Ventilation Flashcards
Ventilation
The process of brining fresh air into the alveoli of the lungs and removing stale air
Why do we ventilate?
-air needs to be take in so that the oxygen can used in aerobic cell respiration and air needs to be taken out so that co2 produced in respiration can be excreted
-ventilations maintains the conc gradients of o2 and co2 that are needed for diffusion
Where does gas exchange happen?
Between alveoli and adjacent capillaries so the gradients of the two gases are needed
Cartilage rings
Keep the trachea open even when the pressure inside is low and protect is from collapsing
Where are cartilage rings found?
Walls of bronchi and trachea
Air movement
Nose/mouth- trachea- bronchi-bronchioles-alveoli
Ciliated and goblet cells
Play a role in preventing lung infections. Goblet cells produce mucus which traps dust and bacteria and ciliated cells beat their cilia to move the mucus away from the lungs and towards the mouth
Adaptations of gas exchange surfaces
-large SA
-surface permeable to o2 and co2
-thin walls so short distance for diffusion
-moist surface
-a dense network of capillaries
-ventilation ensures that conc gradient is maintained
Type I pneumocytes
Are very thin, flattened cells which are permeable to o2 and co2 and they carry out gas exchange
Type II pneumocytes
Rounded cells which secrete fluid that coats the inner surface of the alveoli. This film of moisture allows O2 to diffuse and then diffuse into capillaries. CO2 can evaporate into the air and be exhaled. This fluid contains a surfactant which reduces the surface tension and prevents the water from causing the sides of the alveoli to adhere. It prevents the collapse of the lung.
Inhaling
-external intercostal muscles contract moving the ribcage up and out
-diaphragm contracts, becoming flatter and moving down
- volume of thorax increases
-pressure inside thorax drops below atmospheric pressure
-air flows into the lungs to equalise the pressures
Exhaling
-internal intercostal muscles contract moving the ribcage down and in
-diaphragm relaxes and returns to its dome shape
- volume of thorax decreases
-pressure inside thorax rises above atmospheric pressure
-air flows out of the lungs to equalise the pressures
Give examples of antagonistic muscles in ventilation
Diaphragm and abdomen wall muscles
External and Internal intercostal muscles
Ventilation rate
Number of inhalations per minute
Tidal volume
Volume of air breathed in or out during one normal breath
Spirometer
A device that measures tidal volume and ventilation rate
Methods to measure tidal volume and ventilation rate
Data logging-using an inflatable chest belt. The belt is placed around the thorax and air is pumped in. A differential pressure sensor is used to measure the pressure variations inside the belt.
Spirometer
Effect of exercise
Increases both the rate and depth of breaths
Causes of lung cancer
smoking
passive smoking
air pollution
radon gas
asbestos and silica
Consequences of lung cancer
-breathing problems, persistent coughing, chest pain, coughing blood
-high mortality rates
Causes of emphysema
Smoking
Air pollution
Genetic cause: deficiency of the enzyme alpha-1-antitrypsin, which inhibits elastase
Consequences of emphysema
Alveoli break down and merge into large air spaces, total volume increases and surface area decreases so gas exchange is less efficient, lungs lose their elasticity, O2 saturation in the blood decreases and CO2 concentration increases.
