Respiratory System Flashcards
Which of the following best describes the pleural cavity?
an air-filled cavity that is slightly lower than atmospheric pressure
an air-filled cavity that is slightly higher than atmospheric pressure
a fluid filled cavity between the parietal pleura and the thoracic wall
a fluid-filled cavity that makes sure the visceral and parietal pleurae remain attached
an air-filled cavity between the visceral pleura and the lung
a fluid-filled cavity that makes sure the visceral and parietal pleurae remain attached
Which of the following explain why the partial pressure of O2 in alveolar air is lower than in atmospheric air?
alveoli contain a mixture of inspired and expired air
the lungs are not completely emptied during each expiratory/inspiratory cycle.
O2 diffuses out of the alveoli into the blood
all
Which of the following is the most important chemical regulator of breathing?
carbon dioxide
sodium ions
potassium ions
oxygen
haemoglobin
carbon dioxide
What is the name of the respiratory variable that is measured using a spirometer when a subject takes a maximal inspiration and then exhales as completely as possible?
tidal volume
total lung capacity
vital capacity
residual volume
expiratory reserve volume
vital capacity
When it is really cold why is it better to breathe through your nose rather than your mouth?
the vibrissae humidify the inspired air
your tongue might get stuck to the roof of your mouth
turbulence in the air flow through the nose helps humidify the air
the air is denser and the resistance of the nasal cavity is lower than the oral cavity
the nasal cavity contains blood vessels that warms the inspired air
the nasal cavity contains blood vessels that warms the inspired air
Which of the following is/are voluntary muscle(s)?
external intercostals
diaphragm
internal intercostals
abdominal muscle
all
Which of the following statements is TRUE?
the bronchial arteries carry blood from the right ventricle of the heart
blood in the pulmonary artery is deoxygenated
blood in the bronchial arteries is deoxygenated
as the bronchial tree generation number increases the amount of cartilage increases
the trachea is lined with D-shaped rings of cartilage
blood in the pulmonary artery is deoxygenated
The respiratory membrane consists primarily of which type of epithelium?
silly ate de cuboidal epithelium
squamous epithelial cells
pseudostratified ciliated columnar epithelium
moist cuboidal epithelium
moist columnar epithelium
squamous epithelial cells
Which of the following statements is/are TRUE?
Lung compliance determines how easy it is to inflate the lungs
Healthy young adults have low lung compliance
People with cystic fibrosis have high lung compliance?
Lung compliance determines how easy it is to inflate the lungs
Which of the following would you NOT find in the lungs?
sympathetic neurones
stretch receptors that detect the degree of stretching of the lungs
irritant receptors that initiate the cough reflex
parasympathetic neurones
chemoreceptors that detect levels of CO2 in inspired air
chemoreceptors that detect levels of CO2 in inspired air
Which of the following is NOT likely to occur in response to hypercapnia?
elevated bicarbonate concentrations in the brain
an increase in the frequency of pulmonary ventilation
increased activity in central chemoreceptors in the medulla oblongata
an increase in the amount of CO2 moving across the blood brain barrier
a decrease in the depth of pulmonary ventilation
a decrease in the depth of pulmonary ventilation
How many cells does a gas have to pass through when it crosses the respiratory membrane?
0
1
2
3
4
2
Why is airway resistance so low in the later generations of the bronchial tree?
Terminal bronchioles are so numerous that collectively they contribute little to the overall airway resistance.
They are able to expand as the lungs expand during inspiration
Their resistance reduces during inspiration
all
Which of the following statements about O2 transport in the blood is TRUE?
each polypeptide in haemoglobin has hydrogen-containing core called a heme group
each heme group has a has a ferrous iron (Fe2+) atom at its core.
around 1.5% of O2 in the blood is bound to haemoglobin
each Fe2+ atom can binds irreversibly to one molecule of O2
haemoglobin consists of three polypeptide chains
each heme group has a has a ferrous iron (Fe2+) atom at its core.
Which of the following functions is part of external respiration?
the movement of CO2 from blood draining from peripheral tissues into air to be expired
the transport of O2 in the blood
the transport of O2 in the blood supplying peripheral tissues
the movement of CO2 from peripheral tissues into the blood
the expulsion of air carrying CO2 during expiration
the movement of CO2 from blood draining from peripheral tissues into air to be expired
How much O2 does a 70 Kg normal man use at rest?
