Urinary System, Lecture 5

Question 1

Acid-Base Balance

Answer 1

hydrogen balance:
- strong regulatory (especially arterial [H+]) since many metabolic processes rely on acid-base balance for optimal function
- normal pH arterial blood: 7.35-7.45
alkalosis > 7.45
-> heading towards alkalosis: decreasing acidity /
increasing alkalinity / increase pH / decrease [H+]

acidosis < 7.35
-> heading towards acidosis: increasing acidity
decreasing alkalinity / decrease pH / increase [H+]

Question 2

Chemical Buffering

Answer 2

• 1st line of defense
• immediate response
• in response to alkalosis - H Buffer releases hydrogen and buffer (reaction to right)
• in response to acidosis - hydrogen binds buffer to form H Buffer (reaction to left)
  ◦ temporarily alter hydrogen - does not eliminate
  hydrogen from body or add it to body
  permanently
  my notes:
• if you want more hydrogen ion forcing to the right
• if you want less forcing it to the left
• acidosis; if we have too many hydrogen, we can bound them to something so there is no more hydrogen concentration
• chemical buffers is a temporary thing, not permanent

Question 3

Chemical Buffering - examples (bicarbonate buffer)

Answer 3

• major extracellular buffer
• in response to alkalosis: carbonic acid releases hydrogen and bicarbonate (reaction to right)
• in response to acidosis: hydrogens binds with bicarbonate to form carbonic acid (reaction to left)

Question 4

Chemical Buffering - examples (phosphate buffer)

Answer 4

• one of major intracellular buffers
• in response to alkalosis: dihydrogen phosphate releases hydrogen and mono-hydrogen phosphate (reaction to left)
• in response to acidosis: mono-hydrogen phosphate binds hydrogen to form dihydrogen phosphate (reaction to left)

Question 5

Chemical Buffering - examples (protein buffer)

Answer 5

• one of major intracellular buffers
• in response to alkalosis: protein releases hydrogen (reaction to right)
• in response to acidosis: protein binds hydrogen (reaction to left)

Question 6

Respiratory Mechanisms

Answer 6

• 2nd line of defense
• minute to respond (takes a bit longer to respond than chemical buffering)
  breathing buffering
• lungs alter ventilation to alter carbon dioxide which alters hydrogen
• in response to alkalosis: reduces ventilation to increase carbon dioxide and increase hydrogen (reaction to right)
• in response to acidosis: increase ventilation to decrease carbon dioxide and decrease hydrogen (reaction to left)
• by altering carbon dioxide we can change reaction to left or right
• watch which side the reaction is asking for (if it is stimulus or response)

Question 7

Renal Mechanisms

Answer 7

• 3rd line of defense
• hours or days to respond (takes the longest time to respond)
  urinary buffer
• kidneys alter hydrogen and/or bicarbonate
  my notes:
• more secretion -> less hydrogen
• less secretion -> more hydrogen
• this is the one that can give you a permanent solution

Question 8

Renal Mechanisms (3)

Answer 8

“filtered” bicarbonate:
- not actual same molecule filter that is reabsorbed
“new” bicarbonate:
- involving monohydrogen phosphate and/or glutamate
bicarbonate reabsorbed:
- proximal tubule – 80%
- loop of Henle – 10%
- distal tubule/collecting duct – variable
hydrogen and ammonium secretion:
- proximal tubule – variable for both
- distal tubule/collecting duct – variable for just hydrogen

Question 9

Renal Mechanisms - Summary

Answer 9

in response to acidosis:
- sufficient hydrogen secreted to reabsorb all “filtered” bicarbonate
- more hydrogen secreted to contribute “new” bicarbonate involving phosphate
and glutamine processes
- secreted hydrogen bound to a urinary buffer and voided as part of urinary
excretion
- urine is acidic

in response to alkalosis:
- hydrogen secretion is inadequate to reabsorb all “filtered” bicarbonate, so
significant amounts of bicarbonate are excreted in urine
- little or no secretion of hydrogen in phosphate or glutamine processes, so
little or no “new” bicarbonate
- urine is alkaline