Respiratory Flashcards
(146 cards)
1
Q
What is the overview pathway of the respiration system from nasal cavity
A
Into the nasal cavity, pharnyx, Larynx, Trachea and then in to left and right bronchi into lots of tubes called bronchioles and then to the respiratory bronchioles, alveolar ducts + sacs and then alveoli.
2
Q
What is the overall definition of respiration and the 3 places it takes place
A
Respiration is a general term for the transfer of gas (CO2 and O2) across a boundary/membrane/somewhere different.
3 places is external, internal and cellular
3
Q
Compare the 3 places that respiration takes place
A
External: transfer of gases from external atmosphere to blood through pulmonary capillaries
Internal: transfer of gases from blood to tissues and interstitial fluid via systemic capillaries
Cellular : where O2 is consumed and Co2 is produced
4
Q
What is Pulmonary Ventilation. How does it relate to ventilatory pump
A
The mechanical bulk movement of air in and out of the lungs. It uses the ventilatory pump= rib cage, associated muscles and diaphragm
5
Q
Compare the two functional classifications of the Respiratory system. What are they
A
Conducting zone: series of cavities, thick walled tubes that conduct air from the nasal cavity to the bronchioles. It warms, cleans and humidifies the air
The respiratory zone: is the tiny thinwalled airways where gas exchange occurs. (respiratory bronchioles -> alveoli)
6
Q
Upper vs lower RTract:
Where is a blockage of the respiratory tract worse.
Where is an infection worse
A
A blockage is worse in the upper conducting pathway because there are more branches in the lower tract.
Whereas an infection is better in the upper tract because the respiratory zone is much closer with blood supply and therefore can grow more easily/ get into the blood
7
Q
What are the anatomical/structural classification of the respiratory system.
A
Upper Respiratory tract : Nose ->larynx
Lower Respiratory tract: Trachea- alveoli
8
Q
What is the three ‘stops’ where oxygen bus goes from outside to inside the body and CO2 goes from inside to outside
A
First stop - ventilatory pump as air
2nd stop- Left cardiac pump (in blood)
3rd stop- Cells in tissue where CO2 is produced.
Co2 then goes to Right cardiac pump and then back to the ventilatory pump
9
Q
What is the overall purpose of the nasal cavity
A
Prepares the air for gas exchange by making it
Warm the air to 37’
Clean - filtering
Wet - humidify (100% saturated)
10
Q
What features of the nasal cavity help to filter the air
A
Vibrissae -coarse hairs filter big particles
Respiratory epithelium mucous
Seromucus gland close to the entrance of nose
11
Q
What features of the nasal cavity help to humidify the air
A
Respiratory epithelium mucous helps to transfer moisture to dry air
Seromucus gland close to the entrance of nose
12
Q
What features of the nasal cavity help to warm the air
A
Rich blood supply underneath the epithelium that is vasodilated and close to the surface to allow heat exchange
13
Q
What are Turbinates (bones) structure and function
A
3 conchae of the lateral nasal cavity wall (sup, mid, inf) that increase the SA of the nasal cavity. It slows the air and causes turbulence. This allows the air to slow down for filtering, warming and humidifying.
14
Q
What is the movement of mucocillary escalator in the respiratory epithelium - where is it moving things
A
The cillia move the mucus layer on top in a concerted mexican wave towards the throat
15
Q
What is the structure and function of the paranasal sinuses
A
They are cavities behind the lateral nasal cavity walls connected by little holes make your head light and provide a resonance and tone to your voice.
16
Q
What are the 3 parts of the pharynx and what is the difference between then
A
Nasopharynx which connects the Nasal cavity.
Oropharynx that connects the oral cavity
Laryngopharynx that connects the larynx and throat.
17
Q
How is food kept out of the airway
A
When we swallow, the nasopharynx is closed by the soft palate which pushes the food down into the posterior eosophagus. The bolus of food passively pushes the epiglottis, a flap of elastic cartilage covered in epithelium closed over the air way. Then springs back after food gone
18
Q
What are the generations of branches of bronchi that are part of the conducting zone
A
Main stem bronchi
Lobar bronchi
Segmental bronchi
4-9 Smaller bronchi
10-15 Bronchioles
16-19 Terminal bronchioles
19
Q
What are the generations of branches of bronchi that are part of the respiratory zone
A
20-23 Respiratory bronchi (where air is clean)
24-27 Alveolar ducts
28 Alveolar sacs
20
Q
Describe the main features of the Trachea:
A
Its tube as thick as your thumb anterior to the chest. It has a stiff C shaped rings of cartilage with the posterior ends connected by trachealis muscle.
