Biology 08 - Respiration
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29 terms
Terms | Definitions |
|---|---|
 Respiration | - a broad term referring to: a) the exchange of gases between an organism and its external environment b) the transport of these gases within the organism c) the diffusion of gases into and out of cells - aerobic organisms exchange CO₂ generated during cellular respiration for O₂ obtained from the external environment |
| Lungs | - higher vertebrates' respiratory system where gas exchange occurs at a single respiratory surface |
| Respiratory Airways | - air enters through external nares (nostrils) - nasal cavities, filtered by mucous and nasal hairs - pharynx - larynx (epiglottis closes the larynx when swallowing food) - trachea - two bronchi - bronchioles - alveoli |
| Bronchi & Trachea | - lined by ciliated epithelial cells - filters and traps particles inhaled along with air |
| Alveoli | - clusters of small air sacs - gas exchange between the lungs and circulatory system occurs here - each alveolus is coated with a thin layer of liquid containing surfactant and is surrounded by an extensive network of capillaries - three hundred million alveoli provide approximately 100 m² of moist respiratory surface for gas exchange |
| Surfactant | - lowers the surface tension of the alveoli - facilitates gas exchange across the membranes - reduces high surface tension of the fluid lining the alveoli, preventing alveolar collapse during exhalation |
| Ventilation of the Lungs | - "breathing" - the process by which air is inhaled and exhaled - the purpose is to take in oxygen from the atmosphere and eliminate carbon dioxide from the body - ventilating mechanism is dependent upon pressure changes in the thoracic cavity |
| Thoracic Cavity | - the body cavity that contains the heart and lungs |
| Diaphragm | - a muscle that separates the thoracic cavity from the abdominal cavity |
| Lungs' Membranes | - surrounded by visceral pleura and parietal pleura |
| Interpleural space | - space between two membranes - contains a thin layer of fluid - the pressure differential between the intrapleural space and the lungs (which is essentially atmospheric pressure) prevents lungs from collapsing |
| Pneumothorax | - caused by penetrating injury trauma to the chest - air enters the intrapleural space - intrapleural pressure increases - lung collapses - treated by inserting a needle and withdrawing air from the intrapleural space |
| Stages of Ventilation: Inhalation | - diaphragm contracts and flattens - external intercostal muscles contract - rib cage and chest wall pushed up and out - causes the thoracic cavity to increase in volume - intrapleural pressure decreases - lungs expand and fill with air |
| Negative-Pressure Breathing | - during inhalation, air is drawn in by a vacuum |
| Stages of Ventilation: Exhalation | - is generally a passive process - the lungs and chest wall are highly elastic and tend to recoil to their original positions after inhalation - diaphragm and external intercostal muscles relax - chest wall pushes inward - decrease in thoracic cavity volume casues air pressure in the intrapleural space to increase - lungs deflate, air forced out of the alveoli - internal intercostal muscles contract & pull the rib cage down |
| Control of Ventilation: Medulla Oblongata | - ventilation is regulated by neurons in medulla oblongata, whose rhythmic discharges stimulate the intercostal muscles and/or the diaphragm to contract - neural signals can be modified by chemoreceptors, which respond to changes in the pH and the partial pressure of CO2 in the blood - when CO₂'s partial pressure increases, the medulla oblogata stimulates an increase in the rate of ventilation |
| Control of Ventilation: Cerebrum | - ventilation can be consciously controlled by the cerebrum - if a person tries to hold his breath too long, CO₂ concentration in blood incresaes, medulla oblongata override this attempt and stimulate inhalation |
| Hyperventilation | - deep, rapid breathing - lowers the partial pressure of CO₂ in the blood below normal - chemoreceptors sense this and send signals to the respiratory center, which temporarily inhibits breathing |
| Spirometer | - an instrument to measure the amount of air normally present in the respiratory system and the rate of which ventilation occurs |
| Vital Capacity | - the maximum amount of air that can be forcibly inhaled and exhaled from the lungs |
| Tidal Volume | - the amount of air normally inhaled and exhaled which each breath |
| Residual Volume | - the air that always remains in the lungs - prevents alveoli from collapsing |
| Expiratory Reserve Volume | - the volume of air that can still be forcibly exhaled following a normal exhalation |
| Total Lung Capacity | - vital capacity + residual volume |
| Gas Exchange | - occurs by diffusion across the pulmonary capillary walls and the alveoli - gases move from regions of higher partial pressure to areas with lower partial pressure - deoxygenated blood enters pulmonary capillaries (has lower partial pressure of O₂ than the air in the alveoli - thus O₂ diffuses down its gradient into the capillaries where it binds with hemoglobin - returns to the heart via the pulmonary veins |
| Gas Exchange continued | - partial pressure of CO₂ in the capillaries is greater than of the inhaled alveolar air - thus CO₂ diffuses from the capillaries into the alveoli, where it is released into the external environment during exhalation |
| Pulmonary Capillaries | - a dense network of minute blood vessels surrounding the alveoli |
| At High Altitudes | - partial pressure of O₂ in the atmosphere declines - harder to get enough oxygen to diffuse into the capillaries - the body can compensate by hyperventilation and by polycythemia - the affinity of hemoglobin for oxygen decreases to facilitate unloading of oxygen in tissues - there is greater vascularization of the peripheral tissues |
| Polycythemia | - increasing the production of red blood cells to carry more oxygen |
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