessel does blood enter the kidney?

renal artery

12

What is the pathway of blood to the glomerulus?

1)Renal Artery: Brings blood supply to the kidney; divides into the smaller; Divides into small branches that end as afferent arterioles
2)Afferent Arterioles: Branch out into glomerular capillaries
3)Glomerular Capillaries: Send blood to efferent arterioles
4)Efferent Arterioles: Send blood supply into the peritubular capillaries
5)Peritubular Capillaries: Eventually drains into renal vein
***Major Diff. betwn systemic & renal blood circulation is the presence of 2 capillary beds instead of one

13

Through what vessel does blood enter the glomerulus?

The afferent arteriole carries blood from the renal artery into the glomerulus. The afferent arteriole is a cluster of blood vessels supplying nephrons to a number of excretory systems whereas the glomerulus is a mass of nerve fibres. The efferent arteriole carries blood away.

14

Through what vessel does blood leave the glomerulus?

Blood is filtered from the glomerulus into the glomerular capsule and then passes into renal tubules.

Renal tubules made up of 3 parts:
1) Proximal convoluted tubule
2) Loop of Henle (sometimes called nephron loop)
3) Distal convoluted tubule

15

Where are the peritubular capillaries located?

In the renal system, peritubular capillaries are tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.

Ions and minerals that need to be saved in the body are reabsorbed into the peritubular capillaries through active transport, secondary active transport, or transcytosis.

16

What percentage of total resting cardiac output is received by the kidneys?

Receive 20-25% of resting cardiac output.

17

Approximately how many nephrons are present in each kidney?

one million

18

Know the difference in structure between a cortical nephron and a juxtamedullary nephron.

Cortical nephrons - 80-85% of total nephrons:
- Renal corpuscles lie in outer portion of renal cortex.
- Short loops of Henle - mostly in cortex
- Receive blood from peritubular capillaries

Juxtamedullary nephrons -15 20% of total nephrons
- Renal corpuscles deep in cortex, close to medulla.
- Long loop of Henle - extending into medulla - has thick and thin portions.
-Receive blood from peritubular capillaries and from vasa recta.

19

What do the terms proximal, distal and convoluted mean with respect to renal tubules?

Proximal = part of tube attached to glomerular capsule.

Distal = part of tube further away from glomerular capsule.

Convoluted = part of tube that is tightly coiled rather than straight.

20

What are the 3 parts of a renal tubule?

Renal tubule - where filtered fluid passes from renal corpuscle.

Renal tubules made up of 3 parts:
1) Proximal convoluted tubule
2) Loop of Henle (sometimes called nephron loop)
3) Distal convoluted tubule

21

What are the 2 major components of a renal corpuscle?

Renal Corpuscle - where blood is filtered.

Two components of renal corpuscle:

1) Glomerular capsule (Bowman’s capsule) - double-walled epithelial cup

2) Glomerulus - capillary network contained in the “cup”.

22

Know the detailed structure of a renal corpuscle including the names and locations of the different layers and the names locations and functions of the different cell-types.

Two components of renal corpuscle:
1) Glomerular capsule (Bowman’s capsule) - double-walled epithelial cup
2) Glomerulus - capillary network contained in the
“cup”.

Blood is filtered from the glomerulus into the glomerular capsule and then passes into renal tubules.

Bowman’s capsule - visceral and parietal layers.

Visceral layer - modified squamous epithelia cells
(podocytes - meaning foot cells).
Foot-like projections of podocytes wrap around
endothelium of glomerular capillaries forming the inner wall of the capsule.

Parietal layer - composed of simple squamous epithelium.

23

What is the pathway of fluid flow from the blood entering a renal corpuscle to the renal tubules?

Blood is carried out of the glomerulus by an efferent arteriole instead of a venule, as is observed in most other capillary systems. This provides tighter control over the blood flow through the glomerulus, since arterioles dilate and constrict more readily than venules, owing to arterioles' larger smooth muscle layer (tunica media).

Efferent arterioles of juxtamedullary nephrons (i.e., the 15% of nephrons closest to the medulla) send straight capillary branches that deliver isotonic blood to the renal medulla. Along with the loop of Henle, these vasa recta play a crucial role in the establishment of the nephron's countercurrent exchange system.

The efferent arteriole, into which the glomerulus delivers blood, empties into an interlobular vein.

24

How does the structure of the epithelial wall change along the renal tubules?

