Homeostasis + Breathing

• Homeostasis is the ability of an organism to maintain a constant internal environment. e.g. body temperature
• Homeostasis depends on exchanging materials such as gases, nutrients, and toxic wastes. Diffusion allows for the exchange of these substances.
• Metabolism is the sum of all chemical activities in the body.
• Respiratory system

  
• The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, lungs, and diaphragm.
• Intercostal muscles, attached between the ribs, move the rib cage up or down. 
• Air enters the nose, travels down the windpipe, the bronchus​and the bronchioles, to the alveoli. 
• The lining of an alveolus is only one cell thick.
• Oxygen diffuses through the alveolus and capillary linings, and​ attaches to red blood cells. At the same time, carbon dioxide diffuses from the plasma into​the alveolus.
• Structure of an alveolus

  
• During inhalation, the brain sends signals to the rib muscles and diaphragm to​ contract. The ribs are pulled up and out, and the diaphragm flattens​ downwards.
• In exhalation, the rib muscles and​the diaphragm relax, springing back to their original positions, so air pressure in the lungs increases, and the air is pushed out from​ the alveoli.
• Most carbon dioxide is carried in the plasma.
• We breathe automatically by involuntary reflex action. It is​controlled by medulla oblongata of the brain.
• Asthma is an example of a breathing disorder. This is the inflammation & constriction of the bronchi.
• Structure of skin. Example of homeostasis via excretion of sweat.