WGU pathophysiology D236
1. What is Starling's Law of Capillary forces?
How does this explain why a nutritionally deficient child would have edema?-
ANSWER Starling's Law describes how fluids move across the capillary membrane. There are two major opposing
forces that act to balance each other, hydrostatic pressure (pushing water out of the capillaries) and osmotic
pressure (including oncontic pressure, which pushes fluid into the capillaries).
,Both electrolytes and proteins (oncontic pressure) in the blood attect osmotic pressure, high electrolyte and protein
concentrations in the blood would cause water to leave the cells and interstitial space and enter the blood stream to
dilute the high concentrations.
On, the other hand, low electrolyte and protein concentrations (as seen in a nutritionally deficient child) would cause
water to leave the capillaries and enter the cells and interstitial fluid which can lead to edema.
2. How does the RAAS (Renin-Angiotensin-Aldosterone System) result in in-
creased blood volume and increased blood pressure?
ANSWER A drop in blood pressure is sensed by the kidneys by low perfusion, which in turn begins to
secrete renin.
Renin then triggers the liver to produce angiotensinogen, which is converted to Angiotensin I in the lungs and then
angiotensin II by the enzyme
,Angiotensin-converting enzyme (ACE). Angiotensin II stimulates peripheral arterial vasoconstriction which raises BP.
Angiotensin II is also stimulating the adrenal gland to release aldosterone, which acts to increase sodium and water
reabsorption increasing blood volume, while also increased potassium secretion in urine.
3. How can hyperkalemia lead to cardiac arrest?
ANSWER Normal levels of potassium are between 3.5 and 5.2 mEq/dL. Hyperkalemia refers to
potassium levels higher that 5.2 mEq/dL.
A major function of potassium is to conduct nerve impulses in muscles. Too low and muscle weakness occurs and too
much can cause muscle spasms.
This is especially dangerous in the heart muscle and an irregular heartbeat can cause a heart attack
4. The body uses the Protein Buffering System, Phosphate Buffering System,
and Carbonic Acid-Bicarbonate System to regulate and maintain homeostatic
, pH, what is the consequence of a pH imbalance
ANSWER Proteins contain many acidic and basic group that can be attected by pH changes. Any increase
or decrease in blood pH can alter the structure of the protein (denature), thereby attecting its function as well
5. Describe the laboratory findings associated with metabolic acidosis, metabol-
ic alkalosis, respiratory acidosis and respiratory alkalosis. (ie relative pH and
CO2 levels).
ANSWER Normal ABGs (Arterial Blood Gases) Blood pH
: 7.35-7.45 PCO2: 35-45 mm Hg PO2
: 90-100 mm Hg HCO3-
: 22-26 mEq/L SaO2
: 95-100%
Respiratory acidosis and alkalosis are marked by changes in PCO2. Higher = acidosis and lower = alkalosis
1. What is Starling's Law of Capillary forces?
How does this explain why a nutritionally deficient child would have edema?-
ANSWER Starling's Law describes how fluids move across the capillary membrane. There are two major opposing
forces that act to balance each other, hydrostatic pressure (pushing water out of the capillaries) and osmotic
pressure (including oncontic pressure, which pushes fluid into the capillaries).
,Both electrolytes and proteins (oncontic pressure) in the blood attect osmotic pressure, high electrolyte and protein
concentrations in the blood would cause water to leave the cells and interstitial space and enter the blood stream to
dilute the high concentrations.
On, the other hand, low electrolyte and protein concentrations (as seen in a nutritionally deficient child) would cause
water to leave the capillaries and enter the cells and interstitial fluid which can lead to edema.
2. How does the RAAS (Renin-Angiotensin-Aldosterone System) result in in-
creased blood volume and increased blood pressure?
ANSWER A drop in blood pressure is sensed by the kidneys by low perfusion, which in turn begins to
secrete renin.
Renin then triggers the liver to produce angiotensinogen, which is converted to Angiotensin I in the lungs and then
angiotensin II by the enzyme
,Angiotensin-converting enzyme (ACE). Angiotensin II stimulates peripheral arterial vasoconstriction which raises BP.
Angiotensin II is also stimulating the adrenal gland to release aldosterone, which acts to increase sodium and water
reabsorption increasing blood volume, while also increased potassium secretion in urine.
3. How can hyperkalemia lead to cardiac arrest?
ANSWER Normal levels of potassium are between 3.5 and 5.2 mEq/dL. Hyperkalemia refers to
potassium levels higher that 5.2 mEq/dL.
A major function of potassium is to conduct nerve impulses in muscles. Too low and muscle weakness occurs and too
much can cause muscle spasms.
This is especially dangerous in the heart muscle and an irregular heartbeat can cause a heart attack
4. The body uses the Protein Buffering System, Phosphate Buffering System,
and Carbonic Acid-Bicarbonate System to regulate and maintain homeostatic
, pH, what is the consequence of a pH imbalance
ANSWER Proteins contain many acidic and basic group that can be attected by pH changes. Any increase
or decrease in blood pH can alter the structure of the protein (denature), thereby attecting its function as well
5. Describe the laboratory findings associated with metabolic acidosis, metabol-
ic alkalosis, respiratory acidosis and respiratory alkalosis. (ie relative pH and
CO2 levels).
ANSWER Normal ABGs (Arterial Blood Gases) Blood pH
: 7.35-7.45 PCO2: 35-45 mm Hg PO2
: 90-100 mm Hg HCO3-
: 22-26 mEq/L SaO2
: 95-100%
Respiratory acidosis and alkalosis are marked by changes in PCO2. Higher = acidosis and lower = alkalosis