In descending loop of Henle - simple squamous epithelia for easy exchange of substances

In thick ascending loop of Henle (in juxtamedullary nephrons) epithelia gradually becomes cuboidal and then columnar.

Epithelial cells in thick ascending limb make contact with afferent arterioles of renal corpuscle - become crowded - often called macula densa.

Macula densa in contact with modified smooth muscle fibers of the arteriole wall - called juxtaglomerular apparatus.

25

What is the function of principal cells?

have receptors for ADH and aldosterone.

26

What is the function of intercalated cells?

play a role in homeostatic control of blood pH

27

What happens if one kidney is surgically removed?

If one kidney removed, 2nd kidney enlarges (compensatory hyperplasia).

Enlarged single kidney can filter 80% of amount of blood originally filtered by both.

28

Define: Glomerular filtration

Water and solutes in blood pass from glomerular capillaries into glomerular capsule and then into renal tubule.

29

Define: Tubular reabsorption

Tubular Reabsorption - return of water and other filtered substances to the blood stream.

Reabsorption can occur:

1) Between adjacent tubules -
paracellular reabsorption
2) Through an individual tubular cell - transcellular reabsorption

30

Define: Tubular secretion

Tubular Secretion - process of secreting unwanted substances into the tubules

-some substances (e.g. creatine) are secreted to be eliminated from the body

-- others are secreted to maintain a homeostatic balance e.g. hydrogen ions are secreted to balance blood pH.

31

How much water is filtered through the glomerular capsules of both kidneys each day?

In healthy adults GFR = about 125ml / min in males and 105 ml / min in females. (45 gallons a day in males)

32

Know the definition of net filtration pressure.

Net filtration pressure (NFP) can be defined as the total pressure that promotes filtration.

33

Know the definitions of glomerular blood hydrostatic pressure, capsular hydrostatic pressure and blood colloid osmotic pressure. Do these pressures promote or oppose glomerular filtration?

glomerular blood hydrostatic pressure (GBHP) - PUSHING FORCE - The hydrostatic force which is the mechanical pressure exerted on the fluid of plasma by the pumping of the heart during systole and by the elastic recoil and smooth muscle contraction in the walls of the arteries between heart beats during diastole, and especially by the pressure gradient established between the afferent and efferent arterioles delivering the blood to the glomerulus, which tends to push the plasma filtrate from the capillaries of the glomerulus into the capsular space.

capsular hydrostatic pressure (CHP) - RESISTING FORCE - The hydrostatic force which is the mechanical pressure exerted on the plasma filtrate by the the elastic recoil of the glomerular capsule, which tends to push water and dissolved solutes from the plasma filtrate back into the capillaries of the glomerulus; this is the main force slowing the rate of filtrate production within the renal corpuscle itself.

blood colloid osmotic pressure (BCOP) - RESISTING FORCE - The osmotic force (water concentration gradient) which is the result of differences in water concentration between plasma and plasma filtrate, which tends to pull water from the plasma filtrate and back into the plasma in the glomerular capillaries; it results from the failure of most proteins to leave the plasma and move to the plasma filtrate, therefore, as water leaves, the proteins exert an increasing osmotic "pull" on the water in the plasma filtrate.

34

Know how the glomerular blood hydrostatic pressure, capsular hydrostatic pressure and blood colloid osmotic pressure relate to one another and how to calculate net filtration pressure if given values for each of these different pressures.

Net filtration pressure (NFP) can be defined as the total pressure that promotes filtration.

NFP = GBHP (Glomular blood hydrostatic pressure) - CHP (capsular hydrostatic pressure) - BCOP(blood colloid osmotic pressure)

NFP = 55mmHg - 15mmHg - 30mmHg = 10mmHg

GBHP = glomerular blood hydrostatic pressure
CHP = capsular hydrostatic pressure
BCOP = blood colloid osmotic pressure

35

What and where is the macula densa?

The macula densa provides feedback to the glomerulus.

Epithelial cells in thick ascending limb make contact with afferent arterioles of renal corpuscle - become crowded - often called macula densa.

36

What is the juxtaglomerular apparatus?

Macula densa in contact with modified smooth muscle fibers of the arteriole wall - called juxtaglomerular apparatus.

37

Define Glomerular Filtration Rate (GFR).

GFR = the amount of fluid formed in all the renal corpuscles of both kidney each minute.

In healthy adults GFR = about 125ml / min in males and 105 ml / min in females.

