chapter 44: osmoregulation and excretion Flashcards
What is omsmolarity?
solute concentration of a solution determines movement of water across a selectively permeable membrane
What is osmoregulation?
controls solute concentrations and balances gain and loss of water
What are osmoconformers?
are isoosmotic with their surrondings and do not regulate their osmolarity
What are osmoregulators?
expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
What does stenohaline mean in animals?
they cannot tolerate substantial changes in external osmolarity
What does euryhaline mean in animals?
they can survive large fluctuations in external osmolarity
What are marine invertebrates?
osmoconformers
What are marine vertebrates (and some invertebrates?)
osmoregulators
How does osmoregulation balance the uptake and loss of water and solutes?
driving force for movement of solutes and water is a concentration gradient of one or more solutes across the plasma membrane
What is the osmoregulation of marine animals?
marine fish lose water by osmosis and gain salt by diffusion from food
What is the osmoregulation of freshwater animals?
salts lost by diffusion are replaced in foods and by uptake across the gills
What is anhydrobiosis?
some aquatic invertebrates in temporary ponds lose most of their body water and survive in dormant state
What helps terrestrial animals prevent dehydration?
body coverings
How do desert animals get water savings?
nocturnal lifestyles
What are the different factors that affect amount of energy in osmoregulators?
- how different the animals osmolarity is from its surroundings
- how easily water and solutes move across the animals surface
- work required to pump solutes across the membrane
What is urea?
excretion made by mammals, urea requaires less water than ammonia
What is uric acid?
what insects, reptiles and birds excrete. it is non toxic, is is more energetically expensive to produce than urea
What is ammonia?
what fish excrete
What is the role of the excretory system?
regulates solute movement between internal fluids and the external environments
form urine by refining a filtrate derived from body fluids
What are the key functions of most excretory systems?
- filtration: filtering of body fluids
- reabsorption: reclaiming valuable solutes
- secretion: adding non essential solutes and wastes from body fluids to the filtrate
- excretion: processed filtrate containing nitrogenous wastes released from body/
What is a protonephridium?
a network of dead-end tubules connected to external openings
What is metanephridia?
consists of tubules that collect coelomic fluid and produce dilute urine for excretion
What is the role of malpighian tubules?
remove nitrogenous wastes from hemolymph and function in osmoregulation
How does blood filtrate to urine?
- proximal tubule: reabsorption of ions, water and nutrients, materials are excreted
- descending limb of the loop of henle: reabsorption of water continues due to aquaporin proteins - movement driven by high osmolarity
- ascending limb of the loop of henle: salt diffuse from tubule but not water
- distal tubule: regulates K+ and NaCl concentrates
- collecting duct: carries filtrate through medulla to renal pelvis
What is the antidiuretic hormone?
ADH - is released into the blood when osmolarity of blood rises above set point
What is the reaction of ADH?
when binding ADH to receptor molecules, temporary increase in aquaproin proteins in membrane happens, reducing urine volume and lowers blood osmolarity
