1. Respiration is controlled by nervous and chemical regulation. I- Nervous Regulation : A-Momentary regulation as during swallowing or speech, there is momentary stoppage of respiration B-Continuous regulation : Through some reflex 1.Hering – Breuer reflex 2.Reflexes from baroreceptors 3.Reflex from right atrium (Harrison’s reflex) المحاضرة الثانية عشرة

2. II)- Chemical Regulation : Through changes in CO2 tension, O2 tension, and hydrogen ion concentration of blood (pH) 1-Effect of CO 2 CO 2 is natural stimulus for respiration Increase in CO 2 tension will stimulate respiration reflex 3-Effect of pH of Blood Decrease in pH (acidosis) will stimulate respiration, while increased pH (Alkalosis) will inhibit respiration 2-Effect of O 2 Decrease in O 2 tension will stimulate respiration and vice versa.

3. Some Respiratory Defects : Dyspnea : Means difficulty of respiration. Apnea : Means stoppage of respiration. Hypoxia : Means decrease in O2 supply to the tissues. Cyanosis : Means appearance of bluish colour of skin and mucous membrane due to effective oxygenation. Asphyxia : If external respiration ceases. Anoxia : Means complete deprivation of oxygen.

4. OTHER FUNCTIONS OF THE RESPIRATORY SYSTEM A) Pulmonary Embolization B) Lung Defense Mechanisms C) Metabolic & Endocrine Functions of the Lungs