BIOL 224 FINAL Flashcards
What is osmoregulation?
The process of maintaining salt and water balance across membranes in the body
What is an electrolyte?
A compound that dissociates into ions when dissolved in water, makes up part of the fluids inside an surrounding cells
What is osmosis?
The spontaneous movement of water through a selectively permeable membrane from low solute concentrations to high solute concentrations, works via entropy
Why is osmoregulation important in animals? (2)
Salt and water concentrations in the cells provide an optimal environment for proteins and enzymes to function effectively
If ionic/osmotic/pH conditions in the cell are not ideal then physiological processes will be disrupted
How does water cross the plasma membrane?
Aquaporins
What is tonicity?
Measure of effective osmotic gradient, only influenced by solutes that cannot cross the membrane (hyper/ hypotonic)
What are the two kinds of transport in epithelial cells?
Paracellular transport –> Movement between cells
–> Leaky vs tight
Transcellular transport –> movement across cell membranes
What are the three homeostatic processes?
Osmotic regulation
Ionic regulation
Volume regulation
What is an osmoregualtor?
Osmotic pressure of body fluids is homeostatically regulated and usually different from the external environment
Energetically expensive
terrestrial animals, freshwater fish, some marine fish
What is an osmoconformer?
Maintains an internal environment osmnoticaoly equal to their external environment
mainly found in oceans where ~1000mOsm
High degree of cellular osmotic tolerance
Less energetically expensive
Marine invertebrates, some insects, sharks
Describe the differences in osmoregulation between a marine and freshwater fish
In freshwater fish, –> inside of the fish has more solute = water moves into fish, removes mainly water in dilute urine
In marine fish, –> inside of the fish has less solute than water = water moves out of fish, removes mainly salt and little water through gills and scant urine
What is an osmolyte?
A low molecular weight compound that influences the properties of biological fluids, can also interact with cell constituents and influence protein folding
ex) amino acids and sugars
ex) TMAO –> natural osmolyte that acts as an osmoprotectant
What are the two kinds of osmoconformers?
Euryhaline –> adapted to a wide range of osmotic changes
common to species in intertidal zones, salmon
Stenohaline –> can only live in small ranges of salinity
most freshwater fish cannot survive in a marine environment and vice versa
Are sharks osmoconformers or osmoregualtors? Explain
Sharks are osmoconformers, meaning they are isosmotic to their environment, but the makeup of internal ion concentration is not the same
Sharks use urea as an osmolyte to prevent water loss in the marine environment, keeping salts inside, too much can be bad so this is countered by TMAO
Sharks have slightly higher solute concentration than seawater meaning they do not need to drink water like other marine fish –> can use far less energy to osmoregulate
What is the functional unit of the kidney?
The nephron
Responsible for the formation of urine
What are the four basic nephron processes?
Glomerular filtration –> forming of the primary urine
Tubular reabsorption –> of substances that are needed by the body
Tubular secretion –> of substances to be eliminated
Excretion –> resulting in urine
What does the glomerulus do and where is it located?
Bundle of capillaries situated between two resistance vessels, contained within the bowmans capsule
Glomerular filtration is the first step in urine formation
Explain glomerular filtration
First step in urine formation –> separates plasma from the blood
Driven by blood hydrostatic pressure
Contains small plasma solutes and water
Contains no other cells or proteins
99% of filtrate is reabsorbed
Give a broad overview of the formation of urine
Glomerulus, proximal convoluted tubule (PCT), loop pf Henle, distal convoluted tubule (DCT) and collecting duct (CD)
Describe tubular exchange in the PCT
all tubular exchange with blood is done by a single layer of renal epithelial cells
–>NaKATPase is the main driving force in PCT providing energy for:
—> Cotransport of AA and glucose
—> countertransport of H
—> other molecules
What is the renal threshold and what is the transport maximum
The renal threshold is when glucose transporters are fully saturated and glucose becomes lost in urine
The transport maximum is when all carrier pumps and proteins are occupied
Describe reabsorption and secretion in the PCT
Reabsorption –> 65% of filtered water, same wth Na, 100% of glucose and AA
Secretion –> Urea, uric acid, H+, NH4+
What is the function of the loop of Henle
The Loop of Henle is the U-shaped portion of the tubule divided into three main
segments. Recovers water and sodium chloride from urine and allows production of
urine that is far more concentrated than blood.
