1.2 The Respiratory System

Diffusion

The movement of particles from an area of high concentration to an area of low concentration

Gaseous Exchange

The movement of oxygen from the air into the blood, and carbon dioxide from the blood into the air

Ventilation

air in and out of lungs

External Respiration

Gaseous exchange between lungs and blood

Internal Respiration

Gaseous exchange between capillaries and body cells

What are structures of alveoli that assist gaseous exchange

1. Walls are 1 cell thick - short diffusion pathway

2. Extensive capillary network - lots of blood supply allows quick transport

3. Large surface area - greater uptake of oxygen

Mechanics of breathing in Inspiration

1. Diaphragm - contracts (flattens)

2. Ribcage - moves up and out

3. Muscles used at rest - diaphragm, external intercostals

4. Muscles used in exercise - Diaphragm, External intercostals, Sternocleidomastoid, Scalenes, Pectoralis major

5. Volume - Increase

6. Pressure - Decrease

7. Air - Air rushes in

Mechanics of breathing in Expiration

1.Diaphragm - Relax (dome shape)

2. Ribcage - Moves down and in

3. Muscles used at rest - (passive) Diaphragm + External intercostal relax

4. Muscles used in exercise - Internal intercostals, Abdominals contract

5. Volume - Decreases

6. Pressure - Increases

7. Air - Air rushes out

Tidal Volume

Volume of air breathed in or out per breath

Tidal Volume during exercise

Increases - more oxygen required so depth of breathing increases. Also more inspiratory/expiratory reserve volume used.

Inspiratory Reserve Volume

Volume of air that can be forcibly inspired after a normal breath

Expiratory Reserve Volume

Volume of air that can be forcibly expired after a normal breath

Inspiratory/Expiratory Reserve Volume during exercise

Decreases

Residual Volume

The amount of air that remains in the lungs after maximal expiration

Residual Volume during exercise

Stays the same - held permanently by rings of cartilage

Minute Ventilation

Volume of air breathed in and out per minute

Minute Ventilation during exercise

Increases - more demand leads to breathing increases

Spirometer

A device used to measure the volume of air inspired and expired by lungs

Gaseous Exchange purpose

1. Oxygen into lungs so that it can diffuse into blood and be transported round the body

2. Remove carbon dioxide from blood

Partial Pressure

Pressure exerted by an individual gas when it exists in a mixture of gases

Gaseous exchange at alveoli

1. PP of oxygen is higher at alveoli then pp in capillaries

2. Therefore, oxygen will diffuse from alveoli to capillaries

3. (Reverse for CO2)

Gaseous exchange at muscles

1. PP of oxygen at muscles is lower then pp in capillaries

2. Therefore, oxygen will diffuse from capillaries to muscles

3. (Reverse for CO2)

Oxygen diffusion pathway

1. Alveoli

2. Blood

3. Muscles

Carbon dioxide diffusion pathway

1. Muscles

2. Blood

3. Alveoli

Diffusion gradient

Explains how gases flow from an area of high to low concentration

3 Factors involved in regulation of breathing

1. Neural control

2. Chemical control

3. Hormonal control

Sympathetic nervous system

Increase breathing rate to prepare body for exercise

Parasympathetic nervous system

Lower breathing rate

What regulates breathing rate

The respiratory centre located in the medulla oblongata and uses neural and chemical control

Inspiratory centre

Responsible for inspiration and expiration

Inspiratory Centre pathway for inspiration

1. Receptors

2. Medulla

3. Phrenic nerve

4. Diaphragm + external intercostals

Expiratory centre

Stimulates expiratory muscles during exercise

Factors that affect Neural Control of breathing

1. Mechanical factors - proprioceptors located in joins and muscles provide feedback to respiratory centre to increase breathing during exercise

2. Baroreceptors - detect decrease in blood pressure in aorta and carotid arteries which increases breathing rate

3. Stretch receptors - prevent over inflation of lungs by sending impulses to the expiratory centre and then down intercostal nerves (abdominal + internal intercostals) allowing expiration

Hormonal control of breathing

1.Before exercise, brain sends impulses to renal glands 2. This pumps adrenalin into blood (demand for more o2 + co2) 3. This increases breathing rate

Lack of exercise + poor diet

Reduced cardiovascular endurance - inefficient gas exchange

Smoking effects

1. Reduces number of alveoli____- inefficient gaseous exchange

2. Nicotine constricts bronchioles - increase breathlessness

3. Carbon monoxide binds to haemoglobin rather then o2 - affects o2 transport to muscles = fatigue

4. Damages cell lining in trachea, bronchi , bronchiole - excess mucus leading to coughing and worse inhalation/exhalation