Gas Exchange Flashcards
Understand all the steps in O₂ delivery & CO2 removal
- ventilation (bulk flow): maximizes oxygen levels- air in and out of lungs
2.
Rate of flow depends on
Pressure differential- higher flow with greater difference
Viscosity- lower flow with higher viscosity (thickness)
- air is easier to move because H20 is more viscous
Diameter of tubes- larger = greater flow
Bulk flow
Movement of fluids (water and air) by generating a pressure difference
What influences the rate of diffusion of a gas?
Partial Pressure gradients - F=kA p1-p2/d
- Greater SA= Greater rate of diffusion
- Longer distance of diffusion = Lower rate of diffusion
Partial pressure and why is important to diffusion rates
It’s found in air, water, or hemoglobin
- Affected by solubility
Px=Ptotal x Fx
What is good at storing Oxygen and increases effective solubility
Hemoglobin
What is more soluble in water than oxygen?
CO2
Sea level pressure in torr
1 torr=1 mm Hg (pressure unit)
SEA LEVEL- 760 torr
AIR PO2- 160 torr
What does Px=Ptotal x Fx stand for?
P total- total pressure of the mixed gas
Fx- fraction of the gas mixture that is X (0.21 for oxygen)
How does ventilation in air compare to water?
Air
- high O2 content
- low density and viscosity
- more diffusible (O2>H2o)
- doesn’t absorb much heat
- respiratory system dry
Water
- low O2 content
- low density and viscosity
- less diffusible
- high specific heat
How do increased body size and metabolic rates affect O2 consumption relative to SA?
Greater body size- harder to get oxygen to all tissues
Higher metabolic rate- more oxygen
What are ways animals increase O2 delivery?
- more complex respiratory surfaces to increase SA
- more ventilation = increase PO2
- more circulation = decrease internal PO2
How do simple and complex gills differ?
Simple:
- increases SA for diffusion of oxygen
- ventilation is passive
Complex:
- Greatly increased SA
- active ventilation (one way flow)
- counter current exchange system
How does counter-current exchange increase O2 extraction from water?
Flow is in opposite direction to eachother
- diffusion adds oxy to blood, water is max maintaining gradient for diffusion
- concurrent: reaches equilibrium
Why do gills work well for water but not terrestrial conditions?
External- cheap to move water in one direction (flow through systems)
- no water loss
- rely on buoyancy of water (gravity)
Benefits to terrestrial enrvironments for respiratory systems
- reduces water loss rate
- air is cheaper/easier to move into internal spaces than water (tidal ventilation)
- internal structures are easier to support without water
How do insects exchange respiratory gases with the air?
Tracheal systems
- series of tubes (tracheae) that carry gases directly to and from tissues
- spiracles (opening of tracheae) can be closed to reduce water loss
How do vertebrates exchange respiratory gases with the air?
Lungs (tidal flow)
- SA
- positive pressure ventilation: push air from their mouth (amphibians)
- negative pressure ventilation: expand lungs, drop pressure in the lungs to pull air in
What is the structure of the mammalian respiratory system, and how does it work?
Mammalian lungs exchange gas with blood at alveoli
- series of branching tubes: trachea -> bronchi -> bronchioles -> alveoli
- short diffusion
- large SA
How is ventilation carried out in Mammalian Lungs
Mammalian lungs have high elasticity
- expand thoracic cavity -> drops pressure surrounding lungs -> expands lungs -> alveoli expands -> drops the pressure
What is the structure of the avian respiratory system and how does it work?
Flow through lungs- air entered through the back and go out through the front BUT dont expand
- air sacs expand but do not exchange gases
- gas exchange occurs at parabronchi
How is ventilation carried out in flow through lungs
- air gets drawn in, posterior, air sac expands, thoracic cavity is contracting, air sacs are compressed, air is forced out through the lungs
- Air sac expands, pulls air in from lungs
- exhaled from the anterior air sac out through the mouth
Circulatory system consists of..
Blood vessels, a heart to generate hydrostatic pressure, blood (hemolymph) that moves through vessels
What are the functions of blood in addition to gas transport?
Move gases, move nutrients/waste, distribute hormones/immune system cells, distribute heat, provide hydrostatic pressure
How do open and closed circulatory systems differ?
Open (hemolymph)- vessels empty into sinus, then blood reenters circulatory system. taken to places needs through arteries
- LOW: pressure, rate of flow, control of flow limited, diffusion distance, metabolic rates(slow animals)
Closed (blood)- blood comes out from the heart, goes through arteries, divides into capillaries, recombines up into a vein.
