BIOL125 - Respiration

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  • Created by: Katherine
  • Created on: 19-05-16 21:20
What is external respiration?
It is the physical mechanism that the body uses to get oxygen to cells and release carbon dioxide to the external environment
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What is cellular respiration?
It is the process by which cells harvest chemical energy to form ATP
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In mammals, gaseous exchange is achieved by...
Dual circulatory system
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What is gaseous exchange in water like?
Good buoyancy, low, variable oxygen levels, water freely available, gills, can be external or internal, unidirectional flow, can use counter current exchange
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What is gaseous exchange in air like?
Poor buoyancy, rich in oxygen, need to conserve water, lungs, internal structures, tidal flow system, no counter current system.
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What is the anatomy of the human lungs?
Air enters nasal passages by negative pressure breathing then into, pharynx, larynx, trachea, bronchus, bronchioles, terminal bronchioles. respiratory bronchioles, with alveoli
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How many alveoli do the human lungs contain?
200-300 million
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Each alveolus is wrapped in what?
A fine mesh of capillaries, covering 70% of its area
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During inhaltion, what happens to the radius of an alveolus?
It doubles
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What cells line the trachea and bronchi?
They are lined with pseudostratified columnar epithelium containing ciliated cells and mucous cells.
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What cells line the Alveoli?
Type 1 alveolar cells and type II alveolar cells which secrete liquid surfactant
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What do alveolar macrophages do?
They remove microorganisms, dust, from the alveoli
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What are type I alveolar cells?
They constitue 95% of the surface lining, and form the principal barrier to diffusion between blood and air. They have a flat cytoplasm and few organelles.
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What are type II alveolar cells?
They have numerous vacuoles, in the cytoplasm, with well developed ER and Golgi. They secrete liquid surfactant, which is very important in reducing surface tension of liquid lining the alveoli, so preventing their collapse.
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Are ciliated cells in the alveoli?
No, macrophages roam about and phagocytose dust, bacteria ect. These cells are transported out of the lungs when they migrate to ciliated part of the bronchioles.
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What are pleural membranes?
They are double walled sac around the lungs
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What do visceral pleural membrane do?
They adhere to outside of lungs
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What do parietal pleural membranes do?
They're attached to the chest wall.
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What is the pleural cavity?
It is filled with lubricating pleural fluid
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What is pleural fluid?
It acts as a lubricant, and allows lungs to react ot changes in volume of thoracic cavity with minimal physical stress. Allows some movement of lungs relative to chest wall duing breathing.
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The system can only work is pleural cavity is maintained under what pressure?
Negative pressure, otherwise the suction pressure produced by expansion of the chest would be absorbed by the pleural cavity and transferred to the lungs.
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What is inspiration?
It is an active process, involving contraction of diaphragm and external intercostal muscles.
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During quiet breathing, how is inspiration achieved?
It is achieved by contraction of the diaphragm. Depresses the floor of the thorax and raises the ribcase, so causing an increase in volume inside the thorax. External intercostal muscles also lift anterior end of each rib, causing an increase in c wi
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Where are the accessory muscles?
The back and neck - can help in strenuous exercse
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What is expiration?
It is more of a passive process, especially during normal quiet breathing.
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What happens during expiration?
Throax shrinks as a result of passive elastic recoil of elements of thel ungs that were stretched dring intake of breath.
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What is the elasticity of the lungs due to?
It's due to natural elasticity of lung tissue together with surface tension effects.
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What are the 4 different types of lung volumes?
Tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume
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What is tidal volume?
It is the volume of air exchanged during normal breathing
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What is inspiratory reserve volume?
It is the extra volume of air inhaled by maximum effort
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What is expiratory reserve volume?
Is is the extra volume exhaled with maximum effort
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What is residual volume?
It is the volume of air that remains in the lungs even with maximum expiration (some of which will be in airway passages, trachea, bronci, bronchiole)
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What are the various lung capacities?
Functional residual capacity, inspiratory capacity, vital capacity, total lung capacity
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What is functional residual capacity?
It is the air that remains in the lung after normal expiration
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What is inspiratory capacity?
It is maximal volume that can be taken in after normal expiration
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What is vital capacity?
