To maintain ____, what comes into body must eventually be used or excreted
To be in balance:
Input + _____ = ____ + output
When input exceeds output, there is ____
When output exceeds input, there is ____
- Positive balance
- Negative balance
What determines plasma volume?
Kidney regulation of solute and water content
What determines plasma composition?
Exchange b/w diff compartments of the body (cells, connective tissue, GI tract), as well as sweating and respiration
Filtration at ___, then goes to ___, then to ___
- bowman's capsule
- proximal convulated tubule
- distal convulated tubule
Normal blood volume
High blood volume due to positive water balance
Low blood volume due to negative water balance
What are the inputs of water into the body?
- Ingestion (2.2 L/day)
- Cellular metabolism (.3 L/day)
What are the outputs (where is water lost)?
- Excretion from GI tract (.1 L/day)
- Excretion from urine (1.5 L/day)
- Insensible losses (.9/day) (sweating, respiratory system; anything not from GI or urine)
Total water input = total water output = ___ L/day
Diffusion of water down its concentration gradient
In kidneys, water moves from ___ solute to ___ solute, and there is no ____ force for water to move b/w fluid compartments
Primary solute which causes reabsorption of water
Where is 70% of filtered water reabsorbed & is it regulated or not? If so, what is it regulated by?
- Proximal tubules;
- Not regulated (water moves down concentration gradient so body is not controlling reabsorption)
Where is 30% of filtered water reasborbed and is it regulated? If so, what is it regulated by?
- Distal tubules
- Regulated by ADH
What organ controls osmolarity of
Most water is reabsorbed in the ____, due the mvmt of solutes across tubule to capillary which causes a concentration gradient. Water follows these solutes.
How does ADH regulate water reabsorption? What happens w/out ADH present?
Stimulates the insertion of water channels (aquaporin-2) into apical membrane (collecting duct cells) of distal conv tubule. Without ADH, DCT and collecting duct are impermeable to water, and more water is excreted in urine.
Minimum vol of water that must be excreted in the urine per day
Obligatory water loss
Does ADH increase or decrease urine volume?
What happens to GFR and water filtered & excreted when blood pressure is decreased to less than 80 mmHg?
- GFR is decreased
- Water filtered is decreased
- Water excretion is decreased
What happens to GFR and water filtered & excreted when blood pressure is increased to over 180 mmHg?
- GFR is increased
- Water filtered is increased
- Water excreted is increased
Basically, chgs in GFR work to limit water loss when bp is ___ and increase water loss when bp is ___.
What are the terms for high and
low blood sodium?
Primary solute in ECF which is critical for normal osmotic pressure and to function of excitable cells
Is sodium filtered? Where is sodium reabsorbed? Is sodium secreted?
Sodium is freely filtered and has unregulated reabsorption in proximal tubule, but regulated reabsorption in distal tubule and collecting duct. No.
What regulates sodium reabsorption in distal tubule and collecting duct (thereby regulating water reabsorption)?
Aldosterone (which is secreted from adrenal cortex) and ANP
Steroid hormone secreted from adrenal cortex
How does aldosterone control sodium reabsorption?
On distal tubule cells and collecting duct cells, increases number of Na/K pumps on basolateral membrane, and increases number of open Na/K on apical mem. This increases amt of Na that can move out and be reabsorbed.
___ secretes angiotensinogen
___ secretes renin
___ contains ACE
___ secretes aldosterone
- Kidney juxtaglomerular cells
- Capillary walls
- Adrenal cortex
Enzyme that converts angiotensinogen to angiotensin I
Enzyme that converts angiotensin I to angiotensin II
ACE (agniotensin-converting enzyme)
___ causes secretion of aldosterone from the adrenal cortex
ACE inhibitor decrases amt of ____ produced, which ____ blood vol, which decreases blood pressure
What is the main purpose of renin-angiotensin-aldosterone system?
Controlling uptake of sodium and water
How does angiotensin II affect blood pressure OTHER than by causing aldosterone release? (3)
- Increases mean arterial pressure (MAP) via:
- Vasoconstriction of systemic arterioles
- ADH secretion
- Stimulating thirst
- (Increases amt of water retained)
What stimulates renin release from kidney juxtaglomerular cells? (3)
- Decreased pressure in afferent arteriole
- Renal sympathetic nerve activity
- Decreases in Na+ and Cl- in distal tubule filtrate (causes water retention)
Where is atrial natriuretic peptide secreted & what causes it?