- HIGH: pressures, rate of flow, control of flow significant, diffusion distance, metabolic rates(more active)
What are the two types of hearts?
Peristaltic pumps- part of blood vessels, limited to lower pressures
- wave of contractions pushed blood along
Chambered pumps- specialized structures with one way valves, can generate higher pressures
- thicker muscular walls for high pressure
Different types of blood vessels and their general characteristics
- Capillaries- thin one cell layered walled for slow flow
- Arteries- large diameter, thick, highest speed and pressure
- Arterioles- smaller version but reduces blood flow to particular areas
Return blood back to the heart
- Venules- thin walled and slightly larger than arterioles
- Veins- bigger version of venules, high speed and low pressure
How does blood pressure and flow change in the different vessels?
Pressure drives flow, flow goes from high to low pressure.
- Blood pressure drops as we go from the heart through the capillaries, to the veins and back to the heart
How is blood flow distribution controlled?
Tissues have different metabolic rates at different times, requires increased blood flow to support increased metabolism
Blood flow to tissues is controlled mainly by arteriole diameter
- increased diameter increased flow in active tissues
General pattern of circulation and number of heart chambers in fish, amphibians, mammals and birds.
Mammals and Birds (2 circuits and 4 chambered heart)
- right v pumps blood to lungs, left v pumps blood to the body, and loops
Fish (1 circuit, 2 chambered heart)
- one v pumps blood to gills picks oxygen and travels to body, returns to heart
Amphibians
- No oxygen needed to pick up so it bypasses the lungs
Vertebrates and mammalian circulation
Vertebrates-
- one or two ventricles to generate pressure for circulation
- one or two atria to store and help fill ventricles
- one way valves keep blood flowing
Mammals-
- systemic circuit: carries blood from heart out to tissues
- pulmonary circuit: blood leaves heart and goes to lungs to pick up oxygen and pick up co2
The four chambers and two valve types, and which side of the heart serves which circuit
Atrioventricular (AV) valve- allows blood from atria to ventricles
Semilunar (SL) valve- allows blood from v to arteries
What triggers the heartbeat
Sinoatrial node
How contraction of the heart and the valves generate pressure and flow in the heart
Contraction is triggered by electrical signals traveling through the heart
- the primary pacemaker is the sinoatrial node
- frequemcy (heart rate) is influenced by the nervous and endocrine systems
Systole and Diastole
Systole- when the heart is contracting and generating pressure
Diastole- when the heart is relaxed
What maintains blood circulation during diastole
Ventricle is relaxes and filling with blood, preparing for the next contraction
- blood passes through circulatory system, comes into the. vein, enters the heart, low pressure carries blood through the atria and through the ventricles.
How do you maintain the one way flow?
Atrial pressure > Ventricle pressure = AV valves open
Ventricle pressure < Arterial pressure = SL valves close
Closes SL valves prevents back flow of blood
How do you maintain the one way flow?
Atrial pressure > Ventricle pressure = AV valves open
Ventricle pressure < Arterial pressure = SL valves close
Closes SL valves prevents back flow of blood
With a semilunar valve that does not seal completely when closed, what will occur?
Blood would leank from the artery
When blood gets ejected into the arteries, what allows the arteries to expand
Elastic tension in the walls, pushes the blood out as it shrinks back down.
Approximate PO2 levels in air, the alveoli, tissues, and blood in different locations.
air- 160 torr
alveoli- 104 torr
tissues- < 40 torr
blood- 40 torr
Delivery of oxygen requires
- moving more blood through tissues
- carry more oxygen per each ml of blood
Respiratory pigments
Oxygen is intended because they use metal atoms to bind O2 (copper or iron)
Two major blood pigments
- Hemoglobin- iron based, found in vertebrates and some invertebrates
- bright red, purple/blue
- Hemocyanin- copper based, found in molluscs and arthropods
- bright blue, clear
Characteristics of hemoglobin in vertebrates
Hemoglobin (Hb) is carried in red blood cells
- tetramer: four O2 molecules that consist protein
- 0-100% saturated
What does the oxygen equilibrium curve show
Shows the saturation levels at different partial pressures
The relationship between PO2 and the amount of O2 bound to Hb is non-linear
Understand how CO2 is transported in the blood
- CO2 that enter the blood is converted into bicarbonate.
- ECF becomes more acidic as CO2 increases, CO2 levels can be decreased by increasing ventilation
- Negative feedback loop controlled by cns
