Exam 4: Regulation of Na, Osmolarity, and ECF Flashcards
What does unregulated or insensible fluid loss come from?
Sweat
Stool
Respiratory
What does regulated fluid loss come from?
Renal (urine)
What does unregulated or insensible electrolyte loss come from?
Sweat
Stool
What does regulated electrolyte loss come from?
Renal
When does water diuresis in a normally hydrated person occur?
After ingestion of 1 L H2O
What does excessive water consumption have a little change in?
Plasma mOsm
Urine electrolyte concentration
What does excessive water consumption have a big change in?
Urine mOsm
Urine production
What is water consumption primarily regulated by?
ADH
What is very efficient at absorbing water?
GI tract
What is the formation of dilute urine?
Ingest a large amount of electrolyte free water in excess of needs
Continue to reabsorb electrolytes
Decrease reabsorption of H2O
Decrease ADH release
What is the ability to form concentrated urine dependent on?
Antidiuretic hormone
Renal medullary hypertonicity
What is the formation of concentrated urine?
Continue to reabsorb electrolytes
Increase reabsorption of H2O
Increase ADH release
How is the renal medullary tonicity created and maintained?
The counter-current multiplier mechanism
Describe parallel current flow transfer
Diffusion constant
Time/flow ratio
Once equilibrium established–no further exchange
Less transfer that counter current flow
Describe counter current flow transfer
Diffusion constant
Time/flow ratio
But overall greater transfer than parallel flow–utilizes the whole contract area
What is involved in the regulation of ADH?
Na Blood pressure Thirst control Alcohol α2-agonist
Which has a greater impact on ADH secretion and thirst stimulation, osmolarity or pressure/volume?
Osmolarity
What does blood loss result in?
Loss of fluid and Na equally
What kind of fluid is horse sweat?
Isotonic
What are local renal mechanisms of ECF volume regulation?
Changes in GFR
Changes in tubular reabsorption
Changes in tubular secretion
Changes in hormones
What are systemic mechanisms of ECF volume regulation?
Changes in hormones
Changes in sympathetic activity
Changes in blood pressure
Changes in blood composition
What does angiotensin do?
Stimulates aldosterone
Constricts efferent arterioles
Directly increases sodium reabsorption
Increases systemic BP
What does aldosterone do?
Stimulate Na reabsorption
H2O tends to follow
Complete lack of results in relying only on pressure natriuresis, requires close management
What does ADH do?
Promotes water retention
What does ANP do?
It blocks angiotensin, aldosterone, and ADH