It is the total air moved in and out during maximal inspiration and expiration
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What is total lung capacity?
It is the total of all 4 volumes
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What is anatomical dead space?
It is part of the residual volume, approximately 150mls. It consists of air contained in the conducting zone of the respiratory passages (trachea, bronchi, bronchioles). It's not in the alveoli and so not available for gas exchange
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What does the presence of dead space mean?
That at each intake of breath, the alveoli will contain a mixture of fresh air and oxygen depleted air, and for this reason the respiratory effciency of lungs is much less than that of gills. But more oxygen around in air than in water,
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What is forced vital capacity?
It is the total amount of air that is forcibly blown out after full inspiration.
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How do you measure airflow rates?
Using a modern spirometer with pressure transducer - accurately measures flow rates as well as volume of air breathed in and out and connects directly to computer
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What else can be used to measure air flow rates?
Peak flow meters are used by asthma sufferes to measure peaj expiratory flow ratess
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What are restrictive lung diseases?
They are characterised by reduced lung volume with preserved airflow - pulmonary fibrosis involved scarring of the lung with alveoli being replaced by fibrotic tissue.
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What are obstructive diseases?
The airways are partly obstructed (muscus, inflammation) so airflow is impeded - most common causes are asthma and smoking
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What is a treatment to obstructve lung disease?
B adrenergic receptor agonists as bronchodilators. Corticosteroids and other anti-inflammatories. combination of the two.
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The elastic behaviour of lungs has two components:
Elasticity and surface tension
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What is surface tension?
Due to atraction of molecules in a liquid. Molecules at the interface between gas and liquid have no attractive forces from the gas to balance those from the liquid, which creates a tensio at the surface dependent on compostion of the liquid.
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In a spherical object, where are the forces of surface tension directed?
Towards the centre of curvature, creating a collapsing force, which must be overcome in order to expand the bubble.
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What happen as the alveolus expands?
Additional pressure is required to overcome these surface tension effects. T changes with the size of the alveolus, and is greater the smaller the alveolus.
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What is Laplace's law?
P = 2X T/r
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What does P stand for?
Translung distending pressure
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What does T stand for?
Wall surface tension
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What does r stand for?
Radius
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As R goes down, does P go down or up?
It goes up
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What does lung surfactant do?
It lowers the surface tension of the fluid lining the alveoli, to prevent collapse.
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What is the normal surface tensio for water?
It's mN/m and in the lungs it can dop to less than 2mN/m
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Lung surfactant consists of 35 - 40% of the lipid ....
Dipalmitoyl phosphatidylcholine (DPPT) together with other lipids and proteins.
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What is respirator distress syndrome caused by?
Surfactant deficiency
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Without surfactnat, what can't the lungs do?
They can't inflate properly
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How is RDS syndrom treated?
By use of mechanical respirators and administration of artifical surfactant
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How can sever RDS be treated?
By administration of a special oxygenated liquid to the lungs
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From laplace's law, alveoli require a greater distending force to counteract effects of surface tension than larger ones but...
Surfatanct in the lungs reduces surface tension more in small alveoli than in larger ones, and so adjusts surface tension to correcpond to alveolar size
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What is the composition of air?
78% Nitrogen, 21% oxygen, 0.93% argon, 0.03% carbon dioxide
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What is fick's law of diffusion?
R = D X A X Deltap/d
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What is R?
Rate of diffusion
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What is D?
Diffusion constant
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What is A?
Area of over which diffusion takes place
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What is Delta P?
Difference in partial pressures
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What is d?
Distance
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How can R be optimised?
By increasing A and decreasing d, which applies to the human lung system. A is large (tennis court) and d is only two cells thick (alveolar cells)
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Is the PO2 in the alveolus higher than, or lower than, that of fresh air and why?
Lower due to mixing of fresh air and oxygen depleted air at each inspiration
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Is water good at dissolving and carrying carbon dioxide?
Yes.
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How is oxygen transported in the blood?
In combination with haemoglobin inside red blood cells n the form of oxyhaemoglobin.
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How many polypeptide chains does Haemoglobin have?
4, each with a haem group and central iron atom which binds to O2.
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How many O2 molecules can Hb carry?
4
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What shape is HbO2?
