Regulation of Breathing A negative feedback system Mechanism to restore conditions to their original state Diaphragm and intercostal muscles contract Thoracic cavity increases Inspiration occurs medulla oblongata Regulation of Breathing  CO2 in the blood  CO2 in the blood Pressure receptors in alveoli Thoracic cavity decreases Expiration occurs Diaphragm and intercostal muscles relax Brain releases acetylcholine

Gas Exchange External Respiration Internal Respiration: Respiratory system and circulatory system Internal Respiration: Circulatory system and cells

External Gas Exchange Alveoli are surrounded by capillary beds Low-oxygen blood is pumped from the heart through the pulmonary artery  arterioles  capillaries Oxygen diffuses from the alveoli  capillaries Carbon dioxide diffuses from the capillaries  alveoli Oxygen-rich blood is carried from capillaries  venules  pulmonary vein  heart Heart then circulates the blood around the body

Internal Gas Exchange Oxygen diffuses from the blood  cells Carbon dioxide diffuses from the cells  blood

Hemoglobin Red blood cells contain hemoglobin, a pigment protein with an iron centre Hemoglobin has a high affinity for oxygen and readily binds with oxygen to form oxyhemoglobin Hemoglobin increases the efficiency of gas exchange by removing oxygen from the blood plasma. Therefore oxygen will continue to diffuse into the blood

Fun Facts! Noses: Whales: “Nose” is a blow hole on top of the head Pigs: Noses act as a rooting device Elephant: Nose used for manipulation Sneeze: Reflex action caused by the irritation of the nasal passages Hiccup: a spasm of the diaphragm; The sound comes from the epiglottis dropping down over the glottis Snoring: uvula vibrates and causes noise; happens only when air passage through the mouth is small as when we are sleeping. Laughing: consists of deep inspiration (breathing in) followed by a series of short, spasmodic, expirations (breathing out); crying is similar Yawning: indication of boredom, fatigue, and/or lack of oxygen; it is a deep inspiration with the mouth fully open Sighing: prolonged expiration