Niyogi Lectures 1-4

Question 1

Why is there a constant urgent need of oxygen in animals?

Answer 1

anaerobic respiration cannot occur without oxygen and not enough ATP is produced to maintain the energy to support life. If carbon dioxide builds in the body it can be toxic.

Question 2

Respiration is broken into what three parts?

Answer 2

(1) External respiration: transport of O2 into and CO2 out of the body
(2) Internal respiration: transports O2 into and CO2 out of cells
(3) Cellular respiration: intracellular catabolic reactions that convert stored energy to ATP

Question 3

Define a gas-exchange membrane.

Answer 3

a thin layer of one or two simple epithelia that separates internal tissues from the environmental medium (whether that be water or air).

Question 4

External respiration is a process by which:

Answer 4

environmental O2 ===> membrane ===> tissues
dissolved CO2 ===> membrane ===> environment

Question 5

Outline the physics of diffusion (Fick’s Law) and its application to the diffusion of respiratory gases.

Answer 5

Question 6

How small does an animal need to be to rely on diffusion of O2 alone?

Answer 6

Diffusion alone is sufficient only for very small animals such as rotifers.

Vertebrate muscle require O2 partial pressure of ~40 mmHg. Atmospheric O2 partial pressure is 160mmHg. Using Fick’s law, the distance inside the tissue where O2 partial pressure reaches a minimum of 40 mmHg is ~1mm.

Question 7

Why does oxygen requirements increase with mass?

Answer 7

because the diffusion distance increases and the surface area gets proportionately smaller. Thus, the need for respiratory organs with larger surface area and a shorter diffusion distance.

Question 8

How do animals prevent respiration from being diffusion limited?

Answer 8

Mammals and birds are endothermic so they produce their own body heat, which requires a higher metabolic rate and, therefore, more oxygen consumption.

Reptiles, amphibians, and fish however, have a lower metabolic rate because their bodies allow their internal temperature to change with the environment.
Yellow fin tuna is an exception because they grow so large.

Birds and mammals have much thinner gas exchange membranes (lungs compared to gills or skin) to acomodate for this.

Question 9

Respiration in large animals require multiple steps. What do most vertebrate gas-transfer systems involve?

Key terms: ventilation, perfusion, diffusion

Answer 9

(1) Ventilation: breathing movements that bring in fresh air and expel stale air
(2) Diffusion of gases across the respiratory epithelia
(3) Perfusion: Circulatory system functions in bulk transport of gases
(4) Diffusion of gases across capillary walls

Question 10

What is Dalton’s Law?
Define partial pressure.
How does this relate to respiration?

Answer 10

Dalton’s Law states that total pressure exerted by a gas mixture is the sum of individual pressures exerted by each gas in the mixture.

The partial pressure (Pg) of a gas is its individual pressure in a mixture.

The rate of diffusion of a gas is proportional to its partial pressure within the total gas mixture. So, oxygen and CO2 will flow based on their pressure gradient (high to low).

Question 11

True or false? High altitudes have less oxygen in the air.

Answer 11

False. High altitude reduces the inspired pressure of oxygen, not the percent of oxygen in the atmosphere. The lowered oxygen pressure decreases diffusion dramatically.
Aka oxygen content is the same, the air is just thin.

Question 12

Solubility of oxygen in water _________ as temperature increases.

Answer 12

decreases

Question 13

There is more/less oxygen in water than air.

Answer 13

less

Question 14

Why is water-breathing energetically more expensive than air breathing?

Answer 14

Because water is 1000 times denser and 50 times more viscous than air, oxygen content in water is 3% of that in an equal volume of air, decreasing with water temperature and depth. Hence, much more metabolic energy is required to extract O2 from water than from air.

Question 15

Describe the structure of gills.

Answer 15

Branched and folded invaginations that increase diffusion area. The beating of cilia and the contractions of body muscles pump water through the gills.

Question 16

What are the two types of gills?

Answer 16

internal and external

Question 17

What is the double pumping mechanism in bony and cartilaginous fish?

Answer 17

Also called Buccal pumping

Question 18

What is ram ventilation and what species is it observed in?

Answer 18

Pelagic fish like some sharks and mackerel
Mackerel can’t fully oxygenate their blood if prevented from active swimming

Question 19

Describe the countercurrent flow in gills.
What are the advantages of this?

Answer 19

With concurrent flow, the exchange gradient equalizes so there is oxygen potential wasted. You are left with semi-oxygenated water and blood.
The countercurrent system maximizes the extraction of oxygen from the water and secretion of wastes. This works because P1-P2 remains constant along the length of the secondary lamella (the filaments of the lungs the blood circulates through).

Think of it like a highway but every time you pass by a car you gain an oxygen, you would be much less successful on a one-way double lane.

Question 20

What is the effect of water temperature on gill structure of killfish? How does this help their respiration in warm water?

Answer 20

This allows for greater water flows in between lamella, since warm water is less soluble to oxygen.

