D.6 gas transport Flashcards
Haemoglobin
Is a protein in red blood cells
Haemoglobin is composed of four polypeptide chains, each with an iron-containing heme group that reversibly binds oxygen
As each O2 molecule binds, it alters the conformation of haemoglobin, making subsequent binding easier
Oxygen affinity
Affinity = the attraction between two things
Represented by dissasociation curve
The more O2 attatched to the haemoglobin, the easier it gets for another one to bind
=> As each O2 molecule binds, it alters the conformation of haemoglobin, making subsequent binding easier
Oxygen dissasociation curve
The highest oxygen affinity is in the lungs
How is Co2 transported between the lungs and the tissue?
- Some is bound to haemoglobin to form HbCO2 (binds with globin, NOT heme)
- A very small fraction gets dissolved in water and is carried in solution
- 75% diffuses into the erythrocyte and gets converted into carbonic acid
Co2 transported as Carbonic Acid
- Co2 entres erythrocyte and combines with H2O to form carbonic acid (H2CO3)
- Carbonic acid breaks dissasociates to form H+ and bicarbonate (HCO3–)
- Bicarbonate is pumped out and chlorine is pumped in
- Bicarbonate binds with sodium to form sodium bicarbonate, which travels to the lungs
- H+ makes the erythrocyte more acidic
- Therefore the haemoglobin releases its O2 and takes H+
- When the erythrocyte goes back to lungs for reoxygenation, the bicarbonate ions replace the H+
- Process is then reversed
The Bohr Shift
pH alters the release of O2 by Haemogrobin
Carbon dioxide lowers the pH of the blood which causes haemoglobin to release its oxygen
- This is known as the Bohr effect
More Co2 = less pH
Chemoreceptors
Chemoreceptors in the carotid bodies and in the brain provide sensory information for the Breathing and Cardiovascular functioning.
Chemoreceptors are highly sensitive to changes in PCO2 and in the pH
- Therfore can cause large increases in respiration
When Chemoreceptors sense a change in PCO2 or a pH
- The body responds by regulating blood flow and breathing
Carotid bodies
The point where the carotid artery splits in two, there’s a tiny organ known as the carotid body (CB).
PCO2
Measure of carbon dioxide (CO2) within arterial or venous blood.
Expiratory movements
The process of an organism’s breath leaving it
Inspiratory movements
Air from the outside environment enters the lungs during inspiration
Ventral respiratory group
Frequently assumed to have the vital circuitry responsible for producing the basic breathing rhythm.
Stimulates expiratory movements
Dorsal respiratory group
Located in the distal part of the medulla.
Peripheral chemoreceptors and other types of receptors provide input to it. Responsible for the basic breathing rhythm.
stimulates inspiratory movements
Intercostal Muscles
The muscle groups that run between the ribs and support the formation and movement of the chest wall.
External = contract for inspiration
Internal = contract for expiration
Medulla oblongata
Responds to stimuli from chemoreceptors in order to control ventilation
Increases the the frequency of nerve impulses that are sent to the diaphragm and intercostal muscles
Ventilation changes due to exercise
- Metabolism increases during exercise with a build up of carbon dioxide, and reduction of oxygen. Causing pH levels to decrease.
- These changes are detected by chemoreceptors
- An impulse is sent to the respiratory control centre in the brainstem (medulla)
- A signal is then sent to the diaphragm and intercostal muscles from the medulla
- This increases ventilation
- As ventilation increases, Co2 levels drop and O2 levels rise
- This causes pH to raise and restore
- Long term effects of continual exercise may lead to improved and increased vital capacity
Ventilation changes due to exercise
- Metabolism increases during exercise with a build up of carbon dioxide, and reduction of oxygen. Causing pH levels to increase
- These changes are detected by chemoreceptors
- An impulse is sent to the respiratory control centre in the brainstem
- A signal is then sent to the diaphram and intercostal muscles
- This increases ventilation
- As ventilation increases, Co2 levels drop and O2 levels rise
- This causes pH to raise and restore
- Long term effects of continual exercise may lead to improved and increased vital capacity
Outline the location and role of chemoreceptors that help regulate the ventilation rate.
Chemoreceptors are in the medulla.
They detect lowered body pH from increased respiration, and trigger an increase in ventilation to remove CO2 from the body restoring pH.
List the neural structures that control the rate of ventilation.
Medulla oblongata, brain stem
Outline the feedback loop that regulates the rate of ventilation, including the role of stretch receptors.
Intercostal nerves make intercostal muscles contract
phrenic nerves stimulate the diaphragm to contract
stretch receptors respond to the lung expanding to send signals that lead to the signal telling the muscles to contract to stop.
Describe the relationship between carbon dioxide concentration and blood pH.
Increased CO2 causes Bicarbonate (HCO3-) and H+ ions to form, and H+ ions lower pH. Therefore, higher carbon dioxide concentrations lead to a lower blood pH.
