Final Exam Notes Flashcards
Physiology
the study of how organisms work (form and function)
Design rules for plans and animals
they must obey physical and chemical laws including scaling and they are constrained by evolutionary history, wha can it do with what it already has
Scaling
how do things change when things change in size, as a physiological characteristic
Safety factor
we have two lungs when we really only need the one, and the pancreas is 80% larger than we need it to be function properly … bridges are stronger than they need to be as well
First law of thermodynamics
energy cannot be created nor destroyed
Second law of thermodynamics
entropy (disorder) always increases, it takes energy to remain organized (alive), plants must capture solar energy and animals must eat
Input / Output Budget
plants and animals require to take in the nutrients and energy in order to function - used for maintenance, generating of external work, reproductive fitness and biosynthesis, using energy as efficiently as it can in order to maximize the output (animals are very inefficient, plants are very efficient biomechanical maniacs, but they do perform the same similar things)
Temperature
a measure of the speed or intensity of random motion, animals must adapt to their environment and the temperature in which they live, temperature is the motion by the atoms in the object
Temperature of a substance is proportional to …
the product of the mean square speed of the random molecular motions and the molecular mass
Temperature vs. Heat
temperature is not heat, heat is energy, heat and temperature are related in that energy will influence movements of molecules
Heat
amount of energy in the object
Temperature determines …
the direction of heat transfer - warm to cold
Animals and their environment temperature …
despite the type of animal, there is a constant relationship between the organism and its environment in regards to heat transfers - using convection, evaporation, conduction, radiation, etc … to change the animals temperature, uses its environment
Plants and animals and their environment temperature …
receives radiation heat from the sun either direct or reflected through the clouds, radiation from plants and the sky, this enters the animal, and the animal itself produces heat of its environment
Absolute Zero
when molecules stop moving - there is no energy
15 degrees celcius
where development and growth can occur for many insects and plants
50 to 70 degrees celcius
the machines that carry out metabolism often have denaturing of their proteins near 50 to 70 degrees
37 degrees celcius
body temperature of most mammals
endotherms
generate internal heat
ectotherms
rely on external temperature to determine body temperature
homeotherm
defend a constant body temperature
poikilotherms
allow body temperature to vary
heterotherms
have more than one temperature set point, or switch between homeothermy and poikilothermy
regional endothermy / heterothermy
different body temperatures in different parts of the body
ectotherms and poikilotherms
some amphibians and plants
endotherms and poikilotherms
plants and insects
ectotherms and homeotherms
lizards
endotherms and homeotherms
mammals
relationship between temperature and metabolism in an ectotherm
in humans, metabolic rate (oxygen consumption) is relatively constant because we have constant internal temperature, but ectotherms vary their rate depending on their environment, increasing body temperature, increases metabolic rate in an almost exponential relationship
Q 10
the temperature coefficient is the ratio of the rate of a process at one temperature over the rate of the same process (reaction) at a temperature of 10 degrees lower, how much does the rate of a process change over the space of 10 degrees celsius
What can offset the response of Q10
acclimation
rate increase for many physical and chemical processes
about 1 increase of the rate
rate increase for biological reactions
about 2-3 increase of the rate for biological reactions
how do temperatures changes occur
temperature determines motion and therefore the rate at which molecules encounter one another, more interactions = more reactions, increasing temperature increases the chance for collisions - more interactions and thereby increasing the amount of interactions that occur, temperature also determines the conformation and efficiency of enzymes (Q10)
How do enzymes work
enzymes have an induced fit - requires a specific orientation of the molecules, temperature can affect the rate at which the substrate and enzyme encounter on another, warms = more often = more reactions
Temperature and enzyme effectiveness
the enzyme’s active site can change shape with temperature, changing in binding affinity for substrate (generally warmer = weaker)
What’s the limit of temperature and the enzyme’s effectiveness
once a certain temperature is reached, the binding site of an enzyme begins to change and therefore the substrate is no longer in correct orientation to the enzyme - there is a limit! at too high of a temperature, the enzyme will become denatured and cannot function at all
Relationship between Km and affinity of an enzyme
Km = the amount of substrate required to reach half of the maximum rate of reaction (Vmax), the higher the Km means lower affinity - needs a lot of substrate to reach half of the Vmax, they are opposite of one another (Km and affinity), low Km = high affinity
Enzyme affinity and temperature in the Goby fish
decreasing affinity as the temperature increases, what temperature is optimal? - normally around 30 degrees, the highest temperature is not optimal because it is too efficient because it actually ends up letting go of the substrate (poor catalytically) too easily
Affinity is too high at lower temperatures, therefore …
the enzyme binds too tightly to the substrate making the reaction slower (not released as fast)
Affinity is too low at higher temperatures, therefore …
the enzyme binds too loosely to the substrate making the reaction less likely to occur
Protein’s structure at different temperatures
at higher temperatures it is not as tight as it adopts different conformations and lower temperatures it becomes even more unassembled
Enzyme Adaptation
the same enzyme in different organisms, in different environments have all adapted to function in different temperatures depending on their environment, through adaptation these species have optimized the enzyme function for the environment in which they live
Metabolic Rate
an animal’s rate of energy consumption, the rate at which it converts chemical bond energy to heat and external work, this rate is temperature dependent
Fickle cue
it is not reliable - there are different seasons with different temperatures, not a good environmental cue to tell animals of what to do, plants and animals often use more reliable cues, like photoperiod to govern their seasonality
Thermal inertia
the degree of slowness with which the temperature of a body approaches that of its surroundings and which is dependent upon its absorptivity, its specific heat, its thermal conductivity, its dimensions and other factors
Thermal inertia and size
size does matter - a smaller organism will be more affected in a short term temperature change because a larger organism has more body mass meaning there is more area for heat to be stored
What can an endotherm do physiologically with temperature changes
altering oxygen demand and delivery, change metabolism, change insolation (grow fur), membrane fluidity (more solid composition at low temperatures and more fluid at high temperatures) and enzyme denaturation (chaperon / heat shock proteins, change the enzyme at the amino acid level in order for them to function more effectively at different temperatures)
Adaptation
genetically controlled trait that though the process of natural selection, confers an advantage to the individual, altered genome
Acclimation
a chronic response of an individual to a changed environment in numerous ways (ex. summer vs. winter), it is an altered genome expression, altered phenotype, using what you already have and changing it for the environment
Enzymes between closely-related species
enzymes have adapted over time to have different optimal temperatures, even though the different species are closely-relted of the same genus, genome isn’t changing but there are different parts expressed or some portions more frequently expressed
Thermoregulation
maintaining constant body temperatures regardless of the environment
Environment of the forest vs. dessert landscapes
going with the flow of the environment is easier in some places than others, it would be easier in the watered environment of the forrest rather than the sun rich environment
Are ectotherms completely at mercy of their environment?