Secreted by artial cells in response to distension of atrial wall
Has opposite action of aldosterone. Increases GFR, causing dilation of afferent arteriole and constrctoin of efferent arteriole. Causes more Na excretion by closing Na channels in apical membrane
Atrial Natriuretic Peptide
___: high plasma K+
___: low plasma K+
___ is an ion which is crucial to the functioning of excitable cells, such as heart cells and neurons
Where is potassium filtered? Is potassium secreted or reabsorbed and where does this take place?
- Filtered in glomerulus freely
- Reabsorbed in proximal tubules
- Both reabsorbed and secreted in distal tubules and collecting ducts (regulated secretion)
How does aldosterone affect
potassium levels in the blood?
B/c it controls Na; Na affects K+ secretion
In the proximal tubule, K+ is reabsorbed b/c of ___ channels in the ____ membrane. In distal tubule and collecting duct cells, K+ is secreted b/c of ___ channels in the ___ membrane.
- potassium; basolateral membrane
- potassium; apical membrane
Inner portion of membrane of cells which line a tubule (tubule epithelial cells)
Outer portion of membrane of cells which line a tubule (tubule epithelial cells)
Outside layer of tubule
Space b/w tubule and capillary
___: high plasma calcium
___: low plasma calcium
Calcium balance is critical b/c it triggers ___ contraction, increases contractility of ___ and ___, and triggers ____.
- cardiac and smooth muscle
When & where is calcium filtered, and when is it not?
- Filtered when there is free plasma calcium; freely filtered in glomerulus
- Not filtered when calcium is bound to proteins
Where does calcium reabsorption occur?
- Unregulated in proximal tubules
- Regulated in thick ascending limbs of loops of Henle & distal tubules
(filtered in glomerulus, reabsorbed in tubules)
What is the most important reason blood pH must be maintained?
To prevent chgs in protein structure
Acid-base disturbance causes:
Change in ___
Change in nervous system: ___
Change in ___ balance
Heart prob: ___
Dilation of ____
- Change in protein structure conformation
- Change in nervous system: excitability of neurons chgsChange in K+ balance
- Heart prob: Cardiac arrhythmiasDilation of blood vessels
What are the inputs of acid from both diet and metabolism? (cause increase in H+ concentration in blood)
- Diet: proteins & fats
- Metabolism: CO2, lactic acid, keto acids
What are the outputs of acids? ie what organs compensate for acid inputs & how do they do it?
- Kidneys excrete H+ ions
- Respiratory system clears the blood of CO2
What are the three defense mechanisms against acid-base disturbances? (in order of occurance)
- 1. Buffering of H ions
- 2. Respiratory compensation
- 3. Renal compensation
How does the body buffer H+ ions extracellularly and intracellularly?
- ECF: via bicarbonate (HCO3- + H+ <--> H2CO3)
- ICF: via proteins and phosphates [protein- + H+ <--> Hprotein] and [H(PO4)2- + H+ <--> H2(PO4)-]
(ie ECF, carbonate takes H; ICF, proteins and phosphates take H)
How does the respiratory system buffer H+ ions? How long to take effect?
- By varying ventilation:
- Increased acidity --> Increased ventilation --> decreased CO2 --> (leads to increase in basicity) (neg feedback)
- Takes minutes
How does the renal system buffer H+ ions? How long to take effect?
- Regulates excretion of H+ ions and bicarbonate in urine
- Regulates synthesis of new bicarbonate in renal tubules
- Takes hours to days to take effect
What is the name of the equation can we use to determine acidosis and alkalosis?
What is ratio of HCO3-/CO2 for 7.4 pH, acidosis, and alkalosis?
- pH 7.4: 20.1
- Acidosis: <20:1
- Alkalosis: >20:1
___: increase in plasma CO2
___: decrease in plasma CO2
- Respiratory acidosis
- Respiratory alkalosis
Decrease in pH through something other than CO2
Increase in pH through something other than CO2
Causes of metabolic acidosis:
Loss of ___ from ___
- High protein diet
- High fat diet
- Heavy exercise
- Loss of bicarbonate from severe diarrhea
- Renal dysfunction
Causes of metabolic alkalosis:
Loss of ___ from ___
- Loss of H ions from excessive vomiting
- Alkaline diet (baking soda)
- Renal dysfunction