Mrs Rex Flashcards
mechanics of breathing
Air always moves from an area of high pressure to an area of low pressure via diffusion.
The greater the difference in pressure, the faster air will flow, so to get air into lungs (inspiration), the pressure needs to be lower here than in the atmosphere.
To get air out (expiration), air pressure needs to be higher in the lungs than the atmosphere.
Increasing the volume of the thoracic cavity (chest cavity) will reduce the pressure of air in the lungs.
Decreasing the volume of the thoracic cavity will increase the pressure of air in the lungs, forcing the air out.
Gaseous exchange
Diffusion
Partial pressure
Getting oxygen in the air into the lungs so that it can diffuse into the blood and be transported to the cells of the body, and the removal of carbon dioxide from the blood.
Partial pressure is the pressure exerted by an individual gas when it exists within a mixture of gases
Diffusion is the movement of gas molecules from an area of high concentration to an area of low concentration
Gaseous exchange at the alveoli
The partial pressure of oxygen in the alveoli is higher than in the capillary blood vessels.
This is because oxygen has been removed by the working muscles so its concentration in the blood is lower, so is it partial pressure.
The difference in partial pressure is referred to as the concentration/diffusion gradient and the bigger this gradient the faster diffusion will be.
Oxygen will diffuse from the alveoli into the blood until the pressure is equal in both
Gaseous exchange at the muscles
Partial pressure of oxygen has to be lower at the tissues then in the blood for diffusion to occur.
As such, in the capillaries and membrane surrounding the muscle the partial pressure of oxygen is 40mmHG and it is 100mmHG in the blood. This allows oxygen to diffuse from the blood into the muscle until equilibrium is reached.
Lung volumes
Long volume is the movement of air into and out of the lungs.
Taking air into the lungs is inspiration and moving air out is expiration.
At rest we inspire and expire approximately 0.5 L of air. The volume of air inspired or expired per breath is referred to as the tidal volume.
The volume of air inside or expired per minute is referred to as minute ventilation and can be calculated by multiplying the number of breaths taken per minute (approximately 12) by the tidal volume
Tidal volume
Volume of air breathed in or out per breath
Minute ventilation
Number of breaths (Per minute) x tidal volume = minute ventilation
The volume of air inspired or expired per minute and can be calculated by multiplying the number of breaths taken per minute (approximately 12) by the tidal volume
12 x 0.5 = 6 litres/min
Inspiratory reserve volume (IRV)
Volume of air that can be forcibly inspired after a normal breath
Expiratory reserve volume (ERV)
Volume of air that could be forcibly expired after the normal breath
Residue volume
The amount of air that remains in the lungs after Maximal expiration
Spirometer trace
Spirometer is a device that is used to measure the volume of air inspired and expired by the lungs.
The volume of air we breathe in and out can be measured using this.
An individual breathes in and out of the sealed chamber through a mouthpiece. This makes the chamber inflate and deflate and as this happens a pen recorder traces the breathing movements onto a chart. The machine is calibrated so that breathing volumes can be calculated.
Effects of exercise on volumes and minute ventilation
Changes in minute ventilation occurred during different types exercise. As you would expect the more demanding a physical activity is the more breathing increases to meet the extra oxygen demands.
