Respiration

Control of breating

Ventilatory control is governed by the respiratory control centre of the brian. The medulla oblongata.This can stimulate chemical, nueral and hormonal stimuli to stimulate changes to breathing.

• Chemoreceptors: inform brain of excessive levels of co2 and insufficient oxygen at the working muscles. They also cause increases in respiration.
• Hering - breur: stretch receptors in the lungs, respond to excessive inflation by initiating inhibitory impulses. These stimulate expiration until the lungs recoil to a safe size.
• Irritants: causes reflexes to keep airway clear by means of coughing.
• Proprioceptors: located in muscles and joints, and dectect movement.
• Stressors: detect emotional and pain stimuli and respiration can be controlled voluntary for a short time.

Mechanics of breating

• Stimulation of the phrenic and intercostal nerves cause the contraction of breathing muscles.
• The pressure in the lungs is lower than in the atmosphere causing inspiration to occure.
• during inspiration the contraction of the respiratory muscles, diaphragm and intercostal muscles cause the thoratic cavity to increase in size, causing the lungs to expand.
• Air rushes into the lungsfrom the air
• expiration begins as the elastic recoil of the respiratory muscles causes the lung pressure to increase, causing the lung pressure to increas and forcing the air out.

Differences between breathing at rest and during exercise

Breathing at rest

Breathing during exercise

Largely passive

Largely active

Expiration almost completely passive

Expiration is more active

Shallow breathing

Deep breathing

Slow breathing

Fast breathing

Smaller percentage of CO2 expired

High percentage of CO2 expired

Primary respiratory muscles only

Primary and secondary muscles used

Gaseuos Exchange

Two major functions:

• Fill blood with oxygen to be transported to the muscles and tissues
• remove carbondioxide from the blood produced by metabolic processes in the muscles and tissues.

Each gas within a mixture exerts pressure which is equal to its percentage within that mixture (partial pressure). The partial pressure of oxygen within the alveoli is much higher than it is in the surrounding capillaries therefore causing oxygen to diffuse…