It is lined with the respiratory epithelium that has mucocilary escalator towards the nasopharynx.
21
Q
Where does the oesophagus sit in relation to the trachea
A
It is dorsal to the trachea lying on the trachealis.
22
Q
What are main trends in the diameter, epithelia as you continue branching into 2 from bronchus/trachea to bronchioles further
A
The diameter reduces. The complexity of the cells decrease (less conditioning needed)
The epithelia height reduces in the form of going from pseudostratified columnar to cuboidal to squamous because we need to have thin cell layer for gas diffusion to be good.
23
Q
What are the layers within the bronchus wall from air to before the alveoli
A
Pseudostratified cillated columnar epithelium + goblet cells
Smooth muscle layer
Mucous glands
Cartilage plates
24
Q
What are the two sources of mucus in the trachea and bronchus
A
Goblet cells and mucous glands
25
What are the layers within the bronchioles wall from air to before the alveoli
Simple cilliated columnar/cuboidal epithelium + club cells
Smooth muscle
26
Are the alveoli part of the bronchus/bronchiole wall?
No
27
What are the main differences between the structure of bronchus walls vs bronchiole walls
Bronchus still air conditioning whereas Bronchioles not really so Bronchus has 2 places for mucous but Bronchioles have club cells that secrete a watery secretion that helps with hydration and antimicrobial enzymes
In bronchus smooth muscle layer doesn’t rlly keep it open bc it has cartilage to do that, but in Bronchioles It doesn’t have Cartilage so smooth muscle layer is important for bronchodilation/constriction and controlling air to respiratory zone
28
What is the mechanism of acute asthma attack and how is it treated
Triggered by heat, pollen, dust etc there is rapid bronchoconstriction which reduces airflow to respiratory zone. Treated with bronchodilators which relax smooth muscle (salbutamol)
29
Describe the 3 structures of the respiratory zone
The respiratory bronchioles that have same wall structure as other bronchioles but have small buds of alveoli where gas exchange can take place
Alveolar ducts: tubes formed by alveoli
Alveolar sacs: bunch of alveoli that extend from one branch
30
Describe the cells in the alveolar wall
Type 1. Squamous pneumocyte, thin bordering with capillaries for gas exchange
Type 2: Surfactant cells: secrete surfactant liquid which keeps the alveolar open
Type 3: Alveolar Macrophage: wandering cell, last line of defense against microbes
31
What is the importance of surfactant in alveolus and how does it relate to Work of breathing
Surfactant prevents the collapse of the alveolus on expiration by decreasing surface tension. Made of phospholipid that repels each other. This reduces the work of breathing
32
What is work of breathing
the energy required to get air in (inspire) and inflate the structures
33
Identify what constitutes a diffusion barrier - also called Blood air barrier (0.5 um)
It has squamous pneumocyte facing the air space. The basement membrane of Sq. pnu. is fused with the basement membrane of capillary endothelium to make it uniquely
Then there is the capillary endothelium that opens to blood plasma
34
What type of respiration takes place at the diffusion barrier and what type of disease can affect it
External respiration. Fibrosis increases the connective tissue in the basement membrane layer which increases distance for diffusion and therefore can lead to hypoxic blood.
35
What are the main subdivisions of the lung and what bronchi supply them
There is a right lung and left lung supplied by 1’ bronchi
There are 2 left lobes and 3 right lobes supplied by 2’ bronchi
There are 8 left segments on the left and 10 segments on the right. Each supplied with its own 3’ bronchi and blood supply.
36
What covers the blood vessels, lymphatic fluid and air supply to the segments of the lung
connective tissue
37
What is the clinical significance of lung segments
Surgeons can remove localised tumours in the lung within 1 or 2 segments without excessive leakage of blood or air from other segments
38
What is the structure of the pleurae
The visceral pleura covers each lung and the parietal pleura covers the thoracic cavity. The place where the ends join is at the hilum. This is filled with a pleural space with a thin layer of pleura fluid.
