Human Breathing

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Human Breathing notes
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Human respiratory system -Composed of a pair of lungs + series of tubes. -Located in chest (aka thorax or thoracic cavity). -Base of thorax formed by muscle (diaphragm) this separates it from the abdomen. -Ribs +intercostal form wall
Parts of respiratory system
Nose -Nostrils separated by septum. Breathing through nose is beneficial because the air is: -filtered/cleaned by hairs +mucus in nostril -moistened -warmed moist, warm air passes more easily from lungs into bloodstream
Pharynx -in it theres a flap of tissue (epiglottis) which prevents food + drink from passing into trachea -below epiglottis is larynx which contains 2 vocal cords which vibrate to produce sound.
Trachea and subdivisions -Bronchi + higher bronchioles are made of muscle + elastic fibres +rings of cartilage which prevents tubes from closing. -All tubes are lined with mucus and cilia. -Muscus is sticky + traps small particles -Cilia create upward current which moves mucus upwards.
Lungs -Each lung is enclosed by pair of pleural membranes , outer- lines chest wall + diaphragm, inner- lines lungs. -Pleural cavity is gap between 2 pleura it contains liquid which lubricates membranes + reduces friction during breathing.
Alveoli -Tiny, hollow, balloon-like air sacs. -Function-> gas exchange -Provide a huge surface area for gas exchange -Thin walled -Moist surfaces -enclosed in network of blood capilliaries.
Gas exchange Break down of food with help of oxygen.
Carbon dioxide and water -Carbon dioxide +water pass out of cells by diffusion. (cytoplasm has higher conc of CO2 + H2O than blood plasma -In the lungs, CO2 + H2O diffuse from the blood plasma into the alveoli.
Oxygen and Transport of gases -Passes from the alveoli into the blood + then passes from the blood into the body cells. -Oxygen is mainly transported by combining with haemoglobin to form oxyhaemoglobin. -CO2 + H2O both carried in blood plasma.
Inhalation -Message sent from brain to intercostal muscles + diaphragm. -These muscles use energy (in form of ATP) to contract. -Ribs pulled up + out + diaphragm curves down -Volume/size of chest cavity increases. -Pressure decreases -External air pressure now higher + air is forced into lungs.
Exhalation -Intercostal muscles + diaphragm relax. -Ribs move down + in + diaphagm curves up -Volume / size of chest cavity decreases -Pressure increases + air is forced out of lungs
Effect of exercise on the rate of breathing + composition of air for a person at rest. -Exercise increases rate of respiration. -Body experiences lower levels of available oxygen. Oxygen: inhaled 21% , exhaled 14% Carbon dioxide: inhaled 0.04% , exhaled 5.6% Water concentration: inhaled low , exhaled high.
Breathing disorders: asthma Symptoms: noisy, wheezy breathing + feeling of breathlessness External causes: Common allergens like pollen, animal dander, house dust and dust mites, also stress or anxiety. Internal causes: Lower bronchioles become inflamed and narrow. (no cartilage to keep them open) Prevention: Avoiding allergens + use inhalers, these prevent the bronchioles from reacting to allergens. Treatment: Inhale drugs that cause the bronchioles to widen or inhale steroids.
Control of human breathing -Rate of human breathing controlled by the brain (in the medullla oblongata). -The brain controls by monitoring levels of CO2 in blood that passes through it. -CO2 is slightly acidic gas, it dissolves in water to for, a weak acid called carbonic acid. -Special centres in the brain detect the slight drop in pH. -CO2 operates as a controlling factor in gas exchange in both plants and animals.
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