respiration pt1 Flashcards
Why can unicellular and small multicellular organisms rely on diffusion for gas exchange?
they have high surface area to volume ratio
larger size limits surface area available for diffusion and increases the diffusion distance
what do larger organisms rely on for gas exchange (2)
bulk flow and diffusion
what does bulk flow refer to during gas exchange in larger organisms
ventilation (moving air/water over respiratory surface [gill/lung])
circulation (transport of gases in the circulatory system)
What is the Fick equation?
How is it used to understand gas diffusion rate?
Rate of diffusion = D * A * (dC/dx)
D= diffusion coefficient
A= area of the membrane
dC/dx= gradient
tells us how rate of diffusion changes if area of membrane or gradient is changed
what is convection, diffusion, and perfusion?
convection: bulk flow of air/water towards membrane (ventilate to achieve convection)
diffusion: molecules passing through the membrane
perfusion: blood transport the acquired materials away
modified Fick equation that tells us oxygen consumption or transfer rate
MO2= (K*A(PO2 a/w- PO2b))/ t
MO2 refers to oxygen consumption or transfer rate
K= Krogh’s diffusion constant (diffusion coefficient * solubility)
A= surface area of the barrier
PO2 a/w- PO2b= partial pressure gradient for oxygen between blood and air/water
t= thickness of the barrier
what characteristics of a barrier maximize the rate of gas diffusion?
large surface area, low thickness, larger partial pressure (by increase in ventilation)
What does Dalton’s Law of partial pressure state?
sum of all partial pressures is equal to the total pressure of the mixture
(in a gas mixture each gas exerts its own partial pressure-> exerts independently)
What is the driving force for gas diffusion
partial pressure
PO2 at sea level
PO2= 159mmHg
what must first happen to the gas molecules in the air in order to diffuse into a cell?
first dissolve in liquid
What does Henry’s law state?
the concentration of gas in a liquid is proportional to its partial pressure
[G]= Pgas * Sgas
Pgas= partial pressure of the gas
Sgas= solubility of the gas
Why is there a higher [O2] in air than water at the same PO2?
because solubility of O2 is higher in air
what happens to O2 solubility in warmer water?
solubility is lower
relationship between CO2 and O2 solubility in water
CO2 is 30 times more soluble than O2 in water
Boyle’s law + equation
P1V1= P2V2
for gases only bc liquids are virtually incompressible
rate of flow (Q) is determined by
Q= (delta)P/R
pressure difference inside and outside
R= resistance
why do cilia of pond snail embryos beat faster in hypoxic conditions?
to mix things up, increase circulation of new gases to surroundings, enhance O2 delivery to embryo
why do boundary layers exist?
what effects does the boundary layer have?
boundary layers exist at a cell surface due to resistance which reduces flow rate
lower flow rate-> medium poorly mixed at cell surface-> low PO2 diff. across membrane-> low diffusion
animals more than a few millimeters thick use one of which 3 respiratory strategies?
CIRCULATING THE EXTERNAL MEDIUM THROUGH BODY (sponges, insects)
DIFFUSION OF GASES ACROSS THE BODY SURFACE ACCOMPANIED BY CIRCULATORY TRANSPORT (cutaneous respiration, skin must be thin and moist, most aquatic invertebrates, some amphibians, eggs of birds)
DIFFUSION OF GASES ACROSS A SPECIALIZED RESPIRATORY SURFACE ACCOMPANIED BY CIRCULATORY TRANSPORT (gills+lungs-> thin+ moist, vertebrates)
3 types of ventilation
NONDIRECTIONAL (medium flows over surface in unpredictable pattern, maybe some small animal stuck on rock in tidal zone)
TIDAL (medium moves in and out of chamber)
UNIDIRECTIONAL (fish)
from where do gases enter the blood
at the respiratory surface
how can relative movement of blood and respiratory medium at respiratory surface affect efficiency of gas exchange?
contact time
thickness of membranes
directions of flow
what does little PO2 difference between (exhalant) medium and blood at respiratory surface (just before blood leaves respiratory surface) indicate?
little effect of the thickness of respiratory epithelium and/or boundary layer-> gas exchange very efficient
why is exhalant medium PO2 lower than inhalant medium PO2?
