Chapter 40: Water & Electrolyte Balance In Animals

Which of the following substances is not usually found in filteterate from the blood?

plasma proteins and blood cells

What is an electrolye?

a compound that dissociates into ions when dissolved in water

what electrolyes do cells usually have?

Na+, Cl- , K+ and Ca 2+

water & electrolyte balance is associated with what?

animals produce _______ to _______ waste, and this leads to water loss

• excretion

• urine , excrete

how do electrolytes and water move through organisms?

diffusion and osmosis

what is diffusion?

diffusion is the movement of uncharged substances down their concentration gradients

what is osmosis?

osmosis is the movement of water down its concentration gradient across a semipermeable membrane

what are two important things to know abt a solutions osmolarity?

it is the concentration of solutes in solution

• measured in osmoles/L

what happens if solutes are seperated by selectively permeable membrane?

water move from side w low osmolarity to high

what is osmotic stress? how do organisms fix it?

occurs when concentration of dissolved substances in a cell or tissue is abnormal (diff from set points)

• organisms fix it via osmoregulation

what is osmoregulation?

process by which organisms control concentration of water and solutes within their body

do all animals encounter osmotic stress? which animals DO NOT need to osmoregulate? why?

• no

• jellyfish and sponges do not need to osmoregulate because the seawater is a constant ionic and osmotic environment, and it nearly matches electrolytes concentrations found within these animals

if an animal (like jellyfish and sponge) do not need to osmoregulate what are they called?

osmoconformers

what does isosmotic mean?

solute concentrations inside and outside animals are equal (same osmotic pressure)

• seen w jellyfish and sponges in seawater

what do osomoregulators do? who is an example?

they actively regulate osmolarity inside their bodies to achieve homeostasis

ex: bony fishes and terrestrial animals

why is osmoregulation required in marine vertebrates ?

because seawater is HYPERSOMOTIC to their tissues, therefore the bony fishes need to keep the osmolarity of their tissues lower than that of sea water

in some animals, water tends to flow by osmosis out what?

gill epithelium. ions can diffuse into the gill epithelium down their concentration gradient

how do marine bony fishes replace lost water?

drinking large quantities of seawater

how do bony fishes get rid of excess electrolyes?

they pump ions into the seawater

how do fishes lose electrolytes?

by excreting small quantities of highly concentrated urine

freshwater fishes osmoregulate differently than those that live in the ocean because?

they gain water and lose solutes. freshwater is HYSOMOTIC to fishes tissues

what does it mean that freshwater fishes are hyposmotic to the fishes tissues? what will happen if freshwater fish do not get rid of incoming water?

the gain of water across gill epithelium puts them under osmotic stress

• if they do not get rid of incoming water their cells will burst & they will die

in order for freshwater fishes to achieve homeostatsis what must they do? how do they replace electrolytes?

they must excrete large amounts of water in their urine and they do not drink.

• they replace electrolytes by eating food or actively transporting them into the body

do terrestrial animals lose water to their enviornment? how?

Yes, often by evaporation, panting, urine

which cells in respiratory structures have moist surface to promote gas exchange in animals? why is it important?

epithelial cells

• this is important because it allows a large amount of water loss thru evaporation, and there is a trade off between gas exchange and osmoregulation

how do animals replace water?

drinking, ingesting food, or by metabolic pathways

how do solutes move across membranes?

by passive or active transport

what is passive trasnport?

driven by diffusion along an electrochemical gradient and DOES NOT require an expenditure of energy

what is active transport?

when a source of energy powers the movement of a solute that establishes an electrochemical gradient

what is primary active transport?

primary active transport is used to move ions against their gradients (ex: sodium potassium pump)

what is secondary active transport?

aka cotransport, they rely on membrane proteins that use electrochemical graident established by pump during primary active transport

what are symporters vs anitporters

part of secondary active trasnport/cotranspoty

symporters move solutes in the same direction

antiporters move solutes in the opposite directions

how does water follow by osmosis in cells?

often thru aquaporins

excress amino acids and nucelic acids in animal cells are broken down into what? why is this important? how does it impact water balance?