280 ml/min
40 ml/min
4 ml/min
94 ml/min
90 ml/min
280 ml/min
Pulmonary Ventilation
Pulmonary Ventilation involves the cyclical movement of air with a relatively high concentration of O2 into the lungs during inspiration and the expulsion of air carrying elevated levels of CO2 during expiration.
External Respiration
External Respiration is the transfer of the O2 in inspired air to blood supplying peripheral tissues and the removal of CO2 from blood draining from peripheral tissues into air destined to be expired.
Gas Transport
Gas transport is the transport of O2 in the blood supplying peripheral tissues and CO2 draining from peripheral tissues
Internal respiration
Internal respiration is the delivery of O2 to cells of peripheral tissues and the removal of CO2 from these cells by gas exchange.
oxygen utilisation at different levels of physical activity
Humans at rest use O2 at approximately 4ml/min/Kg of body weight. During strenuous exercise this can increase to 40ml/min/kg in untrained subjects and up to 90ml/min/Kg in elite athletes.
Major parts of the nasal cavity and their function
- pseudostratified epithelium - secretes viscous mucus - prevents hazardous particles reaching lower airways
- ciliated epithelial cells - pushes mucus and embedded particulate matter back into pharynx
- hairs (vibrissae) protruding down into airflow - trap larger particles
- specialised sensory epithelium (olfactory mucosa) located on the superior surface that contains specialised chemoreceptors - detect odours in inspired air and responsible for sense of smell
- extensive network of blood vessels - warms the inspired air and thereby prevents harmful cold air reaching the body core
Understand the relationship between the nasal and oral cavities and understand the functional significance of the latter in breathing.
During strenuous activity, the mouth and oral cavity become an additional conduit for inspired air. Due to their larger diameter, represents a lower resistance pathway than the nose and nasal cavity and therefore are used when larger volumes of gas exchange are required. However the inspired air reaching the pharynx through the oral cavity is not filtered, humidified or warmed to the same level.
Pharynx and its 3 major compartments and their function
Nasopharynx: The region located immediately behind the nasal cavity, which normally acts as conduit for air.
Oropharynx: The region located behind the oral cavity and continuous with the nasopharynx, which acts as a conduit for both air and foodstuffs.
Laryngopharynx: This is the most inferior compartment of the pharynx, which connects the oropharynx with the larynx.
Larynx and its functional significance
A complex structure made up of 9 distinct pieces of cartilage and it physically connects the pharynx to both the oesophagus and trachea. It is easily palpatable on the anterior surface of your neck. The larynx performs 3 important functions:
- Controls the movement of air into and out of the trachea during breathing
- Ensures that food is directed into the oesophagus (not trachea) during swallowing
- Contains the vocal cords and is therefore responsible for sound production
Be able to describe the structure of the trachea and understand the functional significance of the C-shaped cartilaginous rings and the pseudostratified epithelium.
Relatively long (12cm in adults) thick (2.5cm in diameter) cartilaginous tube that links the larynx with the bronchial tree of the lungs.
Consists of 16-20 C-shaped cartilaginous rings that are linked by connective tissue.
The open face of the rings is on the posterior surface adjacent to the oesophagus and is sealed by a smooth muscle layer.
Functional attributes:
- The C-shaped cartilages prevent the trachea from collapsing and blocking airflow
- The intermittent nature of the cartilage rings allows a great deal of flexibility that does not restrict head movements or changes in length of the trachea that accompany inspiration and expiration
- The smooth muscle layer permits the oesophagus to protrude into the trachea during swallowing. This would not be possible if the tracheal cartilages were continuous.
Like the nasal cavity, the trachea is lined by a layer of _________ ______ which secretes a ____ _____ that inhaled particles adhere to. This prevents these particles reaching and thereby blocking the lower airways. The epithelial cells are _____ and activity of these pushes the mucus and embedded particulate matter back up into the _____- where it is swallowed and digested. This process is termed ______ ______.
pseudostratified epithelium
viscous mucus
ciliated
pharynx
mucociliary clearance
Components of the ventral body cavity. The walls of the ______ _____ are formed by the ____ ____ and its associated muscles. The base of the thoracic cavity is formed by the _____, which also separates it from the other component of the ventral body cavity, the __________ ______. The thoracic cavity contains a number of vital organs such as the _____, ______ and major _______ _____. The _____ passes through the thoracic cavity, as it extends from the _____ to the _______. Plays a important role in _________ ________.
