The Respiratory System Learning Objectives 1 To understand

The Respiratory System Learning Objectives 1. To understand the structure of the respiratory system 2. To be able to explain the mechanics of breathing.

Functions • Pulmonary ventilation – the inspiration and expiration of air. • Gaseous exchange ü External respiration – the movement of oxygen into the blood stream and carbon dioxide into the lungs. ü Internal respiration – the release of oxygen to respiring cells for energy production and collection of waste.

Keywords • • • Rib cage Sternum Lungs Intercostal muscles Diaphragm Thoracic cavity Inspiration Expiration Passive Active

Mechanics of breathing – at rest • Inspiration is an active process – the muscles contract. • Expiration is a passive process – the muscles relax to their natural state. • Inspiration – what happens? • Expiration – what happens?

Inspiration or expiration? 1. External intercostal muscles contract – lifting the rib cage and sternum up and out. 2. External intercostal muscles relax – lowering the ribcage and sternum down and in. 3. The diaphragm relaxes and returns to a dome shape. 4. The diaphragm contracts and flattens. 5. The volume inside thoracic cavity and space inside the lungs increases. 6. The volume inside thoracic cavity and space inside the lungs decreases. 7. The pressure increases to above atmospheric pressure. 8. The pressure is lowered to below atmospheric pressure. 9. Air rushes in. 10. Air rushes out.

Breathing during exercise • Additional muscles are recruited to give a larger force of contraction and move the ribs and sternum up and out further. • Becomes an active process as the natural relaxation does not provide enough force for breathing rate to increase. • Additional muscles are recruited to give a larger force of contraction to create a greater downward and inward movement. • Sternocleidomastoid and pectoralis minor are recruited. • The internal intercostal muscles and rectus abdominus are recruited. • This increases the volume further and decreases the pressure further. • This decreases the volume and increases the pressure more than at rest. • More air is expired. • More air is inspired.

Additional muscles recruited during inspiration and expiration during exercise

Learning Objectives • To know how respiration is regulated. • To understand what happens to tidal volume, breathing rate and minute ventilation during exercise. • To be able to explain what happens to minute ventilation at varying intensities of exercise and give reasons why.

Respiratory Control • RCC receives information from sensory nerves and send impulses through motor nerves to change the rate of respiratory muscle contraction. • Inspiratory centre stimulates inspiratory muscles to contract. • Expiratory centre is inactive at rest, but will stimulate additional expiratory muscles to contract during exercise.

AT REST • IC is responsible for the rhythmic cycle of breathing. • Intercostal nerve – makes external intercostal muscles contracts • Phrenic nerve – makes diaphragm contract This causes thoracic volume to be increased, lowering pressure. Air will be inspired. After approximately 2 seconds, stimulation will stop and the inspiratory muscles relax.

DURING EXERCISE • Breathing depth and rate must be increases to meet the demand for oxygen. • Sensory nerves relay information to RCC where IC and EC are initiated. Inform the IC which increases stimulation • Chemoreceptors of the diaphragm and external intercostals to contract with more force. It also recruits • Thermoreceptors additional muscles to contract. The greater contractions increases the depth of • Proprioceptors inspiration. • Baroreceptors Inform the EC on the extent of lung inflation. If the lung tissue begins to become excessively stretched, the ERC stimulates additional expiratory muscles to contract.

Respiratory System measure Definition Breathing rate (f) Volume of air inspired or expired per minute. It is lower in an aerobic athlete than their untrained counterpart due to more efficient gaseous exchange and transport. Tidal volume (TV) Represents the number of inspirations and expirations taken in one minute. An average is approximately 12 -15 per minute. Minute ventilation (VE) Volume of air inspired or expired in one breath. An average is 500 ml. The value varies dramatically depending on the size of the lungs and the thoracic cavity, age, gender, fitness and any respiratory condition such as bronchitis. Of the 500 ml approximately 350 ml reaches the alveoli for gaseous exchange. The other 150 ml remains in the airways and is known as dead space.

Respiration • What would the equation be based on the definitions on the page before? VE = TV x f (l/min) • Work out the VE for the following athletes: f TV Untrained 12 -15 breaths/min 500 ml Trained 11 -12 breaths/min 500 ml VE

Breathing Rate • Watch a partner’s back rise and fall. • Over 15 seconds count how many breaths they take. • Multiply this number by 4 and present them with their breathing rate. Discuss why some people’s breathing rates may be higher/lower than others.