Possible mechanism of emphysema
Cilia do not move, so mucus with pathogens builds up causing infections. The recruited phagocytes produce elastase and other proteases which digest elastic fibre in lung tissue. Free radicles and other components of tobacco smoke impair the activity of alpha-1-antitrypsin
Treatment of emphysema
Symptoms can be alleviated by supply of oxygen-reach air, breathing techniques to reduce breathlessness, bronchodilators and surgery to remove damaged lung tissue
Ways CO2 is carried by the lungs in three ways
-a small amount is carried is CO2 dissolved in plasma
-more is carried bound to haemoglobin
-even more is converted into hydrogen carbonate ions in RBCs
Describe how CO2 becomes hydrogen carbonate ions
CO2 diffuses into RBCs. The reaction is catalysed by carbonic anhydrase. Carbonic acid dissociates into hydrogencarbonate and hydrogen ions. The hydrogencarbonate ions move out of the RBCs by facilitated diffusion an dissolve in the plasma. A carrier protein is used that simultaneously moves a chloride ion into the RBC through the chloride shift to prevent the balance of charges from being disturbed. The hydrogen ions cause the pH to drop
Normal blood pH
7.35-7.45
Describe the mechanism to when there is an increase in CO2 in the blood
Chemoreceptors in the walls of the aorta, carotid arteries and medulla oblongata detect blood pH changes. When a decrease in pH is detected, chemoreceptors send impulses to the respiratory control centre in the medulla oblongata. The respiratory control centre sends impulses via nerves to the diaphragm and intercostal muscles causing them to increase the rate of contraction. The increase in ventilation rate speeds up the rate of CO2 removal from the blood, so blood pH rises and remains within its normal range. It helps repay the oxygen debt after anaerobic cell respiration
Structure of haemoglobin
Consists of four globin and four heme groups. The oxygen saturation of haemoglobin is 100% if all haemoglobin molecules in the blood are carrying four oxygen molecules.
Oxygen dissociation curve for haemoglobin
The degree to which oxygen binds to haemoglobin is determined by the partial pressure of oxygen(conc). The percentage saturation of haemoglobin with oxygen at each partial pressure of oxygen is an indication of haemoglobin’s affinity for oxygen. From the graph, we can determine the concentration of oxygen in the tissues and lungs (tissues towards the start and lungs at the end). The curve is sigmoid and this is because interaction between the four subunits in haemoglobin make it more stable which four oxygen are bound. The release/binding of one oxygen triggers a conformation change that causes haemoglobin to more rapidly/bind subsequent oxygen. Thus there is significant change over a narrow partial pressure of oxygen (steep graph). At low concentrations of oxygen, ie. muscles, oxygen is released.
A shift to the left of the oxygen dissociation curve
Increased affinity for oxygen
A shift to the right of the oxygen dissociation curve
Decreased affinity of haemoglobin for oxygen
Bohr shift
The increased release of oxygen by haemoglobin in respiring tissues
Describe the Bohr shift
In respiring tissues, oxygen is used up so partial pressure of oxygen decreases and more co2 is released so partial pressure of co2 increases. The increase in co2 concentration increases the acidity of the blood bc more co2 means more carbonic acid which has dissociated into hydrogencarbonate ions and hydrogen ions. The pH drop decreases haemoglobin’s affinity for oxygen so curve shifts to the right. This is because hydrogen ions bind to haemoglobin and causes a conformation change resulting in oxygen release. Less saturation at a given partial pressure of oxygen means more oxygen is released.
Myoglobin
Protein used to store oxygen in muscles. It consists of one globin adn one heme group and so the curve is not sigmoid
Oxygen dissociation curve for myoglobin
The oxygen curve for myoglobin is to the left of the curve for adult haemoglobin showing that myoglobin has higher affinity for oxygen and becomes saturated at lower oxygen levels. At moderate partial pressures of oxygen adult haemoglobin releases oxygen and myoglobin binds it. Myoglobin only oxygen releases when partial pressure of oxygen in the muscle is very low- delaying anaerobic respiration
Fetal versus adult haemoglobin
Fetal haemoglobin has higher affinity for oxygen so the dissociation curve is shifted to the left. Oxygen that dissociates from adult haemoglobin in the placenta binds to fetal haemoglobin which only releases it once it enters the tissues of the fetus
High altitude
Partial pressure of oxygen is lower than at sea level. Haemoglobin may not become fully saturated as it passes through the lungs. Some athletes train there for endurance and improved performance
Mountain sickness
Muscular weakness, rapid pulse, nausea and headaches
Adaptations to high altitudes
Muscles produce more myoglobin, denser capillary network and more mitochondria, ventilation rate increases and more RBCs are produced. Larger SA of lungs, larger tidal volume, haemoglobin with increased affinity for oxygen.