NO - the sum of all heat inputs and outputs should be zero, including radiation, convection, conductance, latent heat exchange (transpiration / evaporation) and metabolism
Radiation in plants
they can minimize radiation in the heat absorbed or lost by changing leaf colour (red or white in sunny and green in shaded area) or their leaf angle
Convection in plants
changing leaf shape (how much of the leaf is exposed to the sunlight), more pointy leafs in the sun environment, more rounded within the shade, heat exchange with air molecules
Behavioural thermoregulation in plants
rolling leaves and pointing them vertically reduces sun interception, saving water, maximize sun exposure and minimizing water loss
Behavioural thermoregulation in lizards
lizards move around the island to their optimal temperature, they are not evenly distributed - movement is a behavioural change
Lat heat of vaporization of water
2270 kJ / kg
If you are hot and have a glass of cold water
it is more effective to dump it on your head than it is to drink it in order to cool off faster and more efficiently
If you are already sweating and have a glass of cold water
it is better to drink it because your body is already maximally evaporating
Impact of CO2 levels on leaf temperature
in areas of higher CO2 levels - the leaves do not transpire as much because they already have enough CO2 for survival, therefore their stomates are closed and evaporation is no longer performed, therefore they have higher leaf temperature
Where does ectotherm heat come from?
metabolism, futile cycling / alternative oxidase pathway (in plants) and muscle contractions (in animals)
Alternative oxidase pathway in plants
the product is mostly water, there is no proton pumping, therefore no energy (ATP) is formed
Use of metabolic heat in plants
to warm up tissues to a more optimal physiological temperature, to attract pollinators in early spring - increases odour diffusion and provide warmth for ectothermic pollinators, less energy that the pollinators have to use if the plant itself is warmer
Heat generation for insects when they are in flight
greater heat production as the air temperature is cold, less energy has to be expended when the air temperature is warmer
During brooding young for the queen bee
it will increase its metabolism in order to produce more heat when the air temperature is lower
bees defending the nest
bees will come together forming heat together to kill enemy
why are fish ectotherms
fish can generate heat (like anything else with metabolism), but they have problems keeping it because they are surrounded by thermally-conductive water, they are in a medium that exchanges energy so quickly, too thermally conductive, that the fish cannot maintain a higher body temperature
Why are ectotherms ectotherms when they generate internal heat?
ectotherms don’t generate heat that contributes to interna function, but all organisms generate some heat through metabolism
Rete mirabile
warm arterial blood looses heat to the cooler venous blood which goes back to the heart / core, allows for very effective counter-current exchange of heat
Red muscle
high myelin - very metabolically active, therefore their temperature is elevated above water temperature, they have more continuous activity, heat comes from the normal heat produced by contractile activity of the red muscles, the only different is the heat is retained, red muscles undergo more quick, shorter bursts of activity
Regional endothermy in some bony fish
allows long migration through water at different temperatures, to allow better performance as a predator chases the prey int colder water, and it improves in power output of muscles
Overview of metabolism
metabolism is the breakdown of complex molecules into simple molecules, energy is required to break down the molecules
Light dependent reaction of photosynthesis
uses water to produce oxygen, uses ADP, NADP and produces ATP and NADPH, energy input comes from photons to cause charge displacment, photochemistry takes place
Light independent reaction of photosynthesis
uses carbon dioxide to produce sugars and uses ATP and NADPH to produce ADP and NADP, energy input from light dependent reactions
Light = energy
shorter wave lengths have higher energy contents and this can actually be too damaging to photons, longer energy wave lengths have lower energy contents and is not sufficient enough for photochemistry
Optimal wavelengths and energy for photosynthesis
visible spectrum around 450 or 500 because this is where chlorophyll a and b can efficiently absorb light to be transferred on to the photosystems (more than 600 nm nothing will happen)
Pigments
are molecules that absorb photons, generally coloured in the wavelength they reflect
Fluorescents
energy is lower because energy is lost
chlorophyll a and b and beta carotene
absorbs higher energies than what is used during photosynthesis (than that absorbed by photosystem I and II)
Where are photosystems I and II found
photosystem I is found in the stroma and photosystem II is found in the thylakoid membrane, linked through mobile electron carriers
Behavioural adaptation of chloroplasts
deep light - the chloroplasts clumped together excuse they try to absorb as much light as possible and they become separated in a strong light
How much energy actually needs to be present from photosynthesis
only about 10% of sunlight is actually needed for photosynthesis
Energy transferring to the reaction centre
the reaction centre doesn’t absorb much energy itself, light absorption occurs in the antenna complex (can include chlorophyll a and b) that capture incoming light, they transfer energy towards the reaction centre (found within photosystem I and photosystem II)
it is movement of energy, not movement of electrons in this portion, energy from harvested photons is transferred to the reaction centre, electron movement takes place at the reaction centre
two photosystems required in oxygen involving organisms - mainly plants
Photosynthetic photosystems
photosystem II receives the energy of the photon and water is oxidized to give the photosystem II an electron and protons remain in the lumen, the electron is taken by an electron mobile carrier (PQ) to cytochrome c where another proton is pumped into the lumen using some of the energy from that electron, then another electron mobile carrier (PC) takes the electron to photosystem I where the energy is used to reduce NADP to NADPH
The milieu interieur
term to describe the internal environment of organisms as distinct from the external environment, internal conditions held constant despite changes on the outside in their environments (ex. blood glucose, temperature, pH)
conformity
variations
regulation
regulates no matter what the external environment conditions are
mixed conformity and regulation
animals that do both, most animals have some factors they regulate closely but others they allow to conform
advantage of regulator
not required to stay in a certain environment, can move more, they don’t have to constantly adapt to a changing environment
disadvantage of regulator
requires a lot of energy, especially costly for temperature
advantage of conformity
energy is much less
disadvantage of conformity
body most have mechanisms to deal with the constant change of the environment
zone of tolerance
sets limits of where the organism can live, due to limits of regulation, range of which an organism can regulate its internal conditions, at each extreme they must conform, if these zones are reached, their fitness decreases
Homeostasis
the coordinated physiological processes which maintain most of the constant states in the organism, relatively stable internal physiological environment, usually involving extensive feedback mechanisms
How does homeostasis work?
there is a controlled variable (ex. pH, temperature), and a sensor (hypothalamus) compares the value of this controlled variable to the set point (what it should be) and sends a signal to the effectors of the body to begin working on changing the value back to the set point
Negative feedback loop
it shuts off once the set point is reached
On / Off vs. proportional control negative loop
measures how far you are to the set point and gives a more strong or weak control depending on how off it is from the value
Control in homeostasis
hormonal (ex. insulin and glucagon), neuronal (vasoconstriction), biochemical and molecular (ex. cytoplasm composition)
Fever - homeostatic
when you have a fever, the set point is altered, it is still regulated but at a new set point, regulated very closely, little fluctuation when you have a fever in body temperature
Positive feedback
control system reinforces deviation of a controlled variable from set point (ex. oxytocin in breast feeding), change promotes more change in the system
Scaling definition
the study of structural, mechanical and physiological properties change with changing size, an organisms size affects its structures and mechanisms
Sizing of an animal and its body mass
as linear size doubles, body mass increases 8 folds (2 to the power of 3), bones get bulkier and longer
isometric scaling
things change by the same factors, direction proportionality, length is doubled therefore mass is doubled, linear relationship
isometric scaling on a graph
slope is 1 and intercept is 0
allometric scaling
proportionality changes with size, relationship is not 1:1 (allo means other), non-linear relationship
allometric scaling on a graph
slope is more or less than 1, intercept may or may not be 0
Using scaling to understand physiology
summarizing huge data sets, predicating unknowns, can look for deviations (residual analysis), there can be evolutionary signals in the similarities as well
Heart rate vs. Heart weight
heart weight relative to body size remains the same, but heart rate changes dramatically for different organisms
Catabolism
breakdown of molecules to release energy
Anabolism
use of energy to assemble molecules
isolated systems
will eventually decay to randomness (entropy increasing), no energy or matter is exchanged
open systems
exchange heat with its surroundings, will not decay to disorder, will remain in organized state
energy definitions
capacity to do mechanical work (force x distance) or capacity to increase order
energy that can do physiological work
chemical, electrical, mechanical can do physiological work (to do physiological work in order to maintain organized state of the organism)
