Niyogi Lectures 1-4 Flashcards
Why is there a constant urgent need of oxygen in animals?
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.
Respiration is broken into what three parts?
(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
Define a gas-exchange membrane.
a thin layer of one or two simple epithelia that separates internal tissues from the environmental medium (whether that be water or air).
External respiration is a process by which:
environmental O2 ===> membrane ===> tissues
dissolved CO2 ===> membrane ===> environment
Outline the physics of diffusion (Fick’s Law) and its application to the diffusion of respiratory gases.
How small does an animal need to be to rely on diffusion of O2 alone?
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.
Why does oxygen requirements increase with mass?
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.
How do animals prevent respiration from being diffusion limited?
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.
Respiration in large animals require multiple steps. What do most vertebrate gas-transfer systems involve?
Key terms: ventilation, perfusion, diffusion
(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
What is Dalton’s Law?
Define partial pressure.
How does this relate to respiration?
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).
True or false? High altitudes have less oxygen in the air.
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.
Solubility of oxygen in water _________ as temperature increases.
decreases
There is more/less oxygen in water than air.
less
Why is water-breathing energetically more expensive than air breathing?
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.
Describe the structure of gills.
Branched and folded invaginations that increase diffusion area. The beating of cilia and the contractions of body muscles pump water through the gills.
What are the two types of gills?
internal and external
What is the double pumping mechanism in bony and cartilaginous fish?
Also called Buccal pumping
What is ram ventilation and what species is it observed in?
Pelagic fish like some sharks and mackerel
Mackerel can’t fully oxygenate their blood if prevented from active swimming
Describe the countercurrent flow in gills.
What are the advantages of this?
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.
What is the effect of water temperature on gill structure of killfish? How does this help their respiration in warm water?
This allows for greater water flows in between lamella, since warm water is less soluble to oxygen.
Define trachea
invaginations of the outer epidermis that branch repeatedly
Describe the tracheal system of insects for gas exchange.
Air enters and leaves through spiracles, trachea branches into tracheoles
How do bird respiratory systems compare to human ones?
Birds have multiple air sacs instead of lungs all connected by bronchi
Describe crosscurrent gas exchange in birds.
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).
Explain the anatomy of the bird lung.
Describe the mammalian respiratory system
Mammalian lungs are surrounded by pleural sac, what are these sacs called and how are they ordered?
Summarize human lung volume and capacities in terms of tidal volume and other relevant terms.
Define TLC, TV, FRC, RV, and VC
How does tidal gas exchange of mammalian lungs compare to that of cross-current avian lung gas exchange.
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?
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
Why is hemoglobin needed in the blood?
Oxygen is not very soluble in plasma water, so the carrier protein Hemoglobin (Hb) transports sufficient amounts of oxygen.
Explain how oxygen diffuses from alveolar air into the blood using the term partial pressure.
Partial pressure of oxygen is higher in alveolar air than in blood in capillary networks surrounding alveoli (oxygen high to low).
Describe the structure of the iron-containing, oxygen transporting metalloprotein hemoglobin that is present in the red blood cells of almost all vertebrates.
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.
This image depicts Hemoglobin-oxygen dissociation curve. What causes this trend?
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.
What is the effect of pH on hemoglobin-O2 dissociation? Why does pH have a greater impact on body tissues than the alveoli?
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.
How does oxygen diffuse from the blood into body tissues? What is occurring with carbon dioxide during this process?
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.
There are two ways CO2 is transferred from body cells to blood: fast and slow. Describe the fast way.
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
There are two ways CO2 is transferred from body cells to RBC: fast and slow. Describe the slow way.
Some CO2 released into the blood and combines with plasma H2O to form HCO3- and H+ in the plasma
What is carbonic anhydrase (CA) and it’s function in the body?
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.
How is CO2 transferred in the lungs?
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
Why does CO cause tissue hypoxia?
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.