*The liquid entering the loop of Henle is the solution of salt, urea, and other substances not reabsorbed by the PCT.
*The thin descending limb, is permeable to water.
*The liquid reaching the bend of the loop is much richer in salt and urea than the blood plasma is.
*The thin ascending limb receives lower volume of fluid. Is the diluting segment of the nephron. –> Impermeable to water but permeable to ions:
*Ion concentration becomes more and more hypotonic from the bottom to the top.
*The loop of Henle establishes an osmotic gradient in the medulla via the use of urea, reabsorbs another20% of water
Explain what happens when fluid reaches the DCT?
Fluid reaching the DCT is about 20% of the original filtered volume
*This fluid is hypotonic relative to plasma
*~7.5% of the filtered Na+ is reabsorbed in DCT & connecting tubule
*DCT is not usually permeable to water, but later nephron segments are
Describe optional and obligatory reabsorption in the DCT and CD
Aldosterone increase
–>Expression of luminal Na⁺ channels, and
–>Number of Na⁺/K⁺-ATPase pumps
—>*Stimulate Na⁺ reabsorption and K⁺ excretion;
ADH control expression of aquaporins
–>*Physical pathway for water to pass through cells;
Both hormones control the quantity of water that is reabsorbed;
Atrial natriuretic peptide;
–>A hormone secreted by the atria of the heart
–>Inhibit Na+reabsorption.
How is mineral balance regulated in the DCT and CD?
Hypothalamic osmoreceptors detect increases
in blood osmolarity(Sp.) and respond with:
Increase ADH secretion from the posterior pituitary gland.
–>*Acts on the kidney to reabsorb water from the forming urine.
Inhibit aldosterone secretion
–>*Causes elimination of Na+
Increases ANP secreted from the atria of the heart.
–>*Decreases Na+ reabsorption.
these changes all target the principle cells of the DCT
Explain Hormonally controlled reabsorption of Ca2+ in the DCT & CT
Obligatory reabsorption Ca2+ occurs mainly in the PCT.
But parathyroid hormone (PTH) secreted by the parathyroid glands control Ca2+ reabsorption.
Target the principal cells of the ascending loop of Henle DCT and CD.
What are the nitrogen compounds that animals must excrete?
Ammonia (NH3) –> very toxic
Urea
Uric acid
a combo
What are the three methods to excreting ammonia (NH3)?
Ammonotely –> Nh3 can be safely transported and excreted from the body in diluted solutions, animals with plenty of water excrete ammonia as their primary waste
Some get rid of it through diffusion through respiratory surfaces (tadpoles)
energetically expensive
Ureotely –> other animals detoxify ammonia by converting it to urea
mammals, most amphibians, some terrestrial invertebrates
requires much less water
–> in ruminants, after synthesis in the liver, urea enters the rumen via saliva
Uricotelic –> water is conserved even more by the formation of uric acid
energetically more expensive, but less toxic b/c very insoluble
used by many reptiles and birds –> ostrich is the exception
What is the role of the kidney in acid base regulation?
Intercalated cells in the DCT & collecting ducts participate controlling pH in the internal media.
α-intercalated cells secrete protons via an apical K+/H-ATPase and reabsorb bicarbonate by a Cl/HCO3 exchanger, located in the basolateral plasma membrane.
b-intercalated cells secrete bicarbonate by an apical Cl/HCO3exchanger
What is both the biochemical and physiological definition of respiration?
Biochemical –. metabolic process by which an organism obtains energy by oxidizing nutrients an releasing waste products
Physiological definition –> movement of O2 form the outside environment to cells within tissues and removal of CO2 to the environment
How does O2 get from the air to the mitochondria? (4)
Ventilation
Diffusion of O2 into blood
Perfusion –> passage of fluid thru system to organ or tissue
Diffusion –> of O2 from tissues to mitochondria
What is external respiration
gas exchange through thin membrane, only works on very small animals, diffusion has to follow ficks law which dictates maximum rate of diffusion and can be used to compare to body size
Why did circulation evolve?
