Extreme Living Flashcards
High altitude environments
Cold temperatures
Presence of snow and ice
Windy
Dehydrating
High UV radiation
Low pO2 -hypoxia
Respiration at altitude- conforming to hypoxia
Oxygen consumption for many species reflects no real control of the amount of oxygen taken in but rather this reflects the amount of oxygen in the air.
Freshwater fish have the highest rates of oxygen consumption when the oxygen levels are highest but as oxygen partial pressure (= tension) drops the fish have to reduce the amount of oxygen they take in – they conform to what is available
Respiratory adaptations in high altitude amphibians
Folded skin surface area and cutaneous capillaries penetrate to outer layers of skin to maximise cutaneous gas exchange
smallest erythrocytes recorded for an amphibian but the greatest blood content – this means that there are lots of blood cells carrying haemoglobin but they are small, which aids in minimizing friction during blood flow.
Lowest metabolic rate
Ventilate skin by ‘bobbing’ behaviour to allow water to flow over skin
Ventilate small lungs —> increases metabolic rate
Response of reptiles to high altitude hypoxia
Higher oxygen carrying capacity by increasing red blood cell count, haemoglobin concentration and hematocrit
Differences on the themolecular level with constituent components of the globulin molecules having genetic differences
Hypoxia response in birds and mammals
Hyperventilation
Kidneys increase excretion of (HCO3)- = leads to respiratory acidosis which elevates respiration rate
Change in haemoglobin affinity
Hematocrit
Percentage by volume of red blood cells in blood
Hematocrit
Percentage by volume of red blood cells in blood
Altitude sickness
Low arterial blood concentrations and blood acidity
Leads to firstly mild cerebral oedema and secondly increasing pulmonary oedema (by pulmonary capillaries constricting)
Adaptation to altitude in birds and mammals
Increased lung volume and heart mass
No increase in hematocrit- no increase in blood viscosity
High-affinity haemoglobin (curve shifts to left)
Higher capillary density in left ventricle of heart
Bar-headed goose
molecular changes with changes in the enzyme kinetics of cytochrome c oxidases that catalyse oxygen reduction in oxidative phosphorylation. This effect is due to a single amino acid change in the COX subunit 3 of the enzyme. Bar-headed geese have changed an enzyme system that is highly conserved in all other vertebrates but the functional change has provided them with a physiological advantage that allows them to fly at high altitude
Chinese pika
Reduce pulmonary vasoconstriction responses
Larger right ventricle that provides greater pulmonary perfusion of blood
No increase in haematocrit
Andean coot
increased capillarity in muscles
Reduced muscle fibre diameter
Oxidative enzyme function comparable to sea level birds
Altitude training
Low altitude native visit high altitudes
Elevated erythropoietin leads to red blood cell formation so higher haematocrit
Oxygen carrying capacity increases from 20 to 28 mL O2 per 100 mL blood
Not adaptive phenotypic plasticity but is maladaptive because blood viscosity increases placing extra workload on heart
No long-term physiological adaption to altitude
Hypoxia tolerance in birds’ eggs
Atmospheric hypoxia → depressed metabolism and slow growth
Faster diffusion leads to:
Increased diffusion of O2 across the shell into egg
Increased loss of CO2 from egg
Increased loss of water vapour (H2O) from egg → dehydration
High altitude and diffusion
Air is less dense so molecules diffuse faster
Hydration problems of eggs at altitude
Water vapour diffuses faster at lower pressures
Compensation for hypoxia in eggs – higher conductance could lead to dehydration
Increasing altitude leads to a decrease in eggshell permeability but only to a lower limit
Compromise between need to retain water to also allow O2 in
Mammalian embryos at altitude
Higher uterine blood flow
Higher erythrocyte mass
Increase in placental weight and placental-to-foetal weight ratios
Reduction in thickness of placental exchange epithelia
Decrease in inter capillary distance
Maternal hyperventilation
Evolution of viviparity in lizards
-live birth
often associated with high altitude populations of lizards. This is often attributed to colder temperatures – females can bask to raise body temperature and aid embryonic development. Any eggs laid at altitude would be at temperatures that would not support embryonic development.
There is also some evidence that hypoxia may also drive evolution of viviparity because the female lizard can regulate its degree of arterial oxygenation
As you increase does the percentage of oxygen in the air change?
No
- still 21%
Just lower partial pressure of oxygen
Which vertebrate has been seen at the highest altitude?
Bar-headed goose
What are two maternal adaptions to high altitude in pregnant mammals
Increase in uterine blood flow
Decrease in placental exchange epithelia
Which animal has a larger right ventricle that provides greater pulmonary perfusion of blood?
Chinese pika
Why would a human lose consciousness at 7,000 m?
