Ion and Water Balance Flashcards
What are the two main body fluids?
Inttracellular and extracellular
What is intracellular fluid?
the fluid that exists
within cells
What are the three types of extracellular fluid?
- Blood plasma and lymph
- Interstitial fluid : in the spaces
between cells and tissues of the body. - Cerebrospinal Fluid
What is osmosis?
Osmosis is the diffusion of water across a membrane in response to osmotic
pressure caused by an imbalance of molecules on either side of the membrane.
What is osmoregulation?
Osmoregulation is the process of maintaining salt and water balance (osmotic balance) across membranes within the body
Why is osmoregulation important?
Without a mechanism to regulate osmotic pressure, or when a disease damages this mechanism, there is a tendency to accumulate toxic waste and water, which can have dire consequences.
What is a hypertonic solution? What happens when a cell is in a hypertonic environment?
High salt concentration. Water exits cell to balance it out. Tend to shrink.
What is a hypotonic solution? What happens to cells when placed in this environment?
Higher salt concentration within cells, water enters cell to balance. Tend to swell.
What is an isotonic solution?
Equal balance inside and outside of cell.
What is an electrolyte?
Electrolyte is a solute that dissociates into ions when dissolved
in water.
What is a non-electrolyte?
- A non-electrolyte, does not dissociate into ions during water
dissolution.
What are stenohaline organisms? What environments can they live in?
can tolerate only a relatively narrow range of salinity. Restricted to either fresh or saltwater and are incapable of osmoregulation in opposite environment.
What are euryhaline organisms?
can tolerate a relatively wide range of salinity are referred to as euryhaline organisms. This is possible because some fish have evolved osmoregulatory mechanisms to survive in all kinds of aquatic environments.
Is the diffusion of salt/ions across semi-permeable membranes facilitated or passive?
Active
What is facilitated diffusion?
Facilitated diffusion requires protein-based channels for moving the solute.
Why are salt/ions moved by facilitated diffusion?
If electrolyte ions could passively diffuse across membranes, it would be impossible to maintain specific concentrations of ions in each fluid compartment,
What is active transport? What does it require?
Active transport requires energy in the form of ATP conversion, carrier proteins, or pumps in order to move ions against the concentration gradient
Why do people die of dehydration when stranded in the ocean despite being surrounded by water?
Stranded in ocean, drinking salt water:
No matter how much they drink, they will get dehydrated as the body will try to remove as much water as possible to get the high salt concentration out of the body.
What is the relationship between freshwater fish and their environment? What does this mean?
Hyperosmotic; inside of the body contains more salt than outside, thus water tends to enter the body more readily.
What are the challenges of freshwater fish? What solutions do they have to manage this?
Challenges:
* Gaining too much water
* Losing too much salt
(because the environment is relatively hypotonic)
Solutions:
* Drink less or no water
* Osmoregulate:
* Excrete very dilute urine
* Actively transport salts back through the gills
What is the relationship between saltwater fish and their environment? What does this mean?
Hyposmotic; more salt outside the body than inside, water tends to exit the fish.
What are the challenges of saltwater fish? What solutions do they have to manage this?
Challenges:
* Losing too much water
* Too much salt in their system
Solutions:
* Drink seawater
* Osmoregulate:
* Excrete very concentrated urine
* Actively remove excess salts through gills
What relationship do marine invertebrates have with their environments? How does this work? Provide an example.
- Most marine invertebrates, maybe isotonic with sea water (osmoconformers)
- Their body fluid concentrations conform to changes in seawater concentration
- Body fluid salt concentrations comparable to those of the environment
- Ex. Sharks have rectal glands that help with this
Explain rectal glands in sharks. How is this conforming and not regulating?
glands that assist in excreting extra salt if needed (not there for osmoregulation, but to conform to the environment the shark is in)
Explain the evolutionary timeline of osmoregulation.
- Membrane channels and pumps
- Malphigian tubes
- Nephron
- Kidneys
What is a nephron?
The smallest functional unit of a kidney.
List the components of a nephron.
Renal corpuscle
Proximal convoluted tubule (PCT)
Nephron loop
Distal convoluted tubule (DCT)
Collecting duct
Papillary duct
What is contained in the renal carpuscle?
Glomerulus
Where does the nephron interact with blood?
Renal carpuscle
Does blood enter the nephron?
No, just water, ions and small molecules.
What happens in the renal carpuscle?
Filtrate is produced.
What happens in the proximal convoluted tubule?
Reabsorption of water, ions and organic nutrients.
What are the two parts of the nephron loop?
Descending thin limb, thick ascending limb
What happens in the descending thin limb of the nephron loop?
Further reabsorption of water.
What happens in the thick ascending limb of the nephron loop?
Reabsorption of Na+ and Cl-
What happens in the distal convoluted tubule of the nephron?