thoracic cavity
rib cage
diaphragm
abdominopelvic cavity
lungs
heart
blood vessels
oesophagus
pharynx
stomach
pulmonary ventilation
the primary organs of the respiratory system and together they fill the majority of the space in the thoracic cavity not occupied by the heart.
lungs
the most significant features of the lungs and the volume it occupies
the small air-sacs termed alveoli where gas exchange between the air in the lungs and blood occurs. Although the lungs only occupy a volume of around 5-7 litres the large number of alveoli provide a surface areas for gas exchange of over 80m2.
the relationship between the pleurae, the lungs, the wall of the thoracic cavity and the pleural cavity.
lungs are wrapped in a double-layered continuous sheet of connective tissue know as pleurae:
outer layer - parietal pleura
fluid-filled cavity between outer and inner layers - pleural cavity
inner layer - visceral pleura
pleural cavity: the fluid-filled cavity between layers of pleura allows the lungs to move smoothly over the ______ ____ during inspiration and expiration. However separation of these 2 layers is prevented by ______ _____. Consequently the lungs normally follow the walls of the thoracic cavity as the _____ of the thoracic cavity changes during inspiration and expiration.
thoracic wall
surface tension
volume
a major constituent of the lung volume and mass
bronchial tract
the function of the bronchial tract and how it is formed
to transport air in the trachea to and from the alveoli where gas exchange with the blood can take place. The bronchial tract is formed by the progressive branching of the airways. Each level of branching is referred to as a generation with the left and right bronchi (that supply the left and right lungs respectively) being the first generation.
as the _______ of the bronchi _____ (i.e. as the generation number ________) the amount of cartilage, mucus-secreting cells and cilia gradually _______ while the relative amount of smooth muscle in the airway wall ______.
diameter
decreases
increases
decreases
increases
conducting zone
generation 4 (cartilage disappears and airways now less than 1mm in diameter are known as bronchioles) -> generation 16 (less than 0.5mm in diameter and known as terminal bronchioles)
no gas exchange is possible and so this portion of the bronchial tract is the conducting zone
respiratory zone
generation 17 (a few alveoli begin to appear on the bronchiole and known as respiratory bronchiole) -> generation 20 (alveolar ducts) -> generation 23 (alveolar sacs made up of alveoli)
As gas exchange takes place in each of these successive generations, the region from generation ~17 to the alveoli is collectively referred to as the respiratory zone
Pulmonary arteries containing ________ blood from the _____ ventricle. These arteries enter into each lung adjacent to the ______ ______ and branch extensively along with the bronchial tract. Eventually these form a complex network of ______ that surround the alveoli and other elements of the respiratory zone. These capillaries are only __-__ microns in diameter so red blood cells are only just able to pass through them and come in close proximity to the respiratory airways as they do so. As a consequence of gas exchange within the respiratory zone, the blood in these capillaries becomes ______ and is returned to the heart through the _________ ____.
deoxygenated
right
primary bronchi
capillaries
8 -10
oxygenated
pulmonary veins
Bronchial arteries containing _______ blood from the ______ ventricle of the heart. These arteries also branch extensively along with the _______ _____ but provide oxygenated blood to the ______ airways and associated tissues so that they can continue to perform the oxidative metabolism that is required for them to function. Blood from the bronchial capillary networks supplying the upper airways leaves the lungs through the _______ ____. However blood from the bronchial capillaries supplying the lower airways leaves the lungs along with the _______ blood in the __________ ____.
oxygenated
left
bronchial tree
conducting
bronchial veins
oxygenated
pulmonary veins
the innervation of the lungs and the functional significance of the autonomic system
The bronchi and bronchioles are innervated by the parasympathetic and (to a lesser extent) the sympathetic division of the ANS.
parasympathetic
bronchioles - constriction
pulmonary capillaries - dilation
mucus secretion - increased
sympathetic
bronchioles - relaxation
pulmonary capillaries - constriction
mucus secretion - decreased
the innervation of the lungs and the functional significance of the somatosensory system
The lungs contain a number of different classes of primary sensory neurones that provide the central nervous system with information about the status of the airways:
○ Stretch receptors that detect the degree of stretching of the lungs during inspiration
○ Irritant receptors that detect chemicals and irritants that could damage the lungs and initiate the cough reflex to expel them
○ Nociceptors that detect pain associated with the pleurae
Pulmonary ventilation
Pulmonary ventilation refers to the movement of air into the lungs during inspiration and the movement of air out of the lungs during expiration.