39
What is the function of the pleurae
The pleural fluid allows the pleurae to slide past each other without friction. It also prevents the two layers from being separated, allowing the movements of the thoracic wall and diaphragm to affect the volume in the lungs.
40
What is the mechanics of the muscles that help inspiration
In inspiration the external intercostal muscles contract and the diaphragm contracts.
External intercostal muscles causes inspiration because as they contract the ribs pivot around their joints in the vertebral column and lift the rib cage up and out.
When Diaphragm contracts, it flattens the central tendon which pulls the dome downwards and increases the volume of the thorax
41
What are the mechanics of the muscles that help expiration
Expiration is a passive process at rest where diaphragm passively relax and rib cage returns to resting position. In active processes the internal intercostal muscles (at right angles to external intercostal muscles) contract and drag the rib in and down.
42
What is the ratio of intercostal muscles to diaphragm with rest breathing vs exercise breathing
At rest, movement of the ribcage is 25% and diaphragm is 75%, however in exercise the ribcage contributes more to exercise
43
Describe the structure of the diaphragm: shape and components
Dome shaped platform that has a central part of thin connective tissue (aponeurosis) callled central tendon and lateral margins of skeletal muscle attaching to the sternum and vertebrae.
44
Define respiration
To extract oxygen fro the air and together with the cardiovascular system transport it to respiring tissues
2. To remove carbon dioxide from respiring tissues and exhaust into the atmosphere
45
As respiration evolved from diffusion in protozoa, to lungs in reptiles and mammals what were the main factors that drove the change
There was increase in the size of the tissue, therefore distance for diffusion increased.
Increase metabolic rate means more gas needed
46
List the main muscles associated with breathing and their nervous innervation
Diaphragm is innervated by phrenic nerve which comes from phrenic motor nucleus (C3-C5)
-The internal (exp) and external (insp) intercostal muscles are innervated by the internal and external intercostal nerves that come from the intercostal motor neurones (T1-L1)
-The abdominal muscles are innervated by the abdominal nerve which comes from the abdominal motor neurones (T7-L1)
47
Where do the nerves that innervate the muscles for breathing go to from the spinal cord
These motor neurons are excited by the brainstem (medulla oblongata +pons) which makes a neural rhythm to control expiration and inspiration to occur not at the same time. However there is the ability to voluntarily adjust breathing
48
When are the abdominal muscles involved breathing
During active expiration. (eg cough, laugh, exercise) Doesn’t contract at rest.
49
What is the intra pleural pressure vs the intra pulmonary pressure
The intra pleural pressure is the pressure inside the pleural cavity outside the lung and the intra pulmonary pressure is the pressure within the lung, within the respiratory zone
50
How does the respiratory volume , intra pulmonary pressure and intra pleural pressure change during inspiration
The pleural pressure decreases from a negative pressure to an even more negative pressure. This causes the intra pulmonary pressure to go from atm down to negative pressure. This causes air to move from higher pressure (atm) to lower pressure, increasing volume of air in lungs. As volume increase to a peak the pulmonary pressure rises back up to atm (in a cup shape) .
51
How does the respiratory volume , intra pulmonary pressure and intra pleural pressure change during expiration
The intra pleural pressure starts to rise from its most negative point back to becoming less negative as air leaves. This causes the pulmonary pressure to become more positive relative to atm. This means that air moves out so the volume decreases from the peak of the bell curve back down to 0.
52
Why is it important for the pleural cavity to have a negative pressure in regards
This means that the visceral and parietal membranes stick together joining the chest wall to the lungs. This means that the lung doesn’t collapse
53
What is Pneumothorax
Thoracic puncture wound where air rushes into the chest and there is a loss of the negative pressure of the pleura. The lung moves away from the chest wall and deflates and its hard to maintain those changes in pressure to inflate the lungs
54
How does the lungs inflate
As the diaphragm and intercostal muscles contract they increase the volume of the intra pleural space and this also increase the volume of the intra pulmonary space This means that the pressure of the intra pleural space decreases. As a result the atm tries to equalise the pressure by pushing air inside the lungs.
