Urinary System Flashcards
What system varies the concentration of urine?
Medullary countercurrent system
What is the range in osmolarity in urine?
100-1200
What is osmolarity of urine when body is in perfect balance?
300
What is rate of 300 mOsm
1 ml/min
What is osmolarity of hypotonic urine
Less than 290
Rate of excretion if over hydrated
25ml/min
What is osmolarity of urine with dehydration
Greater than 290-300
Rate of urine production if dehydrated
0.3 ml/min
True/false: osmotic gradient in renal medulla persists and allows reabsorption of h2o regardless of hydration
True
Where is the highest osmotic gradient in kidney?
Medulla near renal pelvis
What structure creates osmotic gradient?
Juxtamedullary loops of henle
What part of all nephrons use the osmotic gradient to vary h2o concentration?
Distal tubules and Collecting ducts
What is descending loop permeable to?
H20
What is descending loop NOT permeable to?
Na+
What is ascending loop permeable to?
Na+
What is ascending loop NOT permeable to?
H20
What will raise osmolarity of interstitial space of medulla?
Sodium
What is osmolarity of urine in ascending loop?
100
If no more h20 is reabsorbed in distal and collecting duct, what is osmolarity of urine?
100
If h20 is reabsorbed at distal and collecting, what is max osmolarity of urine?
1200
What is another name for vasopressin?
ADH
Where is AHD produced?
Hypothalamus
Where is ADH released from?
Posterior pituitary
What does ADH bind to in kidneys?
Receptors at epithelial cells in distal and collecting duct
What type of system does ADH act through?
2nd messenger
What does ADH increase in renal cells?
Cyclic AMP
What does cyclic amp increase in renal cells do?
Increases # of lumenal Aquaporins
What does an increase in ADH do?
Increases concentration of urine because is causes more h20 to be absorbed
True/false: ADH cause h20 reabsorption independent of Na+
True
Kidneys play a part in long term regulation of plasma volume. This affects what long term?
BP
Decrease in Na does what to ECF (plasma) volume
Decreases it
How does body monitor plasma volume?
By BP regulation
What sensory receptors monitor BP
Baroreceptors
What 2 baroreceptors monitor short term regulation (few minutes) of BP?
Aortic arch
Carotid sinus
Which baroreceptors monitor long term BP regulation?
Renal baroreceptors
Why can renal baroreceptors monitor BP long term?
They never adapt to BP change; have a set point
Where are renal baroreceptors located?
Juxtamedullary apparatus
How do kidneys regulate blood pressure?
By controlling blood volume
How do kidneys control blood volume?
By controlling sodium
What part of JXA sense pressure of afferent arteriole and monitors BP constantly?
Granular cells
If BP decreases, what enzyme do granular cells release to increase blood volume?
Renin
What does renin do?
Converts a protein produced by liver (angiotensinogen) to angiotensin 1
What is angiotensin 1?
Hormone
Is angiotensin 1 active?
No
What converts A1 to A2?
Angiotensin converting enzyme (ACE)
Where are high levels of ACE found?
Organs (Lungs)
Is A2 active hormone?
Yes
What does A2 do?
Increases blood Na+ and volume
What is considered the rate limiting enzyme in the production of A2?
Renin
How does A2 increase Na+ absorption?
Acts on adrenal cortex to make aldosterone
How does aldosterone increase plasma volume?
Increases Na+ absorption on distal and collecting
How does vasoconstriction from A2 affect plasma volume?
1) Raise systemic BP
2) decrease urine production
3rd way A2 increases plasma volume
Enhances auto regulation system to decrease GFR
Does A2 stimulate Na/H exchangers in proximal to increase net Na+?
Yes
5th way A2 increases plasma volume
Stimulates thirst and ADH release in hypothalamus
Summary of how A2 changes plasma volume
1) increases Na+ reabsorption
2) decreases GFR
3) increase h20 intake and absorption
2 elements that control body water
1) kidneys
2) thirst
True/false: control of h20 thru kidneys and thirst is a negative feedback loop
True
Where does negative feedback of water control start
Hypothalamus
Part of brain near hypothalamus that sense plasma composition
Circumventricular organs (CVO)
What are 2 Central Osmo Receptors
SFO
OVLT
If plasma is too concentrated, what does hypothalamus release from posterior pituitary
ADH
What does ADH do at distal and collecting
Increase H20 reabsorption
What is plasma osmolarity threshold to release ADH
280 mOsm
What happens if plasma osmolarity falls below 280?
ADH gets shut off and dilute urine is produced
What percent increase above 280 in plasma osmolarity will trigger release of more ADH
1%
What do SFO and OVLT increase if plasma osmolarity increases
Thirst
What part of brain control’s sympathetic nerve activity output
Brain stem
Thirst and ADH get stimulated by
Osmolarity increase
BP decrease
Where is ADH metabolized in body?
Liver
If liver is diseased, what happens to rate of ADH breakdown?
It is diminished and plasma ADH increases (bad)
How does pain, fear, trauma affect plasma osmolarity?
Increase sympathetic activation and inappropriate release of
ADH
What does alcohol consumption do that affects plasma is osmolarity?
Decreases ADH production
Increases dehydration