PO2 decreases bc O2 is taken by blood from the medium
under optimal conditions, blood PO2 will approach…
exhaled air PO2
3 ways blood can flow relative to the flow of the medium with unidirectional ventilation
concurrent
countercurrent
crosscurrent
disadvantage of concurrent flow
medium PO2 start high, blood PO2 start low (high PO2 diff.)
as O2 is taken from medium, PO2 decreases
blood PO2 approaches the lowered PO2 of medium
advantage of countercurrent flow
blood PO2 start low, medium PO2 start high
counter current so low O2 medium lines up w/ low O2 blood, high O2 medium lines up w/ high O2 blood
O2 diffusion can occur when medium is high PO2 or low PO2 as blood PO2 is lower
blood PO2 approaches PO2 of fresh O2 filled medium
advantage of crosscurrent flow
blood PO2 start low, medium PO2 start high
diff. capillaries calibrate w/ medium of diff. PO2 levels
some blood equilibrates to high PO2 then leaves system
mixture of high PO2 and low PO2 blood allows blood PO2 level higher than exhalent medium
advantages of having specialized respiratory surfaces (gills and lungs) (6)
allows rest of skin to be thick/protected
can be protected in body cavity; allows it to remain moist (can select what is breathed in)
high effective surface area
highly vascularized (low diffusion distance)
highly ventilated (w/ control over ventilation rate)
synchronized w/ circulatory system
O2 solubility in air is 30 times greater than O2 solubility in water, how does this impact O2 uptake?
to get the same amount of O2, 30 times more water needs to be ventilated than air
water breathers are geared for O2 uptake and don’t need to worry about CO2 excretion because…
CO2 solubility in air is similar to water, for the amount of water they use for O2 uptake, water breathers will have enough water to get rid of CO2
Water is more dense and viscous than air. What are the implications for cost of ventilation?
need to work harder/ use more energy to move the viscous medium. unidirectional ventilation helps them save energy
how do sponges and cnidarians facilitate gas exchange/ventilation?
circulate water through an internal cavity using flagella, gases diffuse directly in and out of cells
how do echinoderms (sea cucumbers) facilitate gas exchange/ ventilation?
use muscular contractions to pump water tidally into respiratory tree
how do molluscs facilitate ventilation?
contractions of mantle pump water unidirectionally past gills, blood flow is counter current
how do jawless fishes (lamprey and hagfish) facilitate ventilation/ gas exchange?
use muscle to pump water through respiratory cavity, water enters mouth and leaves through gill opening
ventilation is unidirectional
blood flow is countercurrent
what changes can agnathans (lamprey) make to their ventilation/ gas exchange when feeding or not feeding?
not feeding: similar to hagfish, water flow from mouth to gill and exit through gill opening (unidirectional)
feeding: mouth attached to prey, ventilation tidal through gill openings
steps of ventilation in elasmobranchs
expand buccal cavity
draw water into buccal cavity via mouth and spiracles
mouth and spiracles close
muscle around buccal cavity contract->force water past gills and out of gill slits
in elasmobranchs, blood flow is ____ to medium
countercurrent
what is a special method of ventilation that active teleost (boney) fish can use?
ram ventilation (swimming w/ mouth open, swimming musculature results in unidirectional water flow over the gills, energetically efficient bc just using swimming energy)
what is special for respiratory structures and ventilation in terrestrial crabs?
gills are stiff-> don’t collapse in air
branchial cavity itself is highly vascularized-> act as primary site for gas exchange
advantage of the tracheal system in insects
air-filled tubes open to outside via spiracle-> O2 directly diffuses into cells
gas diffuse over very small distances
no need for circulatory system for O2
takes advantage of high O2 conc. in air
disadvantage of the tracheal system in insects
uses a lot of space
how does insect ventilation work
contraction of abdominal muscles or movements of thorax
can be tidal or unidirectional
expansion and contraction of tracheae
5 types of respiratory structures in air breathing fishes
reinforced gills that do not collapse in air
highly vascularized mouth or pharyngeal cavity
highly vascularized stomach or intestine
specialized pockets of the gut
lungs
(ventilation of air breathing organ is tidal using buccal force similar to other fish)
where do O2 uptake and CO2 excretion occur in Arapaima gigas?
