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97 Cards in this Set
- Front
- Back
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Why is haemoglobin necessary to oxygen transport in the blood? |
Because oxygen is very insoluble in water and the amount which dissolves into it is not sufficient |
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What is the proportion of haemoglobin-bound oxygen to dissolved oxygen? |
98.5% to 1.5% |
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What is HHb? |
Reduced or deoxygenated haemoglobin |
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What is HbO2? |
Oxygenated haemoglobin |
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What is the OHDC? |
Oxygen/Haemoglobin Dissociation Curve |
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What shape is an OHDC? |
S-shaped |
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What does the shape of an OHDC indicate about haemoglobin's affinity for O2? |
It is not linearly correlated to the oxygen saturation of Hb |
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In what geographic condition is Hb less saturated? |
High altitudes |
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Why does Hb affinity change? |
To allow oxygen to be released where it is needed |
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In what way does Hb affinity change? |
Increases in high O2 concentration, decreases in low O2 concentration |
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How does exercise impact O2 affinity? |
Decreases significantly |
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What factors affect the OHDC? |
Temperature, pH, CO2, 2,3 DPG |
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What happens to the pH of exercising muscle? |
It decreases |
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Why does the pH of exercising muscle decrease? |
The production of lactic acid |
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How does low pH impact O2 affinity? |
Decreases |
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How does high temperature impact O2 affinity? |
Decreases |
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How does high CO2 concentration impact O2 affinity? |
Decreses |
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How does increased 2,3 DPG impact O2 affinity? |
Decreases |
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How does 2,3 DPG reduce O2 affinity? |
By binding to Hb and changing its structure slightly |
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What is hypoxia? |
Oxygen deprivation |
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How does CO2 travel from tissues to the alveoli? |
Dissolving in plasma and within RBCs |
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How does the majority of CO2 travel from tissues to the alveoli? |
In the RBC as bicarbonate |
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How does CO2 travel in RBCs? |
Binds to globin or is converted to bicarbonate |
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What is formed when CO2 binds to globin? |
Carbaminohaemoglobin is formed |
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How does CO2 become bicarbonate in RBCs? |
It reacts with water to form carbonic acid, then is catalysed by carbonic anhydrase to become H+ and CO3- |
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Why does bicarbonate formation occur much more in RBCs than in plasma? |
There is no CA in plasma |
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What ion moves into RBCs as a result of bicarbonate formation? |
Cl- |
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What problem is created by bicarbonate formation? |
Creation of H+ ions, lowering pH |
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How are H+ ions buffered by RBCs? |
They bind to Hb |
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What happens to Hb which is bound to H+ ions? |
It becomes reduced |
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What happens to bicarbonate when Hb is reduced? |
It moves out of the cell down its electrical gradient |
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What happens to compensate for exit of bicarbonate from RBCs? |
Water and Cl- enter |
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How is CO2 unloaded? |
Bicarbonate re-enters the RBC and Cl- diffuses out, H+ ions are released by Hb, carbonic acid is reformed, CA binds to catalyse breakdown into CO2 and water |
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What are the concentrations of O2 and CO2 in the lungs? |
High O2 concentration, low CO2 concentration |
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What happens when O2 binds to haem groups on Hb? |
CO2 bound to globin is decoupled and released |
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What does O2 release when binding to Hb? |
H+ |
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How is the influx of H+ handled differently with O2 binding and CO2 binding? |
Bicarbonate influx vs. Hb buffering |
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How do fetuses receive O2 / remove CO2? |
Through the mother's blood traveling through the placenta |
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What is the problem with blood transfer through a placenta? |
Size-- the pressure of O2 is significantly lower by the time it reaches fetal capillaries, causing low O2 transfer |
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What adaptations exist in fetuses to circumvent low O2 concentrations? |
Fetal haemoglobin, change in 2,3 DPG sensitivity, double Bohr effect, high RBC concentrations |
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How is foetal haemoglobin different than regular haemoglobin? |
It has a much higher O2 affinity, and does not have any beta chains |
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Why does fetal Hb not have beta chains? |
Because they are sensitive to 2,3 DPG-- no beta chains=higher O2 affinity |
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What is the double Bohr effect? |
Fetal blood gives its CO2 to maternal blood, lowering its pH and oxygen affinity, causing it to further release O2 |
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What is the RBC count in fetal blood compared to regular blood? |
Significantly higher |
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What are the elements of a generic homeostatic control center? |
Receptors, control centers, and effectors |
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How is breathing controlled homeostatically? |
A chemical or mechanical input passes through chemoreceptors or mechanoreceptors. The signal passes through the central respiratory centre, which effects change through the respiratory muscles |
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What does it mean that thoracic skeletal muscle has no pacemaker? |
It isn't like the heart in that it cannot contract autonomously |
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Where are the central respiratory centers? |
The brain |
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How many regions compose the CRCs? |
4 |
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Which respiratory centers lie behind the pons? |
The pneumotaxic and apneustic areas |
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How is the central respiratory center divided? |
Into the ventral and dorsal respiratory center |
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What is another term for the pneumotaxic and apneustic areas? |
The pontine respiratory group |
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What respiratory centers lie on the medulla oblongata? |
The ventral & dorsal respiratory centers |
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What function is controlled by the ventral respiratory center? |
Expiration |
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What function is controlled by the dorsal respiratory center? |
Inspiration |
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What areas are contained in the pontine respiratory group? |
Pneumotaxic and apneustic areas |
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Which part of the brain establishes breathing?
