13 - Electrolyte Homeostasis PPT (QUIZ 3) Flashcards
Welcome to the last deck for quiz 3! I am going off of what Dr. Allie highlighted in class, with a few cards here and there being information I thought would be good to know. Are you ready?
Which three ions can be found in the bone matrix?
- Phosphate (85% resides here)
- Calcium
- Magnesium
Phosphate and calcium combine to form _____________ which makes up the hard bone matrix of bones and teeth.
Calcium phosphate (this gif took me forever)
What does magnesium help strengthen?
The hard bone matrix of bones and teeth
Where else can phosphate be found?
ICF and ECF
Phosphate is an important component of what monomers?
Nucleotides (for DNA, RNA, ATP synthesis, and more!)
Phosphate is a buffer for what ion?
Hydrogen
How much phosphate should you eat per day?
1 gram
What percentage of phosphate will be filtered by glomerular capillaries?
90%
Where will filtered phosphate be reabsorbed and what percentage?
In the PCT, 70%
What cotransporter helps reabsorb phosphate?
Sodium-phosphate cotransporter (it’s in the name)
What happens when phosphate hits its transport maximum (TM) in the body?
The remaining phosphate gets excreted.
Parathyroid hormone inhibits which cotransporter?
Sodium-phosphate cotransporter
PTH’s inhibition on the sodium-phosphate cotransporter does what exactly?
It decreases phosphate’s TM (more phosphate gets excreted) which increases phosphaturia (increased wasting of phosphates in urine).
Why would we need to release PTH if all it’s doing is suppressing phosphate? That’s a bad thing right?
WRONG! It is good, because when the body is breaking down bone matrix to retrieve calcium, phosphate also gets released. We need the calcium, not the phosphate. Therefore the excess phosphate from bone matrix breakdown gets excreted.
Where is calcium MOST present?
BONES!!! (99%)
Where is the other 1% of calcium found?
In ICF and ECF, specifically in the plasma
What are the three fates of the ICF/ECF calcium?
- It can be bound to albumin
- It can be bound to an anion like phosphate or citrate (make sens rye)
- The rest is ionized or in a free state
Where can we get calcium in our diet?
Dairy
Where is 67% percent of filtered calcium reabsorbed?
In the PCT (note: that “67% reabsorbed” number is the same amount as sodium)
Where does 8% of calcium get reabsorbed and monitored by PTH?
In the DCT
PTH ____________ blood calcium levels.
increases
When blood calcium level decreases, PTH is released on what three organs?
- Bones (activates osteoclasts)
- Intestines (increases Ca2+ absorption)
- Kidneys (increases Ca2+ reabsorption)
What other two molecules regulate calcium homeostasis?
- Calcitonin (related to osteoblasts)
- Vitamin D (promotes Ca2+ reabsorption)
- Calcitonin does the exact opposite of PTH, it __________ plasma Ca2+ levels and __________ renal Ca2+ excretion.
(A) decreases; increases
(B) increases; decreases
(C) decreases; decreases
(D) none of these
(A) decreases; increases
Magnesium- nature’s muscle relaxer. Where’s it found in highest quantity?
- Bones
- Skeletal muscles
What food contains Mg2+?
Obviously there’s more but there’s only one example on the slides now after we crossed the others out.
Kale
How much Mg2+ should you consume a day?
400mg
Where is magnesium absorbed?
The GI tract
What filters 80% of plasma Mg2+?
Glomerular capillaries
Why can’t 100% of plasma Mg2+ be filtered by glomerular capillaries?
Some of it is bound to proteins!
Potassium (K+) time! Where is most of our potassium found?
In the ICF (98%)
How is potassium removed from our cells?
- Through sweat
- GI tract
- Kidneys (excreted)
K+ balance depends on total amount of potassium in the body, which boils down to what two factors?
Potassium intake vs potassium excretion (External potassium balance)
K+ balance also depends on what factor (besides external potassium balance)?
Internal potassium balance: distribution of K+ between ICF and ECF
What does -emia signify?
Blood
What is hyperkalemia?
When K+ excretion is less than K+ intake (POSITIVE K+ BALANCE)
What is hypokalemia?
When K+ excretion is more than K+ intake (NEGATIVE K+ BALANCE)
Where does 67% of potassium get reabsorbed after crossing glomerular capillaries?
The PCT
In the thicc ascending loop of Henle, how is potassium reabsorbed?
Using the sodium-potassium-chloride cotransporter!
Which two structures are responsible for adjusting the amount of K+ excreted?
The DCT and collecting duct
What’s a helpful fact to remember about aldosterone?
Aldosterone keeps less K+
(TRUE/FALSE): Aldosterone regulates K+ homeostasis.
(TRUE)
How does aldosterone regulate K+ homeostasis?
It increases sodium and water reabsorption to bring BP back up, which results in increased K+ secretion.
Eating a diet high in K+ could lead to hyperkalemia. Luckily, lots of insulin gets released to do what?
Increase activity of sodium-potassium ATPase, so more potassium can get inside the cell
ATP is required for exercise. Burning ATP opens K+ channels thus increasing ECF K+ concentration. What does this do for your muscles while you exercise?
It dilates skeletal muscle arterioles allowing more blood flow to your muscles!
What’s another way K+ can leave the cells?
Through cell lysis (happens during burns or chemo)
- When cell membranes break down, it leads to _____________.
(A) hyperkalemia
(B) hypokalemia
(A) hyperkalemia
POTASSIUM SHIFT QUESTIONS! When do we observe an outward shift of K+?
(Outward shift meaning it leaves the cell/ICF)
- Decreased insulin
- Cell lysis (burn, chemo)
- H+/K+ exchange in acidosis (H+ into cell, K+ out)
- Increased osmolarity (K+ follows H2O out)
- Exercise (burning ATP)
When do we observe an inward shift of K+?
(Inward shift meaning it enters the cell/ICF)
- Increased insulin
- H+/K+ exchange in alkalosis (K+ into cell, H+ out)
- Decreased osmolarity (K+ follows H2O in)
Na+ balance describes what?
Na+ excretion = Na+ intake
What does Na+ balance determine?
ECF vol, blood vol, BP
What organ is the cornerstone of sodium homeostasis?
THE KIDNEY
67% (the magic number lol) of sodium is reabsorbed where??
The PCT!!! (see you knew that before you saw the answer)
NA+ can be reabsorbed in the thick ascending loop (TAL), the early DCT, and the late DCT/collecting duct. What special factor exists at the late DCT/collecting duct for Na+ reabsorption?
They feature principal cells which have EPITHELIAL SODIUM CHANNELS (ENaC) to respond to aldosterone!
What describes a POSITIVE Na+ BALANCE?
- Increase in Na+ retained
- Increased Na+ in ECF
- ECF expansion
- Increased BV and BP
What describes a NEGATIVE Na+ BALANCE?
- Increased Na+ excretion/loss in urine
- Decreased Na+ in ECF
- ECF contraction
- Decreased BV and “bood” pressure
How do natriuretic hormones respond to increased ECF volume?
They increase GFR and natriuresis (which means renal Na+ and water secretion) thereby lowering ECF volume.
When is atrial natriuretic hormone released?
When volume receptors detect atrial wall stretch, ANP gets released by cells in the atria
When is brain natriuretic hormone released?
LAST CARD!
When volume receptors detect ventricular stretch, BNP gets released by cells in the ventricles
You’re all done! Great work! Now master it!
