Fluid and electrolyte balance

Question 1

What are the 4 parameters in which homeostatic mechanisms maintain fluid/electrolyte balance

Answer 1

-Fluid volume
-Osmolarity
-Concentrations of individual ions
-pH

Question 2

Describe fluid and electrolyte balance

Answer 2

Question 3

How does ECF osmolarity affect cell volume

Answer 3

Question 4

How is fluid and electrolyte balance an integrative process

Answer 4

Question 5

Describe water balance

Answer 5

Question 6

How do kidneys conserve water

Answer 6

Question 7

How does the renal medulla create concentrated urine

Answer 7

Question 8

How does vasopressin control water reabsorption

Answer 8

Question 9

Describe vasopressin induced aquaporin insertion

Answer 9

Question 10

What stimuli control vasopressin secretion?

Answer 10

Question 11

Explain vasopressin (AVP) production and secretion

Answer 11

Secretion:
-Increased osmolarity
-Decreased blood volume
-Decreased blood pressure

Question 12

What creates the hyperosmotic interstitium and why isn’t it reduced as water is reabsorbed?

Answer 12

Question 13

What is the renal countercurrent exchange system

Answer 13

Question 14

What is the function of the counter current multiplier (loop of henle)

Answer 14

Question 15

What is the function of the counter current exchanger (vasa recta)

Answer 15

Question 16

Explain active transport in the loop of Henle

Answer 16

Question 17

How does urea contribute to the osmolarity of the medullary intersitium

Answer 17

Question 18

Summarize the components involved in water balance

Answer 18

Question 19

Explain homeostatic responses to salt ingestion

Answer 19

Question 20

How does aldosterone help control Na+ balance

Answer 20

Question 21

Explain how aldosterone acts on principle cells

Answer 21

Question 22

Explain aldosterone secretion

Answer 22

Question 23

Explain the Renin-Angiotensin pathway

Answer 23

Question 24

What are the effects of angiotensin II

Answer 24

Question 25

How do pharmaceutical companies treat hypertension

Answer 25

Use ACE inhibitors -Preventing the conversion of ANGI to ANGII leads to relaxation of the vasculature and lower blood pressure -other options include AT receptor antagonists and renin inhibitors

Question 26

What is atrial natriuretic peptide (ANP) and how does it promote Na+ and water excretion?

Answer 26

-Peptide hormone produced and secreted by specialized myocardial cells primarily in the atria of the heart -increased blood volume causes increased stretch of the atria, causing the specialized myocardial cells to release ANP -Some produced in cardiac ventricles and some neurons in the brain (BNP) brain natriuretic peptide (used as biological marker)

Question 27

Explain the importance of potassium balance

Answer 27

Question 28

what are the behavioural mechanisms of salt and water balance

Answer 28

-Behavioural responses are critical in restoring the normal state, particularly when ECF volume decreases or osmolarity deviates -Drinking water is normally the only way to replace lost water and eating salt is the only way to raise the body's Na+ content -The act of drinking relieves thirst, water does not actually have to be absorbed -unknown receptors in the mouth/pharynx respond to water by decreaseing thirst and decreasing AVP release

Question 29

Explain integrated control of volume and osmolarity

Answer 29

-The CV system responds to changes in blood volume and pressure, the renal system responds to changes in blood volume and/or osmolarity and behavioural mechanisms resond to both \ 1. eating salty foods and drinking liquids at the same time, net results = ingestion of hypertonic saline (salt>water) -Need to excrete solute and liquid to match what was taken in 2. If salt and water ingested is equivalent to isotonic solution 3. Drinking pure water without ingesting solute -Kidneys cannot excrete pure water, so some solute would be lost in this situation, compensation is imperfect 4. Eating salt without drinking water, increases ECF osmolarity shifting water from cells to ECF -Triggers intense thirst and kidneys make concentrated urine 5. Water and solutes would be lost in sweat but only water is replaced -Can lead to hypokalemia or hyponatremia -Sports drinks help to replace fluid and solutes lost 6. Dehydration could be due to heavy excercise (water loss from lungs can double, sweat loss can increase from 0,1-5L) or diarrhea (excessive fluid loss in feces) -can results in inadequate perfusion (decreased blood volume) and cell dysfunction -Increase water intake 7. Hemorrhage, need blood transfusion or ingestion of isotonic solution 8. May result from incomplete compensation for dehydration but is uncommon

Question 30

What are the physiological responses triggered by decreased blood pressure/volume

Answer 30

Question 31

What are the physiological responses triggered by increased blood pressure

Answer 31

Question 32

What are the physiological responses triggered by increased and decreased osmolarity

Answer 32

Question 33

Why is aldosterone not secreted when decreased ECF volume (blood pressure) is caused by severe dehydration?

Answer 33

-During severe dehydration decreased ECF volume (blood pressure) would signal to increase aldosterone release but at the same time an increased osmolarity inhibits aldosterone release -Osmolarity control in this situation reigns and aldosterone is not secreted, if it were that would cause Na+ reabsorption which would worsen the already high osmolarity

Question 34

Explain the function of each mechanism involved in homeostatic response to severe dehydration

Answer 34

Results in: 1. Rapid attempt by the CVCC to maintain blood pressure (depending on volume loss CVCC response may not completely restore pressure) 2. Restoration of volume by water conservation and fluid intake 3. Restoration of normal osmolarity by decreased Na+ reabsorption and increased water reabsorption and intake