Response to exercise • Look at each of the graphs and make a quick sketch of them in your book. • What is each graph telling you? And WHY is this happening? • Leave a gap under each graph you draw and write to stick a small piece of paper. You will be comparing your thoughts to what is actually happening.

What is this graph showing you?

What is this graph showing you?

What is this graph showing you?

VE Graph - task • Draw a graph of VE in relation to time based on the information given to you. • Before exercise, during exercise and recovery should be on your x-axis and VE on your y-axis. • You should draw 3 lines for the different intensities of exercise. Does your graph look like this?

Breathing and response to exercise Breathing rate increases in proportion to the intensity of exercise until we approach our maximum of around 5060 breaths per minute. In sub-maximal, stead-state exercise, breathing rate can plateau due to the supply of oxygen meeting the demand from the working muscle. Tidal volume increases initially in proportion to exercise intensity at sub-maximal intensities, up to about 3 l. Tidal volume reaches a plateau during sub-maximal exercise intensity because increased breathing rate towards maximal intensities does not allow enough time and requires too much muscular effort for maximal inspirations or expirations.

Breathing and response to exercise Minute ventilation is a combination of what happens to tidal volume and breathing rate. VE increases in line with exercise intensity. During sustained sub-maximal intensity exercise, minute ventilation can plateau as we reach a stead state of exercise. This is because supply = demand for oxygen and waste removal. During light intensity there is an initial anticipatory rise due to the release of adrenalin. A rapid increase in VE at the start of exercise due to increased f and TV to increase oxygen delivery and waster removal. A steady state VE throughout the sustained intensity exercise as oxygen meets as supply = demand. During maximal exercise VE does not plateau as exercise intensity continues to increase. There is a growing demand for oxygen and waste removal which VE must continually try and meet. TV will plateau and the continued rise in VE will be due to increased f.

What have you learnt so far about respiration?

Gaseous exchange and respiration To understand the process of gaseous exchange. To be able to differentiate between external and internal respiration. • To explain the differences in partial pressure of oxygen and carbon dioxide at rest and exercise. • To be able to explain how the diffusion gradient changes. • •

Task 1 • Using your flip learning research, put together the tarsia based around the learning objectives.

Task 2 • Complete the picture detailing what is happening at rest with gaseous exchange. • You have a list of key things to include on the picture.

Task 3 • There are 2 exam questions based around your flip learning research that you need to answer.

Dissociation of oxyhaemoglobin Learning Objectives • To understand the dissociation of oxyhaemoglobin at rest and during exercise. • To know what the Bohr shift is. • To be able to explain factors that affect the Bohr shift

Task 1 Read the passage and answer the following questions: 1. How many oxygen molecules can a haemoglobin molecule carry? 2. Where does association between oxygen and haemoglobin happen? 3. How much blood is saturated with oxygen as it leaves the alveoli? 4. When does oxygen more readily dissociate with haemoglobin? 5. What is this known as?

Haemoglobin is a protein able to carry four oxygen molecules. The amount of oxygen that associates with haemoglobin is determined by the partial pressure of oxygen (PO 2). It readily associates with oxygen when the partial pressure of oxygen is high to form oxyhaemoglobin. This occurs at the alveoli where the partial pressure of oxygen tops 100 mm. Hg and so blood leaving the alveoli is almost 100 per cent saturated with oxygen. As the partial pressure of oxygen decreases, the haemoglobin more readily dissociates with oxygen, releasing it to the respiring tissues, such as the muscle. This relationship is known as the oxyhaemoglobin dissociation curve.

Task 2 Look at the 2 graphs and answer the following questions: 1. At rest what is the approximate PO 2 in the muscle tissue? 2. At rest, what % of oxygen dissociates from the haemoglobin? 3. What happens to this oxygen? 4. What happens to the remaining oxygen that has not dissociated? 5. As exercise intensity increases what is the PO 2 in the muscle tissue? 6. What happens to the % of oxygen dissociating from the haemoglobin? 7. Why does this happen?

Bohr Shift