Homeostasis, Kidney, and Electrophysiology
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| what is the marker used to measure total body water? | tritiated water
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| what is the marker used to measure extracellular fluid? | inulin and mannitol
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| what is the marker used to measure plasma? | albumin and evans-blue
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| what is the equation for the anion gap? | Na= Cl + HCO3 + 10
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| what is the anion gap? | unmeasured anions
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| what must be present to see the effects of osmotic pressure? | hindrance
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| what is the difference between osmolality and tonicity? | osmolality- concentration of particles per solution; tonicity- refers to whether there is net movement of water
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| what are the starling forces? | favoring filtration- hydrostatic (blood) pressure and COP of interstitial fluid; favoring reabsorption- COP of plasma and tissue pressure
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| what is the equation for plasma osmolality? | P(osm)= 2(Na) + glucose/18 + BUN/2.8
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| what is the difference between garden variety capillaries and glomerular capillaries? | garden variety- filtration and reabsorption so COP is always the same; glomerular- BP is always higher than COP so it's ALWAYS filtration, COP increases along length
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| how much fluid enters the tubule? ie. what is the GFR? | approx. 20% of the RPF ~ 180 L/day
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| what happens to the GFR and RPF when you constrict the afferent arteriole? efferent arteriole? | AA- GFR and RPF decrease; EA- GFR increases, RPF decreases
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| what is splay? | the point where the plasma concentration exceeds the transport maximum
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| what is clearance? | the volume of plasma that is free of a stated material in one minute; the ratio of amount of substance excreted to the plasma concentration
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| what is the equation of clearance? | CL= UV/P = GFR
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| what is inulin and what is its clearance equal to? | inulin is a substance that is filtered at the glomerulus but neither reabsorbed or secreted; its clearance is equal to GFR
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| what is the equation for flow? | flow= UV/(arterial - venous difference)
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| what is the equation for RPF? | RPF= UV/(arterial - 0)
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| what is PAH and what does its clearance equal to? | PAH is a substance that is almost completely cleared from the kidney, thus almost equal to RPF; its clearance is equal to the ERPF (flow through the nephrons)
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| what is the filtration fraction? | FF= GFR/ERPF ~ 20%
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| what is GFR usually measured by? | creatinine
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| what are the 2 variables in creatinine clearance? | GFR x P = k
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| what events happen in the first half of the proximal tubule? | (1) Na/X symport; (2) Na/H antiport; (3) Na/K pump (4) Cl is not transported its concentration is increasing
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| what happens in the second half of the proximal tubule? | (1) Na/H antiport; (2) Na/K pump; (3) Cl is transported in; (4) end result: NaCl reabsorption
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| what is the osmotic classification of reabsorption in the proximal tubule? | isosmotic
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| what happens in the descending limb of the loop of Henle? | passive transport; increased permeability to water
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| what happens in the thick ascending limb of the loop of Henle? | (1) Na/2Cl/K symport; (2) Na/H antiport; (3) Na/K pump; (4) impermeable to water (known as diluting segment)
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| what is the osmotic classification of the thick ascending limb? | limb is hypoosmotic to the solution
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| what happens at the early distal tubule? | (1) Na/Cl symport; (2) Na/K pump; (3) impermeable to water
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| what is the osmotic classification of the early distal tubule? | DT is hypoosmotic to solution
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| what happens in the late distal tubule and collecting tubule? | principal cells secrete aldosterone; alpha intercalated cells secrete H and reabsorb bicarb; beta intercalated cells secrete bicarb and reabsorb H
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| in the distal tubule and collecting duct, what influences water reabsorption? | ADH
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| what are the permeabilities of the descending and thin and thick ascending limbs? | descending limb- highly permeable to water; thin ascending- highly permeable to salt (passive); thick ascending- impermeable to water, but site of very active NaCl transport
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| what happens in the presence and absence of ADH? | presence- urine more concentrated; absence- urine more dilute
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| how is ADH release triggered? (2 ways) | osmoreceptors in hypothalamus and volume receptors
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| what is free water clearance? | the difference between urine volume and osmolar clearance; C(H2O)= V - C(osm)