An S shape - this reflects the dissociation curve reflects molecular interaction among the 4 haem groups.
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When o2 is is bound to 1 or more haemes, the remianing haem groups have an increased affinity for O2 called?
Positive cooperativity
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How is carbon dioxide transported on HB?
It is bound with amine groups to form carbaminohaemoglboin
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Is oxyhaemoblobin a strong co2 binding agent?
No
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How is breathing controlled?
Automatically, but it can be voluntarily suspended or altered
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Can automatic breathing remain in brain dead individuals?
Yes
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What is Odine's curse?
A rare genetic disease is which the patient stops breathing when asleep.
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What is Odine's curse caused by?
Failure of autonomic control of breathing - impaired response to CO2 increase and O2 decrease in the blood. It can also result from severe brain or spinal trauma.
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What does the forebrain do?
It initiates breathing patterns that have emotional connotations (e.g. gasps, sighs, laughs)
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What does the motor cortex do?
It issues modifications to breathing for purpose of speech and volitional control
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What does the cerebellum do?
It participates in breathing modulations associated with postural changes
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The rate and depth of breathing are regulates so that PCO2 in arterioal blood is kept close to...
40mm HG
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But this can be overridden when...
Arterial oxygen tension drops below 60mm Hg (only likely at high altitiudes)
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What is respiratory rate
It is the no of breaths per minute
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What is the minute respitatory volume?
Respiratory rate x tidal volume
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What is MRV?
5 litres/ minute.
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Does CO of O2 have much more an effect on the rate of breathing?
CO2 levels have much more of a pronounced effect on the rate of breathing than O2 levels.
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What happens if CO2 levels increase?
Many biochemical mechanisms are affected because of lowering of pH in the blood tissues, which is normally regulated. Carbamino haemoglobin builds up and is less able to transprt oxygen. Difference in partial pressures of CO2 at tissues is reduced,
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What does this lead to?
Leads to rapid breathis, shortness of breath, confusion, flushed skin, mucle twitches.
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Each breath is initated by... in the ...
A central respiratory controlled in the brain stem at the base of the brain.
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Brain stem neurons send signals to where?
To the diaphrahm and external intercostal muscles.
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Various sensors report back to the central controlled the results of this action, what are these receptors?
Chemoreceptors, proprioceptors.
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What are proprioceptors?
These are stretch receptors that monitor lung volume
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Where are they found?
In lungs and in respiratory muscles
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What do they do?
They cause inhibition of inspiration and promotion of expiration upon lung inflation
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How many sets of chemoreceptors are there?
2 - Central chemoreceptors and peripheral chemoreceptors
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What are central chemoreceptors?
Responsive to arterial PCO2 by monitoring the acidity (H+ concentraion_ of the cerebrospinal flid (CSF) that bathes the brain and spinal cord
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What are peripheral chemoreceptors?
Responsibe to arterial PCO2, PO2 and H+ concentration
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Where are the central chemoreceptors located?
On the ventral surface of medulla oblongata in the brain stem.
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The chemosensitive cells are bathed in CSF which has a PCO2 equilibrium with arterial PCO2. CSF carbon dioxide combines with water to form carbonic acid which dissociates to form hydrogen ions and bicarbonate:
CO2 + H2O -> H2CO3 -> HCO3 + H+
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The CSF hydrogen ions diffused where?
Into the tissue to stimulate the medullay chemoreceptors
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Where are the central chemoreceptors located?
In the medulla oblongata (brain stem)
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Where are the peripheral chemoreceptors located?
In the carotid bodies of carotid arteries ( branch from aorta) and also in the aorta itself (aortic bodies)
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What does the pons do?
It can alter the output reponse generated by the main respiratory controller
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What does the medulla have?
It has the primary centres responsible for generation of respiratory rhythm
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What is an irritant receptor?
It is located throughout airways and lungs. It responds to mechanical or chemical irritation and elicit complex reflexe such as sneezes or coughs.
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How is blood pressure regulated?
Sensors and thier afferents, Central controller, efferents and effectors
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What are the sensors and their afferents?
Baroreceptors (in the aorta and carotid arteries) measure mean arterial pressure
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What is the central controller?
Cardiovascular control centre (in the medulla) receives this information and co-ordinates an appropriate
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