Question 21

Define trachea

Answer 21

invaginations of the outer epidermis that branch repeatedly

Question 22

Describe the tracheal system of insects for gas exchange.

Answer 22

Air enters and leaves through spiracles, trachea branches into tracheoles

Question 23

What is the limiting factor in insect tissue size? Why?

Answer 23

The length of tissue diffusion path limits the size of the tissue because simple diffusion in tracheoles can only transport oxygen so far.

Question 24

How have larger insects adapted to the limitations of diffusion?

Answer 24

They use ventilation systems involving the opening and closing of spiracles and abdominal muscles

Question 25

How do bird respiratory systems compare to human ones?

Answer 25

Birds have multiple air sacs instead of lungs all connected by bronchi

Question 26

Describe crosscurrent gas exchange in birds.

Answer 26

Air is circulates through bronchi tubes where the blood becomes oxygenated by various air sacs. Blood flow branches into multiple streams and concurrent meeting points with the air flow, thus the blood is slightly less oxygenated the further down the airflow the blood branch is. Oxygenic pressure of blood leaving the breathing organ is higher than that of exhaled medium (air).

Question 27

Explain the anatomy of the bird lung.

Answer 27

Question 28

Why are bird lungs more efficient in absorbing oxygen than human lungs?

Answer 28

Because of their structure, they are given several opportunties for gas exchange with each blood flow branch, while the human lung does so once per breath cycle in each alveoli.

Question 29

How are birds that fly at extremely high altitudes physiological adapted?

Answer 29

(1) increased hypoxic ventilation response (2) larger lungs (3) their hemoglobin have a greater affinity for oxygen (4) higher capillarity in flight muscles (5) greater aerobic capacity in the flight muscles

Question 30

Describe the mammalian respiratory system

Answer 30

Question 31

What are the sequentially branching airways of mammalian lungs called and how are they ordered in the body?

Answer 31

the trachea divides to form two primary bronchi primary bronchi branch and rebranch into bronchioles Bronchioles branch multiple times and eventually end in tiny outpocketings known as alveoli.

Question 32

Mammalian lungs are surrounded by pleural sac, what are these sacs called and how are they ordered?

Answer 32

Question 33

Boyle's law states that pressure and volume are inversely related to one another. How does this knowledge apply to mammalian lungs?

Answer 33

When the air is exhaled out of the lungs, there is a greater pressure allowing for air to rush into the lungs when a breathe is taken.

Question 34

Summarize human lung volume and capacities in terms of tidal volume and other relevant terms.

Answer 34

Question 35

Define TLC, TV, FRC, RV, and VC

Answer 35

Question 36

How does tidal gas exchange of mammalian lungs compare to that of cross-current avian lung gas exchange.

Answer 36

Question 37

Explain the system of regulation of lung ventilation using the terms central controller, sensors, and effectors.

Answer 37

sensors: chemoreceptos in the lungs and stretch receptors detect CO2, O2, and pH as well as abdominal expansion. This information is sent to the control centre: which is the pons and medulla, as well as some other sections of the brain that relay messages to the effectors: aka the respiratory muscles which circles back to the sensors

Question 38

What role do peripheral chemoreceptors play in controlling breathing and how is the information circulated in the body? How are their signals carried to the brain? Which part of the brain?

Answer 38

Peripheral chemoreceptors in the aortic bodies within the aortic arch and carotid arteries monitor the pressure of CO2 and pH, secondarily monitoring O2 pressure. Information travels via the vagus nerve and glossopharyngeal nerves to the respiratory centres in the medulla and pons

Question 39

Many people infected by Covid-19 suffer from severe respiratory problems. Why and how does corona virus disrupt oxygen uptake in our lungs?

Answer 39

Covid-19 damages the cells involved in oxygen absorption in the alveoli by causing fluid and debris from the cells to leak into the alveoli space (pneumonia) which effects their ability to absorb oxygen from air.

Question 40

Oxygen is transported in blood cells two different ways, one much more than the other. What are they?

Answer 40

The protein Hemoglobin (Hb) in red blood cells binds with oxygen using iron molecules. This accounts for more than 98% of the oxygen in the blood. There remaining oxygen (less than 2%) is dissolved in the plasma, which is the liquid portion of blood.

Question 41

Why is hemoglobin needed in the blood?

Answer 41

Oxygen is not very soluble in plasma water, so the carrier protein Hemoglobin (Hb) transports sufficient amounts of oxygen.

Question 42

Explain how oxygen diffuses from alveolar air into the blood using the term partial pressure.

Answer 42

Partial pressure of oxygen is higher in alveolar air than in blood in capillary networks surrounding alveoli (oxygen high to low).

Question 43

Describe the structure of the iron-containing, oxygen transporting metalloprotein hemoglobin that is present in the red blood cells of almost all vertebrates.

Answer 43

Composed of 4 polypeptides (single linear chain of many amino acids (any length), held together by amide bonds), each with a heme group (non-protein group of iron atoms) at the centre. This is the part that binds to the oxygen specifically.