38

What will happen if GFR is too high?

If GFR too high - needed substances may pass out of body too quickly.

39

What will happen if GFR is too low?

If GFR too low - everything may be reabsorbed including some waste products.

40

FILTRATION FRACTION --

Define the term filtration fraction.

Approximately what is the filtration fraction in a healthy individual?

the ratio of the glomerular filtration rate (GFR) to the renal plasma flow (RPF).

Filtration Fraction, FF = GFR/RPF

The filtration fraction, therefore, represents the proportion of the fluid reaching the kidneys which passes into the renal tubules. It is normally about 20%.

41

FILTRATION MEMBRANE --
What are the components of the filtration membrane?

glomerular capillary endothelial cells
glomerular basement membrane
podocytes of visceral layer of glomerular capsule

42

FILTRATION MEMBRANE --
How do the endothelial cells in the glomerulus differ from those in capillaries in other locations?

The endothelial cells of the glomerulus contain numerous pores (fenestrae) that, unlike those of other fenestrated capillaries, are not spanned by diaphragms. The cells have fenestrations that are 70 to 100 nm in diameter. Since these pores are relatively large, they allow for the free filtration of fluid, plasma solutes and protein. However they are not large enough that red blood cells can be filtered.

43

FILTRATION MEMBRANE --
What is the function of mesangial cells?

Mesangial cells are specialized cells around blood vessels in the kidneys, at the mesangium. They are specialized smooth muscle cells that function to regulate blood flow through the capillaries, usually divided into two types, each having a very distinct function and location:

Extraglomerular mesangial cells
Intraglomerular mesangial cells

44

FILTRATION MEMBRANE --
What is the function of the basal lamina in the glomerulus?

Filtration barrier -- The filtration barrier is composed of the fenestrated endothelium of the glomerular capillaries, the fused basal lamina of the endothelial cells and podocytes, and the filtration slits of the podocytes.

The barrier permits the passage of water, ions, and small molecules from the bloodstream into the Bowman's space. The barrier prevents the passage of large and/or negatively charged proteins (such as albumin).

The basal lamina of the filtration barrier is composed of three layers. The first layer is the lamina rara externa, adjacent to the podocyte processes. The second layer is the lamina rara interna, adjacent to the endothelial cells. The final layer is the lamina densa which is a darker central zone of the basal lamina. It consists of the meshwork of type IV collagen and laminin which act as a selective macromolecular filter

45

FILTRATION MEMBRANE --
What type of tissue makes up the basal lamina?

The basal lamina consists of a mixture of collagens, laminin (glycoprotein), perlecan (heparan sulphate glycoprotein), entactin (glycoprotein). These proteins can bind to each other to make a highly crosslinked extracellular matrix as shown in this diagram.

46

FILTRATION MEMBRANE --
What are pedicels?

Pedicels are the long processes of the podocytes that wrap around the capillaries, and leave slits between them. Blood is filtered through these slits, each known as a slit diaphragm or filtration slit

47

FILTRATION MEMBRANE --
What are filtration slits?

slits between the pedicels of the podocytes

48

GLOMERULAR FILTRATION --
How do mesangial cells contribute to the ability of the glomerular capillaries to filter large volumes of fluid?

TBD

49

GLOMERULAR FILTRATION --
Why are the glomerular endothelial cells leaky? How much more leaky are they than other endothelial cells?

TBD

50

GLOMERULAR FILTRATION --
What makes the glomerular blood pressure higher than mean arterial blood pressure?

TBD

51

MECHANISMS OF REGULATION OF GFR --

a) Adjusting blood flow into and out of glomerulus.

b) Altering glomerular surface area available for filtration.

TBD

Achieved by renal autoregulation, neural regulation and hormonal regulation.

52

MECHANISMS OF REGULATION OF GFR --

Describe the myogenic and tubuloglomerular feedback mechanisms of autoregulation.

TBD

53

MECHANISMS OF REGULATION OF GFR --

What is the role of nitric oxide in tubuloglomerular feedback?

From where is it secreted?

How is it regulated?

TBD

54

MECHANISMS OF REGULATION OF GFR --

Is GFR increased or decreased by sympathetic nervous system activation?

TBD

55

MECHANISMS OF REGULATION OF GFR --

What neurotransmitter is released by these sympathetic neurons and what receptors are
activated to influence GFR?

