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BIOL240W > Exam 4 - Osmoregulation and Excretion in Humans (parts 1, 2, and 3) > Flashcards

Exam 4 - Osmoregulation and Excretion in Humans (parts 1, 2, and 3) Flashcards

1
Q

What do humans excrete in addition to excess salts and water?

A

toxins

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2
Q

What is urinary excretion?

A

elimination of wastes that are products of cell metabolism

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3
Q

What is defecation?

A

elimination of feces that are waste products of the digestive system

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4
Q

What other systems does the urinary system interact with?

A

cardiovascular system, endocrine system, and respiratory system

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5
Q

What are the two goals of the kidneys?

A
  • removing metabolic wastes/toxins

- osmoregulation

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6
Q

In addition to the major functions, what else other functions do the kidneys have?

A
  • alter pH by absorbing or secreting protons

- alter blood volume by absorbing or secreting water

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7
Q

What is the functional unit of the kidney?

A

the nephron

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8
Q

What are the characteristics of nephrons?

A
  • cellular, tube-like structures

- intimately associated with capillary beds

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9
Q

What is the pathway of the urinary system?

A
  • nephrons from kidneys connected to ureters
  • ureters connect to bladder
  • bladder connects to urethra
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10
Q

What percent of cardiac output goes to the kidneys?

A

20%

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11
Q

What is filtration?

A

initial movement of molecules from capillary into nephron

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12
Q

What is reabsorption?

A

movement of molecules in nephron back into capillary

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13
Q

What is secretion?

A

movement of a molecule from the capillary back into the nephron after filtration

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14
Q

Which toxic, nitrogenous wastes are removed by the kidneys?

A
  • urea
  • uric acid
  • creatine
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15
Q

What are the two types of nephrons?

A
  • juxtamedullary (near edge of medulla)

- cortical (in cortex)

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16
Q

What are the five regions of the nephron, and their functions?

A
  • glomerular (Bowman’s) capsule: filtration
  • proximal convoluted tubule: secretion and reabsorption
  • nephron loop (Loop of Henle): secretion and reabsorption
  • distal convoluted tubule: secretion and reabsorption
  • collection duct: secretion and reabsorption
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17
Q

What are the vessels associated with nephron blood supply?

A
  • afferent arteriole: blood flow to glomerulus
  • glomerulus: capillary bed
  • efferent arteriole: blood flow leaving glomerulus
  • peritubular capillaries: associated with PCT and DCT
  • vasa recta capillaries: associated with Loop of Henle
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18
Q

How much initial filtrate is produced each day?

A

180 L

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19
Q

How much urine is actually produced and transported to the bladder each day?

A

1.5 L

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20
Q

What is reabsorbed by the kidneys?

A
  • 99% of the water

- nearly all sugars, amino acids, vitamins, organic nutrients

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21
Q

What are the characteristics of osmotic concentration?

A
  • also known as osmolarity
  • measure of solute concentration
  • in kidneys, looking at Na+ and Cl- solute concentrations
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22
Q

What are the steps of the urinary system?

A
  • initial filtration of blood at the filtration membrane
  • reabsorption/secretion at the PCT
  • salty medulla in the nephron loop
  • reabsorption/secretion at the DCT
  • water conservation in the collecting duct
23
Q

What are the characteristics of initial filtration?

A
  • occurs at the filtration membrane and is non-specific
  • filtration occurs at “filtration slits”
  • anything small enough to fit between splits enters nephron
  • cells and large proteins are trapped in capillaries
24
Q

With normal kidney function, which molecules are present in plasma but not in filtrate?

A

proteins and blood cells

25
Q

What are the functions of the proximal convoluted tubule?

A
  • passive and active transport
  • reabsorption of water, ions, glucose, and amino acids
  • secretion of nitrogenous wastes and toxins
26
Q

What is the main function of the nephron loop?

A

use active transport to move Na+ and Cl- into the kidney medulla

27
Q

What are the characteristics of the nephron loop?

A
  • descending limb is only permeable to water
  • osmolarity of medulla increases moving away from cortex
  • water moves via osmosis through aquaporins and is reabsorbed into the blood concentrating the filtrate
  • ascending limb is only permeable to ions
  • NaCl diffuses out of thin segment
  • NaCl is actively transported out of thick segment to dilute filtrate
28
Q

What are the characteristics of the distal convoluted tubule?