• broken down into ammonia (NH3)

• ammonia is toxic to cells because it raises pH

• animals excrete nitrogenous waste directly as ammonia or convert it to other nitrogen containing compounds that are then excreted out the body

how is ammonia excreted in each animal:

• freshwater

• marine bony fishes

• mammals

• birds, repiles and arthropods

freshwater: urine & across the gills into water along a concentration gradient

marine bony fishes: across gills into water along a concentration gradient

mammals and adult amphibians: enzymes convert ammonia to less toxic urea and excrete it via urine

birds/reptiles/ arthropods: convert ammonia to uric acid and can be excreted as dry paste

ammonia excretion requires a lot of water loss but _______ _______

while

uric acid requires no water loss but takes up ________ ______

little energy

alot of energy

does osmoregulation depend on habitat

yes

who are the osmoregulators and who are the osmoconformation?

osmoregulators are bony fishes, osmoconformation are sharks, rays

what do osmoregulators do?

maintain lower blood osmolarity by drinking sea water, replace water lost in osmosis, very energy costly

what do osmoconformers do?

blood contains low conc of ions but high conc of urea, increase in blood osmolarity—isosmotic w sea water therefore,little water loss, and require energy expenditure to protect fishes from toxic effects of high urea concentration

do sharks excrete salt against their concentration gradient, and how?

they use their rectal glands, and yes they do

in land vertebrates, osmoregulation occurs mainly where?

kidney (water and electrolyte balance) and excretion of nitrogenous waste

which _______ _____ brings blood containing nitrogenous wastes into the kidney?

which _______ _______ brings clean blood away from the kidney?

renal artery

renal vein

urine formed in the kidney is transported via long tube called the ________ to a storage organ called the ________

ureter

bladder

from the bladder urine is transported to the body surface via a tube called the ______ and is then excreted out

urethra

kidneys mass is made of up of? what do they do?

nephrons: they are responsible for water and electrolyte balance

most of the nephrons are located in the outer region of the kidney aka . what is the inner region

the cortex

inner region is the medulla

how are the cells in the kidney able to manage and move water?

they set up strong osmostic gradients in the interstital fluid surrounding the nephrons. by regulating gradients and specific channel proteins, kidney cells exert precise control over loss or retention of water ana electrolytes

what is the 4 steps of excretory system

1) filtration (filtering body fluids)

2) reabsorption (reclaiming valuable solutes nephrons → capillaries)

3) secretion (adding toxins and nonessential solutes and wastes from body fluids to the filtrate)

4) excretion (filtrate containing nitrogenous wastes released from the body)

what are the 5 parts of the kidney you should know

renal corpuscle

proximal tubule

loop of henle

distal tubule

collecting duct

what happens in the renal corpuscle

it filters blood, forming a filtrate consisting of ions, nutreints wastes and water

what does the proximal tubule do?

epithelial cells that reabsorb nutrients, ions & water from filtrate into blood

what does the loop of henle do?

establishes a strong osmotic gradient in the interstital fluid surrounding the loop

does osmolarity increase or decrease as the loop of henle descends into the medulla

increases

what does the distal tubule do?

resabsorbs ions and water in a way that helps maintain water and electrolye balance

what does the collecting duct do?

may reabsorb more water

why are blood vessels important that surrounds the mammalian kidney

they bring waste containing blood into the nephron and then take away the molecules and ions that are reabsorbed from the initial filtrate

urine formation begins in the ________ _________, which is made up of the ________and _________ _________

renal corpuscle

glomerulus

bowmanns capsule

what is the glomerulus? what does it do? what is the bowmans capsule?

the glomerulus is a cluster of capillaries that bring blood to the nephron from the renal artery

• the bowmans capsule is the region of the nephron that surrounds the glomerulus

is filtration based on size?

yes small molecules can end up in filtrate but large molecules such as proteins and blood cells can not make it through. Filtration can also be based on blood pressure

renal corpuscles of a human kidney produces about ______ liters of filtrate per day and about _______ of it is reasborbed back into the body

180

99%

when filtrate leaves the bowmans capsule they enter what? this tube has what?

proximal tubule: it has microvilli facing the lumen that increases epithelial sa

does proximal tubule function in active or passive transport of molecules out of the filtrte?

active transport

what is the model of molecular mechanisms involved in selective reabsorption? (4)

1) active transport creates Na+ gradient

2) Na + Gradient is used to remove solutes from filtrate

3) removed substances diffuses into blood

4) water moves into the blood via osmosis

fluid from the proximal tubule goes where?

loop of henle

what do nephrons do?

produce urine under hormonal control

what does the loop of henle do?

establishes a strong osmotic gradient in the interstitial fluid surrounding the loop (also important for reabsorption) 