TBD

56

MECHANISMS OF REGULATION OF GFR --

How does atrial natriuretic peptide (ANP) influence GFR? What cells secrete ANP?

TBD

57

MECHANISMS OF REGULATION OF GFR --

How does angiotensin II influence GFR? What regulates the secretion of angiotensin II?

TBD

58

MECHANISMS OF REGULATION OF GFR --

What is renin?

TBD

59

MECHANISMS OF REGULATION OF GFR --

What does angiotensin-converting enzyme (ACE) do? How are ACE inhibitors used
clinically?

TBD

60

TUBULAR REABSORPTION --

Define: Paracellular reabsorption

TBD

61

TUBULAR REABSORPTION --

Define: Transcellular reabsorption

TBD

62

TUBULAR REABSORPTION --

Define: Apical membrane

TBD

63

TUBULAR REABSORPTION --

Define: Basolateral membrane

TBD

64

TUBULAR REABSORPTION --

Define: Passive Transport

TBD

65

TUBULAR REABSORPTION --

Define: Active Transport
Secondary Active Transport
Symporter
Antiporter

TBD

66

TUBULAR REABSORPTION --

Define: Secondary Active Transport

TBD

67

TUBULAR REABSORPTION --

Define: Symporter

TBD

68

TUBULAR REABSORPTION --

Define: Antiporter

TBD

69

TUBULAR REABSORPTION --

Describe two methods of transcellular reabsorption of sodium ions in the proximal convoluted tubules.

Be sure to know what is happening at each membrane surface, what is transported to the plasma and what is transported to the luminal fluid.

TBD

70

TUBULAR REABSORPTION --

How is glucose transported out of the proximal convoluted tubule cells?

TBD

71

TUBULAR REABSORPTION --

How are sodium ions transported out of the proximal convoluted tubule cells?

TBD

72

HORMONAL REGULATION OF TUBULAR SECRETION AND REGULATION OF PH --

What are the two major hormones in regulation of electrolyte balance? From where are they secreted and where do they act?

TBD

73

HORMONAL REGULATION OF TUBULAR SECRETION AND REGULATION OF PH --

What hormone inhibits electrolyte and water reabsorption?

atrial natriuretic peptide (ANP)

74

HORMONAL REGULATION OF TUBULAR SECRETION AND REGULATION OF PH --

What is the major hormone in regulation of water reabsorption?

Antidiuretic Hormone (ADH)

75

HORMONAL REGULATION OF TUBULAR SECRETION AND REGULATION OF PH --

How is the pH of blood regulated by the kidneys? What is the role of carbonic anhydrase? What
happens to the excess protons? What happens to the bicarbonate ions?

The bicarbonate buffering system is an important buffer system in the acid-base homeostasis of living things, including humans. As a buffer, it tends to maintain a relatively constant plasma pH and counteract any force that would alter. In this system, carbon dioxide (CO2) combines with water (H2O) to form carbonic acid (H2CO3), which in turn rapidly dissociates to form hydrogen ions (H+) and bicarbonate (HCO3- ) as shown in the reactions below.


CO2 + H2O = H2CO3 = HCO3- + H+



The carbon dioxide - carbonic acid equilibrium is catalyzed by the enzyme carbonic anhydrase; the carbonic acid - bicarbonate equilibrium is simple proton dissociation/association and needs no catalyst.



Excess Hydrogen is secreted into urine, and Bicarbonate is reabsorbed into blood.

76

DIURETICS --

What is a diuretic?

substances that increase the rate and volume of urine production by the kidneys

77

DIURETICS --

What effect do diuretics have on urine volume?
What effects do diuretics have on blood volume?

Increase urine volume,
Decrease blood volume

78

URINALYSIS --

Define: Urinalysis

Evaluation of the volume and physical, chemical and microscopic properties of urine.

79

URINALYSIS --

Define: Specific gravity

Specific gravity (density) is the ratio of the weight of a substance to the weight of an equal volume of water.

80

URINALYSIS --

What causes the color in urine?

Color occurs because of bile breakdown products - produces a pigment called urochrome.

Concentrated urine is darker than dilute urine.

Some food substances add color e.g. beets.

Some medications and diseases affect color.

Kidney stones may produce blood in urine.

81

URINALYSIS --

What is the normal pH range of urine? What may influence pH?

Ranges between 4.5-8.0

High protein diet - more acidic

Vegetarian diet - more alkaline

82

URINALYSIS --

What factors may influence the specific gravity of urine?

