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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
What are the functions of the proximal convoluted tubule?
- passive and active transport - reabsorption of water, ions, glucose, and amino acids - secretion of nitrogenous wastes and toxins
26
What is the main function of the nephron loop?
use active transport to move Na+ and Cl- into the kidney medulla
27
What are the characteristics of the nephron loop?
- 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
What are the characteristics of the distal convoluted tubule?
- 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
What conditions can occur if problems with the DCT prevents proton absorption and secretion?
- metabolic acidosis (too many protons) | - metabolic alkalosis (too few protons)
30
What is the concentration of carbonic acid in the blood dependent on?
the level of CO2 in the body and the amount of CO2 gas exhaled through the lungs
31
What causes respiratory acidosis?
CO2 excess
32
What causes respiratory alkalosis?
CO2 deficiency
33
What is hypercapnia?
- too much carbon dioxide - increase in protons - decrease in pH - acidic blood
34
What is hypocapnia?
- too little carbon dioxide - decrease in protons - increase in pH - basic blood
35
What are the characteristics of the collecting duct?
- 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
How does the osmolarity of forming urine change as it moves through the Loop of Henle?
- begins being isosmotic withe blood - becomes very hypertonic at bottom of loop - becomes very hypotonic at top of loop
37
What is a solvent?
substance that can dissolve a solute
38
What is osmolarity?
osmoles of solute per liter of solution
39
What is osmolality?
osmoles of solute per kilogram of solvent
40
What are the steps of creating an osmotic gradient within the renal medulla?
- 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
What is the glomerular filtration rate?
the amount of filtrate produced per minute
42
What three pressures present in the glomerulus affect glomerular filtration rate?
- 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
What happens if GFR is too high?
- excessive urination | - damage to kidneys
44
What happens if GFR is too low?
- inadequate filtration | - build up of toxins
45
How do carido/vasomotor mechanisms try to regulate GFR?
- try to lower blood pressure/GFR when GFR is too high | - try to raise blood pressure/GFR when GFR is too low
46
What hormones are involved in raising GFR when blood pressure is low?
- renin - angiotensin - aldosterone - antidiuretic hormone
47
What is the juxtaglomerular apparatus?
collection of cells that monitor and adjust GFR
48
What types of cells are in the juxtaglomerular apparatus?
- juxtaglomerular cells | - macula densa cells
49
What are the characteristics of juxtaglomerular cells?
- in the afferent arteriole | - secrete renin in response to signal from macula densa cells
50
What are the characteristics of macula densa cells?
- in the DCT | - monitor urine in DCT and tell juxtaglomerular cells how fast urine is moving
51
How do macula densa cells work?
- 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
How do hormones react to low blood pressure?
- 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
What are the characteristics of ADH?
- 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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