Question

Describe the 2 phases of ventilation: inspiration and expiration. make sure to include activity of muscles involved, the pressure and volume of the lungs during each phase, and sources of neural control for these processes.

Answer 1

The 2 phases of ventilation are inspiration and expiration.

Inspiration

• The main inspiratory muscle include diaphragm, external intercoastal , and scalene muscles
• Accessory muscle include strenocleidomastoid , pectoralis major, pectoralis minor, serratus anterior, latissmus dorsi and serratus posterior superior.
• Due to increase in volume of lung due to expansion of lungs ,there will be decrease in intra alveolar pressure which is below the atmospheric pressure ,about -1 cm H20
• The volume of lung that can be accomodated during inspiration is the sum of all volume compartments , about 6000ml or 4-6 L.
• Dorsal respiratory group of neuron located in the dorsal part of medulla help in inspiration
• The neurons are located in nucleus of tractus solitarius.
• The central and perpheral are chemoreceptor, which help respiration
• peripheral chemoreceptor will detect the oxygen level in the blood,and send signal to DRG and inspiratory signals are passed to inspiratoy muscles.

Expiration

• Internal intercoastals, rectus abdominis,external and internal obliques and transverse abdominis help in expiration
• During expiration, air collapses , lung volume decreases and causing increase in intra alveolar pressure above +1 cm H20
• The amount of air in lung after exhalation decreases, which is about 1800-2200 mL.
• The source of neural control is Ventral respiratory group of neuron, which is located to ventro lateral medulla.
• Pneumotaxic center located in upper pons help in regulation of rhytm of respition and breathing rate.
• Pneumotaxic center is anatagonistic to apneustic center.
• When the level of carbon dioxide increases, result in giving information to VRG causing expiration by passing information to expiratory muscles.