More dilute urine has a lower specific gravity.

83

BLOOD TESTS TO ASSESS KIDNEY FUNCTION --

Understand why these components in the blood indicate poor renal function:

Blood urea nitrogen
Plasma creatine

In renal disease GFR may increase dramatically.
Blood Uria Nitrogetn would rise because urine concentration mechanisms disrupted.

High plasma creatinine indicates poor renal function.

84

RENAL PLASMA CLEARANCE --

What does the term renal plasma clearance mean?

Renal Plasma clearance is the volume of blood that is cleared of a particular substance each minute in ml /min (milliliters /minute).

Dependent on glomerular filtration, tubular reabsorption, and tubular secretion.

85

DIALYSIS --

What is dialysis?

Know the difference between renal dialysis and peritoneal dialysis.

Dialysis: Artificial cleansing of blood when kidneys fail.

Hemodialysis - directly filters blood and then returns cleansed blood - uses an artificial membrane in a machine called a hemodilayzer

Peritoneal dialysis - uses the peritoneal membrane of the abdominal cavity as the dialysis membrane.

86

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the basis of the following diseases:
Urinary tract infections

Any infection of part of the urinary system resulting in microbes in the urine.

Painful, burning and/or frequent urination.

Must be treated early . If kidneys become inflamed scar tissue forms that impairs function.

Cranberry juice prevents attachment of E.Coli bacteria to lining of bladder. Antibiotics often required to effectively treat the infection.

87

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the basis of the following diseases:
Glomerulonephritis

- inflammation of the kidneys that involves the glomerulus.

Often caused by allergy to toxins produced
by streptococcal bacteria Glomeruli become swollen and fail as a filtration membrane. Protein and erythrocytes appear in urine.

88

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the basis of the following diseases:
Acute renal failure

Renal Failure: Decrease or cessation of glomerular filtration.

Acute Renal Failure (AFR) - kidneys abruptly stop working -common in major trauma and blood loss.

May be reversible.

89

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the basis of the following diseases:
Chronic renal failure

Renal Failure: Decrease or cessation of glomerular filtration.

Chronic Renal Failure (CFR) - progressive And irreversible decline in kidney function - in later stages must be treated with dialysis and possible kidney transplant surgery.

90

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the basis of the following diseases:
Polycystic kidney disease

- an inherited disorder

- Kidney tubules become full of cysts (fluid filled capsules)

- Non-cystic tubules die by apoptosis (programmed cell death).

Liver, pancreas, spleen and gonads may undergo same process.

91

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the basis of the following diseases:
Diabetic kidney disease

Diabetics often suffer glomerular damage - proteins leak into urine.

Untreated diabetes mellitus causes damage to a number of organs including liver and kidneys.

92

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the meaning of the following medical terms:
Azotemia

presence of urea and other nitrogencontaining substances in blood (azot = nitrogen, -emia = condition of blood).

93

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the meaning of the following medical terms:
Dysuria

painful urination.

94

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the meaning of the following medical terms:
Polyuria

excessive urination.

95

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the meaning of the following medical terms:
Uremia

toxic levels of urea in blood.

96

RENAL DISEASES AND MEDICAL TERMINOLOGY --

Know the meaning of the following medical terms:
Urinary retention

failure to urinate.

97

BODY FLUIDS --
Know the meaning of the terms intracellular fluid and extracellular fluid.

Intracellular Fluid (ICF) - within cells.

Extracellular Fluid (ECF) - outside cells.

98

BODY FLUIDS --
What are the two components of extracellular fluid?

Extracellular Fluid (ECF) - outside cells.
80% of ECF is interstitial fluid (within tissues) and 20% is plasma.

99

BODY FLUIDS --
How are the different body fluid compartment separated?

1) The plasma membrane of cells
2) Blood vessel walls

100

REGULATION OF WATER GAIN --
What are the 3 major sources of water in the body?

1) Metabolic Water (produced by body processes)
2) Ingested foods
3) Ingested liquids

101

REGULATION OF WATER GAIN --

Which 3 organs are responsible for water loss?

1) Lungs
2) Skin
3) Kidneys

102

REGULATION OF WATER GAIN --

What is the response to dehydration?

