3.1.1.3 The Respiratory system Learning objectives To be able to identify different lung volumes. To understand the process of gaseous exchange. To be able to define diffusion and partial pressure and its affect at the alveoli and body cells. To understand the processes of external respiration and internal respiration. To understand the roles of the receptors in the regulation of ventilation. To explain the impact of a poor lifestyle on the respiratory system.

Understanding the respiratory system This involves the LUNGS and works closely with the cardiovascular system. Watch me Watch me What is the key function of the respiratory system?

Lung Volumes The volume of air inspired or expired per breath is referred to as the tidal volume. The volume of air inspired or expired per minute is the minute ventilation and can be calculated with the equation below: Number of breathes x Tidal volume = Minute Ventilation (per min) e.g. 12 breaths x 0.5 litres = 6 litres per minute.

Lung volumes can be shown on a spirometer trace. The total lung capacity is calculated by adding the vital capacity of the lungs to the residual volume: Lung volumes can be shown on a spirometer trace.

Change during exercise Lung Volumes Complete the table below from the information provided. Lung Volume Definition Average value at rest Change during exercise Tidal Volume Inspiratory Reserve Volume Expiratory Reserve Volume Residual Volume Minute Ventilation (VE = TV x f)

Inspiratory Reserve Volume Tidal Volume The volume of air inspired or expired per breath Average – 0.5 litres Change during exercise – (increase) Inspiratory Reserve Volume The volume able to be forcibly inspired during normal breathing Average – 3.0 litres Change during exercise (decrease)

Expiratory Reserve Volume The volume able to forcibly expired, after a normal breathe Average – 1.3 litres Change during exercise – Small decrease Residual Volume The volume of air that remains in the lungs after forced maximum expiration Average – 1.2 litres No change

Minute ventilation (VE) = Tidal Volume (TV) X Breathing Rate (f) Ventilation is the amount of air breathed in one minute. Average – 6.0 litres Changes during exercise = BIG increase Minute ventilation calculation Minute ventilation (VE) = Tidal Volume (TV) X Breathing Rate (f) VE TV f At rest – 7,200 ml/min = 600 ml X 12 At submax – 60,000 ml/min = 2400 ml X 25 At max – 121,000 ml/min = 2200 ml X 55

Minute Ventilation Depth and rate of breathing increase in direct proportion to the intensity of the exercise. Depth and rate of breathing increase because: 1. Working muscles demand oxygen 2. Need to remove carbon dioxide

Changes to minute ventilation during exercise The more demanding the physical activity, the more breathing increases to meet the extra oxygen demand. Maximal Exercise Sub-Maximal Exercise a = anticipatory rise b = sharp rise in minute ventilation c = slower increase d = steady state e = rapid decline in minute ventilation f = slower recovery as body systems return to resting levels Think. Pair. Share - Look at the 2 graphs, what are the differences?

Gas exchange Watch me During inspiration why does air enter the lungs?

Principles of Diffusion and Partial Pressure of gases A gas will always move from an area of high pressure to an area of low pressure. Alternatively…. A gas will always move from areas where there is more of it, to areas where there is less of it.

Diffusion in the lungs Gases will always move from areas of high pressure to areas of low pressure. Air Lungs

Partial Pressure Atmospheric air is made up of 3 gases Nitrogen - 79 % Oxygen - 21 % Carbon Dioxide – 0.03 % Partial Pressure explain movement of gases within the body. Pressure is measured in … mmhg (millimetres of mercury) Together the gases exert a pressure of 760mmHg

Partial Pressure The individual pressure a gas exerts, when in a mixture of gases. PO2 = 160 mmHg PCO2 = 0.3mmHg

Partial Pressure of O2 and CO2 in the body Partial pressure of oxygen in the alveoli is higher than the partial pressure of oxygen in the blood. In alveoli PO2 = 100mmHg In blood PO2 = 40mmHg Why? Oxygen has been removed by the working muscles. So the concentration of oxygen in the blood is lower. Therefore partial pressure is lower.

Diffusion Partial Pressure of O2 and CO2 in the body Gas will always move from areas with a higher partial pressure to areas with a lower partial pressure until equilibrium is reached. Diffusion This is called: In alveoli PO2 = 100mmHg In blood PO2 = 40mmHg Therefore oxygen will diffuse into the blood until the pressure is equal in the alveoli and the blood.

60 mmHg Partial Pressure of O2 and CO2 in the body The difference between any two pressures is called : Diffusion gradient = 60 mmHg In alveoli PO2 = 100mmHg In blood PO2 = 40mmHg The bigger or steeper the diffusion gradient the quicker diffusion will occur.

Gaseous Exchange Internal respiration O2 diffuses from systemic capillaries into cells CO2 diffuses from cells into systemic capillaries External Respiration CO2 diffuses from pulmonary capillaries into alveoli O2 Diffuses from alveoli into pulmonary capillaries

Internal Respiration Internal respiration occurs because of the following factors: Available surface area, which varies in different tissues. Partial Pressure gradient Rate of blood flow varies (e.g. metabolic rate of tissue)

Internal Respiration CO2 and O2 Exchange This is ONE capillary surrounding a tissue cell.