what energy cannot do physiological work
heat
chemical bond energy
the energy liberated or required when atoms are rearranged into new configurations, totipotent (can be harnessed and used for other mechanisms, it drives everything else)
electrical energy
the energy that a system possesses by virtue of the separation of the positive and negative charges (potential), does physiological work as well (totipotent) (ex. membrane potentials used to pump other things across the membrane)
Mechanical energy
the energy of organized matter in which many molecules move simultaneously in the same direction, totipotent / high grade (ex. moving a limb or circulating blood)
High grade energy vs. low grade energy
high grade energy also known as totipotent can be used to perform physiological work while low grade work cannot, it is considered waste
heat energy
the energy of random motion, all matter above absolute zero temperature possesses heat energy, it is low grade and considered a waste
why is heat important if it is a low grade energy
heat is important because it determines temperature which influences physiological rates, but does not do direct physiological work
calorie
amount of energy (heat) to raise the temperate of 1 gram of water by 1 degree
power
rate of energy used per unit of time
Input / Output budget, more detail
all absorbed chemical energy (energy that can be absorbed in the body) is either stored in chemical energy or eventually converted to heat, efficiency of ATP to mechanical work is about 25% (that actually moves you around, must is internal muscle movement, or heat production / loss)
Biosynthesis in input budget
energy is kept within the body (growing or fat storage) or energy that exists the body (ex. skin lose, gametes)
Efficiency of metabolism
very inefficient - about 75% of energy is lost by heat (rearranging molecules is expensive)
Maintenance of the input budget
all of this energy eventually ends up at the heart (ex. body temperature, pumping blood)
External work energy use in input budget
movement of stuff outside of body (ex. moving yourself or other things), friction that is created through movement produces heat
measuring metabolic rate through direct calorimetry
metabolic rate is measured directly from the amount of heat released by an organism, melts ice surrounding it which is then measured
measuring metabolic rate through indirect calorimetry
metabolic rate is calculated from the concentrations of oxygen consumption and carbon dioxide production or by material balance (energy in - energy out), indirect because you are measuring the products of metabolism
Heat produced between different energy molecules from food sources
much more heat is produced when the animal is burning off lipids or proteins, but there is very little to no change of heat for carbohydrates being used in metabolism
Basal metabolic rate
in endothermic homeotherms, done in fasting and resting conditions
Standard metabolic rate
used for animals that do not alter their temperature (ectothermic poikilotherms), still in fasting and resting conditions at a defined temperature
Fixed metabolic rate
daily energy expenditure of a free living animal
Allometric scaling of metabolic rate
a larger animal eats a lot more food, but when the amount of food is scaled to the amount of energy it needs, a smaller animal eats much more than its body weight for the energy it needs, but a larger animal does not need as much energy from the food compared to its larger body weight
weight-specific metabolic rates
when you get small, your metabolic rate gets much higher, this relationship may be due to smaller animals having a greater surface area for their mass therefore they will be losing heat at a greater rate (maintaining same body temperature requires higher metabolic rate to produce more heat)
Costs of Activity
measuring the oxygen consumed and carbon dioxide produced during different locomotion activity
Animals that swim and energy costs
the energy cost exponentially increases with speed
runners and the energy costs
the energy cost linearly increases with speed
smaller animal vs. larger animal and energy costs
smaller animals have a higher energy cost than a larger animal to go the same speed, takes a lot of energy for small animals to get somewhere in good speed
Costs of activity in flying birds
when a bird flies faster they get lift, but they also have to overcome drag which means more energy is needed, when a bird flies slowly they are just hovering but they need to overcome the force of gravity - high energy, middle speeds requires less energy then higher or lower speeds
The metabolic ceiling
metabolic rate that is the limit of the organism, metabolic machinery (ex. heart, liver) is what contributes to their metabolic limit
how much energy should a parent animal give to their children
they found it was about 4 to 5 times their BMR
Higher BMR requires …
a bigger heart, or more efficient liver to support this
Aerobic activities and BMR
for activities like aerobic activities you can perform 6 to 8 times your BMR
Multiples of your BMR sustained
this will only be sustained for a few minutes, multiples of your BMR can only be done for shorter timer periods (no longer than a few weeks), this requires continuous food and energy replacement through the time for the longer time periods, it takes larger, more expensive organs to support greater peak metabolic rates
Endothermic homeotherms and their physiological features
maintain a high and stable body temperature using internal heat, high resting metabolic rate (cellular, tissue and whole animal levels), and insulation (fur, feathers, blubber) is usually present to retain heat
Thermal neutral zone
range of temperatures where the metabolic rate does not change for an endotherm, getting below a certain point (the lower critical temperature) the metabolic rate must increase to increase body temperature and further mechanisms must kick in
Vasoconstriction
when you are cold, your blood vessels can vasoconstrict in order to keep the blood further from the skin and keep heat in
vasodilation
when you are too hot, your blood vessels dilate in order for the blood to get closer to your skin and the heat can be evaporated out through sweat glands and leave the body
Mechanisms to change thermal conductance
thermal conductance is how easier it is for an organism to gain or lose heat, can change this through vasoconstriction, vasodilation, pilomotor response, ptilomotor response and posture changes
pilomotor response
contraction of smooth muscles of the skin caused by cooling and resulting in goose bumps
ptilomotor response
response of the smooth muscles of the skin during periods of excessive heat
postural changes
a postural position more curled up in order to preserve body heat or huddling - huddling close with others of your species in order to warm yourself up
Arteries and veins maximizing heat retention
if the artery is right next to the vein, the heat will move from the high temperature of the artery to the low temperature of the vein which keeps the heat within the core and keeps the paws (extremities) colder during cold temperatures
Arteries and veins minimizing heat loss
if the artery and vein are further apart, heat will not be exchanged until the capillaries in the paws which results in warmer extremities and lower core body temperature
Cold adapted animals and thermal conductance
cold adapted animals have a lower thermal conductance than tropical animals
Reducing thermal conductance mechanisms
foxes have larger coats in the winter to reduce thermal conductance, have lower thermal conductance during the winter than in the summer
Shivering
caused by non-synchronous muscle contractions and generates excess heat
Shivering and hamsters
if they are acclimated to a higher temperature, their muscles will have very high electrical activity as they shiver to keep warm in low temperatures, but in hamsters when they are acclimated to a lower temperature, their muscles do no have to work as hard in shivering and therefore have much lower electrical activity during shivering at cold temperatures, but they still work harder than in warm temperatures
Non-shivering thermogenesis
production of excess heat by ion leaks and uncoupling in the mitochondria in brown adipose tissue used for ATP synthesis which used for uncoupling of ions, no net ATP but it does produce a lot of wasted heat
Brown adipose tissue
has a lot of mitochondria to produce this extra heat, it is specialized for non-shivering thermogenesis
Upper critical conductance
at the UCT - conductance is maximal, above the UTC, excess heat can be stored allowing the animal’s temperature to drift up (which saves it a lot of water) or heat can be lost through evaporation, heat can also be lost through sweating, licking, panting and gular flutter
Aerobic metabolism
is dependent on the exchange of oxygen and carbon dioxide from the environment
Relying only on diffusion for gases
it is too slow to maintain the rates of gas exchange needed to support the metabolism of larger organisms, for very small organisms, diffusion would be affective because its size allows this movement - larger surface area relative to its mass / volume
Gas exchange in respiration
getting oxygen out of the external medium and into the cells - often via the circulatory system and getting carbon dioxide out of the cells and into the external medium
where is the oxygen
about 21% of the air in the atmosphere is oxygen, but very little dissolved in water, therefore water breather must process a lot of water in order to absorb the oxygen they need, air breathers have a larger concentration of oxygen available for breathing therefore less air processed
Partial pressure
each gas in a mixture (either a gas or a solution) exerts their own pressure, partial pressure is the amount of pressure that the gas of interest exerts
Partial pressures of gases in the atmosphere
21% of oxygen, 78% of nitrogen, 0.93% argon and 0.04% of carbon dioxide
Difference in partial pressures and environments
partial pressure of air will be slightly lower in a lecture hall or crowded room because we are breathing oxygen in, going up in elevation air is thinner and therefore contains a lower oxygen concentration
Gases dissolved in liquids
not the same as having air bubbles, partial pressure of a gas in a liquid is proportional to the partial pressure of that gas in the air
Why wouldn’t a gas contribute to partial pressure in a solution?
