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bio 364 > osmoregulation 4 > Flashcards

osmoregulation 4 Flashcards

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Biology 101 flashcards
1
Q

proximal tubule function

A
  • most solute, salt, nutrient, and water reabsorption
  • excretion of most toxins
  • cells abundant with mitochondria and microvilla, specialized for energy-dependent solute transport
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2
Q

loop of henle descending limb function

A

-water reabsorption

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3
Q

loop of henle ascending limb

A

-solute reabsorption

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4
Q

distal tubule

A

-reabsorption completed for most solutes, plus K+, H+ secretion

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5
Q

collecting duct

A
  • drains multiple nephrons
  • carries urine to renal pelvis
  • final osmotic balance
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6
Q

what compounds are filtrated back out after reabsorption?

A

H+, NH4+, toxins, drugs, K+

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7
Q

proximal tubule filtrate

A
  • Na’s active transport out of prox tube cells allows cotransport of nutrients against their gradients out of lumen and into prox tube cells, with water following by osmosis
  • 2/3 of water and NaCl are filtered by the proximal tubule; remaining filtrate is relatively high in wastes, low in nutrients, and reduced in volume
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8
Q

loop of henle purpose

A

descending and ascending each differential create a countercurrent multiplier for reabsorption of both water at solutes

  • accomplished via descending being permeable only to water, decreasing volume of urine and making it more concentrate (still a net loss of water back into body)
  • ascending limb impermeable to water, and the concentrated urine allows reabsorption by diffusion gradient in ascending limb in lower portion, while solutes are actively transported in upper part, resulting in primary urine becoming more dilute
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9
Q

countercurrent multiplier of loop of henle

A
  • concentrated urine from water reabsoprtion at the descending limb allows reabsorption of solutes by diffusion gradient on the ascending limb
  • this also results in low osmolarity near cortex, and high osmolarity deep in medulla
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10
Q

distal tubule process

A
  • hormones control final absorption of electrolytes and water, and final conc of urine in collecting ducts
  • leaves mostly urea and other wastes in filtrate
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11
Q

distal tubule hormones

A
  • parathyroid hormone
  • aldosterone
  • vasopressin/ADH
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12
Q

aldosterone

A

increases K+ secretion (Na/K ATPase, K channel; active if Na+ blood levels are low, causes reabsorption of NaCl into tissues, with water following by osmosis, reducing urine volume

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13
Q

parathyroid hormone

A

increases Ca2+ reabsorption

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14
Q

vasopressin/adh

A

-increases water reabsorption during dehydration by activating aquaporin expression

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15
Q

struture of distal tubule and collecting duct

A

principal and intercalated cells, the latter containing microvilli, which maintaion acid-base regulation through excretion of H+ and bicarbonate

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16
Q

collecting duct

A
  • drains multiple nephrons
  • carries urine to renal pelvis
  • final osmotic balance
  • further regulation of ion and water balance
  • reabsorption of Na+
  • K+ absorption or secretion
  • pH balance
  • urea reabsorption
17
Q

excretion/micturition

A
  • after urine is produced, it leaves kidney and enters urinary bladder via ureters
  • urine leaves bladder via urethra; schincters of smooth muscle control flow of urine out of bladder, which are controlled by spinal cord reflex arc
18
Q

hormones affecting kidney function

A
  • steroids from adrenal gland, such as aldosterone, are slow response
  • peptide hormones from hypo-pit axis like vasopressin are rapid response
19
Q

dietary factors that affect urine output

A
  • diurectics=stim excretion of water

- antidiuretics=stim water reabsorption

20
Q

glomerular filtration rate

A

-determined by pressure across glomerular wall
-three forces: glomerular capillary hydrostatic pressure
2. bowman’s capsule hydrostatic pressure
3. oncotic pressure=osmotic pressure due to PROTEIN CONC. in blood
(pg 508)

21
Q

glomerular cap hydrostatic pressure determined by

A

cardiac output
systemic bp
efferent artery vasoconstriction

22
Q

bowman’s caopusle hydrostatic pressure is caused by

A

glom cap hydrostatic pressure

23
Q

oncotic pressure caused by

A

osmotic pressure due to protein conc in blood

24
Q

intrinsic regulators of GFR

A
  1. myogenic regulation
  2. tubuloglomerular feedback
  3. mesangial control
  4. pressure natriuresis
25
Q

myogenic regulation

A
  • constriction/dilation of afferent arteriole via smooth muscle cells:
  • -as blood flow increases, bp increases, and there is increased hydrostatic gradient
  • in response afferent arteriole constricts, decreasing GFR, creating a -ve feedback loop to regulate GFR, as pressure is increased to increase GFR when it is lowered
26
Q

tubulorglomerular feedback

A
  • juxtaglomerular apparatus (afferent arteriole); macula densa cells (distal tubule) controls diameter of afferent arteriole
  • they are positioned sidebyside so dilation/contriction of distal tubule will affect afferent arteriole
27
Q

mesangial control

A
  • special smooth muscle cells regulate blood flow through caps
  • increased flow causes stretching, which increases permeability of the filter
  • results in changes in GFR independent of vascular effects
28
Q

pressure natriuresis

A
  • small number of vessels penetrate the medulla of kidney without passing through a glomerulus
  • when BP increases, pressure of these vessels increases, renal interstitial hydrostatic pressure increases, reducing ability of tubule to recover solutes and water from primary urine, leading to more urine excretion and lowering of bp
  • thus creates a negative feedback loop on blood pressure and renal arterialpressure/filtration
29
Q

longterm mechanisms of GFR

A
  • baroreceptor activation at SNS decreases MAP causes vasocontriction of aff/eff vessels, decreased GFR and increased recovery of Na+, water conservation and increase blood volume
  • decreased renal circ=increased peripheral resistance=increased MAP
  • endocrine hormones also control bf and gfr
30
Q

endocrine hormones involved in blood flow and GFR

A

angiotensin 2= vasoconstrictor, decreases GFR

-prostoglandin=vasodilator, increases GFR

bio 364 (24 decks)

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