O2 uptake from air breathing organ
majority of CO2 excretion occurs across the gills
steps/phases blood goes through in water breathing fish
-> heart pumps deoxygenated blood to gills
-> blood oxygenated at gills
-> travel to tissues
-> deoxygenated blood goes back to heart
steps/phases blood goes through in air breathing fish in normal conditions
-> deoxygenated blood passes through heart
-> pumped to gills
-> oxygenated at gills
-> blood travels to tissues
-> deoxygenated blood goes back to heart
steps/phases blood goes through in air breathing fish in hypoxic conditions
-> deoxygenated blood passes through heart
-> pumped to gills
-> blood goes to lung and oxygenated there
-> blood goes back to heart
-> blood goes through non-functional gill arches
-> blood travels to tissues
-> deoxygenated blood goes back to heart
why do air breathing fishes still have functional gill arches
gills are still important for ion regulation and acid-base balance
why does oxygenated blood coming from the lung pass through non-functional gill arches
if oxygenated blood go through functional gill arches in hypoxic water-> animal will lose O2 from blood to water
why do deoxygenated blood always need to go through functional gill arches?
for CO2 removal
what is the gas exchange site on gills and lungs in birds and lungs in mammals called
lamellae
parabronchi
alveoli
Types of respiratory structures in amphibians (3)
Cutaneous respiration
External gills (juvenile salamanders and axolotls)
Simple bilobed lungs (more complex lungs in terrestrial frogs and toads)
type of ventilation in amphibians
Tidal using buccal force pump
Type of ventilation in reptiles
Tidal ventilation
Rely on suction pumps to create negative pressure for aspiration
Separation of feeding and respiratory muscles
Mechanisms to change volume of chest cavity
Characteristic of bird lungs
Stiff, change little in volume
Between posterior and anterior air sacs
Fresh air from outside goes to posterior air sac first
Air flow and blood flow through parabronchi
Unidirectional air flow
Crosscurrent blood flow
Two main parts of respiratory tract in mammals and what they include
Upper respiratory tract: mouth, nasal cavity, pharynx, trachea
Lower respiratory tract: bronchi and alveoli (gas exchange surface)
Each alveoli is wrapped by…
Capillary network
Explain the pleural sac of mammalian lungs
Fluid-filled balloon that surrounds the lung
Pleural membrane encloses pleural cavity, which is filled with pleural fluid
Outside of pleural membrane is attached to rib cage
How does the pleural sac help keep lung expanded
Intrapleural sac pressure is subatomic (slightly negative bc chest + lung elastic recoil pulls in opposite directions)
Helps pull wall of lung to chest wall
What happens when the pleural membrane is punctured
Draws air into intrapleural space bc of negative pressure
Pleural cavity expands
Lung collapses
Work required to breathe is influenced by (3)
Lung compliance (high compliance = easy to stretch)
Lung elastance (high elastance = easy to return to original shape)
Airway resistance
What does fibrotic lung disease do
Scarring thickens walls of lungs
Reduces lung compliance
Make inhalation difficult
Impact of surfactants to lung compliance
Aqueous fluid will make alveoli stick together bc of surface tension cause by h-bonds
Surfactants produced by type II alveolar cells reduce surface tension
Increase lung compliance and reduce work needed to breathe
How does emphysema impact the lung
Walls of alveoli break down-> changes surfactant quality
Increases lung compliance (walls thinner) but reduce lung elastance
Exhalation usually passive-> exhalation more difficult
Formula for airway resistance
Flow = deltaP / R
If resistance increases, a greater deltaP is needed to maintain the same airflow
Define bronchoconstriction
What can cause this?
Constriction: reduction in airway radius
Stimulation of parasympathetic nervous system
Histamine
Irritants
Define bronchodilation
What can cause this?
Dilation: increase in radius
Stimulation of sympathetic nervous system
Circulating epinephrine
(binds to beta-2 receptors)
High alveolar PCO2
Why can PCO2 lead to bronchodilation?
