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bio 205-physiology > lec 23 & 24- water and electrolyte balance > Flashcards

lec 23 & 24- water and electrolyte balance Flashcards

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1
Q

what is an electrolyte?

A

a compound that dissociates into ions when dissolved in water, precise balance is crucial (e.g. Na+, Cl-, K+ and Ca2+)

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2
Q

what is water and electrolyte balance associated with?

A

excretion, excreting waste leads to water loss

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3
Q

what are the three environments where water and electrolyte balance must be maintained?

A
  1. Freshwater
  2. Marine
  3. Terrestrial
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4
Q

how do electrolytes move through organisms?

A

they move via osmosis and diffusion

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5
Q

what is needed for diffusion to occur?

A

a concentration gradient made from a difference in solute concentrations

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6
Q

what are the three steps to diffusion across a permeable membrane?

A
  1. separation of solutes
  2. diffusion- each solute undergo a net movement along concentration gradient
  3. equilibrium- solutes move back and forth but at equal rates
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7
Q

how does water move?

A

from regions of low solute concentration to regions of high solute concentration

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8
Q

what is hypertonic?

A

when outside concentration is higher than the cell, water moves out by osmosis causing cell to shrink

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9
Q

what is hypotonic?

A

when outside concentration is lower than the cell, water moves into the cell by osmosis causing cell to swell

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10
Q

what is isotonic?

A

when both outside and inside concentration is the same, cell remains the same

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11
Q

what is the name of the process by which organisms control the concentration of water and solutes within their bodies?

A

osmoregulation

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12
Q

what are some animals that don’t osmoregulate in water called?

A

osmoconformers, the sea water already matches their electrolyte concentrations in their bodies (e.g. jellyfish, sponges)

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13
Q

what is isosmotic?

A

when solute concentrations in an animals bodies are the same as outside

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14
Q

what are most marine and freshwater fishes and terrestrial animals that osmoregulate called?

A

osmoregulators

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15
Q

what is hyperosmotic?

A

when fishes keep the osmolarity of their tissues lower than that of seawater

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16
Q

is there a known pump that moves water?

A

No

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17
Q

what mechanism moves water through the membrane?

A

pumps that transport ions to set up osmotic gradients, water follows by osmosis (often through aquaporin)

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18
Q

how do seawater fishes osmoregulate?

A

-they lose water by osmosis in the gills, gain electrolytes by diffusion, and lose excess electrolytes by active transport

-this is because they have a low osmolarity inside, while the sea has high osmolarity

-under osmotic stress because they lose water and gain solutes

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19
Q

how do freshwater fishes osmoregulate?

A

-they gain water by osmosis, lose electrolytes by diffusion and gain the limited electrolytes by active transport

-this is because they have high osmolarity inside, while low outside

-under osmotic stress because they gain water and lose electrolytes

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20
Q

how do land animals osmoregulate?

A

-the lost water from urine, sweating, or panting is replaced by drinking water, by ingesting water from food, or by metabolic pathways
-electrolytes are gained from eating

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21
Q

where does osmoregulation occur in land animals?

A

in the kidney, responsible for water and electrolyte balance and excretion of waste

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22
Q

what is one of the nitrogenous wastes in the body?

A

-ammonia, excess amino acids and nucleic acids are broken down into it

-toxic to cells because it raises pH

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23
Q

how do freshwater fish get rid of nitrogenous waste?

A

-dilute ammonia to a low concentration then secrete it in urine
-ammonia diffuses across the gills into water along concentration gradient

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24
Q

how do mammals and adult amphibians excrete nitrogenous waste?

A

-convert ammonia into less toxic urea and excrete it in urine

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25
Q

how do bird, reptiles, and terrestrial arthropods excrete nitrogenous waste?

A

-convert ammonia into uric acid, secreted as a dry paste

26
Q

what are the trade offs between turning nitrogenous waste into ammonia, urea, and uric acid?

A

-ammonia requires a lot of water loss, but low energy
-urea requires medium water loss, but high energy
-uric acid requires low water loss, but high energy loss

27
Q

how is water moved in the kidney?

A

by osmotic gradients set up by active transport of ions

28
Q

is the formation of the filtrate in the kidney selective?

A

no

29
Q

is reabsorption in the kidney selective?

A

yes, for molecules and ions

30
Q

where is the kidneys located?

A

in the back side of the body

31
Q

what brings blood with nitrogenous wastes to the kidney?

A

renal artery

32
Q

what takes clean blood from the kidney away?

A

renal vein

33
Q

what transports urine into a storage organ in the kidney?

A

the ureter

34
Q

what is the storage organ for the kidney?

A

the bladder

35
Q

through what tube is urine excreted from?

A

the urethra

36
Q

what are the small structure in the kidney responsible for water and electrolyte balance called?

A

the nephrons

37
Q

where are most of the nephrons located and where do some extend to?

A

most are located in the outer region called the cortex, and some extend to the inner region called the medulla

38
Q

what are the 4 regions of the nephrons that are closely related to the collecting duct?

A
  1. the renal corpuscle filters blood, forming a filtrate made of ions, nutrients, wastes and water
  2. the proximal tubule has epithelial cells that reabsorb nutrients, ions, and water from filtrate into blood
  3. The loop of Henle establishes a strong osmotic gradient in the interstitial fluid surrounding the loop
  4. The distal tubule reabsorbs ions and water in a way that helps maintain water and electrolyte balance
  5. The collecting duct may reabsorb more water to maintain homeostasis, urea moves from urine to interstitial fluid at base of duct that is contributing to the gradient made by the loop of Henle
39
Q

what brings blood to the nephrons for filtration?