The lungs are relatively passive entities. They are not themselves able to produce the pressure changes required to move air into and out of the alveoli where gas exchange occurs. The changes in lung volume associated with breathing are entirely dependent upon the lungs being contained within the sealed thoracic cavity.
Due to the close relationship between the wall of the thoracic cavity and the lungs changing the volume of the thoracic cavity produces the pressure changes in the lungs that are responsible for moving air into and out of the lungs during inspiration and expiration respectively.
Boyle’s law
Boyle’s law is a gas law, stating that the pressure and volume of a gas have an inverse relationship
volume changes that take place in the lungs during inspiration
During quiet breathing, inspiration is produced by an increase in thoracic cavity volume due primarily by the contraction of the diaphragm. The diaphragm is a skeletal muscle that forms the base of the thoracic cavity and when relaxed is dome-shaped. When the diaphragm contracts it flattens, pulls down the curved surface and consequently the volume of the thoracic cavity increases. Due to the resultant pressure changes in the lung this increase in thoracic cavity volume causes air to flow into the lungs.
During physical exertion, the increase in oxygen demands are met by increasing the volume of inspiration by the recruitment of muscles in addition to the diaphragm. The external intercostal muscles (located between the ribs) act to lift the rib cage and separate the ribs. Together with an increased force of contraction of the diaphragm this increases the volume of the thoracic cavity further.
volume changes that take place in the lungs during exspiration
During quiet breathing, expiration is a passive process (there is no requirement for the contraction of any muscles). Relaxation of the diaphragm together with the inherent elasticity of the chest wall and lungs causes the thoracic cavity to decrease in volume. Due to the resultant pressure changes, air flows out of the lungs.
During exercise however expiration becomes an active process. The internal intercostal muscles (another set of muscles positioned between the ribs) contract and pull the ribs closer together. In addition the abdominal muscles contract and push the liver and other visceral organs up towards the diaphragm. Collectively these movements cause a reduction in the volume of the thoracic cavity and produce a forced expiration.
the significance of the negative intrapleural pressure and the consequences of a pneumothorax
- pressure inside pleural cavity at rest is slightly lower than atmospheric pressure
- the pleural space is a partial vaccuum - if connected to the atmosphere, air would move into it
- in humans, intrapleural pressure is around 5cm H2O below atmospheric pressure (-5 cm H2O) at rest
- consequence of 3 phenomena
1. elastic recoil of the lungs
2. tendency of the chest wall to expand
3. high surface tension produced by the pleural fluid in the pleural cavity
The lungs and thoracic wall are constantly trying to _____ _____ from each other but this is prevented by the _______ _______ created by the _____ ______. The net effect is a _____ pressure which keeps the lungs _____ and ensures that changes in _______ _______ volume are followed by changes in the volume of the _____.
pull away
surface tension
pleural fluid
negative
inflated
thoracic cavity
lungs
pressure changes that take place during inspiration
- onset, volume of the thoracic cavity increases & intrapleural pressure begins to decrease ( more -) and the lungs expand in attempt to reduce pressure
- pulmonary pressure decreases, now lower than atmosphere
- air flows into lungs
- once pulmonary pressure is equal, no longer a pressure gradient, air stops moving in
pressure changes that take place during expiration
- thoracic cavity decreases, intrapleural pressure increases from -10cm H2O to -5 cm H2O
- lungs recoil and decrease in volume
- pulmonary pressure increases, now higher than atmospheric pressure
- there is a pressure gradient that forces air out of the lungs -> expiration
Jean Poiseuille was a ____ physician who died in ___. As part of his studies into blood flow he found that the rate of ____ was dependent upon the ________ and ______ of the tube and the ______ difference between the ends.