gases that have reacted chemically do not contribute to partial pressure in solution because it is no longer the same chemical (that you were measuring the partial pressure of before), only free gas molecules contribute to the overall pressure of the mixture
Henry’s Law
gas dissolved in solution, its concentration is a product of its partial pressure and its solubility in a liquid
Gases solubility in water
oxygen has a very low solubility in water, while carbon dioxide is quite a bit higher
Solute Diffusion - the Fick Equation
net movement of a molecule, moving mostly from high to low but some move from low to high concentration and therefore it must be termed as a net movement, rate of net movement of a molecule is influenced by the diffusion coefficient, the concentration gradient and the area availability of diffusion
What factors influence the rate of diffusion of gas molecules?
the partial pressure gradient, surface area available for diffusion, diffusion coefficient, molecular mass (larger = slower diffusion), distance / width of the membrane (larger = slower diffusion)
What factors of gas diffusion are constant?
molecular weight of the gas, diffusion coefficient and solubility of the gas
What factors of gas diffusion can be changed?
area available for diffusion, partial pressure gradient and width of the membrane can all be altered
What determines the diffusion of gases?
the partial pressure of a gas, not absolute concentration of the gases
Convection vs. diffusion
convection can break dependence on diffusion, and enhance gas movement, diffusion has its limits, organisms have to rely on convection or bulk flow to move gases over larger distances
Gas transport in animals
often is a combination of convection and diffusion
tidal convection
in and out breathing, ventilates lungs
Movement of gases in respiration
the partial pressure of oxygen is higher in the atmosphere than in our lungs, therefore it moves inwards during inhalation through convection and partial pressure of carbon dioxide is greater in the lungs than the atmosphere therefore causing carbon dioxide to exit during exhalation
breathing out very deeply during exercise
when you breathe out very deeply during exercise you can lower the partial pressure even less in the lungs and therefore the partial pressure gradient between the lungs and the atmosphere is even greater and therefore more oxygen enters in the next inhalation
diffusion of gases into the bloodstream
partial pressure is higher in the arteries / capillaries than it is in the tissues of the body, therefore oxygen diffuses to the tissues and is used in the body
constant new flood of blood from the heart with high partial pressures
unidirectional flow (convection) in the circulatory system
larger distance than diffusion, partial pressure in the blood moving trough to extremities lowers as it is used up by the tissues
diffusion from capillaries into tissues
substantial partial pressure drop as the oxygen is diffused from the capillaries to the tissues (mitochondria) where respiration actually occurs, fairly steady decrease of oxygen partial pressure throughout the circulatory system
In the absence of active transport, the diffusion of solutes is driven by the chemical potential of the solute, by contrast, dissolved gases can diffuse against a concentration gradient, this is because …
differences in partial pressure govern gas diffusion
impact of reduced partial pressure of oxygen - adaptation to elevation
two different elevations - higher up, the partial pressure is much less than at sea level
main difference of the population of people living at these two levels is their adaptation to the reduced partial pressure of oxygen primarily through large lung capacity
if the partial pressure gets too low, it can cause respiratory distress
regardless of the the partial pressure of oxygen in air coming in, the population of people have very similar partial pressures of their venous blood
Animal gas exchange
external environment medium and internal body tissues separated by some gas-exchange membrane
getting rid of waste (carbon dioxide) the opposite way from the taking in of oxygen
only works if you have higher partial oxygen pressures on the outside and lower on the inside, and higher partial carbon dioxide pressure on the inside than on the outside
partial pressure of one gas to another does not matter, the movement of these gases only rely on the partial pressures of the same gas in opposite environments
gas exchange membrane
a thin layer of tissue consisting typically of one or two simple epithelia which separates the internal tissues of the animal from the environmental medium (air or water)
lungs
internal organs that contain the medium of the oxygen required, are invaginated
external gills
project into external environmental medium (evaginated - external), surrounded by the medium
internal gills
still considered evaginated because they are a continuation / external to the body cavity, evaginated from the body and project into a superficial body cavity through which the environmental medium is pumped
Ventilation is active if ..
the animal creates the ventilatory currents of air or water that go down to and come from the gas exchange membrane, using forces of suction or positive pressures that it generates by use of metabolic energy
Ventilation is passive if ..
environmental air or water currents directly or indirectly induce flow to and from the gas exchange membrane
rate of O2 uptake (active ventilation) =
volume of the medium and difference between the concentration of inhaled and exhaled gas, rate because it is a continuous process (time factor), how much is taken up by the organism over net time
O2 extraction efficiency
what proportion of the oxygen coming in compared to oxygen be removed
Mammals efficiency of O2 extraction
27% efficiency
Four anatomical variations of gas exchange
tidal gas exchange, cocurrent (concurrent) gas exchange, countercurrent gas exchange and cross-current gas exchange
Tidal gas exchange
inhalation and exhalation of air - common mechanism for mammals
air in lung is able to exchange gas with the bloodstream, diffusional transportation requires close contact
partial pressure of oxygen in the blood cannot be greater than lung
short distances and close contact required
not as efficient as other cases
Cocurrent (Concurrent) Gas exchange
whenever the medium is in close contact with the blood - moving in the same direction (diagram on the left)
how much time it has in contact between the blood and the medium dictates how much gases are exchanged
this can be maximized (the time of contact) to maximize oxygen absorption
diffusion of oxygen and carbon dioxide between medium and blood along contact axis
found in some gill
50-50 equilibration at best
Countercurrent gas exchange
always higher partial pressure in the medium relative to the blood, always exchange to the blood stream
distance for medium to travel in the opposite direction of the blood will determine the efficiency of gas exchange
diagram on the right
diffusion of oxygen and carbon dioxide between medium and blood along contact axis
found in some gill types
much higher extraction efficiency
Cross-current gas exchange
blood coming in always at very low partial pressure relative to the medium
blood system divided into many routes in order to maximize contact points and time for efficient exchange
found in bird lungs
diffusion of oxygen and carbon dioxide between medium and blood along contact axis
high extraction efficiency due to unidirectional medium flow
Carbon dioxide arterial partial pressure in water breathers
the partial pressure of carbon dioxide in the blood leaving the breathing organs is always similar to the carbon dioxide partial pressure in the ambient water, regardless if tidal, co-current, counter-current or cross current
Carbon dioxide arterial partial pressure in air breathers
the partial pressure of carbon dioxide in the blood leaving the breathing organs is usually far above the carbon dioxide partial pressure in the atmosphere because you need the partial pressure gradient in order for carbon dioxide to leave the lungs and exit the body