Antidiuretic hormone (ADH) from the posterior pituitary
– stimulates thirst
– increases permeability of principal cells of collecting
ducts to assist in water reabsorption
– very concentrated urine is formed

• ADH secretion shuts off after the intake of water

• ADH secretion is increased by:
– large decrease in blood volume
– severe dehydration and drop in blood pressure
– vomiting, diarrhea, heavy sweating or burns

103

REGULATION OF WATER GAIN --

What is the hormonal response to solute loss?

Angiotensin II and aldosterone promote reabsorption of
Na+ and Cl- and an increase in fluid volume
– stretches atrial volume and promotes release of ANP
– slows release of renin & formation of angiotensin II
• increases filtration rate & reduces water & Na+
reabsorption
• decreases secretion of aldosterone slowing
reabsorption of Na+ and Cl- in collecting ducts
• ANP promotes natriuresis or the increased excretion of
Na+ and Cl- which decreases blood volume

104

REGULATION OF WATER GAIN --

What happens if excessive water accumulates in the body?

When water is consumed faster than the kidneys can excrete it, water intoxication may result

105

ELECTROLYTES IN BODY FLUIDS --
Define the term electrolyte.

Electrolyte - an ionic compound that breaks apart into positive and negative ions in solution

106

ELECTROLYTES IN BODY FLUIDS --

Name 4 major functions of ions in the body.

– Because they are more numerous than nonelectrolytes, electrolytes control the osmosis of water between body compartments.

– maintain the acid-base balance required for normal cellular activities.

– carry electrical current, which allows production of action potentials and graded potentials and controls secretion of some hormones and neurotransmitters. Electrical currents are also important during development.

– cofactors needed for optimal activity of enzymes.

107

ELECTROLYTES IN BODY FLUIDS --

What unit is used to compare electrolytes in body fluids?

To compare the charge carried by ions in different
solutions, the concentration is typically expressed in
milliequivalents/liter (mEq/Liter), which gives the
concentration of cations or anions in a solution.

108

ELECTROLYTES IN BODY FLUIDS --

Know the major roles of the following electrolytes in the body: Sodium ions

Sodium (Na+) is the most abundant extracellular ion.

• Most abundant extracellular ion
– accounts for 1/2 of osmolarity of ECF

• Average daily intake exceeds normal requirements

• Hormonal controls
– aldosterone causes increased reabsorption Na+
– ADH release ceases if Na+ levels too low--dilute urine lost until Na+ levels rise
– ANP increases Na+ and water excretion if Na+ levels too high

• Excess Na+ in the body can result in edema. Excess loss of Na+ causes excessive loss of water, which results in hypovolemia, an abnormally low blood volume.

109

ELECTROLYTES IN BODY FLUIDS --

Know the major roles of the following electrolytes in the body:
chloride ions

Chloride (Cl-) is the major extracellular anion.

• Most prevalent extracellular anion

• Moves easily between compartments due to Cl- leakage channels

• Helps balance anions in different compartments

• Regulation of chloride ion balance
– passively follows Na+ so it is regulated indirectly by aldosterone levels
– ADH helps regulate Cl- in body fluids because it controls water loss in urine

• Chloride ion shift across red blood cells membranes with buffer movement.

• Chloride ions play a role in forming HCl in the stomach.

110

ELECTROLYTES IN BODY FLUIDS --

Know the major roles of the following electrolytes in the body:
potassium ions

Potassium (K+) is the most abundant cation in intracellular fluid.

• K+ is involved in maintaining fluid volume, impulse conduction, muscle contraction.

• K+ is exchanged for H+ to help regulate pH in intracellular fluid

• The plasma level of K+ is under the control of mineralocorticoids, mainly aldosterone (from the adrenal cortex).

• Helps establish resting membrane potential & repolarize nerve & muscle tissue

• Control is mainly by aldosterone which stimulates principal cells to increase K+ secretion into the urine

• abnormal plasma K+ levels adversely affect cardiac and
neuromuscular function K+ helps establish resting membrane potential & repolarize nerve & muscle tissue

• Control K+ balance is mainly by aldosterone which
stimulates principal cells of distal convoluted tubule to
increase K+ secretion into the urine

• abnormal plasma K+ levels adversely affect cardiac and
neuromuscular function

111

ELECTROLYTES IN BODY FLUIDS --

Know the major roles of the following electrolytes in the body:
bicarbonate ions

Bicarbonate (HCO3-) is a prominent ion in the
plasma.

• It is a significant plasma anion in electrolyte balance.