A
  • reabsorption of water is influenced by hormones
  • secretion of extra wastes
  • important site of proton absorption/secretion
  • works with respiratory system to balance pH
29
Q

What conditions can occur if problems with the DCT prevents proton absorption and secretion?

A
  • metabolic acidosis (too many protons)

- metabolic alkalosis (too few protons)

30
Q

What is the concentration of carbonic acid in the blood dependent on?

A

the level of CO2 in the body and the amount of CO2 gas exhaled through the lungs

31
Q

What causes respiratory acidosis?

A

CO2 excess

32
Q

What causes respiratory alkalosis?

A

CO2 deficiency

33
Q

What is hypercapnia?

A
  • too much carbon dioxide
  • increase in protons
  • decrease in pH
  • acidic blood
34
Q

What is hypocapnia?

A
  • too little carbon dioxide
  • decrease in protons
  • increase in pH
  • basic blood
35
Q

What are the characteristics of the collecting duct?

A
  • main function is to absorb more water
  • relies on solute gradient created by the nephron loop
  • osmosis drives water reabsorption
  • also influenced by hormones
36
Q

How does the osmolarity of forming urine change as it moves through the Loop of Henle?

A
  • begins being isosmotic withe blood
  • becomes very hypertonic at bottom of loop
  • becomes very hypotonic at top of loop
37
Q

What is a solvent?

A

substance that can dissolve a solute

38
Q

What is osmolarity?

A

osmoles of solute per liter of solution

39
Q

What is osmolality?

A

osmoles of solute per kilogram of solvent

40
Q

What are the steps of creating an osmotic gradient within the renal medulla?

A
  • long nephron loops create the gradient and act as countercurrent multipliers
  • vasa recta preserve the gradient and act as countercurrent exchangers
  • collecting ducts use the gradient to adjust urine osmolality
41
Q

What is the glomerular filtration rate?

A

the amount of filtrate produced per minute

42
Q

What three pressures present in the glomerulus affect glomerular filtration rate?

A
  • blood hydrostatic pressure: blood pressure in the glomerulus (out)
  • colloid osmotic pressure: pressure exerted by blood proteins (in)
  • capsular pressure: pressure exerted by filtrate in glomerular capsule (in)
43
Q

What happens if GFR is too high?

A
  • excessive urination

- damage to kidneys

44
Q

What happens if GFR is too low?

A
  • inadequate filtration

- build up of toxins

45
Q

How do carido/vasomotor mechanisms try to regulate GFR?

A
  • try to lower blood pressure/GFR when GFR is too high

- try to raise blood pressure/GFR when GFR is too low

46
Q

What hormones are involved in raising GFR when blood pressure is low?

A
  • renin
  • angiotensin
  • aldosterone
  • antidiuretic hormone
47
Q

What is the juxtaglomerular apparatus?

A

collection of cells that monitor and adjust GFR

48
Q

What types of cells are in the juxtaglomerular apparatus?

A
  • juxtaglomerular cells

- macula densa cells

49
Q

What are the characteristics of juxtaglomerular cells?

A
  • in the afferent arteriole

- secrete renin in response to signal from macula densa cells

50
Q

What are the characteristics of macula densa cells?

A
  • in the DCT

- monitor urine in DCT and tell juxtaglomerular cells how fast urine is moving

51
Q

How do macula densa cells work?

A
  • when GFR decreases, filtrate moves more slowly through nephron
  • slower movement of filtrate causes greater reabsorption of NaCl
  • filtrate becomes more dilute than normal due to outward movement of NaCl
  • macula densa cells detect the dilute filtrate and respond by triggering JG cells to release renin
52
Q

How do hormones react to low blood pressure?

A
  • renin released by JG cells
  • renin activates protein called angiotensinogen in blood, a precursor to angiotensin I
  • angiotensin I is activated to angiotensin II by ACE
  • angiotensin II results in increased blood pressure
  • stimulates secretion of aldosterone, which stimulates Na+ and water reabsorption
  • stimulates secretion of ADH, which triggers more water reabsorption
53
Q

What are the characteristics of ADH?

A
  • produced by hypothalamus in response to dehydration
  • causes the production of aquaporins in collecting duct
  • allows for faster uptake of water
  • aquaporin production decreases as rehydration occurs
  • alcohol blocks ADH production

BIOL240W (23 decks)

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