Low oxygen - detection and response
whole body scale - increasing gill or lung ventilation (increasing rate of breathing = more oxygen)
intracellular, cell scale - hypoxia-inducible factors 1 and 2 (HIF-1 and HIF-2) increase in concentration in a cell when the cell experiences hypoxia to increase the secretion of erythropoietin which enhances production of red blood cells and therefore greater oxygen carrying capacity of the blood and promote angiogenesis - the development of new blood capillaries
Gas exchange membrane area scales …
allometrically with body weight - almost linear, birds and mammals are higher (they have higher surface area for gas exchange), more than fish, amphibians and reptiles but this does not mean they have larger lungs
Gas exchange membrane area between endothermic homeotherms vs. ectotherms
endothermic homeotherms have greater gas exchange membrane area than ectotherms of the same body mass
Gas exchange membrane thickness
does not scale - no matter how large the animal is, the membrane thickness does not really change, mammals and birds have much thinner gas exchange membranes than most other organisms of the same body weight, reptiles have thickness similar to birds and mammals than fish
How to breathe water
fast ventilation - more water across respiratory surface = more oxygen to absorb, efficient absorption would predict countercurrent exchange as common mechanism, high vascularized system with a larger surface area
Breathing by fish
considered external gills, countercurrent mechanism of gas exchange, flow opposite to that of blood, volume is key to fish breathing high volume, uni-directional, countercurrent flow
Breathing by amphibians
primary mechanism is through the skin, gills are important for breathing at the beginning, but diminishes later in life, but skin breathing remains important through the amphibian’s life, mix of water and air breathing, mechanism of breathing changes with life stages
breathing by reptiles
primarily air breathers, little gas exchange through skin, single chamber for breathing, all gas exchange is through the surface membrane of this uni-chamber, unidirectional gas exchange, not tidal flow, increased surface area for gas exchange
Breathing by mammals
huge surface area - so many divisions, 23 divisions in the lungs, many branches / brachii, flow of gas is convectional and diffusional, last terminal brachii contains alveoli which is where diffusion of gases actually occurs, convectional movement through the upper tracts of the lungs, but lower at the alveoli diffusion takes over
Residual volume
what air is left (stale air) after you exhale your maximum breath, helps to prevent a collapsed lung, volume at the end of resting expiration, motionless gas
Air exchanged during breath
about 500 mL of air exchanged
Site of gas exchange
alveolus
Total lung capacity
all of the four volumes added together (TV, IRV, ERV, and RV) typically around 6L of air, because residual volume is so difficult to measure, it becomes difficult to measure total lung capacity, so we often just measure vital capacity
Vital capacity
the amount of air that can be breathed in and out of the lungs, the movable air (TV, IRV and ERV), but does NOT include the residual volume because it is too difficult to measure, maximal breath in and maximal breath out
Inspiratory capacity
the volume of air that can be inspired, sum of tidal volume and the inspiratory reserve volume
Expiratory capacity
the volume of air that can be exhaled, sum of the tidal volume and the expiratory reserve volume
Breathing by birds
two air sacs that move air in and out, between the two they have an array of parabronchi where gases are exchanged, cross current gas exchange, tidal gas exchange in and out of the system, air comes into the posterior air sac, air that was already there is pushed through the parabronchi, exhaling - emptying of air sac to the trachea and emptying of the posterior air sac to the parabronchi, uni-directional flow of air through parabronchi
Breathing by Terrestrial invertebrates
linked spiracles (openings in the body wall) throughout the body, relatively passive but there are ways to open and close spiracle openings, vascularized for gas exchange through trachea walls, diffusion of gases through trachea
Gas exchange in photosynthesis
getting CO2 out of the external medium (air) and into the leaf - usually via diffusion through the stomata, but this allows diffusion of other gases as well, the most important is water movement
Diffusion of gases occur based off …
partial pressure gradient between the SAME gas, move from high partial pressure of a gas to a region of low partial pressure of that same gas
Hydraulic pressure of leaves
this resistance to water varies depending on growth conditions and water potentials of the leaf (ex. leaves growing in shaded conditions exhibit greater resistance to water flow than do leaves in higher light)
Stomata
pore in the leaf surface that allows access from the outside to air spaces inside the leaf, more than 90% of all gas exchange occurs at this sight, can open and close, but while open it is good for CO2 uptake but allows water to leave (bad for water loss)
Location of stomata for C3 dicot plant
often found on the under side of the leaf
Structure of a monocot stomata
surrounded by thin guard cells with subsidiary cells sitting on each side (epidermal cells surround guard cells)
How do stomata open and close
microfibrils can bend but do not stretch, water makes cell swells along the lines of least resistance, regulating in flow and out flow of water and gas exchange through this movement
Why would the stomates be closed?
during temporal regulation, the stomata can be closed during the night because CO2 demand is low will little light available and they can also be closed when the soil water is less abundant and therefore the stomata will remain closed or open very little even on a sunny morning to try to minimize water loss and dehydration
Why do the cells swell to open the stomata?
water uptake is driven by potassium and chloride influx, solute concentrations increase and therefore water flows into the cells to dilute the solution which increases the tugor pressure of the guard cells causing them to swell
Guard cell swelling throughout the day
the potassium and chloride influx initiates this early in the day, over the course of the day after reaching maximum, the gradient across the membrane for potassium almost completely diminishes and then sucrose content builds up through photosynthetic activity and is used to maintain high osmotic state throughout the day - keeps high tugor pressure of the guard cells
Guard cells shutting
as sucrose levels drop at the end of the day, the aperture closes (sucrose and potassium levels low)
How is stomatal opening and closing regulated?
responds to internal CO2 partial pressure - if carbon dioxide is too low, the stomata will open to allow more carbon diode to diffuse into the leaf, and it closes in response to water stress, also ATPase is light responsive therefore responds to light to influence photosynthetic activity to produce sucrose
C4 plant photosynthesis
spatial separation of initial CO2 fixation and the calvin cycle, when CO2 first enters the solution it is modified into HCO3- (carbonic acid), therefore maintaining gradient of CO2 partial pressure, promoting further uptake of CO2, carbonic acid is modified into malate acid and is moved to the bundle of sheath cells where it can build up and be broken down into pyruvate
Advantage of C4 plant spatial separation
spatially separating where CO2 enters the cells and where it is actually used maximizes the likelihood of carbon fixation and reduces oxygen competition
CAM Plant photosynthesis
temporal separation of CO2 influx and photosynthesis, stomata are open and CO2 can come into the leaf when it is cooler at night, reduces water loss from open stomata at night and then photosynthesis occurs during the day time when the light is available, therefore difference in timing usage of CO2
How to maximize oxygen and CO2 movement in the bloodstream?
