water/electrolytes Flashcards
what direction does osmosis move water?
from low to high concentration of solute (to dilute) or from low to high osmolarity (concentration of solutes)
what do hypertonic and hypotonic mean?
hypertonic = higher concentration outside of cell, water will move out and cell becomes flaccid
hypotonic = higher concentration inside of cell, water moves in and cell becomes turgid
what are osmoconformers and what do they do?
- sharks, rays etc
- matches their electrolyte concentration to its aquatic surroundings (no need for regulation)
- blood has low ion concentration and high urea (makes it isosmotic)
what osmotic stress do salt water fish experience and how do they resolve it?
- seawater concentration > internal concentration (hyperosmotic)
- water tends to move out
- resolves by drinking water to replace loss, but gains excess of electrolytes
- electrolytes are actively pumped back into surroundings
what osmotic stress do fresh water fish experience and how do they resolve it?
- water concentration < internal concentration (hyposmotic)
- water tends to move in
- must get rid of excess water through urine
- electrolytes diffuse through gills
how do terrestrial animals lose water and how do they resolve this?
- loses water through evaporation
- drinks water + eats for electrolytes
- gets rid of excess through urine
how do different types of animals get rid of ammonia/nitrogenous waste?
freshwater fish: diluted and excreted through urine
bony fish: diffuses through gills
mammals: converted into less toxic urea and extreted through urine (high water cost but low energy)
birds/reptiles: converted into uric acid and excreted as a paste (low water cost but high energy
sharks: actively secretes salts out rectal gland (Na/K pumps)
what are the steps for salt excretion?
1) Na-K pump pushes Na out of epithelial cells into interstitial fluid
2) Na, K and Cl enter cell following Na gradient
3) Cl channels let Cl ions out through lumen into environment
4) Na channels allow Na to exit into lumen
what organs are involved in nitrogenous waste disposal?
- kidneys (produces urine)
- ureter (transports urine)
- bladder (stores urine)
- urethra (excretes urine)
what are the five parts of a nephron?
1) renal corpuscle
2) proximal tubule
3) loops of henle
4) distal tubule
5) collecting duct
what happens during urine filtration? what part of the nephron?
- renal corpuscle (glomerulus + bowmans capsule)
- small molecules go through filtration pores to be absorbed
- large molecules stay in blood and continue through nephrons
what is GFR?
- glomerular filtration rate
- rate at which filtration occurs in the glomerulus
what happens in the proximal tubule?
- selective reabsorption of salts (active) and water (osmosis)
- Na-K pump moves Na in
- Na activates cotransporters that move solutes from filtrate into blood, water follows
- most of reabsorption here
- high SA from microvili
what happens in the loops of henle?
descending loop:
- salty surroundings cause passive transport of water out
thin ascending loop:
- passive transport of Na and Cl
thick ascending loop:
- active transport of Na and Cl
what is the myogenic response for GFR?
- blood enters from afferent arteriole
- if blood pressure increases, smooth muscle cells contract to control blood flow