A

blood vessels

40
Q

what are the parts of the renal corpuscle and what does it do and what do the parts do?

A

-the renal corpuscle creates urine and it is made of the glomerulus and the bowmans capsule
-the glomerulus is a cluster of capillaries that bring blood to the nephron from the renal artery, filtration takes place
- the bowmans capsule is the region of the nephron that surrounds the glomerulus, recieves the filtrate to send down
-glomerous capillaries have large pores that surround cells whose membranes fold into slits and ridges

41
Q

what is filtration based on in the renal corpuscle?

A

-it is based on size
-large molecules remain in the blood and cannot enter the nephron, while small molecules and solutes are pushed through the pores into the bowmans capsule

42
Q

what is filtration paired with to reduce water loss?

A

filtering large volumes of blood paired with reabsorption allows waste excretion with minimal water loss

43
Q

what is the rate of production of filtrate through the glomerulus called?

A

glomerular filtration rate (GFR)

44
Q

what are the two regulations of the GFR and what do they contain?

A

intrinsic regulation:
1. myogenic response
2. tubuloglomerular feedback
3. messangial control

extrinsic regulation:
-hormones circulating blood can regulate GFR and kidney function

45
Q

what is the myogenic response of the intrisic regulation of the GFR?

A

it is when the smooth muscle cells of the afferent artiole constrict to reduce blood pressure

46
Q

what causes the tubuloglomerular feedback to occur?

A

macula densa cells of the distal tubule senses salt concentration in the distal tube and send a paracrine signal to the smooth muscle cells

47
Q

what is the pathway of myogenic regulation?

A
  1. increase in arteriolar pressure causes increased glomerular capillary pressure, increasing glomerular filtration pressure and increasing GFR
  2. increase in arteriolar pressure causes stretch of arteriolar smooth muscle, which causes contriction, increasing resistance of afferent arteriole, causing decrease in glomerular capillary pressure, and decrease in glomerular filtration pressure, resulting in decrease of GFR

-overall increased artery blood pressure causes either more glomerular capillary pressure increasing filtration and GFR or increased artery pressure causes contriction which lowers glomerular capillary pressure, causing lower filtration and GFR

48
Q

what is the pathway of tubuloglomerular feedback?

A
  1. increase in arteriolar pressure increases glomerular capillary pressure increasing filtration and GFR. increase in GFR increass flow at macula densa causing it to release chemical signals to cause constriction and lower glomerular capillary pressure
49
Q

what does the proximal tubule do and contain?

A

the proximal tubule has small microvilli facing lumen which increase surface area and cause reabsorption

50
Q

what are the 4 steps to selective reabsorption of the proximal tubule?

A
  1. Na+/K+ pump in the basolateral membrane removes intracellular Na into interstitial fluid so Na from lumen can enter due to gradient
  2. in the apical membrane Na+-dependent cotransporters use the gradient to remove ions and nutrients from filtrate
  3. solutes that move into the cell diffuse across the basolateral membrane into nearby blood vessels
  4. water follows ions from the proximal tubule into the cell and then into the blood vessels
51
Q

why is the osmolarity of the tubular fluid unchanged in the proximal tubule?

A

because the water reabsorption is proportional to solute reabsorption

52
Q

what does the loop of henle do and contain?

A

-fluid from the proximal tubule goes down the loop of henle into three parts:
1. descending limb- highly permeable to water resulting in extraction and impermeable to solutes
2. thin ascending limb- highly permeable to Na and Cl, impermeable to water
3. thick ascending limb- The osmolarity of interstitial fluid is low, so now Na and Cl are extracted by active transport

-the osmotic gradient stimulate water and ion flow that in turn maintains the gradient

53
Q

where do the water and salts that diffuse out of the loop of henle go?

A

into the vasa recta which is a network of blood vessels, they enter the blood stream to be used

54
Q

what does the distal tubule and collecting duct do?

A

distal tubule and collecting duct- fine tune filtrate by reabsorbing Na, Cl, and water. filtrate from loop of henle (mostly contains urea) goes through here.

55
Q

what controls changes in the distal tubule and collecting duct?

A

hormones

56
Q

what hormone causes reabsorption of Na in the distal tubule if Na is low in blood?

A

aldosterone

57
Q

what hormone is released when dehydrated?

A

antidiuretic hormone (ADH), saves water

58
Q

what are the 2 effects ADH has on epithelial cells in the collecting duct?

A
  1. triggers release of aquaporins in the apical membrane increasing water reabsorption
  2. increases permeability to urea, which is reabsorbed into surrounding environment (helps create a gradient for water reabsorption)
59
Q

what does alcohol do to ADH?

A

lowers the release of it, causing increased peeing due to lack of reabsorption

60
Q

what is the difference in the collecting duct with ADH present and absent?

A

present- more aquaporins in collecting duct, urine is hyperosmotic compared to blood
absent- few aquaporins in collecting duct, hyposmotic urine relative to blood

61
Q

how does urine move from the final altering spot called the collecting duct out of the body?

A

moves from the kidneys into the ureter than the bladder until urination

bio 205-physiology (29 decks)

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