carbon dioxide reacts with water to become carbonic acid - no longer dissolved gas, therefore PCO2 is lowered and removal of CO2 is larger anymore continuous from the tissues to the blood (larger partial pressure gradient), when oxygen binds to hemoglobin in the blood you can get more oxygen because oxygen is no longer a free gas and therefore PO2 is maintained low
O2 Transport-respirtatory pigments
these pigments increase the oxygen carrying capacity of the blood
Oxygen binding to iron in a heme molecule
iron is not oxidized (electrons are not exchanged), therefore it can still be reversed when oxygen needs to leave the blood
Heme
is a porphyrin ring complexed with an iron atom
Myoglobin
monomeric protein with a single heme molecule in muscles
Hemocyanins
do not have iron, they are blue and contain copper, they have multiple O2 binding sites, bright blue blood when oxygenated (found in squids and lobsters)
Chlorocruorins
have a modified porphyrin ring with iron to bind with oxygen but they are green, they are found in some marine worms
Hemerythrins
non-porphyrin but do contain iron proteins that occur intracellularly in muscle and blood cells, they are found in some types of worms and brachiopods
Hemoglobin
found in blood and may have up to four heme-globin molecules (subunits), typical pattern is two alpha and two beta globins, shows cooperated binding that alters the O2 binding affinity of other globin molecules - when one subunit binds to oxygen, it changes the conformation of the other globin molecules and therefore increases its affinity with oxygen - 300 x greater for the 4th O2 to bind to the last globin molecule than the first
Myoglobin vs. Hemoglobin
myoglobin shows no cooperativity because is is a monomer and always has greater O2 affinity than hemoglobin
at any PO2 where the tissues are, it will bind oxygen greater than hemoglobin, this is important because myoglobin in your muscle cells will always take the oxygen from the hemoglobin and get oxygen into the muscle (one way transport), no matter how low the PO2 will get in the muscles or how hard you are exercising)
animals such as seals and whales that have to dive for long periods of time have very red muscles because they are a high saturation of myoglobin that stores oxygen for later use and can never be lost to hemoglobin
P50
measure of the binding affinity of a respiratory pigment of oxygen, the PO2 needed to reach 50% saturation, a low P50 means you have a high binding affinity (less oxygen is needed to reach full saturation)
Low P50 environment
not a lot of oxygen in their normal habitat (ex. earthworms that live underground), higher affinity associated to get the oxygen it needs
Hematocrit
the fraction of blood volume made up by red blood cells, this can vary and is maximal at about 55% (for birds) and around 45% for humans, used to measure how much hemoglobin is found in the blood cells, the oxygen capacity of the blood
Hematocrit testing tube
cells that pack down at the bottom will be the erythrocytes (red blood cells) and platelets, the plasma will pack up at the top of the tube, measured with a ruler to get the fraction
Having hematocrit above 55%
it would not be fluid enough to move through the circulatory system effectively, too many red blood cells would reduce the amount of plasma in the blood which carries glucose and takes waste away from the tissues
Factors that affect P50 - Bohr Effect
increased carbon monoxide and fetal hemoglobin will cause a shift to the left of the curve and decreased pH (more acidic environment), increased carbon dioxide, increased temperature will cause the oxygen dissociation curve to shift to the right therefore increasing the partial pressure of oxygen needed to saturate hemoglobin
Amphibians, Turtles, Lizards and Snakes
three chambered heart and systemic and pulmonary circuits are not completely separated, skin plays a role in gas exchange
Amphibian’s Circulatory System
left side of their heart pumps oxygenated blood to the tissues of the body which takes all of the oxygen and then the deoxygenated blood goes from the tissues to the right side of the heart to be pumped to the lungs or to the skin to receive oxygen, but the lungs are more effective in gas exchange, therefore the blood from the heart goes to the left side of the heart to be pumped to the tissues, while the blood from the skin has little oxygen and is pumped through the right side of the heart circuit again
Turtles, Lizards and Snakes’ Circulatory Systems
left side of the heart pumps blood to the skin and to systemic tissues and the oxygenated blood of the skin joins with the deoxygenated blood of the systemic tissues to be pumped through the right side of the heart to the lungs to be oxygenated there, they also have a septum which is like a wall on each side of the skin’s blood flow
Right-Left and Left-Right shunts
dividing of the blood flow between the two sides of the heart by shutting off the blood flow to the lungs when animals dive under water and have to hold their breathe, and therefore the pulmonary flow is diverted to the skin where gas exchange must occur and to the systemic tissues, turning off this shunt will allow blood to go back to the lungs
Right systemic aorta and right-left shunts
right systemic aorta is another blood vessel that leaves the right side of the heart and joins with the flow of the left side of the heart, they are connected by a valve known as the Cog valve and this Cog valve is open when they dive and shut off the right side of their heart, therefore both sides of the heart will pump to the systemic circuit
Invertebrates with closed circulation
octopuses and squids have closed circulatory systems with three hearts - two brachial hearts, and one systemic heart, blood contains hemocyanin (blue protein in blood that contains copper), blood goes to the gils to receive oxygen and then rejoins the blood from the body again
Invertebrates with open circulation
arteries do not go to capillary beds, they flow into large sinuses (open cavities) that directly bathe the organs and tissues to provide oxygen, they have very low resistance therefore high flow is achieved and this is effective
Crustacean’s heart
one chambered heart with an ostia (one way valve) that opens and closes for blood flow
Crayfish’s circulatory system
cor frontale (another, smaller heart) that ensures good blood flow to the nervous system and the heart
Insect’s circulatory system
has nothing to do with oxygen transportation, it is only used for the transportation of waste and fuel
The Mammalian heart
2 atria (thinner walls), 2 ventricles (thicker walls due to higher pressure to withstand), 2 atrioventricular valves and 2 semilunar valves of the aorta and the pulmonary artery, left side of the heart receives oxygenated blood from the pulmonary vein and delivers the blood through the aorta to the tissues of the body, the right side of the heart receives deoxygenated blood through the inferior or superior vena cava and then delivers deoxygenated blood to the lungs through the pulmonary artery
isovolumetric
the pressure is not large enough to open the valves to let the blood leave, therefore it is the same volume but the pressure is building up
Five Stages of the Cardiac Cycle
- atrial systole (atria contracts)
- early ventricular systole (isovolumetric ventricular contraction)
- ventricular systole (rapid ejection period - blood phase)
- early ventricular diastole (isovolumetric ventricular relaxation)
- late ventricular diastole (ventricular filling)
Systole
contraction of the heart
Diastole
relaxation of the heart
Cardiomyocytes
gap junctions are intercalated discs between these cells, and these cells sit at a relatively negative charge and when one depolarizes, all those connected to it will also depolarize because of the gap junctions connecting them and also because their membranes are quite leaky to the electrical charges
SA Node
spontaneously depolarizes, this is known as the pacemaker of the heart because its speed of contraction dictates the speed of the rest of the heart, this depolarization spreads rapidly among the cells of the aria causing contraction of the atriums and this signals the AV node to spread the signal down the bundle of HIS to do to the very bottom of the ventricles and contract the ventricles from bottom up
Movement of fluids through the xylem
negative pressure used to pull fluids through the xylem
Movements of fluids through the phloem
osmotic pressure / positive pressure to push the fluid through the xylem
Osmotic Potential
osmotic potential is based on overall solute concentration, osmotic adjustment means changing solute concentration to change water potential
Water cannot be moved …
actively!
Movement of water
water movement requires protein channels called aquaporins - can be regulated to control water movement, water follows the overall solute gradient (from areas of high to low solute concentrations), no energy expended
Moving water requires …
the creation of a solute gradient, some ion pumps that only work in one direction to create gradient (uniporters), semipermeable membranes are an essential factor, drives the influx of water
Water movement by osmosis
water moves to the side in which has the most solute in order to equilibrate the sides by diluting that side, across a semipermeable membrane to water
Isotonic osmotic system
active influx of ions creates equal solute concentrations across the membrane, solutions inside and outside are considered isotonic - this will cause water to move in both directions, but there is no NET movement of water (Note: these do not have to be the same solutes to maintain isotonicity, isotonic solution)
Water moving down a pressure gradient
water potential is influenced by gravity, dissolved solutes and effect of hydrostatic pressure, and water normally moves towards the lower (more negative) water potential
Where do cells get the water in plants?