To bypass the limits imposed by diffusion –> reduces distance between tissues and PP O2/CO2
Explain the benefits of respiration in an aquatic environment
O2 more soluble in cold water than warm
Respiratory surface can be kept wet
Rate of diffusion is slower
Ventilation in a one way direction –> gills –> water moves one way over gills while blood goes the other –> maximizes P and O2 diffuses as a very high rate
CO2 is 20 times as soluble in water meaning excretion can be achieved by ventilation required to get O2
I think i know the hemoglobin stuffs, its allosteric, cooperative, high o2 affinity etc
yea
What does carbonic anhydrase do?
catalyze rapid interconversion of Co2 and H2O to bicarbonate and H+
Helps get CO2 out
What are gills?
Respiratory organs with extensions of the body respiratory surfaces
Provides a high surface area used by aquatic organisms to efficiently extract dissolved O2 from water and to excrete CO2
What are the two kinds of gills?
External gills –> extend out from body, no protective coverings, use tentacle like structures –> small molluscs
Internal gills –> protected by body chambers, currents of water are directed over the gill
What are the two kinds of ventilation in fish?
Double pumping mechanism –> bony fish, creates pressure gradient by opening and closing of mouth
Ram ventilation –> pelagic fish like some sharks and mackerl, breathe by moving forward
What are gill lamellae?
Thin plate-like structures with a capillary blood network
–> increased the surface area of contact with the environment to maximize gass exchange
–> primarily occurs along the length of the secondary lamellae
–> the tissue is only one cell layer thick
Why are countercurrent gas exchangers so efficient?
PO2 in the gills is higher than P02 in blood
Explain gas exchange in large and small insects
In small insects –> simple diffusion through tracheoles
In large insects –> ise ventilation via the opening and closing of spiracles
In insects co2 is taken up by HCO3 resulting in negative pressure that opens spiracles
Explain how birds breathe via cross current exchange (6)
The air sacs, which collectively contain several times as much air as the lungs, are not respiratory surfaces.
*Bird lungs are rigid and do not expand or contract.
*The air sacs do,
Air flow only in one direction through the lungs
*Rather than in and out, as in other vertebrates.
Two cycles of inhalation and exhalation are needed
Air always flows through the lung from back to front
*through an array of fine, parallel tubes that are surrounded by a capillary network.
Blood flows in a direction across that of the air-flow
*Crosscurrent exchange.
*Bird lungs extract more O2from the air than the lungs of mammals do, but less than with the countercurrent exchange system seen in fish.
PO2 of blood leaving the breathing organ is higher than exhaled medium
How do birds fly at high altitudes?
Reduce the O2 demand by lowering metabolism
Decrease temperature in lungs –> increasing O2 loading
Describe the branching that occurs in the mammalian lung
Trachea forms two primary bronchi
Bronchi branch into bronchioles
Bronchioles branch and eventually become alveoli ~300mil total
Explain how gas exchange in the mammalian lung occurs by ventilation and perfusion
ventilation refers to the movement of air in and out of the lungs
negative pressure mechanism –> air is exhaled passively, diaphragm plays role
air is forced into the lungs via positive pressure by muscle contractions
perfusion is the circulation of blood in the pulmonary capilleries
tidal ventilation, uniform pool, ppO2 is lower in blood than fresh air meaning it diffuses
How do we control our breathing?
Peripheral chemoreceptors
Monitor PPCO2, pH, and PO2 (second response)
How do amphibians breathe?
Via positive pressure breathing, effectively swallow the air
little folding in lungs and high efficiency because CO2 is easily lost via skin
Describe circulation in protostomes such as sponges and cnidarians
have no specialized circulatory systems
Products of digestion exchange via diffusion
Sponges use water to aid digestion
Cnidarians have a gastrovascular cavity attached to their mouth
Describe open circulatory systems and where they are found
Found in many invertebrates
Flows hemolymph through vessels, empties into open body cavity, no arteries or veins
Hc is suspended in hemolymph and not attached to blood cells
some insects have accessory hearts for each wing and leg which help pump as a part of the digestive process