Question 44

In mammals, how much of the red blood cell dry content do hemoglobin comprise?

Answer 44

96%

Question 45

How does hemoglobin bind with oxygen? How many oxygen can one hemoglobin bind at a time?

Answer 45

Oxygen binds to each ferrous iron (Fe2+) of the heme group in a reversible manner Hemoglobin can bind up to 4 oxygen molecules

Question 46

This image depicts Hemoglobin-oxygen dissociation curve. What causes this trend?

Answer 46

The sigmoid shape results from co-operativity: the binding of oxygen in one site increases the affinity of the other sites. This is because large quantities of oxygen combined with hemoglobin maintain a large partial pressure gradient between oxygen in alveolar air and in blood plasma. AKA the oxygen is bound so there is less in free oxygen in the alveoli and when the hemoglobin is saturated and there is plenty oxygen available, the pressure decreases.

Question 47

What three environmental factors influence the affinity of hemoglobin?

Answer 47

temperature, pH and CO2 content

Question 48

Are hemoglobin more or less saturated at higher temperatures?

Answer 48

less

Question 49

Where is the shift in oxygen partial pressure following a temperature change most dramatic, the lung or tissue capillarary?

Answer 49

tissue capilararies this is because temperature affects the binding strength of hemoglobin and the PO2 is higher in the alveoli than the blood in capillaries, so they are more sensitive to changes

Question 50

What is the effect of pH on hemoglobin-O2 dissociation? Why does pH have a greater impact on body tissues than the alveoli?

Answer 50

Low pH reduces the hemoglobins affinity for oxygen, so more oxygen is released In the capillaries of body tissues the pH is ~7.2 so hemoglobin holds less oxygen and the blood is subject to greater variation in pH (due to CO2 content or substances ingested) while the pH of the lungs is relatively constant.

Question 51

How does oxygen diffuse from the blood into body tissues? What is occurring with carbon dioxide during this process?

Answer 51

The oxygen diffuses from the high concentration blood to the low concentration tissues. First the oxygen detaches from the hemoglobin of the RBC and dissolves in the plasma. The oxygen diffuses through the walls of the capillaries to interstitial fluid and then from there to the tissue cells, which both have a lower oxygen pressure than blood plasma. All while this is happening, CO2 is diffusing from the high concentration tissues to the low concentration blood in a reversed manner. About 10% dissolves in the blood plasma and 70% is converted into H+ and HCO3- (bicarbonate) ions. The remaining 20% combines with hemoglobin.

Question 52

There are two ways CO2 is transferred from body cells to blood: fast and slow. Describe the fast way.

Answer 52

CO2 diffuses into RBC and combines with hemoglobin forming carbaminohemoglobin. Some CO2 combines with H2O inside the RBC to form HCO3- and H+. Then the H+ combines with hemoglobin and HCO3- is transported out of RBC to plasma

Question 53

There are two ways CO2 is transferred from body cells to RBC: fast and slow. Describe the slow way.

Answer 53

Some CO2 released into the blood and combines with plasma H2O to form HCO3- and H+ in the plasma

Question 54

What is carbonic anhydrase (CA) and it's function in the body?

Answer 54

A metalloenzyme that requires Zn2+ Catalyzes the rapid interconversion of CO2 and H2O to biocarbonate and H+ in the blood (plasma and RBC). This greatly increases the bodies ability to convert CO2 (1million molecules/sec) and contributes to transport CO2 out of tissues. This is essential for maintaining acid-base balance in blood and other tissues.

Question 55

How is CO2 transferred in the lungs?

Answer 55

In the lungs, the pressure of CO2 is higher in the blood than the alveolar air, thus H+ detaches from hemoglobin in the RBC and HCO3- and H+ combine in RBC to produce CO2 and H2O, with the use of carbonic anhydrase CO2 is thus released from the hemoglobin and the bicarbonate in the RBC CO2 leaves the RBC and enters blood plasma The HCO3 remaining in the blood plasma that didn't enter the RBC to combine with H+ released from the hemoglobin reacts with the free H+ in the plasma to produce the remaining CO2 content CO2 then diffuses across the alveolar membrane to be expelled through air

Question 56

How does Antarctic icefish survive without hemoglobin?

Answer 56

Low metabolic rate large heart, wide blood vessels, large gills, and no scales increase blood flow and amount of oxygen that diffuses into their blood Oxygen diffuses into their circulating blood plasma from the frigid seawater by way of the fish's enlarged gills and smooth skin cold seawater has higher oxygen capacity

Question 57

Why does CO cause tissue hypoxia?

Answer 57

Hypoxia is a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis; this can result from inadequate oxygen delivery to the tissues due to low oxygen pressure in the blood (hypoxemia). CO has a greater binding affinity to hemoglobin than oxygen and a shift occurs in oxygen-hemoglobin dissociation curve, making it a hyperbola. With this shift, capacity of hemoglobin to deliver oxygen to tissues decreases, with resultant development of tissue hypoxia.