Lecture 17 Flashcards
what muscle is especially sensitive to fluctuations in plasma K+
Cardiac muscle
Potassium and what moves in opposite directions in acid base balance
H+
acidosis leads to what effect on K+
rise in extracellular K+
Alkalosis leads to what effect on K+
Higher intracellular levels
what percent of K+ is lost in filtrate
10
Most potassium is reabsorbed where
PCT
Ascending limb of loop of henle
Where is k+ secreted
DCT
principal cells of collecting duct
Why do we need to be constantly eating potassium
Because we secrete so much of it
What effect does aldosterone have on potassium
Increased secretion
Where is most calcium found
In bone
Name 4 things calcium is important for
Muscle contraction
Bone density
NT release
Second messengers
Where is PTH secreted from
Parathyroid glands
What does PTH do
Increases blood calcium
What does PTH sacrifice to maintain blood calcium levels
Bone density
What increases blood calcium levels
PTH
What calcium affecting hormone is important for kids but not adults
Calcitonin
What does calcitonin do
Decreases blood calcium
Stimulates bone deposition, inhibits reabsorption
What percent of filtered calcium is reabsorbed
98
What are the 3 targets of PTH
bone
small intestine
kidneys
Why does PTH have the opposite effect on phosphate than calcium
Phosphate will bind to calcium and decrease the levels in blood
What does PTH target in bone
Osteoclasts
What does PTH target in the small intestine
Activation of Vitamin D
What percent of filtered phosphate is reabsorbed in PCT
75
What process is involved in reabsorption of phosphate
Active transport
How much phosphate is reabsorbed in absence of PTH
up to Tm
How much phosphate is reabsorbed in the presence of PTH
reduced reabsorption
What does calcitonin inhibit
Osteoclasts
What effect does calcitonin inhibiting osteoclasts have
No breakdown of bone to release calcium
What is the arterial pH
7.4
What is the venous pH
7.35
What is the intracellular pH
7.0
Name 4 sources of acid
Breakdown of proteins containing phosphorus
Anaerobic metabolism of glucose
Fat metabolism
Transport of CO2 as bicarbonate
What acid comes from Breakdown of phosphorus-containing proteins
phosphoric acid
What acid comes from anaerobic metabolism of gluocse
Lactic acid
What acid comes from fat metabolism
fatty acids
ketone bodies
What acid comes from loading and transport of CO2 as bicarbonate
H+ ions
What is alkalosis
blood pH higher than 7.45
What is acidosis
blood pH lower than 7.35
What is a strong acid
Acid that fully dissolves in a solution
What is a weak acid
One that doesn’t dissolve completely in a solution
Are buffers weak or strong acids
weak
How does a buffer being a weak acid help the acid base balance
They have the ability to soak up hydrogen ions
Name the three ways blood H+ levels are regulated
Chemical buffer systems
Respiratory center in brain stem
Renal mechanisms
What is the fastest way to regulated H+ in blood
Chemical buffer system
What is the slowest way to regulate blood H+
Renal mechanism
Name the regulatory of H+ mechanisms in order from fastest to slowest
CHemical buffer
Respiratory
Renal
Name the blood H+ regulatory mechanisms in order of most to least effective (in terms of capacity etc)
Renal
Respiratory
Chemical buffer
Why is it difficult to reabsorb bicarbonate
Tubule cells are almost completely impermeable to bicarbonate in filtrate
Why do we need to keep replenishing bicarbonate?
It’s breathed out as CO2
What cation accompanies bicarbonate into peritubular capillaries
Sodium
What surface is inpenetrable to bicarbonate
Apical surface
What is the formula for bicarbonate
HCO3-
What is the formula for carbonic acid
H2CO3
Describe the pathway that a bicarbonate ion must take to get into the brush border cell
Converts to carbonic acid with a H+
Carbonic acid converts to H20 and CO2
H2O and CO2 go into brush border cell
They get converted to carbonic acid again
Carbonic acid turns into H+ and bicarb
How does bicarbonate get into the peritubular capillaries from the brush border cell
It either uses sodium as a cotransporter or chlorine as an antiporter
When a H+ enters the filtrate, what takes it’s place
A sodium ion
What are the two ways to create new bicarbonate ions
Phosphate buffer system
NH4+ excretion
What is the weak base in the phosphate buffer system
HPO4 2-
Is HPO4 2- a weak or strong base
Weak
When is 75% of phosphate NOT reabsorbed
During acidosis
What type of brush border cell in the collecting duct actively secrete H+
Type A intercalated
How does the phosphate buffer system work
In the brush border cell, water and co2 make carbonic acid, which turns into hco3 and h+.
The h+ is secreted into the filtrate binding to hpo42- to make h2po4-.
New bicarb gets into capillary via cl antiporter
how is bicarbonate generated in PCT cells with NH4+ secretion
by metabolism of glutamine
What is the amino acid used to make bicarb
glutamine
What is glutamine
The aa used to generate new bicarb
How many new bicarbs are made via gluatmine
2
What are the products of glutamine metabolism in the PCT
2 NH4+ (ammonium)
2 HCO3-
Is NH4+ a weak or strong acid
Weak
When do we deal with bicarb excretion
only during alkalosis
What type of cells in the collecting duct function to get rid of bicarbs
Type B intercalated cells
What causes respiratory acidosis
Hypoventilation
When does respiratory alkalosis occur
hyperventilation
Why does hyperventilation cause respiratory alkalosis
They breathe out more CO2 than normal, makes the pH higher
If a rxn shifts to the left, what is produced more
Reactants
If a rxn shifts to the right, what is produced more
Products
Adding more reactants causes the reaction to shift to the
RIght
Increase in product causes the reaction to shift
Left
Decrease in product causes the reaction to shift
Right - more product
Decrease in reactant causes the rxn to shift
Left - make more reactant
How does hypoventilation cause respiratory acidosis
You can’t eliminate enough CO2, causing your pH to lower
What can cause metabolic acidosis
Getting rid of bicarb too quickly, diarrhea, alcohol, ketone bodies, kidneys arent getting rid of acid
What can cause metabolic alkalosis
Too little acid in the body
Lots of vomiting - more bicarb, eating too much sodium bicarb, too much aldosterone
Respiratory based pH disturbances center around which molecule
CO2
Metabolic based pH disturbances center around which molecule
HCO3-
Is co2 acidic or basic
Acidic
Is HCO3- acidic or basic
Basic
pH : 7.6
C02 : 24 mmHg (35-45)
HCO3- : 23 (22-26)
Resp alkalosis, not compensating
pH : 7.48 (7.35-7.45)
C02 : 46 mmHg (35-45)
HCO3- : 33 (22-26)
Metabolic alkalosis
Compensating slightly
pH : 7.3 (7.35-7.45)
C02 : 68 mmHg (35-45)
HCO3- : 28 (22-26)
Respiratory Acidosis, Compensating
pH : 7.0 (7.35-7.45)
C02 : 23 mmHg (35-45)
HCO3- : 12 (22-26)
Metabolic acidosis, compensating
pH : 7.6 (7.35-7.45)
C02 : 31 mmHg (35-45)
HCO3- : 25 (22-26)
Respiratory Alkalosis Not compensating
