Osmoregulation

Question 1

Intracellular fluid

Answer 1

Fluid/H2O inside the cell. Humans: 28L of total body H2O

Question 2

• Extracellular fluid

Answer 2

Fluid outside the cell. Made up on interstitial and plasma

Question 3

• Interstitial fluid

Answer 3

H2O between cells, internal environment. Humans: 11.2 L of total body H2O

Question 4

• Plasma

Answer 4

Extracellular component of blood. Humans 2.8L of total body H2O

Question 5

• Internal environment

Answer 5

Cells constantly consuming O2 and nutrients from internal environment, releasing CO2 and waste products to internal environment

Question 6

External environment

Answer 6

Plasma has exchange with external environment through actions of lungs, intestines, and kidneys. Plasma also has free exchange with interstitial fluid, and thereby maintains constancy of internal environment

Question 7

Osmoregulation

Answer 7

Maintenance of a nearly constant osmotic pressure in blood plasma

Question 8

Ion regulation

Answer 8

Maintenance of a nearly constant concentration of inorganic ions in blood plasma

Question 9

Volume regulation

Answer 9

Maintenance of a nearly constant water volume in blood plasma

Question 10

Fluid balance

Answer 10

inputs and outputs. In order to maintain ECF osmolality and volume, must achieve H2O balance and Na+ balance
o Inputs: drinking and eating, metabolic H2O as result of cell respiration
o Outputs: Urinary H2O and solute loss, Fecal H2O and solute loss, and Evaporative H2O loss (breathing, sweating)

Question 11

U/P ratio

Answer 11

Urine Concentration Solute(s)/Plasma Concentration Solutes(s) by varying U/P ratio, kidneys can modify blood plasma, affect interstitial fluid properties

• U/P = 1, isotonic urine
• U/P > 1 Hypertonic urine
• U/P

Question 12

Kidneys:

Answer 12

Filter blood plasma, remove appropriate amount of H2O and plasma solutes

Question 13

Kidney Renal artery:

Answer 13

Supply blood to kidney

Question 14

Renal vein:

Answer 14

Drain blood

Question 15

Ureters

Answer 15

Transport urine to bladder

Question 16

Bladder

Answer 16

Holds urine

Question 17

Cortex:

Answer 17

Outer region of kidney. Contains Glomeruli, proximal and distal tubules, and pertubular capillaries

Question 18

Medulla

Answer 18

Loop of Henle, Vasa Recta capillaries (Humans have multiple medullary pyramids, rodents have a single medulla)

Question 19

Glomerulus:

Answer 19

Site of filtration, plasma into nephrons

Question 20

Nephron

Answer 20

site of reabsorption and secretion. About 800,000 per kidney in humans

Question 21

Bowman’s capsule:

Answer 21

surrounds glomerular capillaries, collects ultrafiltrate leaving glomerular capillaries

Question 22

Proximal tubule

Answer 22

60-70% of H2O and Na+ are reabsorbed into pertitubular capillaries.
All transport dependent on active pumping of Na+ and Na+K+ATPase
Have a lot of mitochondria

Question 23

Distal Tubule:

Answer 23

• Depends on relative number of Na+ channels and Na+K+ATPase pumps
• Aldosterone (secreted if plasma volume is low) determines how many Na+ transport proteins are present
• DT H2O permeability matches Na+ reabsorption rate, equal reabsorption of Na+ and H2O increases plasma volume

Question 24

Loop of Henle:

Answer 24

• H2O Reabsorption: only occurs in the descending limb of loop (AQP-1 present in these cells)
• Na+ reabsorption: only present in the ascending limb of loop necessary proteins present.
• Differential reabsorption of H2O and Na+ in this segment critical for forming concentrated urine (diluting plasma osmolarity)
• Creates a vertical osmotic gradient from cortex to papilla

Question 25

Collecting ducts

Answer 25

many nephrons drain into individual collecting ducts to ureters. Have tubular reabsorption
AVP action → increase H2O reabsorption from CD, forming urine with higher U/P ratio

Question 26

Filtration

Answer 26

125 ml plasma/min; 180L/day

Question 27

Reabsorption:

Answer 27

movement from tubular lumen to blood; 178.5L/day

Question 28

Secretion

Answer 28

movement from blood to tubular lumen; additional venue for rapidly removing substances from blood

Question 29

Excretion:

Answer 29

anything not reabsorbed is excreted; 1.5L/day

Question 30

Glomerular capillary

Answer 30

Highly permeable capillaries with loads of fenstra

Question 31

Podocyte

Answer 31

inner epithelial layer of Bowman’s capsule, retrict filtration of large, negatively charged molecules (think proteins).

Question 32

Blood pressure (PGC):

Answer 32

blood pressure within glomerular capillaries tends to force fluid out

Question 33

Colloid osmotic pressure (𝛑GC):

Answer 33

Proteins aren’t filtered so osmolarity in glomerular capillaries slightly higher than that in bowman’s capsule, pulls H2O back in capillaries

Question 34

Hydrostatic pressure (PBC):

Answer 34

Fluid in capsule exerts hydrostatic pressure, pushes fluid back into glomerular capillaries

Question 35

Na+K +ATPase

Answer 35

found in Proximal Tubule, Distal Tubule

Question 36

NKCC co-transporter

Answer 36

protein that aids in the active transport of Na, K and Cl-

Question 37

Aquaporin (AQP-1, AQP-2, AQP-3):

Answer 37

Forms pores in membrane. AQP-1: Proximal tubule, AQP-2: collecting duct,

Question 38

Single effect:

Answer 38

o Refers to the difference in osmotic concentration between the descending limb/interstitial fluid and adjacent ascending thick limb.
o Due to active Na+ transport of epithelial cells in ascending limb
o Due to high water permeability in descending limb, but no water permeability in ascending limb

Question 39

Vasopressin (ADH/AVP/Antidiuretic):

Answer 39

o Regulates the body’s retention of water by
• Increasing water reabsorption in the kidney’s collecting duct
• Determines how many Na+ transport proteins are present
• Increases peripheral vascular resistance → increases arterial bp