French
1869
flow
diameter
length
pressure
Poiseuille’s Law significance for airway resistance
- Air flowing through airways encounters resistance
- the law indicates that this resistance is directly proportional to the radius^4
- means airflow is very sensitive to minor changes in airway diameter
- majority of the total resistance to airflow occurs in the middle of the bronchial tract -> gen 8 - due to the nose, mouth, pharynx and larynx have larger diameter and offer very little resistance
- although the bronchioles and terminal bronchioles have high resistance, there are so many that they contribute little to overall airway resistance
- these smaller airways do not have cartilage, therefore can expand as lungs do during inspiration - this expansion increases their diameter & decreases contribution to resistance
- therefore, highest resistance to airflow occurs in the medium sized bronchioles, being highest at gen 7
the impact of the autonomic nervous system on airway resistance
- parasympathetic division of the ANS contracts smooth muscle layer and decreases the diameter of the airways, termed bronchoconstriction
- noradrenaline and adrenaline from the sympathetic division increase the diameter, termed bronchodilation, which decreases resistance and increases airflow
consequences of asthma or a chest infection on airflow
The diameter of the airways is severely decreased during an asthma attack, by the elevated levels of mucus that are secreted during a chest infection or the presence of foreign bodies
explain the concept of lung compliance and understand how ageing and cystic fibrosis can impact upon it
- compliance describes the distensibility of the lungs during inspiration
- lungs of healthy, young adults distend relatively easily during inspiration and so have relatively high compliance - low levels of muscular force and small pressure changes required to inflate lungs
- ## compliance decreased in cystic fibrosis, as a consequence of ageing, following blockage of airways and result of changes in surface tension of the alveoli - lungs need more muscular force and larger pressure changes to inflate
what is surfactant, where does it come from and its functional significance.
The fluid that covers the alveoli has a special detergent-like lipoprotein known as surfactant, which is synthesised by Type II alveolar cells and dramatically decreases the surface tension of the alveoli. It’s important because:
- the pressure required to stop the alveoli collapsing is reduced
- the pressure required to inflate the alveoli during inspiration is much smaller
- the increased compliance means that less energy is required for inspiration
Define external respiration
the mechanism by which O2 and CO2 are exchanged between the air in the alveoli and blood in the pulmonary capillaries
alveoli are the microscopic ______ ____ that are attached to the ____ of ________ _____ and _______ ____. The diameter of each alveolus varies from __ to ____ microns depending upon the level of lung _____.
air-filled sacs
walls
respiratory bronchioles
alveolar ducts
75
300
inflation
3 types of cells associated with alveoli
Type I cells
Type II cells
Alveolar macrophages
structure and function of Type I cells
form 90% of the surface area of the walls of each alveolus. These are thin and flat squamous epithelial cells supported by a thin basal lamina.
structure and function of Type II cells
- cuboidal in shape and found in clusters adjacent to Type I cells
- approx same no. as type I cells, they only form a small portion of the alveolar surface area
- synthesis and secrete surfactant
structure and function alveolar macrophages
- move freely around the inner surface of alveoli and between alveoli
- find and phagocytose large no.s of particles and micro organisms that find their into the alveoli with each inspiration
- beating of cilia sweep particles back up through airways to be swallowed or expectorated
Closely associated with the ____ surface of each alveolus is a complex network of _________ _______. Often these capillaries will be located between two adjacent _____ and as the ___ _____ ___ flowing through these capillaries have a diameter of only __-__ microns they are only just able to pass through the capillaries.
In a healthy subject at rest, red blood cells are typically in close apposition to the alveoli for a short period of time (~____ ms), but this is typically sufficent time for adequate ___ _____ to occur.
outer
bronchial capillaries
alveoli
red blood cells
8 -10
750
gas exchange
Bronchial capillaries are lined with a _____ layer of ______ _____ cells (endothelium) and are supported by a thin _____ _____.
The only _____ between air in the alveoli and the blood flowing through the pulmonary capillaries are the ___ layers of squamous epithelial cells and their (fused) basal lamina. In most instances this barrier is only ___ – to __ microns thick. This is what is referred to functionally as the _______ ______.
single
squamous epithelial
basal lamina
barriers
two
0.15 – to 0.3
respiratory membrane
Dalton’s Law
states that the total pressure of any gas mixture is the sum of the pressure of each gas in the mixture if it were present on its own in the same. Therefore if we know the composition of a gas mixture and the pressure of the mixture we can easily calculate the concentration of each gas in the mixture. The concentration of each gas in the mixture is referred to as its partial pressure and clearly if the composition of the gas changes or the atmospheric pressure changes then the partial pressure of the gas changes.
