Question

a. Describe the driving force for, and resistance to, the flux of air into the lungs during inhalation.

b. Describe the steps in the human respiratory cycle, and identify the causal mechanisms that allow each step to occur in turn.

Answer 1

a) The driving force for the inhalation of the air into the lungs are the pressure inside the lungs. The pressure in the lungs is created by the contraction of diaphragm, external intercostal muscles and expansion of rib cage which produce a pressure by enlarging the cavity of thorax and drives the air into the lungs during the inhalation of respiration.

The resistance to the air into the lungs during the inhalation is known as the airway resistance which is due to laminar or turbulent flow or it can be also determined by the diameter of the airway.

b) The major steps that involves in the respiratory cycle of human is inspiration and expiration.

Inspiration is the first and foremost step of respiration in which the air enters the nose and passes to trachea. The external intercostal muscles, diaphragm contracts and expand the rib cage and that will directly increase the Thoracic cavity , then the air is driven inside the lungs known as inspiration.

Expiration is the step of respiration in which the air is expelled from the lungs in which the diaphragm relaxes and the thoracic volume reduces that will decrease the cavity of thorax as a passive work the air is exhaled.

The casual mechanism that allows each step is the contraction of the muscle by the nerve stimulation. The diaphragm plays a casual mechanism by contracting and relaxing in inspiration and expiration of human respiratory cycle.