55
How is lung volume measured
With spirometer where the oxygen volume in a floating drum (floating in water) is attached to a tube to breathe into means that while breathing you can push the drum up and down and measure the volume
56
What is the difference between a respiratory volume and capacity
Volume is measured whereas capacity is calculated from the measured values
57
What is the tidal volume
This is the normal resting volume that comes in when you breath (peak to trough)
58
What is the inspiratory reserve volume vs the expiratory reserve volume
Inspiratory reserve is the maximum volume that can be inhaled after the peak of the normal tidal breath. Whereas expiratory reserve is the maximum volume that can be expired after the expiration of a tidal breath
59
What is the residual volume
The volume of air left in lungs after maximum effort exhaling because its trapped underneath collapsed air ways due to expiration forces. It cannot be blown out
60
Compare the inspiratory capacity and the functional residual capacity
Inspiratory capacity is tidal volume + inspiratory reserve volume
Functional residual capacity is the expiratory reserve volume and the residual volume. Thisi also known as the resting point of the lung before the next breathing in
61
What is the vital capacity
Expiratory reserve volume + inspiratory capacity. This the total volume of air that can be inhaled and exhaled.
62
What is Total lung capacity and what parts are measurable
The vital capacity (can measure) + residual volume (can’t measure).
63
What is minute ventilation
This is the respiratory volume over a certain time. (Time derivative)
=the number of tidal respiratory cycles over time (minute) (frequency) x the tidal volume.
64
What is hyperventilation vs hypoventilation
Breathing greater than 6L/min is hyperventilation and Breathing less than 6L/min is hypoventilation
65
What is alveolar ventilation, how calculated and why important
This is the rate of ventilation within the respiratory zone -> actually contributing to respiration.
Va = minute ventilation - dead space ventilation (the air inside the conducting zone (2.2mL/kg/ 0.15 L)
66
How is special residual volume measured
An inert gas that doesn’t enter the blood (eg Helium) is put inside the drum of spirometer instead of oxygen. It is allowed to equilibrate inside the person and therefore C1V2 = C2 (V1 +V2) can be used to find V2 = total lung capacity which can be used to calculate residual volume.
67
How is lung health found from vitalographs
It measures the rate at which you can blow out a maximum expiratory volume. The forced expiratory volume in 1 second is compared to the forced vital capacity (total amount of air you can blow out). If there is a ratio of 80% then healthy
68
What would be the ratio % of the FEV1 to FVC for an asthmatic
It is more difficult to breathe out as more resistance. You cannot blow out as much and not as fast so both FEV1 and FVC would be small
69
What is the passive force behind expiration and what 2 things contribute to it
Recoil force causes expiration. Elasticity of the lungs and surface tension in the lungs.
70
What is elasticity of the lung and what is an example of high elasticity and low
Elasticity is the ability to recover original size and shape after deformation.
High elasticity is associated with coming back to its original shape fast -> double balloons
71
How is elasticity of the lungs generated
The parenchyma tissue surround the alveoli contain elastin and collagen which form a network of springs around the tubes which stretches during inspiration. In expiration is relaxes again during radial traction
72
What is compliance and its relationship with elasticity
Compliance measures how easy it is to stretch something. It is the change in volume / change in pressure. Compliance is opposite to elasticity. If something is more stiff-> more elastic-> but less compliant
73
What is surface tension and how does it contribute to the recoil force
Surface tension is the enhancement of intermolecular attractive forces for molecules at the liquid gas interface
74
What is laplaces law and how does it relate to surface tension
Pressure needed of air to inflate an alveolus is proportional to 2 x the surface tension of surfactant divided by the radius of the alveolus (spherical)
75
Explain the consequences of chronic obstructive pulmonary disease (COPD) to ventilation on lung compliance
COPD-> has degradation of lung tissue resulting in loose elastin. As a result, it has a large change in volume over a small change in pressure. Therefore it has increased compliance so overinflates-> inflated at rest so decreases capacity
76
Explain the consequences of Fibrosis to ventilation on lung compliance
Fibrosis is due to air contaminates causing an increase in collagen fibres= stiff lung. Only a small change in volume over large change in pressure. Therefore it has decreased compliance. This means it can’t get enough air with same amount of pressure
77
Compare the shape of the lungs, size of the midsternal space and other factors of COPD and Fibrosis
COPD has massively expanded lungs whereas Fibrosis has deflated lungs.