High PCO2 -> need to breathe faster and get rid of CO2
What causes asthma and how do asthma inhalers work
Asthma: excessive bronchoconstriction
Inhalers stimulate beta-2 receptors (induce bronchodilation) to relax muscle
What is dead space and what are the two components of dead space during respiration
Air that does not participate in gas exchange
Anatomical dead spaces -> volume of trachea and bronchi
Alveolar dead space-> volume of alveoli that are not perfused
Why does panting help with cooling down
Trachea is an effective cooling region
Takes heat away from the moist surface
What are some challenges animals with long necks have
Very large dead space
Can’t have high trachea diameter bc need to have large lung to compensate for the dead space
ventilation perfusion ratio
V (A) / Q
V(A)= alveolar ventilation
Q= cardiac output
What does efficient gas exchange at respiratory surface require?
Matching of ventilation and blood flow
Air and blood of birds + mammals have about the same O2 content-> V(A)/ Q ratio of 1-> matches O2 delivery at gas exchanger, with ability to transport O2 away
How is ventilation- perfusion matching achieved
Arterials dilate or constrict to distribute blood to well-ventilated alveoli
Low PO2 in alveolus causes contraction of arteriole
Why is constriction of arteriole when low PO2 at alveolus
a) Beneficial
b) Potentially a problem
Benefit: low PO2 often indicates an issue w/ the alveoli so restrict blood from going there and send the blood elsewhere, where the alveoli is functional and pick up O2
Problem: in hypoxic environments, breathe low O2, all alveoli have low PO2-> all arterioles constrict-> problem
why do animals have respiratory pigments and what type of respiratory pigments exist?
solubility of O2 in aqueous fluids is low
respiratory pigments (metalloproteins) contain metal ions which reversibly bind to O2 and increase O2 carrying capacity by 50 fold
what are 3 major types of respiratory pigments
hemocyanin (arthropods and molluscs, usually dissoved in hemolymph, copper)
hemerythrin (sipunculids, brachiopods, etc, usually found inside coelomic cells. iron)
hemoglobin (vertebrates, nematodes, crustaceans, insects, iron)
what is myoglobin?
a type of hemoglobin found in muscles
hemoglobin is a tetromer
myoglobin is a monomer
why is hemoglobin ONLY and ALWAYS contained in red blood cells?
containing Hb in RBCs allow fine-tuning of the micro-environment around Hb to optimize function
how does temperature impact O2 solubility
lower temp -> higher O2 solubility
what is a disadvantage of having high conc. of RBC in blood
high viscosity and harder to move the blood
maximal unloading occurs at…
P50, the PO2 level at which 50% of the hemes (component of Hb) ae saturated with O2
animals alter P50 of Hb to optimize O2 loading and unloading
how is hematocrit and Hb levels elevated during stress (exercise, hypoxia, diving)
release red blood cells from the spleen
as Hb is oxygenated, it goes from what state to what state
from T state (oxygenation difficult) to R state (O2 added more easily)
what is the level of O2 affinity when P50 is low
high affinity
what is the level of O2 affinity when P50 is high
low affinity
what pH and PCO2 changes will reduce oxygen affinity?
why is this change important
decrease in pH or increase in PCO2
by stabilizing T state, resulting in right shift of Oxygen eqm curve (P50 increase)
FACILITATES O2 DELIVERY TO ACTIVE TISSUES THAT ARE PRODUCING CO2
what is the Bohr effect?
why is it important?
changes in pH and PCO2 that stabilizes T state, affect the OEC and thus oxygen affinity
facilitates O2 delivery at tissues and O2 uptake at respiratory surfaces after CO2 is removed and pH increases
what change in temperature will decrease oxygen affinity?
why is this important?
increase in temperature
stabilizing T state-> right shift OEC
PROMOTES O2 DELIVERY TO WARM MUSCLES DURING EXCERCISE
what impact does an increase in organic phosphates have on O2 affinity?
increase in organic phosphate conc. -> decrease O2 affinity by stabilizing T state-> right shift of OEC
more O2 loading
why are organic phosphates important?
without them, P50 will be very low-> low unloading-> tissue won’t get enough O2
important for fine-tuning blood P50
organic phosphates for mammals, birds, and reptiles
mammals: 2,3 DPG
birds: IP5
reptiles: ATP or GTP
what levels are modified during exposure to hypoxia and during development altering Hb-O2 affinity?
organic phosphate levels
how does adding organic phosphates extend life of blood in blood banks?
prevent organic phosphates from being depleted
organic phosphates deleted-> can’t use the blood
