what is aerobic respiration
= release of energy by breakdown of glucose in presence of oxygen
-> produces CO2 and H2O as waste produced
-> generates large amount of energy in the form of ATP
-> occurs in mitochondria
equations of aerobic respiration
C6H12O6 (glucose) + 6O2 (oxygen) -> 6CO2 (carbon dioxide) + 6H2O (glucose
what is anaerobic respiration
= release of energy by the breakdown of glucose in absence of oxygen
-> generates relatively small amount of energy
-> occurs in cytoplasm
equation of anaerobic respiration
glucose -> lactic acid
what happens during vigorous activity
muscle cells need more energy to contract:
1. incr aerobic respiration in muscle cells
-> incr breathing to obtain oxygen
-> incr heart rate to supply oxygen
when continuous muscle contraction occurs:
1. aerobic respiration alone not fast enough to supply incr energy demand
2. anaerobic respiration takes place to meet incr energy demand
- build up of lactic acid in muscles needs to be removed
A. continued fast heart rate
a. transports lactic acid to liver via blood for removal and
b. transports oxygen to liver
B. continued deeper and faster breathing
a. to obtain oxygen to supply to liver - oxygen debt is paid when lactic acid is removed
what is oxygen debt
= amount of oxygen needed to remove lactic acid
human gas exchange system - nose to trachea
- air in nasal passages enters the pharynx
- from the pharynx, air passes into larynx and then into trachea through an opening
human gas exchange system - trachea
-> supported by C-shaped rings of cartilage
|_ keeps lumen of trachea open
-> epithelium = membrane next to lumen that consists of
1. gland cells -> secrete mucus to trap dust particles and bacteria
2. ciliated cells -> have hair-like structures called cilia on their surfaces
|_ sweep dust-trapped mucus up trachea
human gas exchange system - bronchi and bronchioles (singular: bronchus)
-> each bronchus carries air into lung
branches repeatedly, giving rise to numerous bronchioles
|
very fine tubes that each end in a cluster of alveoli
human gas exchange system - alveoli
*gas exchange takes place through walls of alveoli
1. numerous alveoli
-> very large surface area to volume ratio for gas exchange
2. wall of alveolus only one cell thick
-> short diffusion dist for gases
-> higher rate of diffusion
3. thin film of moisture covers inner wall of alveolus
-> allows oxygen to dissolve in it
4. walls of alveoli richly supplied with blood capillaries
-> flow of blood maintains steep concentration gradient of gases
inspiration
- diaphragm muscle contracts and diaphragm flattens
- external intercostal muscles contract while internal intercostal muscles relax
- ribs move upwards and outwards, and sternum moves upwards and forward
- volume of thoracic cavity increases
- as volume increases, lungs expand and air pressure inside decreases
- atmospheric pressure is now higher than pressure within lungs
- air moves into lungs
expiration
- diaphragm muscle relaxes and diaphragm arches upwards
- internal intercostal muscles contract while external intercostal muscles relax
- ribs move downwards and inwards, and sternum moves down to its original position
- volume of thoracic cavity decreases
- as volume decreases, lungs are compressed and air pressure inside increases
- pressure within lungs is now higher than atmospheric pressure
- air is forced out of lungs to exterior environment
breathing model
- rubber sheet (diaphragm) pulled down
- incr in volume causes a drop in air pressure inside bell jar
- atmospheric pressure outside is now higher than in the jar
- forces air to enter and fill up balloons (lungs)
*
Normally, an increased concentration of carbon dioxide is the strongest stimulus to breathe more deeply and more frequently. Conversely, when the carbon dioxide concentration in the blood is low, the brain decreases the frequency and depth of breaths.
diseases caused by tobacco smoke - chronic bronchitis [chronic obstructive lung disease if also have emphysema]
= caused by prolonged exposure to irritant particles found in tobacco smoke
-> epithelium lining of air passages/airways e.g. bronchi becomes inflamed
-> excessive music secreted by epithelium
-> cilia on epithelium become paralysed -> music and dust particles cannot be removed
-> air passages become blocked, making breathing difficult
-> in order to breathe, persistent coughing occurs to clear air passages
-> incr risk of getting lung infections
diseases caused by tobacco smoke - emphysema [chronic obstructive lung disease if also have chronic bronchitis]
= caused by persistent and violent coughing due to bronchitis
-> breakdown of partition walls between alveoli
-> decr surface area for gaseous exchange
-> lungs lose elasticity and become inflated with air
-> breathing becomes difficult
-> wheezing and severe breathlessness
diseases caused by tobacco smoke - lung cancer
= tobacco smoking increases risk of lung cancer