roots and metabolic water (carbs and fats produce large amounts of water, protein = less)
Q (flow rate) =
difference in pressures of two areas divided by the resistance (delta P / r)
Resistance of the tubing is impacted by …
the viscosity of the medium, the length of the tubing and the radius of the tubing (having the most impact)
Xylem
translocates water and inorganic nutrients from the roots to the leaves
Phloem
translocates sugars, proteins and signalling molecules from source tissues (do make their own sugars) to sink tissues (do not make their own sugars), therefore bi-directional
Xylem are made up of …
tracheids and vessels elements - these are cells that are dead at maturity because they require the production of secondary cell walls and this requires death before production
Vessel Elements
primary vessels in angiosperms, end to end stacking plus perforation plates known as pits that connect the vessel elements laterally, some lateral movement of water, but it is slow compared to vertical movement of the water, tend to be shorter and wider than tracheids
Tracheids
primary vessels in gymnosperms, they are elongated cells arranged in overlapping vertical files and contains pits where there is low resistance and a lot of lateral movement of water
Cohesion-Tenson Theory
evaporation at the leaves causes negative pressure, the cohesive properties of the water molecules transfer this tension though the length of the water column, water at the top of a tree develops a large tension (a negative hydrostatic pressure) and this tension pulls water through the xylem
Safety-Efficiency Trade Off
wider vessels create efficient transportation but takes up much more room than thinner vessels and therefore larger impact from an embolism (air bubble) affecting more of the vessel and overall transportation than an embolism in a thin vessels
Large tubing in plants
often occurs in the summer when there is a lot of water available, but in the winter when there is little water available, they will adapt to smaller tubing and more of them
Direction of xylem’s fluids
roots to leaves
Direction of phloem fluids
source to sinks
Mechanism of transportation of xylem
transpiration and cohesion-tension (negative hydrostatic pressure pulling the fluid from the roots up to the leaves)
Mechanism of transportation of phloem
bulk flow (movement of water and all solutes in it)
Phloem
living cells, contain sieve cells connected by sieve plates and they are connected with companion cells, direction of flow is always from source to sink (depending where the energy and water is needed in the plant)
Sieve elements cells
basically water-filled tubes, do not contain a nucleus, vacuole, filaments or ribosomes, key feature is that they are under high tugor pressure (lots of solutes present), between the sieve element cells are holes known as sieve plates that connect them
Companion cells
phloem loading and unloading - these are the metabolically active cells, ATP production and protein synthesis occurs, at the end of the sieve elements
Phloem loading
at the source end, phloem loaded with sucrose by companion cells at source tissues - may be symplastic (passive) or apoplectic (active transport), phloem is loaded with solutes therefore the water from xylem flows to the phloem and this builds up quite a significant pressure (tugor pressure) water moves from high to low pressure
Phloem unloading
at the sink end, the solutes are pulled out of the phloem to be used therefore bulk flow of water and solutes from high to low pressure (pressure driven) out of the high pressure of the phloem to the low pressure of the source cells, lower tugor pressure results
Maintaining Concentration gradient in symplastic loading of the phloem
largely passive diffusion that occurs because of polymer trapping - in the bundle of sheath cells there is a build up of sucrose and this diffuses into the companion cells where sucrose is converted into a different polymer, therefore sucrose cannot equilibrate between the two sides, continuous movement of the water from the xylem to the phloem, uniporter for sucrose therefore uni-directional because sucrose is modified and no longer sucrose
How does water get into the plant
the growing tip of the plant is where the rate of water uptake is highest, most efficient
Root hairs
high surface area and therefore increases absorption efficiency at the roots
How can plants alter nutrient availability?
soil particles tend to have negatively charged surfaces to which cations bind - the plant pumps hydrogen ions (via proton pumping) in order to displace nutrients cations from colloids allowing their uptake, some nutrients are more available (more soluble) in acidic solutions therefore roots can extrude protons to acidify the soil solution and make nutrients soluble
Mobile nutrient deficiency
ex. is a nitrogen deficiency, when the plant does not receive enough of this nutrient from its soil, it pulls it from the oldest leafs therefore the lower leaves die first
Immobile nutrient deficiency
ex. is a calcium deficiency, plant will pull the nutrient from the newest, younger leaves, therefore the leaves higher up will die first
Where is most of the water found in the body?
the human body is filled with about 60% water and most water is found as intracellular fluid (surrounded by a membrane)
Kidneys filter the blood …
glomerulus filtration at about 170 L per day, balance between water going into the body and extraction through urine, feces, breathing, etc …
Water of the body contains …
inorganic ions, organics ions and proteins that exert osmotic pressure
Importance of ion concentrations
ions in the right concentration are needed across membranes for specific gradients and physiological work (ex. nerve function and muscle contractions)
Cells regulate ions and osmotic pressure through ..
their membranes - channels, exchangers, pumps, aquaporin, and diffusion and leakage of ions
Endothelium
is the outside layer of the capillaries and this can vary in composition, tightness and leakage and can contain fenestrations which are holes that allow ions to pass in and out of the capillaries
Difference in ion concentration and osmotic pressure between plasma and interstitial fluid
often not much difference in ion concentration and osmotic pressure between the plasma and the interstitial fluid because they can freely exchange and therefore regulating one gets regulation of the other
Uniqueness of water breathers and their kidneys
a high amount of water is filtered because of low oxygen concentration in water and therefore there is a lot of water and salt exchange in water breathers through their gills
Movement of solutes and water
concentration gradients drives ion movement through diffusion and water moves through osmosis
Regulating and conforming to osmolarity
osmolarity takes into account the ion concentration and volume of water in blood and cells, volume of blood is often kept constant, osmotic pressure however can be modified, some animals keep this closely regulated, others can afford to conform their osmolarity and some animals go between regulation and then switch to conformity at a point outside of their zone of tolerance
Major osmotic, ionic and volume regulators of the blood
kidneys, gills and the skin
Judgement of kidney concentrating ability
can be judged by urine:plasma ration (U/P ratio)
U/P ratios and meanings
if the kidney concentration is lower than 1 it will be almost clear (dilute) because there is more water in the urine than there is solutes, but if the kidney concentration is higher than 1 it will be very concentrated and dark because there is less water relative to the solutes than plasma
What U/P do we want
we want a U/P or kidney concentration of 1 where the urine concentration is equal to that of the plasma concentration, this is isomotic
U/P less than 1 =
hyposmotic
U/P greater than 1 =
hyperosmotic
Cell volume regulation
changes in extracellular osmoticity (tonicity) can cause changes in cell size, cells compensate by changing their internal solute content, osmo-regulators will cause their cells to regulate volume by altering the concentration of the organic solutes (ex. amino acids) rather than ions because ions can hinder gradients needed for function
Living in water - fresh vs. salt water
major ions founds in sea water - huge difference in sodium and chloride and many other ions from sea water to fresh water including magnesium, sulphate, calcium, potassium and bicarbonate
Fresh water
fresh water animals are hyperosmotic to their environment - they gain water and lose ions, large osmotic and sodium gradients from inside to outside therefore salt is lose through diffusion and water is gained through osmosis
U/P ratio of fresh water organisms
well below 1 because constantly gaining water
How do fresh water organisms gain and loose salt and water?
(1) through what they eat
(2) actively takes up sodium and chloride through symporter of the gills and skin, this requires ATP to go against gradient (but passively looses it through diffusion)
(3) salts and water in feces is lost
(4) water enters through diffusion
divalent ions
those retained by the gut and kidneys
monovalent ions
sodium and chloride retained at gills
Salt water
some marine animals are isosmotic and nearly isotonic to their environment or hyposmotic, to the sea water, very high sodium and chloride concentrations especially
Salt water organisms
hyposmotic to their environment means they lose water and gain ions (salts), salt water organisms can drink the water and use it to rehydrate, salts are lost in feces and some in urine, NaCl from the water is going to enter the body and then there is active extrusion of Cl and active or passive outflow of sodium back into the water
Gill NaCl excretion for sodium
gills excrete NaCl against their concentration gradient to maintain internal ionoregulation, NaK - ATPase pumps out 3 sodium and 2 potassium enters (on the basolateral side of the membrane), the only way sodium enters the body is through the sodium chloride symporter
Gill chloride excretion
mitochondria ridge cells (chloride cells) concentrate a lot of chloride ions and this high concentration of chloride drives the movement of chloride out of the cell and into the ocean, rectal gland can secrete lots of chloride
Junctions of the cells of the gills
pretty tight between the cells, but they do actually allow sodium to passively go through to the ocean
How can salt water organisms alter ion movement in and out of the cell?
