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neurologyYou need to know

• The key parts of the human breathing system are the trachea, bronchi, bronchioles, alveoli, lungs, diaphragm, intercostal muscles, and rib cage.
• The alveoli are adapted for gas exchange by having a large surface area and thin walls (one cell thick).
• Gas exchange in the alveoli occurs by diffusion: oxygen moves from the alveolar air into the blood, and carbon dioxide moves from the blood into the alveolar air.
• Inhaled air is mostly nitrogen and oxygen with very little carbon dioxide, while exhaled air is still mostly nitrogen, contains less oxygen than inhaled air, contains more carbon dioxide, and contains more water vapour.
• Air is moved into the lungs (inhalation) when the diaphragm contracts and moves down, and the rib cage moves up and out, increasing the volume of the thorax and decreasing the pressure, drawing air in.
• Air is moved out of the lungs (exhalation) when the diaphragm relaxes and moves up, and the rib cage moves down and in, decreasing the volume of the thorax and increasing the pressure, pushing air out.
• The bell jar model represents the lungs, diaphragm, and chest cavity, but has limitations such as not showing alveoli and not mimicking the elasticity of lung tissue.
• Tidal volume is the volume of air moved into or out of the lungs during a normal breath.
• Vital capacity is the maximum volume of air that can be exhaled after breathing in as deeply as possible.
• Total lung capacity is the total volume of air in the lungs after a maximal inhalation, including the residual air that cannot be exhaled.
• Maximal exhalation into a spirometer can measure vital capacity but not total lung capacity because residual air remains in the lungs.
• Lung volume can vary between individuals due to age, size, fitness, and health conditions.
• During exercise, breathing rate and depth increase to supply more oxygen and remove more carbon dioxide.
• Smoking damages the gas exchange system by destroying alveoli, reducing surface area, and causing diseases such as emphysema and lung cancer.
• Asthma causes narrowing of the airways, making breathing difficult and reducing gas exchange efficiency.
• The key parts of a leaf are the upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, stomata, guard cells, and air spaces.
• The stomata are pores in the leaf that allow gases (carbon dioxide and oxygen) to diffuse in and out.
• The main function of the leaf is to carry out photosynthesis and gas exchange.

• Label a diagram of the human breathing system and a cross-section of a leaf with all key parts.
• Describe in detail two adaptations of the alveoli (large surface area and thin walls) and explain how each aids diffusion.
• Explain, using knowledge of diffusion, how oxygen and carbon dioxide are exchanged in the alveoli.
• Describe and demonstrate the movement of the rib cage and diaphragm during inhalation and exhalation.
• Evaluate the bell jar model by identifying its strengths and limitations as a model of human breathing, and suggest improvements or design a better model.
• Measure vital capacity by inhaling maximally and then exhaling as fully as possible into a spirometer, and record the result accurately using the correct units.
• Compare and interpret vital capacity data from different individuals (such as a child and an adult) and explain the implications for gas exchange.
• Plan and carry out a simple investigation to test the effect of exercise on breathing rate, including collecting and recording data.
• Explain the physiological changes in breathing during and after exercise, linking to increased demand for oxygen and removal of carbon dioxide.
• Explain, with reference to the structure and function of the gas exchange system, how smoking and asthma affect breathing and gas exchange.
• Compare and contrast gas exchange in animals and plants, making links to diffusion and water loss through stomata in plants.