Chapter 40: Osmoregulation Flashcards
Osmoregulation
o Regulation of solute concentrations in blood stream
o Regulation of water in result of the concentrations in the blood stream
- Regulations of important ions (sodium, potassium, calcium)
acid-base balance
Osmoconformers
organisms that maintain a tissue osmolarity similar to their environment
Environment determines a lot of features for the salt concentration, osmotic pressure, etc.
Example: leopard shark
Osmoregulators
do lots of work to maintain osmolarity different from their environment
example: Whitemouth croaker
Marine fish environment
Lives in hypertonic environment
Must excrete solutes
Constantly gaining electrolytes via diffusion
Must retain H20
Freshwater fish
Lives in hypotonic environment
Water constantly going in to dilute its salty body
Must excrete H20
Must retain solutes
Lifestyle strategies to multiple different life stages
Lifestyles can include water changes for some organism
Sea bass in seawater vs. freshwater
Moving into freshwater, active transporter grabs things to transport into membrane
Lifestyle strategies to multiple different life stages
Lifestyles can include water changes for some organisms
Sea bass in seawater vs. freshwater
Moving into freshwater, active transporter grabs things to transport into membrane
Insect osmoregulatory organs
goes from midgut to hindgut
includes malpighian tubules, hemolymph, and midgut & hindgut
Malpighian tubules
: specialized process of secretion
* Actively transport ions and other solutes from hemolymph into tubules; creates concentration gradient, driving water out of tubules to hindgut
* Moves particles out of tissues (from hemolymph) to be excreted
Hemolyph
passes blood in insect, insect blood; balances water and ions
o Have nitrogenous waste, electrolytes, and water in pre-urine
o Has digested food go through hindgut with these
o Will produce final urine and feces, with electrolytes and water excreted out
midgut
absorbs nutrients from insect’s diet
hindgut
responsible for reabsorption of water and ions from feces before excreted
Terrestrial animal osmoregulatory organs unique ability
highly concentrated urine; lose water by evaporation from gas-exchange and other surfaces
Mammalian urinary system
Relies on functional units in the kidneys called nephrons
Maintain salt, water balance
Excrete nitrogenous wastes
**occasionally reabsorbs water, but not common
Most nephrons in cortex, some extend to medulla
Process of urination release
Kidney -> ureter -> bladder -> urethra
Nephrons
multicellular structure that filters out the stuff unwanted, keeps the wanted materials
Three major functions of nephrons
filtration, reabsorption, and secretion
Filtration
The first step in urine formation is filtration, which occurs in the glomerulus, a network of small blood vessels within the nephron.
Blood is delivered to the glomerulus via the afferent arteriole and exits via the efferent arteriole.
As blood flows through the glomerulus, water and solutes are forced through the capillary walls and into the Bowman’s capsule, a hollow structure that surrounds the glomerulus.
This forms a filtrate that contains water, ions, and small molecules, but not larger molecules like proteins and blood cells.
Reabsorption
After filtration, the filtrate passes through the renal tubule, where selective reabsorption occurs.
This is the process by which the nephron reabsorbs useful substances such as glucose, amino acids, and ions back into the bloodstream.
Reabsorption occurs via active and passive transport mechanisms, and it is regulated by hormones such as antidiuretic hormone (ADH) and aldosterone.
By reabsorbing useful substances, the nephron helps to maintain the body’s fluid balance and prevent the loss of important nutrients.
Secretion
The final step in urine formation is secretion, which involves the active transport of certain substances from the blood into the renal tubule.
This includes the secretion of hydrogen ions (H+) and potassium ions (K+) to regulate the body’s acid-base balance, as well as the secretion of certain drugs and toxins.
Secretion occurs in the proximal and distal convoluted tubules, and it is also regulated by hormones such as aldosterone and atrial natriuretic peptide (ANP).