3 regions of the loop of henle

1) descending limb

2) think ascending limb

3) thick ascending limb

which tubule has Na and Cl as solutes, which one has urea as solute?

has Na Cl (ascending), the descending limb aka the distal tubule has urea

what type of passive transport is the descending limb and ascending limb?

descending is passive transport of water because the fluid inside the loop loses water, and moves down its conc gradient

ascending limb passive transport of Na + and Cl -, fluid inside hte nephorn loses Na+ and Cl- in the thin ascending limb

is the thick ascending limb passive or active transport and why?/

active transport of Na+ and Cl-

what happens in each:

filtration

reabsorption

secretion

excretion

filtration: bp drives fluid into slits (in renal corpsucle)

reabsorption: fluid inside nephron goes back to capillaries

secretion: blood goes inot nerphon

excretion: solutes contain mainly urea to be transporteed otu the body

Once filtrate goes into the distal tubule, the fluid is slightly hyposmotic to the blood. solutes contain mainly urea and its always ________. urine that leaves the collecting duct is ______ when individual is well hydrated, but concentrated when an indiviudal. is dehydrated

dilute

what is the vasa recta? what is the result of this?

network of blood vessels that runs along the loop and water/salt move out of loop and diffuse into these blood vessels. the result is that water and electrolytes are returned into the blood

the activity of distal tubule and collecting duct is regulated and altered often in response to what?

osmotic stress

changes in the distal tubule and collecting duct are controlled by what?

hormones

what happens if Na+ levels in the blood are low?

adrenal galnds release the hormone aldosterone which leads to the activation of sodium potassium pumps

what happens when a person is dehydrated? what do these do?

the brian releases antidiuretic hormones—- these causes the collecting duct to have more aquaporins, if you are dehydrated the hormone will create more aquaporins to reabsorb more water, and allows the person to urinate less (water is reabsorbed)

what happens when adh is present vs absent

present: water is conserved and urine is strongly hyperosmotic relative to blood

absent: few aquaporins are found, leaving it relatively impermeable to water and resulting in hyposmotic urine

where is the final place where the composition of the filtrate can be altered. from this location how does urine move?

• collecting duct

• kidneys → collecting ducts → ureters → bladder

what is the RAAS?

a systems that is part of a complex feedback circuit that functions in homeostasis

For example, if there is a drop in blood pressure __________ , JGA releases the enzyme _______. ___________ causes the conversion of Angiotensinogen to Angiotensin I and Angiotensin II, which tells the Adrenal gland to release Aldosterone . 

renin

why is angiotensin II important when released by renin?

raises blood pressures, descreases blood flow to kidneys, stimulates the release of ADH

what does the hormone ANP do?

opposes the RAAS systems, ANP released from the heart in response to stretching, inhibits the releases of renin

ANP acts as a _______ and descreses blood pressure and volume and ENHANCES the excretion of water and sodium

diuretic

List the functions:

• Renal Corpuscle: size selective filtration: forms filtrate from blood

• proximal tubule: reabsorbs electrolyes, nutrienrs, and water

• loop of henle : estabilsihes and maintain osmotic gradient

• descending limb: permeable to water (passive transport)

• thin ascending limb: permeable to Na+ and Cl- (passive transport)

• thick ascending limb: active transport of Na+ and Cl-

do fishes, amphibians, and non avian reptiles have the loop of henle?

no

do avian reptiles produce urine or uric acid?

uric acid

Know that depending on desert animals there will be ________ loops of henle, they will reabsorb a lot more water, they may be active at night. A kangaroo mouse (desert animal) most of the water is produced through metabolism, and it produces little urine 

longer

Filtrate becomes urine in the _____ ________. Urine exiting the collecting ducts moves from the kidneys into the ureters and then is stored in  the bladder until urination  

renal pelvis

descneding limb is permable to ? and is it active or passive?

• water

• passive: moves water out

thin part of ascending limb is permeable to _____ and _____. moves via ________ transport

Na+ and Cl- (leaves)

passive transport via diffusion

thicker segment of the ascending limb has ______ transport and _______ is the main solute bc Na+ and Cl- were removed via passive transport

active

urea

what does counter current flow mean?

fluid moves all the time

urine movmeent order

glomerulus filtration, proximal convoluted tubule, loop of Henle (thin descending limb, thin ascending limb, thick ascending limb), distal convoluted tubule, and collecting duct