Pathophysiology of Sodium Balance Flashcards
T/F: Fat people have a lower fraction of their body weight attributable to water.
T. Since fat contains less water than other tissue, an obeast will have a lower water weight percentage.
ICF and ECF compartments are in ______ equilibrium.
Osmotic
T/F: Urea and other freely permeable solutes effect the movement of water between ECF and ICF.
F. If they are allowed to move freely, they don’t contribute to a gradient.
When will the movement of water across a membrane cease?
- When the concentration gradient dissipates.
2. When the increase in hydrostatic pressure balances out the osmotic pressure.
Do osmotic gradients develop between the vascular and interstitial compartments? Why or why not?
No. The capillary walls are fenestrated and permeable to all sorts of stuff. That’s kind of their job, actually.
How quickly do IV infusions of albumin and dextran cross the capillary wall?
They don’t. They’re much too big to get through the fenestrations.
How quickly do IV infusions of normal saline (.9% NaCl) cross the capillary wall into the interstitial space?
Very quickly. The small molecules can easily cross the barrier.
Definition of effective arterial blood volume. (EABV)
The amount of blood that is detected by volume sensors.
Where are the low-pressure baroreceptors located?
- Cardiac atria
- Left ventricle
- Pulmonary vascular bedr
What role does the brain play in low-pressure baroreceptor control of blood pressure?
In the state of volume expansion, these stretch receptors in the sensory send signals to the medulla and hypothalamus, which then decrease renal SNS activity, leading to a loss of sodium and decreased ECF.
Where are the high-pressure baroreceptors located?
- Aortic arch
2. Carotid bodies at the bifurcation of the carotid.
What role does the brain play in high-pressure baroreceptor control of blood pressure?
In the state of volume contraction, these receptors send a signal to the brain to increase SNS signals to the kidneys. In SEVERE contraction, norepinephrine is also released.
Where are the intrarenal sensors located?
In the JGA that releases renin.
What are the 4 factors that influence renal sodium excretion?
- Glomerular filtration
- Physical factors at the level of the proximal tubule
- Humoral effector mechanisms
- Renal sympathetic nerves.
What is tubuloglomerular feedback? (TGF)
Increased distal delivery of NaCl to the JGA increases arteriolar tone to return GFR to a normal value
What is glomerulo-tubular balance?
Changes in GFR automatically induce proportional changes in tubular reabsorption.
What is “third-spacing?”
Accumulation of fluid in a cavity where it shouldn’t be, leading to ECF depletion
What are Bartter’s Syndrome symptoms?
- Hypokalemia
- Hypomagnesmia
- Metabolic alkalosis
- High renin and aldosterone
- Increased Ca+ excretion
- Normal blood pressure
When does Bartter’s syndrome present?
Early in life
What is the etiology of Bartter’s syndrome?
A mutation in the Na/K/2Cl cotransporter
What is different between Bartter’s and Gitelman’s?
Gitelman’s Syndrome is accompanied by a REDUCED urinary excretion of calcium
When does Gitelman’s present?
In older individuals
What is the etiology of Gitelman’s?
A mutation in the NaCl cotransporter in the distal tubule.
What are the two criteria for orthostatic hypotension?
- A difference greater than 10mmHg in SYSTOLIC pressure between supine and standing
- An increase of greater than 20bpm