What do nephrons do together?
o Interacts heavily with blood supply
the three major functions of nephrons work together to regulate the composition of body fluids and remove waste products from the body.
The kidneys are vital organs that play a critical role in maintaining homeostasis and ensuring the proper functioning of the body’s organs and tissues.
Glomerular Filtration
Phorocyte’s prevent bursting (from fluid pressure)
Some fluid leaks out from blood, carrying solutes
Blood cells and platelets kept in capillaries
Everything else for the most part filtered into space between glomerulus and bowman’s capsule
What does filtration stricly rely on?
blood pressure to push fluid and solutes into space!
Human Example of Nephrons
o Room being reorganized when going after college
Filtration: all your things thrown into a box, no matter what it is from your room
Reabsorption: going through the boxes and keeping certain items you really need/means a lot to you, other things lead to disposal
Secretion: thing you decide to keep is thrown out by someone else anyways (that sucks)
Tubule structres
Important in reabsorption
lumen, epithelial cells, microvillie
Lumen
where filtrate flows through
epithelial cells
line lots of cavities, make up tubule
microvilli
contacts lumen, Moving filtrate’s wanted items through epithelial cells to be reabsorbed back into blood
Reabsorption process of Na/K pump
toward blood supply, because you want sodium to pump back into blood
Pumps potassium in other direction; Active transport
Creating low sodium concentration in epithelial cells/proximal tubule
Glucose is able to be reabsorbed when moved along with sodium; Flows down concentration gradient back into blood ; Chloride vitamins can also be a secondary messenger transport and then facilitated diffusion to be moved back into blood
Reabsorption happening for the most part from ATP from Na/K pump
Selective permeability in Loop
Permeability of tubule changes from descending limb -> loop of henle -> ascending limb (ascending Becomes a saltier area from sodium and chlorides leaving the area)
Three regions in loop of henle
Materials in reference to Reabsorption
o Water and solutes filtered are returned to blood and reabsorbed
o 100% of glucose
o Most Na, Cl, proteins, carbs, Ca2+, vitamins, etc. reabsorbed in proximal tube
o 50% of urea reabsorbed to balance osmotic pressures
o Alterations to the rest of items reabsorbed further downstream
Materials in reference to Secretion
o Elimination of Waste products
o Transport out blood and into kidney tubules for elimination
o Mostly K+ and H+
Affect muscle and nervous system cells ability to repolarize and depolarize, causing (in worst cases) cardiac arrest
ADH
anti-diuretic hormone: causes tubules cells to insert aquaporins channels into their plasma membranes, making it easier to absorb water
Water rentention with ADH
o In the presence of ADH, aquaporins are inserted into collecting duct
Happens into distal tubule and collecting duct primarily; Water conserving method, allows to reabsorb water; Released when plasma osmolarity increases
o Negative feedback loop
o Higher concentrations connect to osmoreceptors in hypothalamus, causing thirst; drinking water creates negative feedback and back into loop with sensor
What happens when water is unavailable?
posterior pituitary gland senses this and will have increased ADH secretion, opening up more channels to reabsorb water from urea if needed
focusing on “as needed” areas in reabsorption
High ADH level
collectin duct highly permeable to water
Low ADH level
collecting duct not permeable to water
Aldosterone
o Targets kidneys
o Increases reabsorption of Na+ and H20 across the distal convoluted tubule
o Increases secretion of K+ into the tubule
o Occurs when blood pressure low, K+ high
Reabsorbing water and sodium brings blood pressure back up
Nitrogenous Wastes
break down of nucleic acids and amino acids (NH3)
Amino and nucleic acids -> catabolism -> ammonia by-product
Organisms with nitrogenous waste of Ammonia
bond fish, aquatic invertebrates
Organisms with ammonia coverted to urea
amphibians, cartilganegous fish
conversion to urea lowers toxicity of waste hanging out in body
Organisms with ammonia converted to uric acid
takes more energy
birds, reptiles, insects