Arterial pO2 is 50% of normal
Physiological factors affecting diving by air-breathing vertebrates
Temperature
Water pressure
Lack of oxygen access
Morphological adaptations of fish to prevent sinking
Hydrofoil fins of sharks that provide lift as they swim
Low-density lipids- improve buoyancy
Gas filled swim bladder to reduce body density
Replace muscle and bone with water to reduce density
The root effect- teleost fish- and the swim bladder
A decrease in pH reduces the oxygen-carrying capacity of haemoglobin
Filling of the swim bladder is achieved by the root effect
Localised blood acidification by tissue-specific addition of lactic acid releases oxygen from the haemoglobin that then moves into the swim bladder.
Swim bladder function
Walls lined with guanine crystals so is impermeable to gas
Inner wall also lined with gas-impermeable epithelium- reduce gas exchange
Rete mirabile in gas gland accepts blood flowing back to body from gas gland - so all excess CO2 and O2 produced in gas gland diffuses back to arteries supplying gas gland
Very high gas pressure obtained
Amount of gas in swim bladder controlled by release via oval window into blood
Effects on metabolism of pressure
Glycolysis enzyme function declines - metabolic depression
Osmolytes that increase cell volume increase – maintain normal enzyme function
Lipids have more polyunsaturated fats – maintain membrane fluidity
More examples of bioluminescence
Physiological responses to diving
Deal with pressure changes
Circulatory changes —> bradycardia (heart rate slows)
Ensure there is sufficient O2 available for the duration of the dive
-O2 bound to blood haemoglobin
-O2 bound to muscle myoglobin
-O2 within the lungs
Allows for aerobic catabolism for a least part of the dive
Some tissues are obligate aerobes (nervous system and heart)
Other tissues can tolerate anaerobic respiration (skeletal muscle)
What does amount of O2 stored in blood depend on
O2 carrying capacity of blood
Blood volume
Degree of O2 saturation at submergence
Myoglobin stores
myoglobin has a high affinity for oxygen and so can be used to store oxygen whilst there is access to air. Terrestrial mammals have relatively little myoglobin per g of wet tissue compared with those species that specialise in deep diving.
O2 remains bound until a critical low partial pressure in muscle tissue – then released to support aerobic ATP production in mitochondria
Reduced blood flow to skeletal muscle during dives quickly reduced muscle pO2 so drives release from oxymyoglobin
Lungs as oxygen stores of diving species
Deep diving mammals have a flexible thorax that can be pushed inwards by external pressures
Air in lungs adds to buoyancy – adds to energy required to remain underwater
At depth alveoli are first to collapse – air comes to lie in parts of lung with poor gas exchange
Air contains 78% nitrogen
Using lungs as an oxygen store depends on the size of the lungs and how much air is present
For their body mass most diving mammals have lung volumes typical of mammals
Many deep-diving species exhale before diving
Decompression sickness
N2 absorption from compressed air source that maintains air pressure in lungs
Lungs remain inflated but the high pressures increase the pN2 and blood equilibrates
Sudden return to the surface releases the pressure allowing the N2 dissolved in blood to form bubbles that block blood vessels
Slow re-surfacing allows the pressure to drop and the N2 dissolved in blood returns to the air in the lungs
Diving bradycardia
Stroke volume unaffected but heart rate declines
Bradycardia is graded according to each dive
Bradycardia matches the cardiac output to the tissues being perfused
Regional vasoconstriction
Blood is not allowed to many part of the animals body during diving by arteries constricting
Vasoconstriction controlled by the sympathetic nervous system
Loss of blood to limbs, skeletal muscles of torso, pectoral muscles, skin and body wall, and various visceral organs.
Blood flows freely to brain, lungs and heart
Partitioning blood flow
Short voluntary dives does not affect circulation - blood is not allowed to many parts of the animals body during diving by arteries constricting
Protracted diving – body becomes subdivided with respect to metabolism
One consequence of this vasoconstriction is that the build-up of lactic acid produced by anaerobic respiration is localized within muscle tissues and not released to the blood.
Metabolic depression
Diving leads to metabolic depression – slows Vo2
Diving involves activity so metabolic rate should go up
Facultative hypothermia
Delay in food processing
Behavioural mechanisms to minimise activity-
active propulsion
The Root effect is used to inflate what organ in teleost fish?
The swim bladder
Bubbles of which gas cause problems in decompression sickness?
Nitrogen
On average, which dives deeper – birds or mammals?
Mammals
When a mammal dives how can oxygen be stored?
dissolved in blood, bound to haemoglobin, bound to
myoglobin and in the lungs
If a sperm whale has a mass of 80 tonnes how many litres of blood does it have?
20,000 litres (80,000 kg x 0.25 l/kg)
If a sperm whale has a mass of 80 tonnes how many litres of blood does it have?
20,000 litres (80,000 kg x 0.25 l/kg)
Oxygen debt
End of the dive the whole body become perfused and so blood lactate increases as it is released from the muscle before being cleared
This process takes a long time because lactate metabolism is slow