selectively locate transporters / exchangers to generate gradients and position the channels on the apical or basolateral (basement) membrane
NaKClCl co-transporter
1 Na, 1 K and 2 Cl molecules in this transporter, all of which must be present in order to function and get all of these molecules out of the cell
What gets the large amount of chloride into the cell?
the sodium gradient allows for the chloride to build up in the cell and leave through the co-transporter of NaKClCl
How is urea used to prevent dehydration and movement of ions in some salt water animals?
lower sodium and chloride concentrations than sea water, therefore hypoionic, but also is hyperosmotic because urea is in high concentration in the body as it build up, allowing urea to build up prevents water loss from the body because it eliminates the water gradient between the fish and the ocean, they retain urea as an osmolyte, and make hyposmotic urine (slightly dilute)
Problem with urea
not very good with proteins, tends to denature the proteins
How to fix the problem with urea
some animals produce trimethylamine oxide (TMAO) as a protective organic molecule to counteract the negative effects of urea on protein structures, ideal ratio between urea and TMAO is 2:1
Salt glands
many non-mammalian marine vertebrates eliminate salt by salt glands, kidneys do some work, but still a lot of salts coming in, located above the eyes, on top of the head, contains lobes each with a canal, actively secretes NaCl, fluid drains out of the nasal cavity
Marine reptiles and salt regulation
almost double the concentration of sodium and chloride then sea water in their salt gland extraction
Living on land and salt regulation
terrestrial animals must balance their water budge, income = loss + storage, air can be very dry, therefore these animals after often at higher risk for dehydration, balance is key, income = eating, drinking, metabolic water, and loss = evaporation, urine, feces and salt glands, storage = bladders, lymph
Different loads of osmolytes in food
if it has a lot of water but also a lot of protein they will have to secrete nitrogen waste and will lose some water, if the food is high in salt it is the same thing (lose more water in your urine to balance out the high salt)
Free water
is available for drinking, larger animals generally can range farther and go longer between drinks (lower water losses), frogs can absorb water through their skin of the pelvis (don’t have to drink)
Metabolic water production
produced from the oxidation of fuels - more water produced from lipids, little from carbs and proteins
Cutaneous evaporative water loss mainly determined by …
layers of lipids and waxes deposited in the epicuticle of the skin and therefore more resistant to water loss with more lipids and waxes (prevents water loss more)
Why do we have a natural gradient to loose water?
air around us is not usually 100% saturated with water, but our body is at 100% usually and therefore there is this natural gradient for water to leave our body, the higher the humidity of the environment the greater the gradient and therefore the greater the water loss
Environment’s influence on exoskeleton
the more dry the environment, the more resistant that the exoskeleton will be to water loss therefore more wax and lipids in the layers of the skin
Temperature’s impact and limit on cutaneous evaporative water loss
cutaneous evaporative water loss is affected by temperature depending on the temperature when the lipid transitions from a solid to a liquid phase, however when lipids melt and transition to a liquid phase they can no longer prevent water loss at this high temperature and therefore this is the limit
Water loss and humidity
higher temperature = higher ability of the air to be able to hold water in the vapour phase, the amount of water that air can hold doubles ever 11 degrees
Respiratory evaporative water loss
depends on the difference in temperature and saturation of inhaled and exhaled air, if you breathe in cold air, even if it is fully saturated it will be increased in temperature in the lungs and therefore its ability to hold water increases and when it is exhaled it actually takes water out of the lungs and therefore you actually lose water
Preventing water loss with cold air ..
this water loss can be prevented by cooling the exhaled air, this is done by using your sinuses (on the EXHALE), inside the nasal cavity there are convoluted air passages specialized for exchanging heat and water with the environment, countercurrent heat and water exchange
Animals that are more efficient at cooling down the air they exhale and preventing water loss
smaller mammals
Total evaporative water loss
total mass specific rate of evaporative water loss is related to body weight due to differences in relative surface area and metabolic rate
What animals have a higher total evaporative water loss?
smaller animals have much higher relative water losses for their body size because cutaneous water losses are high because larger surface area for volume of their body and they have a relatively higher metabolic rate and greater oxygen consumption - breathe more for their size and therefore lose more water through respiration
Weight Specific total evaporative water loss
total mass specific rate of evaporative water loss varies among phylogenetic lineages and is lower in xeric adapted species
animals living in water for some times (ex. crabs) loose a lot of water, amphibians have pretty high water losses because skin is needed for gas exchange (water leaves through the skin - more permeable to water), reptiles are very well adapted to living in hot, dry environments and have very little water loss
mice, rats and birds have low water losses
animals that live in aquatic environments have high water loss and animals living in desserts have very low
Fecal water loss
fecal water loss is greater for animals that each less digestible diets (ex. herbivores > carnivores)
more digestible diets result in less water loss because of less fecal produced (ex. high end dog food vs. cheap)
Urinary Water loss related to…
U/P ratio, salt intake, protein intake and the type of nitrogenous waste produced
Larger U/P ratio and water loss
greater U/P = more water saved (concentrated urine)
High salt diet =
more salt in the food that the body does not need is going to be excreted and water is attracted to the sodium therefore leaves as well
High protein diet =
more water loss, more nitrogenous waste
What animals make more concentrated urine? Why?
smaller mammals make more concentrated urine than larger mammals because kidneys are selected to make more concentrated urine because they already lose so much water
Dessert adapted animals and urine
dry adapted species are especially good at producing concentrated urine (more than the aquatic animals who have a lot of water available)
Amino acids and the urine
amino acids that are no longer needed because you have enough are deaminated, taking the nitrogen off and this requires water to be excreted from the body, but the amount of water needed depends on the nitrogenous base
Most common nitrogenous bases are ..
NH3 (ammonium) which does not require further energy but is very toxic and water soluble therefore can not let it build up and therefore NH3 is converted to NH4
Carnivores vs. Herbivores and water loss
carnivores tend to lose more water in their urine but less in their feces because of high protein, but herbivores have low water loss in urine but high in feces (still greater than carnivores)
Ammonotelic animals
boney fish can afford to produce a lot of ammonium because they can dump a lot through their gils
Ureotelic animals
some reptiles, sharks and mammals only make urea
Uricotelic animals
uric acid is the end product, very concentrated urine, process done after kidneys in the gut
Water storage in different animals
toads and turtles store isosmotic or hyposmotic urine in the bladder
can bring the water from the bladder back into the body if the toad or turtles get too dehydrated
ostriches store water in the coprodeum (no bladder) which can expand highly and can draw water back into their body if they get dehydrated
some frogs can also store water in their lymph (Australian water-holding frog)
Kidney function in mammals
nephrons are microscopic tubules that ultrafilter plasma (blood) and modify the ultrafiltrate by reabsorption of needed solutes (ex. salts, glucose, amino acids) to make urine as the end product, filter blood so that what is left is the nitrogenous bases and water of the urine
ultrafiltration of mammals
takes places in the renal corpuscle, involves filtering the blood from the glomerulus (anatomoses of blood vessels into capillaries, arterial blood) and small things from the blood of the glomerulus get through the fenestrations of the walls of the Bowman’s capsule
ultrafiltration is driven by …
hydrostatic pressure in the glomerulus leading to bulk flow of primary urine, high blood pressure of the capillaries of the glomerulus squeeze fluid through to the Bowman’s capsule, high and low blood pressure also influences the function of the kidneys
PCT of the nephron
reabsorbs most of the ultrafiltrate and key solutes to go back into the blood
DCT of the nephron
differentilly reabsorbs water to set the final urine concentration