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The medulla oblongata |
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Which part of the brain fine-tunes breathing patterns? |
The pons |
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What is the functional difference between the medulla oblongata and the pons? |
The medulla oblongata establishes breathing, while the pons fine-tunes its pattern |
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What nerve signals the diaphragm? |
The phrenic nerve |
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What nerve signals the intercostal muscles? |
The intercostal nerves |
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What signals are sent by the DRC? |
Stimulating the diaphragm and intercostal muscles, and inhibiting VRC neurons |
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How many neurons fire when the DRC is stimulated? |
Initially only a few, but then many due to positive feedback loop |
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What is the function of the VRC? |
To inhibit the firing of inspiration neurons in the DRC, allowing muscle relaxation |
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What is the time pattern between DRC and VRC? |
2 seconds DRC-induced contraction, 3 seconds VRC-induced relaxation |
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What is the difference between quiet and active breathing? |
Active breathing engages the DRC more, inducing stronger and more muscle contraction |
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What is the function of the apneustic center? |
To inhibit expiration centers and initiate inspiration centers by stimulating the DRC |
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How does the pneumotaxis center work? |
It inhibits the apneustic center, firing at maximum DRC activity |
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What CRCs work to cause inspiration? |
The DRC and and apneustic center |
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What CRCs work to cause expiration? |
The VRC and pneumotaxic center |
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What chemical changes in the blood can cause CRC activation? |
Changes in the pressure or concentrations of O2, CO2, and H+ |
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What detects changes in chemical concentration in the blood? |
Chemoreceptors |
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What are the two categories of chemoreceptors? |
Central (in brain) or peripheral (outside of brain) |
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What types of mechanical receptors control ventilation? |
Slow-adapting stretch receptors, rapid-adapting stretch receptors, and C fibers/ J receptors |
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Where are SARs found? |
In smooth muscle throughout the lung |
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What are SARs? |
Slow-adapting stretch receptors |
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What are RARs? |
Rapid-adapting stretch receptors |
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What do RARs respond to? |
Irritants-- smoke, dust, gases |
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Through what nerve do SARs connect to the DRC? |
Vagus nerve |
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What causes coughs and sneezes? |
Activation of RARs |
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What type of response do activated RARs cause? |
Sneezing or coughing |
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What is the function of C fibers/J receptors? |
To induce rapid shallow breathing |
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How do C fibers / J receptors work? |
By sensing the development of interstitial fluid |
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What is the difference between RARS and SARS vs. C fibers? |
RARs and SARs are myelinated fibers, while C fibers are not |
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What are the central chemoreceptors sensitive to? |
Increases in CO2 (by detecting H+ increase) |
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What are the peripheral chemoreceptors sensitive to? |
Decreases in O2 & pH |
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What are the types of peripheral chemoreceptors? |
Carotid & aortic bodies |
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How is hypercapnia handled by the body? |
Central chemoreceptors double the ventilation rate in order to lower CO2 levels |
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What is hypercapnia? |
Too high CO2 concentrations in the blood |
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What is the difference between type I and type II cells? |
Type I cells sense blood composition & produce neurotransmitters, while type II support the cell |
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What molecule most controls ventilation? |
CO2 |
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What can modify the influence of CO2 on ventilation? |
Metabolites and drugs |
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Acidosis and low PCO2 cause what? |
Hyperventilation |
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What is hypoxia? |
Too little O2 in the blood |
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Why is the ventilation response so drastically changed in asphyxiation? |
Because both hypercapnia and hypoxia occur |
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What is the mammalian respiratory diving response? |
After submission in cold water, mammals respond with bradycardia and redirected blood flow to brain |
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What happens when the body acclimatizes to a high altitude? |
Increase in minute volume and RBC count |
