Respiratory system.docx

2 processes Cellular respiration= uses O2 and produces CO2 and energy. External respiration= gas exchange. 4 steps to external respiration. Ventilation/ gas exchange between atmosphere and alveoli. Exchange of O2 and CO2 between air in the alveoli and the blood. Transport of O2 and CO2 by the blood...

2 processes Cellular respiration= uses O2 and produces CO2 and energy. External respiration= gas exchange. 4 steps to external respiration. Ventilation/ gas exchange between atmosphere and alveoli. Exchange of O2 and CO2 between air in the alveoli and the blood. Transport of O2 and CO2 by the blood between lungs and tissues. Exchange of O2 and CO2 between the blood in the capillaries and tissue cells. Non-respiratory functions are to defend and maintain the system. Alveolar macrophages defend against inhaled particles. Route for water loss and heat elimination. Helps maintain acid-base balance. Controls the vocal cords in respiratory tract. Enhances venous return. Airway defences Goblet cells produce mucus. Bronchi epithelial cells produce antimicrobial peptides. Ciliated cells waft mucus. The mucus is made of glycoproteins. Cilia project into the periciliary fluid- a liquid layer secreted by epithelial cells. The action of the ciliary beating and wafts it to the back of the throat. = mucociliary escalator Cystic fibrosis The mucociliary escalator lacks chloride pumps. No fluid-no movement of the hair-like projections-the mucus cannot be wafted so it gets stuck. The bacteria within the mucus cannot be wafted so it builds up, it lives in the warm environment and causes problems. Breathing becomes harder overtime due to build-up of mucus. Cigarette smoke paralyses the cilia. The mucociliary escalator is non-functional. More mucus is released, and the airway gets blocked. The respiratory system consists of the airway, lungs and muscles. Airway= no gas exchange happens here. E.g. trachea The lungs= responsible for gas exchange. E.g. alveoli The muscles= responsible for moving air in and out of the airways and lungs. The branching increases the surface area. Functional features of the alveoli A lot of capillaries for blood supply Thin walls Macrophages Pneumocytes 2 types of alveolar cells Type I are thin, flat and involved in gas exchange. Type II are cuboidal or rounded and secrete pulmonary surfactant. Lungs respond to external pressure. Muscles are also used. To get air into the lungs, we need to create a positive pressure to PUSH air in. To get the air to FLOW in, need to create negative pressure within the lungs. Boyle’s law states the pressure is inversely proportional to volume. Air always flows down the pressure gradient. The law means that as you breathe in, the volume of the lung increases, the pressure decreases which allows the air to flow in. Requirements Structure should be able to change volume (elastic tissues) Walls that don’t collapse (supported structure) Mechanism to modify volume (musculature). The important structures in the process of breathing Diaphragm Intercostal muscles (internal and external) Accessory muscles Inspiration - active Diaphragm contracts. Ribcage moves up and outwards. External intercostal muscles contract Thoracic cavity increases, Pressure in lungs decrease-allows air to flow in Expiration- passive or active Diaphragm relaxes. Ribcage moves down and inwards. External intercostal muscles relax. Thoracic cavity decreases. Pressure in lungs increase- allows air to leave. When expiration is forced: Internal costal muscles are involved not the external and internal costal muscles contracts. Contraction of abdominal muscles (accessory muscles) Oxygen is carried in the blood via haemoglobin. Haematocrit is used to measure the haemoglobin. Binding of Haemoglobin is reversible Oxyhaemoglobin dissociation curve Not linear Haemoglobin is senstitve to oxygen pressure meaning it holds onto the oxygen when there is a lot available. When PO2 decreases, it readily releases the oyxgen. Different factors effect the O2 carriage by Hb pH: bohr effect Decrease in pH Reduces binding affinity of Hb for O2 Shifts the curve to the right Increases oxygen readily CO2 PO2 Cabon diooxide readily dissolves in water to form carbonic acid which is acidic Increased H+ therefore pH reduces down Dissocation curve goes to the right- bohr effect More oxygen released readily Lower PCO2 means pH increases so releases oxygen less and increases binding of O2 with Hb. Temperature Increase in temperature shifts the curve to the right as well. Helps unload O2 more readily as affinity decreases. Carbonic acid dissociates to form H+ and HCO3- HCO3- is caried out of the RBC’s via facillitated diffusion due to high concentrations- electrochemical gradeint To replace the HCO3-, CL- diffuse in to maintain the electrochemical gradeint. = chloride shift. Neural contol of breathing The nerves fire more AP during active ventillation compared to when relaxed/quiet breathing The respiratory centres are in the brain stem Inspiratory and expiratory neurones are in the medulla/pons Chemoreceptors determine the PO2, PCO2 and H+. provides feeback to the breathing centres of the brain to modify the breathing rate and tidal volume. 2 types: central and peripheral