Lesson 25AS PE Anatomy & Physiology

James BarracloughRespiratory System –

Regulation & Gaseous Exchange at the Lungs

Starter

Hangman Prompts

• Gaseous exchange• Oxygen• Carbon dioxide• Thermoreceptor• Baroreceptor• Proprioceptor

Homework Answers

Topic: Respiratory System

Objectives: by the end of the lesson, learners will be able to: • Explain how the respiratory control centre regulates the mechanics of breathing at rest and during exercise• Outline the processes of gaseous exchange that takes place between the alveoli and blood, and between the blood and tissue cells.• Explain the changes in gaseous exchange that take place between the alveoli and blood, and between the blood and tissues cells during physical activity

Respiratory System Activity 1: Quiz You, Quiz MeIn 3s write a quiz for the other group to find answers to (make sure you have the answers too!):Group 1: • Respiratory control centre & effects of altitude• Group 2:• Pulmonary diffusion

30 minutes

THEN SWAP QUESTION PAPERS &15 minutes to answer

Respiratory Control Centre (RCC) • Controlled by nervous system (involuntary)• RCC situated in medulla area of brain• Inspiration: nerve impulses generated & sent to inspiratory

muscles (external intercostals & diaphragm) telling them to contract

• Lasts c.2 secs then stops & expiration occurs passively be elastic recoil of lungs

• During exercise breathing rate increases • So expiratory centre may send impulses to expiratory muscles

(internal intercostals) • This speeds up expiratory process

Respiratory Control Centre

• Chemical composition of blood main influence on respiration rates

• Chemosensitive area in RCC senses changes in blood acidity• Chemoreceptors (in aortic arch & carotid artery) measure this

& concentrations of CO2 & O2• If increases in CO2 detected RCC emits impulses to instruct

respiratory muscles to work harder• Ventilation rate increases • When blood acidity lowered → fewer impulses sent =

decreased respiration rate

Other Factors Controlling Breathing• Proprioceptors & mechanoreceptors: inform inspiratory centre that

movement occurring • Thermoreceptors: inform RCC that heat energy produced & blood

temperature increased• Baroreceptors: send info to expiratory centre re level of lung inflation • Regulation of breathing helped by STRETCH RECEPTORS (in lungs &

bronchioles) • These prevent overinflation of lungs • If lungs stretched excessively - expiratory centre sends impulses to start

expiration• Known as HERING-BREUR REFLEX• Next slide: respiratory regulation during exercise

Effect of Altitude on Respiration

The higher you go (altitude) = less atmospheric pressure

%ages of gases in air = same as at sea level

BUT partial pressures change as altitude increases

e.g. pO2 of arterial blood at 8000ft = c.60 mmHg (c.100 mmHg at rest at sea level)

pO2 in muscles at rest is 40mmHg at both levels

Question

What is the pressure gradient at:• Sea level?• 8000 ft?

• 60mmHg• 20mmHg

Decrease in pressure gradient decreases movement of O2 into muscles & performance suffers

Altitude Training

http://www.youtube.com/watch?v=392CSRdztWc

• Body adapts because of drop in pO2 by c.50%• Increased red blood cell mass & Hb levels • Therefore enhances O2 carrying capacity when

returning to sea level

Altitude Training

Possible Benefits • Increased concentration

of red blood cells (haematocrit)

• Increased Hb concentration

• Enhanced O2 transport

Possible drawbacks

• Expensive• Altitude sickness• Harder to train (less O2)• Possible ‘de-training’• Benefits soon lost when

returning to sea level

Pulmonary Diffusion

Gaseous exchange at the lungs – 2 main functions:1. Provide O2 to blood in turn to supply muscles & tissues2. Remove CO2 from blood due to metabolic processes

Pulmonary Diffusion (Partial Pressure)

Partial pressure:“individual pressure that gas exerts when it occurs in

mixture of gases”

Diffusion:“Movement of respiratory gases from areas of higher partial

pressure to lower partial pressure until equilibrium reached”

Pulmonary Diffusion (Partial Pressure)

Inhaled air has same concentrations as atmospheric air:• 79% Nitrogen • 20.9% Oxygen• 0.03% Carbon Dioxide

Sea level Total Atmospheric Pressure = 769mmHg

Pulmonary Diffusion (Partial Pressure)

• Oxygen in air is c.21%• Nitrogen in air is c.79%• O2 & N exert pressure of 760 mmHg

pO2 (Partial Pressure of O2)

pO2 = Barometric x Fractionalpressure concentration = 760 mmHg x 0.21

= 159.6 mmHg

Activity

Can you work out partial pressure in the atmosphere of:1. Carbon Dioxide (pCO2)2. Nitrogen (pN)

pCO2 = Barometric (760) x Fractional (0.0003) = 0.228 mmHgpressure concentration

pN = Barometric (760) x Fractional (0.79) = 600.4 mmHg pressure concentration

Pulmonary Diffusion (Partial Pressure)

• Partial pressure of gases explains movement of gases within body

• Accounts for processes of gas exchange between:• Alveoli & blood • Blood & muscles/tissues

Pulmonary Diffusion(Gaseous Exchange at Lungs)

• Imbalance between gases in alveoli & blood → PRESSURE GRADIENT = movement of gases across respiratory membrane

• O2 from alveoli → blood, CO2 from blood → alveoli• The special adaptations of the alveoli for gas exchange

are:– Thin walls – Huge surface area – Covered in capillaries to provide blood – A wet lining to dissolve gases

http://www.youtube.com/watch?v=EFCj9STCvdI

Pulmonary Diffusion(Diffusion Gradient)

• pO2 of Blood in pulmonary capillaries = 45 mmHg (most O2 used in working muscles)

• Pressure gradient = c.60 mmHg → forces O2 from alveoli into blood until pressure is equal on both sides

• pCO2 in blood = 45 mmHg; pCO2 in alveolar air = 40 mmHg → pressure gradient 5 mmHg

• CO2 moves from pulmonary blood into alveoli & is expired

IN SIMPLE TERMS → DIFFUSION GRADIENT = PARTIAL PRESSURE OF GAS ON 1 SIDE OF RESPIRATORY MEMBRANE – PARTIAL PRESSURE OF GAS ON OTHER SIDE

Extension Activity

• What are the acute & chronic effects of exercise on the respiratory system?

Recap

http://www.teachpe.com/multi/relationship_cardiovascular_respiratory_system.htm

Homework

Next Lesson…

• Describe the transport of oxygen & the oxyhaemoglobin dissociation curve