What is extracellular fluid volume dependent on?
Intake and output of fluid and sodium
If the kidneys cannot maintain homeostatic balance of sodium, what 3 systemic adjustments can be made to help?
- Chg blood pressure
- Chg circulating hormones
- Chg in sympathetic nervous system
If the kidneys are damaged and have impaired sodium excretion, what changes can help alleviate this?
Increase blood pressure to maintain normal sodium excretion (but long term high BP is damaging as well)
What is pressure diuresis?
Blood pressure raises & the urinary output increases to compensate and protect the body from BP increase.
What is the term for when blood pressure raises and sodium excretion increases as a result?
Pressure natriuresis
T/F: Pressure natriuresis and pressure diuresis usually occur concurrently.
True
If fluid intake is greater than urine output, where will the fluid accumulate temporarily?
Blood & interstitial spaces (thus incr blood volume and extracellular volume)
T/F: Salt sensitive individuals will see an increase in BP with very little salt intake.
True
Activation of the sympathetic nervous system will cause a dilation or constriction of renal arterioles?
Constriction–> decreased GFR
What are the big 4 hormones regarding kidney influence?
Angiotensin II
Aldosterone
ADH (Vasopressin)
Atrial Natriuretic Peptide (ANP)
Which hormone is considered one of the body’s most powerful controllers of sodium excretion?
Angiotensin II
High levels of sodium lead to (increased/decreased) production of renin?
Decreased
Decreased renin leads to decreased levels of ____, causing an increase in secretion of sodium.
Angiotensin II
T/F: Angiotensin II causes blood volume to increase.
False: Angiotensin II has little impact on extracellular volume or blood volume
Salt sensitive people have __ levels of sodium with a ___ renin secretion.
High; high (these individuals need excessively high BP to cause renin secretion to decrease)
What effect does increased aldosterone have on sodium and water reabsorption?
Aldosterone–> Incr. sodium and water reabsorption
What effect does increased aldosterone have on potassium excretion?
Aldosterone–> Incr. potassium excretion
T/F: When fluid deprived, ADH levels would be increased.
True
What is the effect of increased ADH?
Incr. reabsorption of fluid
Excrete sodium
Is fluid diluted or concentrated when there is an increase in ADH?
Concentrated, (ADH=thirsty and hold onto your fluids)
What causes a release of atrial natriuretic peptide?
Stretch receptors in the cardiac atria
Atrial natriuretic peptide would have what effect on GFR and reabsorption rate of sodium?
GFR would increase,
Sodium reabsorption would decrease, (or increased sodium excretion)
T/F: In a healthy individual, a small increase in arterial pressure will cause an increase in sodium excretion to maintain balance.
True
If fluid and proteins are leaking into the interstitium (edema), how do the kidneys respond?
Retain salt and fluid to restore blood volume
T/F: Congestive heart failure will only cause extracellular fluid volume to increase.
False: Incr. extracellular fluid volume (by 200% or more)
AND incr. blood volume (by 15-20%)
How will nephrotic syndrome & liver cirrhosis affect extracellular fluid volume & blood volume?
(Both conditions have decreased protein)
Increased extracellular fluid volume
Normal blood volume
Where is 98% of the body’s potassium contained?
In cells
T/F: Insulin is important to help uptake potassium into cells after a meal therefore insulin shots are vital for those with diabetes.
True, without insulin shot they may experience symptoms of hyperkalemia
What is aldosterone’s role in potassium balance?
Aldosterone increases cellular uptake of potassium.
What is Conn’s Syndrome and what effect will that have on potassium?
Conn’s= excess aldosterone which will lead to hypokalemia
What effect will Addison’s Disease have on potassium?
Addison’s= deficient in aldosterone which will lead to hyperkalemia
What effect will beta-adrenergic stimulation (ex: epinephrine secretion) have on potassium?
Moves potassium into cells
What is metabolic acidosis?
Increased extracellular potassium levels
Contrast w/ metabolic alkalosis, a decrease in extracellular potassium levels
65% of potassium is reabsorbed in the ___ ___ and 25-30% is reabsorbed in the ___ ascending limb of the loop of Henle.
65%-proximal tubule
25-30%-THICK ascending limb
Daily variations in potassium excretion are handled where?
Late distal tubules
Cortical collecting tubules
What are principal cells and where are they found?
Specialized epithelial cells in the late distal and collecting tubules that secrete potassium for excretion.
What is the 2 step process of principal cells excreting potassium?
