B3.1 Gas exchange - human*

three physiological processes

ventilation

gas exchange

cellular respiration

ventilation

exchange of air between atmosphere and lungs - through breathing

gas exchange

exchange of oxygen and carbon dioxide between the alveoli and bloodstream via passive diffusion

cellular respiration

release of ATP from organic molecules

enhanced by presence of oxygen

ventilation has to happen before this

purpose of ventilation

• Oxygen is consumed by cells during cellular respiration and carbon dioxide is produced as a waste product.

• hence O2 is constantly being removed from the alveoli into the bloodstream and CO2 is continually being released

• The lungs function as a ventilation system by continually cycling fresh air into the alveoli from the atmosphere.

• help O2 levels stay high in alveoli (and diffuse into the blood) and CO2 levels stay low (and diffuse out the blood)

• The lungs very large surface area increase the overall rate of gas exchange.

effect of exercise on ventilation rate

rate exercise increase

atp demand increase

cellular respiration increases

need more o2 so breathe faster

CO₂ product increase

cant because caused acidity (avoidance)

breathe out faster

Hence, the ventilation rate increases.

Adaptations for Gas Exchange in terms of sa:v

Specialized respiratory surfaces to increase sa:v

Thin respiratory surfaces reduces the distance that gases need to diffuse, enhancing the rate of exchange.

Circulatory systems transport gases and nutrients to and from cells, compensating for the increased diffusion distances caused by a lower surface area to volume ratio.

Large organisms have evolved specialised structures to facilitate gas exchange such as

arge SA in relation to volume of organism

Permeability to O2 and CO2

Thin tissue layer to minimise diffusion distance

Moist surface allows fo gases to dissolve

The higher the concentration gradient, the () the rate of diffusion

faster

structure of alveolus

1. site of gas exchange

2. thin epithelial layer to minimize diffusion distances

3. surrounded by rich capillary network—increases capacity for gas exchange with blood

4. roughly spherical—maximize available surface area

5. internal surface covered with surfactant—dissolves gas—better diffusion to bloodstream

how is a high concentration gradient maintained during gas exchange?

Dense capillary network around gas exchange surfaces

Continuous blood flow

Ventilation

• With air for lungs

• With water for gills

adaptations of mammalian lungs

surfactant

bronchioles

many alveoli

extensive capillary network

alveoli are made of

Type I and II pneumocytes.

Type I pneumocytes

involved in the process of gas exchange between the alveoli and the capillaries

extremely thin - minimising diffusion distance for respiratory gases.

unable to replicate

Type II pneumocytes

secrete alveolar fluid, which contains surfactant.

decrease surface tension

can differentiate to type I

surfactant function

reduces the surface tension to prevent alveoli collapse during exhalation.

dissolve oxygen in liquid

alveoli attached to where and why

ends of the bronchioles

increase surface area for gas exchange

small diameter of bronchioles can

slows down air flow to increase efficiency

Extensive capillary network around alveoli

diffusion distance for gases is always short.

breathing depends on

inverse relationship between pressure and volume

is lung tissue muscular

no

what force air into and out of the lungs

Muscles surrounding the lungs contract and the pressure changes in the thorax

muscles facilitate ventilation

Antagonistic muscles

thoracic cavity

chest pressure

what happens when the thoracic cavity increases (vice versa)

pressure in thorax decrease since more areas for particles to move

hence atmospheric pressure increases and is higher than inside thorax

hence air travel from atmosphere to thorax causing inhalation

inhalation/inspiration

The muscles responsible for inspiration are the diaphragm and external intercoastal muscles

• Diaphragm muscles contract causing the diaphragm to flatten and increase the volume of the thoracic cavity, hence decreasing the pressure of thorax below atmospheric pressure

• External intercostals contract, pulling ribs upwards and outwards (expanding chest)

Air flows into the lungs from outside until it reaches atmospheric pressure

exhalation/expiration

The muscles responsible for inspiration are the abdominal muscles and internal costal

• Diaphragm muscles relax, causing the diaphragm to curve upwards and reduce the volume of the thoracic cavity - increase pressure above atmospheric pressure

• Internal intercostals contract, pulling ribs inwards and downwards (reducing breadth chest)

• Abdominal muscles contract and push the diaphragm upwards during forced exhalation.

Air flows out of the lungs from outside until it reaches atmospheric pressure

cause and risk factors of lung cancer

• uncontrolled proliferation of lung cells - leading to abnormal growth of lung tissues

smoking

pollution

environmental factors eg radon gas

symptoms of lung cancer

coughing blood

weight loss

emphysema what is it and cause

lung condition where the walls of the alveoli lose their elasticity due to damage to the alveolar walls.

result in enlargement of alveoli—lower sav for gas exchange

major cause smoking

symptoms of emphysema

shortness of breath

expansion of ribcage

increase susceptibility to chest infection

phlegm production

cyanosis

respirometry vs spirometry

metabolic activity vs lung activity

if not specify gas = spirometry

Exercise will influence ventilation in two main ways

increase ventilation rate/ tidal volume

spirometry practical

measuring the amount and/or speed at which air can be inhaled or exhaled.

detects the changes in ventilation and presents the data on a digital display

total lung capacity

Volume of air in the lungs after a maximal inhalation

vital capacity

Volume of air in the lungs after a maximal inhalation

residual volume

volume of air that is always present in the lung

tidal volume

Volume of air that is exchanged via normal breathing

expiratory reserve volume

Additional volume of air exhaled after normal exhale

inspiratory reserve volume

Additional volume of air inhaled after normal inhale

factors affecting ventilation rate

height location lifestyle

effect of exercise on respiration

As exercise intensity increases, the volume of oxygen supplied to the tissues also increases

If energy demands exceed oxygen intake, ATP may be produced via anaerobic respiration (producing lactic acid)

The lactic acid is transferred to the liver and requires oxygen to convert it back to a usable form

This extra oxygen required to restore normal body functioning after exercise is referred to as the oxygen debt

less oxygen required to metabolise carbohydrates than fat

This is why there is an increase in carbohydrate metabolism and a decrease in fat metabolism with higher intensity exercise

diagram for lung capacity