• It is a major component of the plasma acid-base buffer
system.
– Concentration increases as blood flows through systemic capillaries due to CO2 released from metabolically active cells
– Concentration decreases as blood flows through
pulmonary capillaries and CO2 is exhaled

• Kidneys are main regulator of plasma levels
– intercalated cells form more if levels are too low
– excrete excess in the urine

112

ELECTROLYTES IN BODY FLUIDS --

Know the major roles of the following electrolytes in the body:
calcium ions

Calcium (Ca+2), the most abundant ion in the body, is principally an extracellular ion.

• It is a structural component of bones and teeth.

• Important role in blood clotting, neurotransmitter release, muscle tone & nerve and muscle function

• Regulated by parathyroid hormone
– stimulates osteoclasts to release calcium from bone

113

ACID-BASE BALANCE --

What are the major actions of buffer systems?

Prevent rapid, drastic changes in pH
Change either strong acid or base into weaker one
Work in fractions of a second
Found in fluids of the body

114

ACID-BASE BALANCE --

What are the 3 principal buffer systems in the body?

– protein buffer system
– carbonic acid-bicarbonate buffer system
– phosphate buffer system

115

ACID-BASE BALANCE --

How do the lungs contribute to acid-base balance?

The pH of body fluids may be adjusted by a change in the rate and depth of respirations

An increase in the rate and depth of breathing causes more carbon dioxide to be exhaled - increasing pH.

A decrease in respiration rate and depth means that less carbon dioxide is exhaled - causes blood pH to fall.

116

ACID-BASE BALANCE --

How do the kidneys contribute to acid-base balance?

The kidneys excrete H+ into urine and reabsorb HCO3 - to aid in maintaining pH.

117

ACID-BASE BALANCE --

What is the normal pH range of blood?

The normal pH range of systemic arterial
blood is between 7.35-7.45.

118

ACID-BASE BALANCE --

Define:
Alkalosis

Alkalosis is a blood pH above 7.45. Its principal effect is overexcitability of the central nervous system through facilitation of synaptic transmission.

119

ACID-BASE BALANCE --

Define:
Respiratory compensation

Compensation refers to the physiological response to an acid-base imbalance.

Compensation is an attempt to correct the problem
– respiratory compensation for renal problem
– renal compensation for respiratory problem

120

ACID-BASE BALANCE --

Define:
Renal compensation

Compensation refers to the physiological response to an acid-base imbalance.

Compensation is an attempt to correct the problem
– respiratory compensation for renal problem
– renal compensation for respiratory problem

121

ACID-BASE BALANCE --

Define:
Respiratory acidosis

Cause is elevation of pCO2 of blood

Due to lack of removal of CO2 from blood, e.g. from emphysema, pulmonary edema, injury to the brainstem & respiratory centers

Treatment
– IV administration of bicarbonate (HCO3-)
– ventilation therapy to increase exhalation of CO2

122

ACID-BASE BALANCE --

Define:
Respiratory alkalosis

Arterial blood pCO2 is too low

Hyperventilation caused by high altitude, pulmonary disease, stroke, anxiety, aspirin overdose

Renal compensation involves decrease in excretion of H+ and increase reabsorption of bicarbonate

123

ACID-BASE BALANCE --

Define:
Metabolic acidosis

Blood bicarbonate ion concentration too low

– loss of ion through diarrhea or kidney dysfunction
– accumulation of acid (ketosis with dieting/diabetes)
– kidney failing to remove H+ from protein metabolism

Respiratory compensation by hyperventilation

Treatment
– IV administration of sodium bicarbonate
– correct the cause

124

ACID-BASE BALANCE --

Define:
Metabolic alkalosis

Blood bicarbonate levels are too high

Cause is nonrespiratory loss of acid, e.g. vomiting, gastric suctioning, use of diuretics, dehydration, excessive intake of alkaline drugs

Respiratory compensation is hypoventilation

Treatment
– fluid and electrolyte therapy
– correct the cause

125

ACID-BASE BALANCE --

What are the symptoms of acidosis?

Acidosis causes depression of CNS--- coma

126

ACID-BASE BALANCE --

What are the symptoms of alkalosis?

Alkalosis causes excitability of nervous tissue---spasms, convulsions & death

127

ACID-BASE BALANCE --

Define:
Acidosis

Acidosis is a blood pH below 7.35. Its principal effect is depression of the central nervous system through depression of synaptic transmission.