TOPIC 3 – LUNG FUNCTION CONTINUED

Learning Outcomes:A – Use independent skills to develop an in-depth understanding of the respiratory centres role on breathing - CS, CJ, SF, RM, CE

B – Explain important key terms in relation to lung capacities and volumes – JH, AC, AA

C – Identify the different key terms associated with lung capacities and volumes – JB, JB, GB

Do Now Task – Draw 2 flow diagrams outlining the mechanics of breathing in the lungs

Give definitions and values for the majority respiratory volumes and capacities at rest and during exerciseInterpret a spirometer traceExplain the principles of diffusion and the importance of partial pressure in the process of gaseous exchangeDescribe the process of gaseous exchange at (a) the lungs and (b) the tissues and musclesDescribe the effects of training on lung volumes and capacities and gaseous exchangeExplain the importance of carbon dioxide in the control of breathing

LUNG VOLUMES AND CAPACITIES

We know we can vary the depth and volume of our breathing and no matter how hard you try you can never completely empty your lungs of air.

This is a good thing because of the moisture around the alveoli would mean that they would stick the lungs together and cause them to collapse.

Meaning we have a large amount of air in reserve in our lungs when we are even produce shallow breaths

Looking at a reading of our lung inspirations and expirations we can then identify the different volumes and capacities they can hold

Tidal Volume – Amount of air breathed in or out per breathWhen we exercise what happened to the depth of our

breathing?Increases

This means the tidal volume also increases as we need to use what air we have in reserve to provide the body with the

required air.What does this air include?Why do we need oxygen?

Vital Capacity – Maximum amount of air exhaled after a maximal inspirationThis does not change whether we are breathing shallow or heavy

Vital Capacity can be measured by a simple equation

VC = TV+IRV+ERVVital Capacity = Tidal Volume + Inspiratory Reserve Volume + Expiratory Reserve

Volume

Inspiratory Reserve Volume = Maximal amount of air forcibly inspired in addition to tidal volume

Expiratory Reserve Volume = Maximal amount of air forcibly expired in addition to tidal volume

Residual Volume – Amount of air left in the lungs after a maximal expirationWhy is there always a residual volume?

Therefore our Total Lung Capacity is everything put togetherTLC = TV + IRV + ERV + RV

MINUTE VENTILATION

Bringing air in and out of our lungs is known as ventilation. Minute ventilation = the amount of air that is moved in and out of the lungs in one minute.

It is a product of our depth of breathing (TV) and the frequency we breath (breaths per minute).

What can affect our minute ventilation?Rate can vary from 12-15 to up to 60 per minute

Tidal volumes can also vary from 0.5 litres during quiet breathing to 3 litresVE = Frequency of breathing x Tidal Volume (ml)

Task

GAS EXCHANGE

What’s the point in breathing?Oxygen in the air – lungs – cells around the body

Air is a mixture of gases but what two are important?Oxygen and Carbon Dioxide

All gases tend to evenly distribute themselves. So if there is a gas on one side of a semi-permeable membrane in high concentration and a lower amount on the other side. These gases will naturally

move to equalise themselves. This process is called?

Diffusion

DIFFUSION

Gases can only move from high pressure to low pressure if there is that pressure distance.

This is called a diffusion gradient. This movement evenly distributes the molecules until there is no

pressure difference. No pressure – No gradient – No diffusion

Diffusion is completely dependent on their always being a pressure gradient

DIFFUSION IN THE LUNGS

The walls of the alveoli are semi-permeable therefore allowing the passage of oxygen and carbon dioxide molecules through it holes. This concentration of gas is known as partial pressure, which is the

pressure exerted by a single gas in a mixture of gases. This is measured in mmHg (millimetres of mercury)

Diffusion in the lungs

SUMMARY

There are a number of factors that make diffusion of oxygen from lungs to blood very efficient.

Permeability of the alveoli and capillary cell walls Short distance from alveoli to capillary Readiness of haemoglobin to combine with oxygen to form oxyhaemoglobin Diffusion gradient caused by partial pressures Large surface area of alveoli Slow movement of blood through thin narrow capillaries Moisture layer enhancing the uptake of oxygen

CONTROL OF BREATHING

Respiration is controlled by the respiration centre in a part of the brain known as the medulla oblongata.

This is located in the brain stem, found between the spinal cord and upper brain. The respiratory centre controls both the rate of breathing and depth of breathing

using both neural and chemical control.http://www.youtube.com/watch?v=F0OBkR00OZE

WHEN AT REST

There is an inspiratory and expiratory centre. During normal breathing the inspiratory centre sends nerve

impulses to the diaphragm and intercostal muscles telling them to contract so we breath in.

After 2 seconds the system stops allowing the above to relax so we breath out.

DURING EXERCISE

Use books to write notes on how there are chemical and neurological changes within the body to allow for breathing to

increase and deepenhttp://www.youtube.com/watch?v=_BFDgTci0ck

Chemical Changes

Neurological Changes

EXAM QUESTIONS

How is ‘breathing rate’ controlled to meet the demands of changing levels of exercise?

The alveoli provide the lungs with a large surface area for diffusion.Name two other structural features of the lungs that assist diffusion.

ANSWERS

A. (Exercise/movement) - more carbon dioxideB. Increased acidity/decrease in pH/increase hydrogen ions (in blood)C. Detected by chemoreceptorsD. (Nerve impulses to) respiratory centre/medulla (of brain)E. Phrenic nerveF. Diaphragm/intercostal muscles/sternocleidomastoids/scalene/pectoralisminor/abdominals

A. Large blood supply;B. Thin/semi-permeable membrane fordiffusion/one cell thick/walls are thin;C. Short distance for diffusion;D. Layer of moisture;E. Slower blood flow/transit time.