Henry’s Law
- blood is not a gas but need to calculate how much gas is present to understand the driving forces for diffusion
- the law states that when a gas is in contact with the surface of a liquid, the amount of the gas which will go into solution is proportional to the partial pressure of that gas and the solubility of the gas in the solution
- V = s.P
- The solubility of gases varies quite significantly and is usually quantified by its solubility coefficient
- The solubility coefficient of a number of gases (at 37 oC) are:
N2, 0.015 ml/LmmHg
O2, 0.030 ml/LmmHg
CO2, 0.680 ml/LmmHg
if oxygen is present at a partial pressure of 80 mmHg, calculate the amount of oxygen dissolved in the 1 litre of solution using the formula ( V = s.P) and the solubility coefficient for O2 (0.030 ml/LmmHg)
V = 0.03 ml/LmmHg * 80 mmHg
V = 2.4 ml/L
define partial pressure
The concentration of each gas in the mixture is referred to as its partial pressure and if the composition of the gas changes or the atmospheric pressure changes then the partial pressure of the gas changes.
the driving forces and mechanisms that are responsible for the movement of O2 from the alveoli into the blood and CO2 from the blood into the alveoli
External Respiration - the mechanism by which gas exchange between the air in the alveoli and blood in the pulmonary capillaries occurs by simple diffusion through the respiratory membrane.
- partial pressures of O2 and CO2 within the alveoli are quantitatively different from those of inspired air because:
- alveoli contain a mix of inspired and expired air because the lungs are not completely emptied and refilled during inspiration/expiration
- air is humidified as it flows through the airways so the concentration of water vapour increases
External Respiration:
______ blood flowing into the lungs through the ________ ______ has a PO2 of __mmHg and a PCO2 of __mmHg. If we compare these values with the partial pressures of the same gases in the alveoli we see large concentration gradients in the directions of the diffusion of O2 (___ mmHg) from the alveoli into the blood and CO2 (__ mmHg) from the blood into the alveoli.
These concentration gradients together with the ___ lipid solubility of O2 and CO2 and the fact that the respiratory membrane is only ____ - to ___ microns thick, means that ___ diffuses from the alveoli into the blood and ___ diffuses from the blood into the alveoli.
Deoxygenated
pulmonary arteries
40
45
104
40
high
0.15
0.3
O2
CO2
External Respiration:
Gas exchange is complete when __ and ___ reach _______ (normally within ____ ms) and as a result of _______ _______ of the blood leaving the lungs in the pulmonary ____ has a high PO2 of ___mmHg and low PCO2 of __mmHg.
O2
CO2
equilibrium
250
external respiration
veins
104
40
the driving forces and mechanisms responsible for internal respiration
Internal Respiration - The mechanism by which O2 and CO2 are exchanged between the blood in peripheral capillaries and the tissues they supply. Like external respiration, the driving force for gas exchange is the concentration gradient of O2 and CO2 and the movement is mediated by simple diffusion.
Internal Respiration:
Blood that has been ______ in the lungs has a PO2 of ___mmHg and a PCO2 of __mmHg. Peripheral tissues are continuously utilising O2 for ______ ______ and are generating ___ as a result. Consequently the PO2 of metabolically _____ tissues is usually _____ than 40 mmHg and the PCO2 _______ than 45mmHg.
These concentration gradients, together with the ____ lipid solubility of the gas, are all that are required to drive O2 into the cells of _____ and _____ CO2 from these cells.
oxygenated
104
40
oxidative metabolism
CO2
active
lower
higher
high
tissues
remove
Internal Respiration:
Gas exchange is complete when O2 and CO2 reach _____ and consequently the blood coming from peripheral tissues and flowing back towards the heart in the ____ ______ has a PO2 of __mmHg and a PCO2 of __mmHg.
