Extreme Living

Question 1

High altitude environments

Answer 1

Cold temperatures
Presence of snow and ice
Windy
Dehydrating
High UV radiation
Low pO2 -hypoxia

Question 2

Respiration at altitude- conforming to hypoxia

Answer 2

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

Question 3

Respiratory adaptations in high altitude amphibians

Answer 3

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

Question 4

Response of reptiles to high altitude hypoxia

Answer 4

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

Question 5

Hypoxia response in birds and mammals

Answer 5

Hyperventilation
Kidneys increase excretion of (HCO3)- = leads to respiratory acidosis which elevates respiration rate
Change in haemoglobin affinity

Question 6

Hematocrit

Answer 6

Percentage by volume of red blood cells in blood

Question 7

Hematocrit

Answer 7

Percentage by volume of red blood cells in blood

Question 8

Altitude sickness

Answer 8

Low arterial blood concentrations and blood acidity
Leads to firstly mild cerebral oedema and secondly increasing pulmonary oedema (by pulmonary capillaries constricting)

Question 9

Adaptation to altitude in birds and mammals

Answer 9

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

Question 10

Bar-headed goose

Answer 10

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

Question 11

Chinese pika

Answer 11

Reduce pulmonary vasoconstriction responses
Larger right ventricle that provides greater pulmonary perfusion of blood
No increase in haematocrit

Question 12

Andean coot

Answer 12

increased capillarity in muscles
Reduced muscle fibre diameter
Oxidative enzyme function comparable to sea level birds

Question 13

Altitude training

Answer 13

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

Question 14

Hypoxia tolerance in birds’ eggs

Answer 14

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

Question 15

High altitude and diffusion

Answer 15

Air is less dense so molecules diffuse faster

Question 16

Hydration problems of eggs at altitude

Answer 16

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

Question 17

Mammalian embryos at altitude

Answer 17

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

Question 18

Evolution of viviparity in lizards
-live birth

Answer 18

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

Question 19

As you increase does the percentage of oxygen in the air change?

Answer 19

No
- still 21%
Just lower partial pressure of oxygen

Question 20

Which vertebrate has been seen at the highest altitude?

Answer 20

Bar-headed goose

Question 21

What are two maternal adaptions to high altitude in pregnant mammals

Answer 21

Increase in uterine blood flow
Decrease in placental exchange epithelia

Question 22

Which animal has a larger right ventricle that provides greater pulmonary perfusion of blood?

Answer 22

Chinese pika

Question 23

Why would a human lose consciousness at 7,000 m?

Answer 23

Arterial pO2 is 50% of normal

Question 24

Physiological factors affecting diving by air-breathing vertebrates

Answer 24

Temperature
Water pressure
Lack of oxygen access

Question 25

Morphological adaptations of fish to prevent sinking

Answer 25

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

Question 26

The root effect- teleost fish- and the swim bladder

Answer 26

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.

Question 27

Swim bladder function

Answer 27

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

Question 28

Effects on metabolism of pressure

Answer 28

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

Question 29

Physiological responses to diving

Answer 29

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)

Question 30

What does amount of O2 stored in blood depend on

Answer 30

O2 carrying capacity of blood Blood volume Degree of O2 saturation at submergence

Question 31

Myoglobin stores

Answer 31

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

Question 32

Lungs as oxygen stores of diving species

Answer 32

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

Question 33

Decompression sickness

Answer 33

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

Question 34

Diving bradycardia

Answer 34

Stroke volume unaffected but heart rate declines Bradycardia is graded according to each dive Bradycardia matches the cardiac output to the tissues being perfused

Question 35

Regional vasoconstriction

Answer 35

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

Question 36

Partitioning blood flow

Answer 36

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.

Question 37

Metabolic depression

Answer 37

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

Question 38

The Root effect is used to inflate what organ in teleost fish?

Answer 38

The swim bladder

Question 39

Bubbles of which gas cause problems in decompression sickness?

Answer 39

Nitrogen

Question 40

On average, which dives deeper – birds or mammals?

Answer 40

Mammals

Question 41

When a mammal dives how can oxygen be stored?

Answer 41

dissolved in blood, bound to haemoglobin, bound to myoglobin and in the lungs

Question 42

If a sperm whale has a mass of 80 tonnes how many litres of blood does it have?

Answer 42

20,000 litres (80,000 kg x 0.25 l/kg)

Question 43

If a sperm whale has a mass of 80 tonnes how many litres of blood does it have?

Answer 43

20,000 litres (80,000 kg x 0.25 l/kg)

Question 44

Oxygen debt

Answer 44

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