RESPIRATION CHAPTER 29

Enduring Understanding All living things perform cellular respiration reactions that break-down biomolecules to convert stored energy into the usable form of energy for all of life which is ATP. • These reactions can occur with oxygen (aerobic) and in some organisms without oxygen (anaerobic). • Aerobic reactions convert more energy than anaerobic reactions, and can lead to muscle fatigue when reactions run in low oxygen situations.

Essential questions How can the lungs keep the body supplied with a continuous source of oxygen? • How does the internal and external respiration mechanism function in the respiratory system? • How does the respiratory system respond to negative influences?

Objectives Analyze how the lungs operate with the blood to supply the body with oxygen and eliminate carbon dioxide Compare and contrast between internal and external respiration Analyze diseases associated with the respiratory system and describe the vectors/infection responsible.

Activities Students will analyze a video on the respiratory system and develop a diagram of how the respiratory system transports oxygen into the body and carbon dioxide out of the body. Create a Venn Diagram that compares and contrast internal and external respiration

--- Research the internet for 5 diseases and/ or infections of the respiratory system, complete research, describe the vector causing the disease or infection, and explain the effect on the human organism. Read Health Watch (page number 578) in your text book and write briefly the dangers of smoking.

Do you know? Why exchange gases? What are some evolutionary adaptations for gas exchange?

Features that facilitate diffusion The respiratory surface must remain moist, because gases must be dissolved in water when they diffuse into or out of cells. Cells lining respiratory surfaces are very thin, a feature that facilitates diffusion of gases through them. All respiratory system must have a large surface area in contact with the environment to allow adequate gas exchange.

An overview of gas exchange Gases move in and out of lungs by bulk flow Oxygen and carbon dioxide are exchanged in the lungs by diffusion Alveoli or air sacs Gases dissolved in blood are transported by bulk flow Oxygen and carbon dioxide are exchanged in the tissues by diffusion During bulk flow, fluids or gases move in bulk through relatively large spaces, from areas of higher pressure to areas of lower pressure.

Respiration Respiration is the process of oxidation of food resulting in the release of energy. In the case of earthworm, gases diffuse through the moist skin and are distributed throughout the body by an efficient circulatory system.

Respiration in Fish Fish create a continuous current of water over their gills by pumping water into their mouths and ejecting it through openings just behind the gills. They can increase the flow of water by swimming with their mouths open. Gills collapse and dry out in air and hence aquatic animals cannot live when they are out of water.

Respiration in Insects The tracheae convey air directly to the body cells. Tracheae subdivide and branch into smaller channels (tracheoles) that penetrate the body tissues and allow gas exchange. Each body cell is close to a tracheole, minimizing diffusion distances. Air enters the trachea through openings called spiracle.

Respiration in Birds The bird lung has evolved special adaptations that allow extremely efficient gas exchange. These adaptations support the enormous energy demands of flight. As a bird breathes in, it draws air through its lungs, where oxygen is extracted, and air is pulled into the air sacs. As the bird breathes out, oxygenated air from the air sacs is forced back through the lungs. This allows the bird to extract oxygen even as it exhales. The bird’s lungs are filled with hollow, thin-walled tubs called parabronchi, which allow air to pass through them in both directions.

THE HUMAN RESPIRATORY SYSTEM The conducting portion consists of nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles leading finally to the alveoli in the lungs.

Gas exchange in the alveoli The two lungs have approximately two million alveoli. Alveoli provide an extensive surface area for diffusion. The alveoli are richly supplied with blood capillaries. The walls of the alveoli consists of a single layer of epithelial cells. Exchange of gases takes place between alveoli and the blood capillaries. The blood in the alveoli is rich in oxygen and the blood in the capillaries is rich in carbon dioxide. Exchange of these gases takes place by simple diffusion.

Transport of gases Transport of oxygen In the alveoli, where the partial pressure of oxygen is high, oxygen combines with hemoglobin to form oxyhemoglobin. Each hemoglobin molecule can bind up to four oxygen molecules. In the tissues oxyhemoglobin disassociates to release oxygen.

Transport of carbon dioxide Approximately 70% of the CO2 reacts with water to form carbonic acid, which splits to form bicarbonate ions. (HCO3-) diffuses into the plasma. About 20% of the CO2 binds to hemoglobin for its return trip to the lungs. The remaining 10% stays dissolved in the plasma as CO2

Mechanism of breathing. What events occur during inhalation and exhalation? Breathing occurs in two stages: (1) inhalation, when air is actively drawn into the lungs, and (2) exhalation when it is passively expelled from the lungs.

Inhalation During inhalation, the chest cavity is enlarged. The diaphragm muscle contracts, drawing the diaphragm downward. The rib muscles also contract, lifting the ribs up and outward. When the chest cavity expands, the lungs also expand with it. The volume of the lungs increases and the pressure decreases. This draws air into the lungs.

Mechanism of Breathing

Exhalation The muscles of the diaphragm relax, and the diaphragm domes upward. The ribs fall down and inward, decreasing the size of the chest cavity. The pressure increases and the air is forced out of the lungs. After exhalation, the lungs, contain air, which helps to prevent the thin alveoli from collapsing.

Simple experiment to demonstrate breathing Breathing rate is controlled by the respiratory center, present in the medulla part of the brain.

.. http://www.youtube.com/watch?v=TaAvhG2SInM&feature=related Effects of smoking Read Page number 578 to know more about effects of smoking.

Effects of smoking on the human respiratory system Nicotine and sulfur dioxide present in the tobacco smoke paralyze the cilia present in the respiratory tract. These cilia otherwise remove inhaled particles. Smoking prevents them from removing. Other toxic particles also stick to these particles and they stick to the walls of the respiratory tract and enter the lungs. Cigarette smoking also impairs the white blood cells that defend the respiratory tract by engulfing the foreign particles and bacteria. In response to the irritation of cigarette smoke, the respiratory tract produces more mucus which also traps foreign particles. Without the cilia to sweep, the mucus builds up and can obstruct the airways; the “smoker’s cough” is an attempt to expel these particles Microscopic smoke particles accumulate in the alveoli over the years until the lungs of heavy smokers are literally blackened. The longer the tissues of the lungs are exposed to the carcinogens on the trapped particles, the greater the chance that cancer will develop.

--- Smoking is a major cause for bronchitis, emphysema. Bronchitis is a persistent lung infection. Symptoms are coughing, increase in mucus production, decrease in the activity of cilia, swelling of the respiratory tract and as a result there is a decrease in air flow to the alveoli. Emphysema: toxic substances in cigarette smoke cause the body to produce substances that make the alveoli to become brittle and ruptured. The lung loses it normal sponge like appearance. The loss of alveoli results in decrease in oxygen supply to all body tissues. Breathing becomes difficult. Carbon monoxide present in high levels in cigarette smoke, binds with red blood cells. This reduces the oxygen carrying capacity of the blood cells and thereby increases the workload on the heart. Smoking also promotes, atherosclerosis or thickening of the arterial walls by fatty deposits. The carbon monoxide also increases the incidence of infertility, miscarriage, lower-birth weight babies in smoking women. Passive smoking poses health hazards for both children and adults. Children exposed to cigarette smoke are more likely to get bronchitis, pneumonia, coughs and decreased lung capacity. They are also likely to develop asthma and allergies. Adults exposed to cigarette smoke are prone to get lung cancer and heart attack.

If a person is choking on food or another object and is unable to breathe, the Heimlich maneuver pushes upward on the victim’s diaphragm and forces air out of his lungs, possibly dislodging the object. It needs to be repeated if necessary.