Secretion of ions, acids, drugs, toxins
Variable reabsorption of water, sodium ions, calcium ions under hormonal control
What happens in the collecting duct of the nephron?
Variable reabsorption of water, reabsorption or secretion of Na+, K+, H+, bicarbonate ions
What happens in the papillary duct of the nephron?
Delivery of urine to minor calyx
Label this image.
I. PCT
II. Renal carpuscle
III. Nephron loop
IV. DTL
V. TAL
VI. DCT
VII. Collecting duct
VIII. Papillary duct
Explain glomerular filtration.
Blood pressure forces water and solutes across the wall of the glomerular capillaries into the
capsular space. Filtration is based on size; small molecules pass through filtration membrane.
How are the osmotic solutions of freshwater fish dealt with in the nephron? (i.e., actively reabosrbing salts & reabsorbing less water)
Solutions:
Actively reabsorb salts:
* Through gills
* Through PCT, DCT and Collecting duct
Reabsorbing less water due
to:
* Large glomerulus
* Absence of loop of Henle
* Short Intermediate segment
* Collecting duct less permeable to
water
How is salt reabsorbed into the body?
[ion] increases in the renal tubule and water leaves the body to decrease
[ion] in the renal tubule (production of dilute urine)
How are osmotic solutions in saltwater fish met in the nephron? (i.e., actively eliminate salts and reabsorb more water)
Actively eliminate salts:
* Through PCT and Collecting duct
Reabsorbing more water due to:
* Small or no glomerulus
* Short PCT and lack of DCT
* Collecting Duct is permeable to water
How is water reabsorbed in the body?
[salt] increase in the body and water moves from renal tubule to decrease
[salt] in the body (production of concentrated urine)
What are the challenges insects face for osmosis?
Losing too much water, dessication
How do insects resolve their osmotic challenges?
- Salts and water from diet and
drinking - Actively balance salts and water
in the Malpighian tubules and in
the hindgut/midgut - Reabsorb further water and salts
in the rectum
What osmotic challenges do mammals face?
- Losing too much water
- Dessication
What osmotic solutions do mammals possess?
Solutions:
* Salts and water from diet and
drinking
* Actively balance salts and water
in the kidneys
* Countercurrent flow of blood
around the nephron ensures ion
and water balance
What osmotic solutions are present in mammals at the nephron level?
- Water reabsorbed in the descending part of the loop of Henle (or nephron loop), DCT and
Collecting duct
Explain the additional example of osmotic solutions on land in the marine iguana.
Spends a lot of time wading in salt water and risks losing too much water and gaining too much salt. The mechanisms of the nephron are not enough to protect against this. Instead, has salt nasal glands that release excess salt.
What is the function of the human excretory system? What are some examples?
Remove waste. Ex. sweat through skin, CO2 through lungs, toxins through urine
What parts make up the human excretory system?
kidneys, ureter, bladder, urethra
What is the function of the renal artery?
supply blood to the kidneys
What are ureters?
ureters are urine-bearing tubes that exit the kidney and empty into the urinary bladder.
How does the body know when to urinate?
The bladder contains sensory nerves, stretch receptors that signal when it needs to be emptied
Where do The arteries, veins, and nerves that supply the kidney enter and exit?
Renal hilum
What are the names of the three layers surrounding the kidney?
Renal fascia - tough connective tissue
Perirenal fat capsule - anchors kidneys in place
Renal capsule
What are the three inner regions of the kidney?
Outer cortex
Medulla
Renal pelvis
What does the kidney do?
Excess water, electrolytes, and wastes are transported to the kidneys and excreted, helping to maintain osmotic balance
What is the function of the renal pelvis?
renal pelvis collects the urine and leads to the ureter
Where are the nephrons located?
In the renal cortex.
What do nephrons do?
nephrons remove wastes, concentrate them, and form urine that is collected in the bladder.
What are the three principal functions of the nephrons?
filtration, reabsorption, secretion
What are the three main parts of the nephron?
renal corpuscle, a renal tubule, and the associated capillary network,
What is the filtrate like once it has made it to the DCT?
By the time the filtrate reaches the DCT, most of the urine and solutes have been reabsorbed. If the body requires additional water, all of it can be reabsorbed at this point
Where does tubular reabsorption occur in the nephron?
In the PCT.
What are the ascending and descending loops in the loop of Henle each permeable to?
acending loop only permeable to sodium and chloride , descending only permeable to water,
Use this image to countercurrent multiplication.
The loop of Henle acts as a countercurrent multiplier that uses energy to create concentration gradients. The descending limb is water permeable. Water flows from the filtrate to the interstitial fluid, so osmolality inside the limb increases as it descends into the renal medulla. At the bottom, the osmolality is higher inside the loop than in the interstitial fluid. Thus, as filtrate enters the ascending limb, Na+ and Cl- ions exit through ion channels present in the cell membrane. Further up, Na+ is actively transported out of the filtrate and Cl- follows.