- ATPase pump takes K from blood into cell (Na from cell into blood)
- ATPase creates high concentration of K, so K passively moves from cell into lumen for excretion
What are the 3 factors that control potassium excretion via principal cells?
- Na-K ATPase Pump activity
- Electrochemical gradient for K between blood and tubular lumen? ( I think he meant cell and tubular lumen but whatever)
- Permeability of luminal membrane for K
When there is a potassium depletion, no secretion of potassium occurs and reabsorption occurs in the ___ cells.
Intercalated
Does aldosterone stimulate secretion or reabsorption of potassium?
Aldosterone–>secretion of K from principal cells
What is the aldosterone-potassium control system?
Negative feedback system:
Incr. plasma K–> Aldosterone secretion–> K excretion
What is the difference between acute and chronic acidosis with regards to potassium secretion?
Acute= Decreases K secretion (by decreasing Na-K ATPase pump activity Chronic= Increases K secretion
T/F: Alkalosis would result in body increasing potassium secretion.
True
T/F: All enzyme systems & body functions are altered by hydrogen ion concentration.
True
T/F: H+ concentration should be kept high compared to other ions.
False; kept low and tightly regulated
T/F: Arterial blood and venous blood should both have a pH of 7.35.
False: Arterial=7.4 & Venous=7.35
What range is intracellular fluid pH kept at?
6.0-7.4
Urine pH concentration ranges from __ to __.
4.5-8.0
Alkalosis occurs when pH of arterial blood is above what?
7.4
___ occurs when pH of arterial blood is below 7.4.
Acidosis
What is considered the 1st line of defense in regulating changes in H+ concentration?
Acid-base buffering system of fluids (acts w/in seconds)
T/F: The acid-base buffering system of fluids is the first line of defense at eliminating H+.
False: Doesn’t eliminate H+, only ties it up until it can be eliminated
What are the 3 buffers used for acid-base regulation?
Bicarbonate
Phosphate
Proteins (for intracellular buffing)
What is the 2nd line of defense in regulating acids/bases?
Respiratory center (acts w/in minutes)
An increase in ventilation will eliminate __from extracellular fluid, thus eliminating H+ overall.
CO2
What is the 3rd line of defense in regulating acids/bases?
Kidneys (act w/in hours to days)
What is the most powerful of the acid/base regulating systems: fluid buffers, respiratory center, or kidneys?
Kidneys
How can the kidneys control the acid/base balance?
Excreting acidic or basic urine (which is why the pH range varies from 4.5-8.0)
What are the 3 mechanisms done by the kidney for regulating extracellular fluid H+ concentration?
- Secretion of H+
- Reabsorb bicarbonate (HCO3-)
- Production of new bicarbonate (HCO3-)
Where can hydrogen ion secretion NOT occur?
Thin descending and Thin ascending limbs in loop of Henle.
T/F: For each HCO3- absorbed, a H+ is secreted.
True
Most bicarbonate reabsorption occurs in the __ __.
Proximal tubule (80-90%)
Where does 10% of bicarbonate reabsorption occur?
Thick ascending limb (any remainder is taken up in the distal tubule and collecting ducts)
H+ is secreted via what mechanism?
Secondary Active Transport
In what regions are H+ secreted?
Proximal tubule, Thick Ascending Limb, & Early Distal Tubule
T/F: Secretion of H+ is coupled w/ the transport of Na+ into the cell.
True
How much acid is formed from metabolism daily?
80 Eq/L
What are the 2 main buffers in the tubular fluid?
Phosphate
Ammonia
During alkalosis, tubular secretion of H+ is increased or decreased?
Decreased (then not enough H+ to complete HCO3- reabsorption)
During acidosis, tubular secretion of H+ is increased which will have what effect on bicarbonate?
Increased reabsorption of bicarbonate b/c of the surplus of H+.
An increase in pressure of CO2 leads to ___ acidosis.
Respiratory Acidosis
What is metabolic acidosis?
Acidosis that results due to a fall in bicarbonate
T/F: Excess hydrogen ions in the renal tubules causes complete reabsorption of HCO3-
True
How do the kidney’s correct alkalosis?
Incr the ratio of bicarbonate to H+ in the renal tubules
If excess bicarbonate cannot be reabsorbed because H+ secretion levels are too low, what type of urine is produced?
Alkaline urine
When does gluconeogenesis occur?
Fasting period
Which amino acids are primarily used by the kidneys in gluconeogenesis?
Lactate, glutamine, glycerol
Low carbohydrate levels trigger ___ release, which leads to ___ release allowing for protein mobilization.
Corticotropin, cortisol
