Renal - Hormonal Regulation of Body SALTS - Lecture 8 Flashcards
What is positive Na balance?
Negative Na balance?
Positive - intake > Na excretion
negative: Intake < excretion
What are the major solutes of ECF?
What are the major determinants of ECF osmolality?
What is the major determinant of ECF volume?
- Na
- Na, Cl, HCO3-
- ECF volume relies on ECF osmolality
increase Na - Increases osmolality - increases H20 reabsorption - decreases osmolality & increases ECF volume
What is ECV? What does this vary directly with in normal individuals?
Portion of ECV volume within the vascular system that is effectively perfusing the tissues
- in normal individuals ECV varies directly with ECF also 1. Volume of vascular system 2. Arterial BP 3. Cardiac Output
Describe how changes in ECF can generate changes in ECV via Arterial BP and Cardiac Output.
Decrease ECF - decrease vascular volume - decrease BP or Decrease CO sensed as decreased ECV
(opposite for increase in ECF)
When are situations in which ECF and ECV vary independently?
DISEASE!
- CHF
- Hepatic Cirrhosis
- Pleural Effusion
What happens in the following conditions?
- Increased Cardiac Atrial Stretch
- Pulmonary Vascular Engorgement
- Increased Cardiac Atrial Stretch –> increased ANP = NATRIURESIS (excretion of Na in urine)
- Pulmonary Vascular Engorgement –> decreased sympathetics & decreased ADH!
= Water Diuresis
What are the 4 afferent sensors monitoring the effective circulating volume?
- Low-Pressure Sensors (venous side of circulation
- atrial stretch
- pulmonary engorgement - High Pressure Sensors (arterial side)
- aortic arch/carotid sinus
- slow tubular flow - Hepatic Sensors
- increased liver pressure
- increased portal vein Na sensors - CNS sensors for Na
- increased Na in carotid artery & CSF
Describe the end result of the following:
- High Pressure Sensors (arterial side)
- aortic arch/carotid sinus
- slow tubular flow
- High Pressure Sensors (arterial side)
- aortic arch/carotid sinus: decrease sympathetics & ADH
- slow tubular flow: stimulation of JGA which increases renin
Describe the end result of the following:
- Hepatic Sensors
- increased liver pressure
- increased portal vein Na sensors
- Hepatic Sensors
- increased liver pressure: decreased sympathetics & Increased Na excretion
- increased portal vein Na sensors: decreased sympathetics & Increased Na excretion
Describe the end result of the following:
- CNS sensors for Na
- increased Na in carotid artery & CSF
- CNS sensors for Na
- increased Na in carotid artery & CSF :
decreased sympathetics & increased Na excretion
What are the efferent effectors regulating effective circulating volume? (3)
- Renal Sympathetic Nerves (salt retention or excretion)
- RAA system: SALT RETENTION
- ANP: Salt excretion
What 3 factors are important in stimulating renin secretion?
- Perfusion Pressure: when reduced, afferent arteriole senses & secretes renin
- Sympathetic Nerve Activity: activation of the fibers that innervate afferent arterioles increases renin (b-adrenergic)
- Delivery of NaCl to the Macula Densa :
tubuloglomular feedback
- decreased delivery of NaCl causes enhanced Renin secretion
When there is increased NaCl sensed by the macula densa in Tubuloglomular Feedback, is renin secretion increased or decreased?
What about increased sympathetic activity?
Decreased perfusion?
- Increased NaCl - Renin secretion REDUCED
- Increased sympathetic = increased Renin
- Decreased perfusion = increased renin
Where is ACE found? What is its function?
In the lung
- functions to convert Angiotensin I to Angiotensin II
What is the function of angiotensin ii? (3)
- Sympathetic Vasoconstriction of afferent arteriole (granular cells)
- Stimulate ADH release from posterior pituitary & thirst
- Stimulate Aldosterone release from adrenal cortex to add new Na-K ATP as pumps
What hormone causes the production of new Na-K ATP as pumps? What is the purpose of these pumps?
Aldosterone
- increase Na reabsorption & K+ secretion & Excretion
- enhanced NaCl reabsorption by proximal tubule, thick ascending limb, distal tubule, and collecting duct
- increase Na reabsorption means increased water reabsorption
Where is angiotensionogen produced?
Liver
The main overall affect of the RAA system is what?
Decrease Na+ and Water excretion
What is the source of ANP? Urodilatin?
ANP - cardiac atria
Urodilatin - kidney (endogenously produced)
What stimuli promote ANP release? (3)
- Increased ECFV
- Increased Arterial Pressure - BP
- Increased Venous Pressure - BP
What are the affects of ANP? (4)
- Decreased ADH –> water diuresis
- Increased GFR –> Natriuresis (increased na excretion)
- Decreased Aldosterone –> decreased Na reabsorption
- Decreased Renin –> decreased AT-II –> decreased Aldosterone (indirect) –> decreased Na reabsorption
What is achieved when Na excretion matches Na intake?
net zero Na balance
When does the kidney reabsorb more than 99% of filtered Na+?
During Euvolemia
What is the percentage of Na reabsorbed in the following:
- PT
- TAL
- DT
- CD
- Proximal Tubule - 67%
- TAL - 25%
- DT - 5%
- CD - 3%
What happens during effective circulating volume expansion? What are the 3 integrated responses to increased ECV?
What happens during Effective Circulating Volume Contraction?
- excess body water is wasted by increasing Na excretion
- Increased GFR
- Decreased Na reabsorption in PT
- Decreased Na reabsorption in CD
- the opposite is true for Effective Circulating Volume Contraction –> deficit in body water is conserved by increasing Na reabsorption in PT and CD and decreasing GFR
What are the two most common causes for generalized edema formation?
- Increased Pc (capillary hydrostatic pressure)
2. Decreased pi C (capillary oncotic pressure)
When fluid is lost to the interstitial, what happens to ECV and plasma volume? What are the clinical results of this (4)?
- ECV and Plasma volume DECREASE
- Pulmonary Edema
- Pleural Effusions (expansion of serous fluid spaces)
- Abdominal Ascites
- Edema of Ankles
How can edema fluid be removed? (what can be administered)
Diuretics
Why is CHF considered a vicious cycle of congestion?
Because fluid moves into the interstitial due to increased venous pressure & thus capillary hydrostatic pressure, there is a consequential decrease in Plasma Volume and ECV
- the decreased ECV is detected by baroreceptors
- sympathetic activity is stimulated
- increased NaCl and H20 reabsorption which increases plasma volume and further exacerbates the issue