equilibrium
venous circulation
40
45
the two mechanisms by which oxygen is transported in the blood and the different carrying capacities of each
- dissolved in plasma - 1.5%
- bound to haemoglobin - 98.5%
functional significance of haemoglobin in oxygen transport and the impact that oxygen binding has on the affinity of haemoglobin for oxygen
- haemoglobin - oxygen-binding protein contained in red blood cells (erythrocytes)
- consists of 4 polypeptide chains each of which has a nitrogen-containing pigment molecule known as a heme group at its core - each heme has a ferrous iron atom at its core - each Fe2+ can bind one molecule of O2 in a reversible fashion - when 02 is bound to haemoglobin, referred to as oxyhaemoglobin (HbO2) and in its unbound state is known as deoxyhaemoglobin (HHb)
reversible reaction of O2 binding to haemoglobin formula
HHb + O2 <-> Hb02 + H+
what is meant by the oxygen-haemoglobin dissociation curve and its physiological significance
- after the 1st O2 molecule has bound to haemoglobin there is conformational change in the haemoglobin that increases its affinity for the next O2 molecule
- as 2nd O2 molecule binds, affinity increases for the 3rd, and so on
- similarly, as oxyheamoglobin dissociates when the local PO2 starts to decline, the progressive loss of each O2 molecule induces a conformational change that progressively decreases the affinity for the remaining O2
During quiet breathing, inspiration is brought about entirely by the contraction of the diaphragm and expiration by relaxation of the diaphragm and elastic recoil of the chest wall and lungs.
During increased breathing activity, contraction of the external intercostal muscles assists with inspiration and contraction of the internal intercostal and abdominal muscles enables forced expiration.
All of these muscles are skeletal (voluntary) muscles which means that they have no intrinsic rhythm and consequently rely on their associated motoneurons to control the timing and force of their contractions.
three mechanisms by which carbon dioxide is transported in the blood and the different carrying capacities of each
- dissolved in plasma - 7-10%
- bound to haemoglobin - 20-30%
- bicarbonate ions - 60-70%
The partial pressure of CO2 leaving peripheral tissues by way of the venous circulation is __ mmHg.
45
the partial pressure of O2 leaving the lungs in the pulmonary capillaries is ___ mmHg
104
Carbon dioxide transport:
Dissolved in plasma
Compared with O2, CO2 has a relatively high solubility coefficient.
Carbon dioxide transport:
Bound to haemoglobin
CO2 is also able to enter red blood cells and bind reversibly to haemoglobin. The resultant complex is known as carbaminohaemoglobin (HbCO2) and the reaction can be written: Haemoglobin + CO2 <-> HbCO2
During quiet breathing, _______ is brought about entirely by the _________ of the ________ and _______ by _______ of the _______ and elastic recoil of the ______ ____ and _____.
During ________ breathing activity, contraction of the _______ _______ muscles assists with _____ and contraction of the _________ _______ and abdominal muscles enables forced _______.
All of these muscles are skeletal (_________) muscles which means that they have no ______ rhythm and consequently rely on their associated __________ to control the timing and force of their contractions.
inspiration
contraction
diaphragm
expiration
relaxation
diaphragm
chest wall
lungs
increased
external intercostal
inspiration
internal intercostal
expiration
voluntary
intrinsic
motoneurones
two groups of neurones within the medulla oblongata that are thought to be responsible for the basic rhythm of breathing
dorsal respiratory group & ventral respiratory group
the dorsal respiratory group
- location
- fire a burst of AP prior to?
- these neurones are directly coupled to?
- are thought to provide? and consequently referred to as?
- originally it was believed that?
- However more recent studies have revealed?
- medulla oblongata
- inspiration
- motoneurons that innervate the diaphragm and external intercostal muscles
- the basic rhythm of inspiration and consequently functionally it is referred to as the inspiratory centre
- pacemaker neurones were responsible for the basic inspiratory rhythm
- the presence of neural networks within the DRG where the rhythmicity is a product of the connectivity between neurones in the circuit. These types of circuits are known as endogenous oscillators.
the ventral respiratory group
- a much more?
- the role of which?
- it is known that it receives?
- neurones make synaptic contact with?
- other neurones contact the?
- a final group of neurones has been shown to make?
- complex network of neurones
- controlling ventilation is still incompletely understood
- synaptic input from neurones in the DRG so is presumably modulated by the inspiratory centre
- the motoneurones innervating the diaphragm and external intercostal suggesting that (like the DRG) it also plays a role in inspiration
- motoneurones of the internal intercostal and abdominal muscles and are thought to be involved in controlling these muscles during forced expiration
- synaptic contact with the motoneurones of the muscles of the upper airways and could be involved in maximising the diameter of these during inspiration and reducing airway resistance
the sites in the pons that inhibit the medullary respiratory centres have been referred to as the
pneumotaxic centre
The site that excites the medulla have been called the
apneustic centre
Numerous sites both inside and outside the ____ modulate the basic _______ generated by the ________ respiratory centres in the way that the pneumotaxic and apneustic centres have been postulated to.
pons
rhythm
medullary
