Control of Ventilation Control of Breathing 2 factors

Control of Ventilation

Control of Breathing • 2 factors control breathing: – Neural control – Chemical control

Neural Control • The respiratory centre in the medulla oblongata of the brain controls breathing. • It is responsible for changing the rate and depth of breathing. • The centre is made up of 2 main areas: – The inspiratory centre – The expiratory centre

Control of Breathing The Inspiratory Centre • Responsible for the rhythmic cycle of inspiration and expiration. • Stimulates the inspiratory respiratory muscles (diaphragm and external intercostals).

Control of Breathing The Expiratory Centre • Inactive during quiet ventilation. • Rate and depth of breathing are detected by stretch receptors in the lungs. • When there is an increase in ventilation, the expiratory centre inhibits the inspiratory centre and stimulates expiratory muscles (abdominals and internal intercostals).

Neural Control Factors influencing neural control of breathing include: • A change in blood pressure - detected by baroreceptors in the arteries – changes ventilation rate. • Proprioceptors in the muscles responding to movement stimulate the respiratory centre, increasing rate and depth of breathing. • Change in body temperature.

Control of Breathing • The respiratory centre responds mainly to changes in the chemistry and temperature of the blood: – When blood p. H lowers (this is due to an increase in hydrogen ions because of an increase in CO 2) the respiratory centre detects this and increases the rate and depth of breathing. – A rise in body temperature increases the rate of breathing but not the depth of it.

Chemical Control • Changes occur through the medulla. • An increase in CO 2 lowers blood p. H (more acidic) and causes an increase in ventilation rate and depth. • An increase in lactic acid production during intense exercise lowers the blood p. H levels • A dramatic drop in PO 2 (due to altitude, asthma or smoking damage) - detected by the chemoreceptors in the arteries increases rate and depth of breathing.

• Games players need to have an efficient cardiorespiratory system and they need to process the information they receive during the game, to enable them to meet the demands of the match. • (a) Describe three structural features of the lungs that assist the diffusion of respiratory gases. (3 marks)

(b)Figure 3 shows the spirometer trace of a games player. (i) What lung volumes are represented by A, B and C? (2 marks) (ii) What would be the effect of a period of continuous running on the spirometer trace for lung volume A? (2 marks)