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| what happens when the free water clearance is positive? negative? zero? | urine is hypoosmotic, hyperosmotic, and isosmotic
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| describe how to differentiate between primary polydipsia, central DI, and nephrogenic DI | first you don't let the patient drink; if the urine osmolality rises, it's primary polydipsia; then you give ADH, if the urine osmolality rises, it's central DI, if not, it's nephrogenic DI
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| describe the renin-angiotensin-aldosterone system | decrease in plasma volume leads to increased renin release from JG apparatus; renin cleaves angiotensinogen in the liver to angiotensis I; angiotensin I is converted to angiotensin II in the lungs; angio II stimulates aldosterone secretion
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| what factors influence renin secretion? | (1) perfusion pressure; (2) sympathetic nerve activity; (3) sodium chloride delivery to macula densa
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| what are the functions of angiotensin II? | (1) stimulation of aldosterone secretion; (2) vasocontriction increasing BP; (3) stiumulation of ADH from posterior pituitary
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| what is the function of aldosterone? | reduces NaCl excretion by stimulating reabsorption by the thick ascend. limb, DT and CT
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| what are the functions of ANP? | (1) vasodilation, increasing GFR and RPF; (2) inhibits renin, aldosterone, and ADH secretion; (3) inhibits NaCL reabsorption by CT
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| what is the stimulus for ANP secretion? | atrial distension which occurs during plasma volume expansion
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| what do diuretics do? | (1) increase rate of elimination of toxic substances; (2) mobilize and reduce edema; (3) control of hypertension
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| what do osmotic diuretics do? | alot of ureabsorbed glucose (diabetics) stays in proximal tubules which holds alot of water, causing polyuria
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| what do carbonic anhydrase inhibitors do? | it reduces reabsorption of bicarb teh secretion of hydrogen; this causes sodium to stuck in the proximal tubule; major side effect is hypokalemia
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| what do thiazides do? | inhibits sodium reabsorption in early distal tubule by Na/Cl symporter
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| what do potassium sparing diuretics do? | it blocks the action of aldosterone on the principle cell of the CT or blocks entry of Na through Na channels; never give to renal failure patients (increase K more)
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| what do loop diuretics do? | they inhibit sodium reabsorption by blocking the Na/2Cl/K symporter in thick ascend limb; VERY potent!
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| what is Gitelman's? | results from a genetic mutation that inactivates thiazide sensitive Na/Cl transport in EDT, leading to hypokalemia and metabolid alkalosis; similar to thiazide abuse
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| what is Barrter's? | several mutations causing inhibition of Na/2Cl/K symporter in ascend limb; similar to loop diuretic abuse
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| what type of ATPases autophosphorylate? | P-type ATPases
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| what are factors that influence ion movement in solution? | diffusion and current flow
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| what the equation for the Nernst potential? | Em= 62 log [K+]o/[K+]i
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| what is accomodation? | the depolarizing shift of threshold with slow stimuli
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| what are some mechanisms responsible for states of membrane refractoriness? | Na channel inactivation and increase in K as K channels open
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| in myelinated nerves, where are the voltage gated Na channels located? the K channels? | Na channels are in the nodes of Ranvier, K channels are in the internodal regions
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| what produces myelin? | Schwann cells (PNS) and oligodendrocytes (CNS)
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| what is the Lloyd/Hunt classification of muscle afferent nerve fibers? | Group I: primary muscle spindle afferents and efferents from tendon organs; II: cutaneous mechanoreceptors; III: deep pressure sensors in muscle; IV: unmyelinated pain fibers
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| what are the presynaptic events in neuromuscular transmission? | AP invades; influx of Ca through Ca channels; ACh released; diffusion of ACh across cleft
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| what are the post synaptic events in neuromuscular transmission? | ACh binds with receptors; activation of cation channel that produces invward Na current (EPC); EPC depolarizes at end-plate region (EPP); EPP initiates AP; contraction of muscle
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| what do synpatotagmin and SNARE complex do? | synaptotagmoin regulates synaptic vesicle exocytosis; SNARE complex causes the fusion so that neurotransmitter can be released
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| what do GABA and serotonin do to presynaptic responses? | GABA inactivates Ca channels so less Ca enters and less ACh is released; serotonin activates Ca channels and causes more Ca and ACh to be released
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| what special thing must ACh do so that the Na and K channels open? | it must bind to 2 sites on the channel
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| what are the 2 types of chemical synapses and what do they do? | excitatory- depolarizes; inhibitory; hyperpolarizes
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