State the effect of exercise on CO2 production.
Exercise results in more CO2 production.
Outline the relationship between CO2 production and blood pH.
When more CO2 is produced, there is more H+ ions, which lowers the blood pH.
Explain how and why hyperventilation occurs in response to exercise.
When exercising, the pH is lowered because of the increased respiration. When pH is low, ventilation increases, resulting in hyperventilation.
- Steps of exercise and relationship to ventilation changes
Fetal haemoglobin Vs Adult haemoglobin
Learning Outcome: Fetal haemoglobin is different from adult haemoglobin allowing the transfer of oxygen in the placenta onto the fetal haemoglobin
Fetal. has a different molecular composition than adult haemoglobin
Fetal. has a higher affinity for oxygen
- this ensures that oxygen is transferred from the mother to the fetus across the placenta
Fetal. Is replaced by adult haemoglobin after birth through cycling of RBC
Mutation on adult hemoglobin
Fetal haemoglobin production can be pharmacologically induced in adults to treat diseases such as sickle cell anaemia
Sickle cell anemia is on the adult haemoglobin, so fetal haemoglobin is induced to treat the disease
Partial pressure
Learning Outcome: Consequences of high altitude for gas exchange
the pressure exerted by a single type of gas when it is found within a mixture of gases
Determined by:
- The concentration of the gas within the mixture
- The total pressure of the mixture
At high altitudes, air pressure is lower and hence there is a lower partial pressure of oxygen
= P(gas)
PO2
PCo2 etc.
At higher altitude why is it harder for haemoglobin to take up and transport O2
At higher altitude there is less air pressure;
Therefore → less PO2 for the haemoglobin
Therefore → respiring tissue will receive less oxygen – leading to symptoms such as fatigue, headaches and rapid pulse (acute mountain sickness) (AMS)
How does the body adapt to lower oxygen levels?
- increase in red blood cell production (to increase oxygen uptake)
- higher hemoglobin count in RBC (causing a higher oxygen affinity)
- increased vital capacity (improving rate of gas exchange)
- increased myoglobin production and vascularisation in muscles
- kidneys secrete more alkaline urine (removal of excess bicarbonates improves buffering of blood pH)
- people living at higher altitudes have higher lung surface area and chest size (higher SA for absorption)
Ideal altitude for althetes training to gain benefits
1500m - 3000m
How the body maintains a blood pH of 7.35 to 7.45
Learning Outcome: pH of blood is regulated to stay within the narrow range of 7.35 to 7.45
maintained by plasma proteins that acts as buffers
The buffering solutions resists changes to pH by removing excess H+ ions (↑ acidity) or OH– ions (↑ alkalinity)
Amino acids may have both a positive and negative charge and hence can buffer changes in pH
→ The amine group may take on H+ ions while the carboxyl group may release H+ ions (forms water with OH– ions)
Pneumocytes
- Inner surface of the alveolus
Type I: very thin -> mediate gas exchange (via diffusion)
Type II: secretion of pulmonary surfactant -> reducing surface tension
Pneumocytes
- Inner surface of the alveolus
Type I: very thin -> mediate gas exchange (via diffusion)
Type II: secretion of pulmonary surfactant -> reducing surface tension
Capillary endothelium cells
Surrounded by a dense network of capillaries -> transporting respiratory gases to and from the lungs
Blood Cells
Carry oxygen through the bloodstream to the body
Electron Micrograph of Lung Tissue
Light Micrograph of Lung Tissue
Electron Micrograph of Lung Tissue
Light Micrograph of Lung Tissue
Analyzing a Oxygen Dissociation Curve
Myoglibin has a higher affinity than haemoglobin because it is formed by only one peptide
There is no allosteric effect in the molecule.
Emphysema
a lung condition where damage to the alveolar walls causes the the walls of the alveoli to lose their elasticity
Emphysema
a lung condition where damage to the alveolar walls causes the the walls of the alveoli to lose their elasticity
Cause of Emphysema
Most cases smoking, or caused by a rare hereditary deficiency of elastase due to a gene mutation
Smoking leading to emphysema
Could also ask for formation of Pulmonary Bullae
- Chemical irritants harm the tissue of the alveolar walls
- Damaged lung tissue triggers phagocytes to the region which produce the elastase
- Elastase breaks down elastic fibres in the alveolar walls
- Alveoli become abnormally enlarged due to the loss of elasticity
- Leading to a lower total surface area for gas exchange
- Degradation of the alveolar walls causes holes to develop. Alveoli can end up merging into pulmonary bullae
Treatments of Emphysema
There is NO cure
* Bronchodilators (puffer)
* Corticosteroids (pill medication)
* Enzyme inhibitor
* Oxygen Supplement - later stage
* Surgery - extreme cases