External Respiration External respiration occurs because of the following factors: The partial pressures of gases in the alveoli differ from those in the atmosphere. Humidification of inhaled air Gas exchange between alveoli and pulmonary capillaries Atmosphere (mmHg) PO2 159 PCO2 0.3 PH2O 3.5

Factors Influencing External Respiration Efficient external respiration depends on 3 main factors: Surface area and structure of the respiratory membrane Partial Pressure gradients Matching alveolar airflow to pulmonary capillary blood flow. Partial pressure gradients affect gas exchange between the alveoli and pulmonary capillaries.

Gaseous exchange at the alveoli The alveoli are tiny air sacks inside the lungs. A dense capillary network supplies them with oxygen. Their walls are extremely thin (only one cell thick) and together they create a huge surface area to allow for a greater uptake of oxygen. Gases can easily pass through the thin walls and travel into the blood stream. With training this process of gaseous exchange becomes more efficient and therefore improves performance.

Gaseous exchange at the alveoli Gaseous exchange is promoted through a number of bodily functions. Capillaries very near to alveoli, so diffusion distance is very short. Large surface area of alveoli allows diffusion to take place. Vast network of capillaries surround alveoli which increases surface area further.

Gaseous exchange at the alveoli Gaseous exchange takes places at two different sites. 1. Lungs Between alveoli and surrounding alveolar capillaries. 2. Muscles Between muscles and surrounding blood capillaries.

How is Ventilation Controlled? The nervous system can increase or decrease the rate, depth and rhythm of breathing. The respiratory centre located in the medulla oblongata of the brain controls breathing. An increased concentration of carbon dioxide in the blood stimulates the respiratory centre to increase respiratory rate.

Control of Ventilation Respiratory Control Centre The inspiratory centre sends out impulses via the phrenic nerve to the inspiratory muscles. The expiratory centre stimulates the expiratory muscles during exercise, when stretch receptors detect changes in the rate and depth of breathing.

Control of Ventilation During exercise, conditions in the body change. These changes are detected by: Chemoreceptors - which detect changes in pH - blood acidity increases as a result of an increase in the plasma concentration of carbon dioxide and lactic acid production. Baroreceptors - which detect an increase in blood pressure. Proprioceptors - which detect movement. Photo by: © LOCOG

Carbon dioxide When exercise stops, carbon dioxide levels, blood pressure and muscle movement all decrease. This is detected by the receptors, which send impulses to the cardiac control centre. An impulse is then sent through the parasympathetic system which stimulates the sinoatrial node and heart rate decreases.

Impact of a poor lifestyle A sedentary lifestyle is a type of lifestyle with no or irregular physical activity. This include sitting, reading, watching television, playing video games, and computer use for much of the day with little or no vigorous physical exercise. Photo by: © http://www.lifetime-weightloss.com/blog/2011/10/26/the-metabolic-effects-of-your-sedentary-lifestyle.html A sedentary lifestyle can impact hugely on the respiratory system.

Impact of a poor lifestyle Photo: © Stock.xchng. http://www.sxc.hu/photo/1319309 Think. Pair. Share - What effects does smoking have on the respiratory system?

Impact of a poor lifestyle Over time smoking reduces the lungs surface area and destroys the alveoli structures. This will reduce gaseous exchange and make the individual feel short of breath and reduce the oxygen transport capacity. Photos: © Stock.xchng. http://www.sxc.hu/photo/1391828

Apply it! The Respiratory system What has stuck with you? Explain the principle of diffusion and how it can be seen in the respiratory system. Describe what is meant by the terms ‘tidal volume’ and ‘minute ventilation’ How is pulmonary ventilation controlled by the body? What is the affect of a poor lifestyle on the respiratory system? The Respiratory system Photos by: LOCOG

Practice it! Exam questions Identify which one of the following statements defines expiratory reserve volume. [1 mark] A The amount of air breathed in or out per breath B The amount of air left in the lungs after maximal expiration has occurred C The amount of air that can be forcibly expelled after a normal breath D The amount of air that can be forcibly inspired at the end of a breath

Practice it! Exam questions 2. While running, a performer will experience changes in lung volumes. Complete Table 3 below to show how the tidal volume, inspiratory reserve volume and expiratory reserve volume change during exercise. [3 marks]

Practice it! Exam questions 3. Explain how the gas exchange system operates at muscles. [4 marks]

Practice it! Marks Scheme: C A. Tidal volume – increases B. Inspiratory reserve volume – decreases C. Expiratory reserve volume – decreases A. Process of diffusion – high concentration/partial pressure to low/down a diffusion gradient B. Requires thin/permeable membranes/short distance C. High pO2 in blood/low pO2 in muscles and oxygen moves into muscles D. Low pCO2 in blood/high pCO2 in muscles and carbon dioxide moves into blood E. Oxygen into myoglobin/ (disassociates) from haemoglobin F. Carbon dioxide dissolves in plasma/ combines with haemoglobin/forms bicarbonate ion