COPD has reduced midsternal space whereas Fibrosis has wide midsternal space
COPD has flattened diaphragm.
Fibrosis has fibrotic tissue
78
Describe the respiratory airway tree
There is the trachea and the bronchi and then 3 lobes on the right and 2 lobes on the left, covered in parenchyma
79
What is the funnel effect
The inverse relationship between the resistance of the air and the amount of flow. As well as the inverse relationship between the resistance and cross sectional area
80
What is the funnel effect in the conducting zone (esp 1’ Bronchi)
The resistance is highest as lowest cross sectional area. As a result has lowest amount of air but highest pressure so fast + turbulent speed
81
What is the funnel effect in the respiratory zone (esp Alveolar duct)
The resistance is lowest as the cross sectional area is greatest. As a result it has highest amount of air but pressure is lower so slow + laminar speed. (allow time for gas exchange)
82
What is the funnel effect in the respiratory zone (esp Alveolar duct)
The resistance is lowest as the cross sectional area is greatest. As a result it has highest amount of air but pressure is lower so slow + laminar speed. (allow time for gas exchange)
83
As you inflate the lungs from residual volume-> functional residual cap-> total lung cap what happens to the airway resistance
The airway resistance decreases because of radial traction where the diameter of the airway increases as the parenchyma is stretched open
84
Describe the ANS control of Airway smooth muscle associated with Parasympathetic Nerves : type of nerve, receptor, result
It goes from vagus nerve (cranial nerve) to Muscarinic receptor. Causes bronchoconstriction
85
Describe the ANS control of Airway smooth muscle associated with Sympathetic Nerves : type of nerve, receptor, result
It goes from spinal cord to beta adrenoreceptors using noradrenaline messenger. Causes bronchodilation
86
How is asthma treated
In asthma there is a huge increase in airway resistance so salbutymol (an beta-adrenoagonist) is taken to dilate the airway smooth muscle and reduce resistance
87
Describe the Hering-Breuer Inflation reflex : Afferent to efferent
Lung stretch receptors (mechanoreceptors in the bronchioles) go through Vagal afferents to the Medulla Oblongata respiratory centres to tell it that it is inflated.
Medulla Oblongata respiratory centre tells the Bronchioles to bronchodilate + beta adreno receptor to help more inflation.
Also terminates inspiration
88
Why is the pulmonary circulation a low pressure system
The heart is working as 2 pumps, pumping the same volume per minute. However the left side of the heart supplying the systemic circuit has to pump blood across larger distance so generates higher pressures compared to right side of heart.
89
What is sheet flow
Capillaries are so dense that their walls touch each other.
The side walls of two adjoining capillaries (arteriole and venule) have erroded away to form a flat sheet held up by pillars of interstitial tissue to allow greater SA contact of Blood with Alveoli membrane.
90
What is vessel distension
decrease in pulmonary resistance
91
How do you measure mean pressure, and why is it measured that way.
MAP= Diastolic pressure + (1/3 (Diastolic-Systolic pressure).
Bc as a pulsatile pump heart spends more time in diastole than systole
92
What is Pulmonary Hypoxic vasoconstriction
This is caused by a restriction in airway to alveoli which means that air takes the path of least resistance. This causes that alveoli to become hypoxic and this causes a local vasocontriction around the blood vessels going to the hypoxic alveoli, directing blood flow to not go there where there isn’t much O2
93
What are the differences in hypoxia in the Arterial circulation vs Pulmonary circulation
What are the differences in hypoxia in the Arterial circulation vs Pulmonary circulation
94
How can you measure the distribution of blood flow up and down the lung
A
Inject an aqueous solution of 133Xe intravenously. The radiation counters can be placed along the chest wall. the amount of radiation will reflect how much blood is flowing through the lung per time
95
What is the difference in blood flow in the top part, middle part and bottom part of lung (upright, resting condition)
In the top, there is not much blood flow because of there is not enough pressure from the heart to push against gravity,
In the middle, there is starting to have some blood flow because there is enough pressure to driving the blood.
At bottom: there is lots of blood flow. This better perfused and better ventilated
96
What is the difference between the PA (alveolar pressure), Pa (artery pressure) and Pv (venous pressure) in the top, middle and bottom of the lung
In the top: PA>Pa>Pv
Therefore the PA squashes down the artery and vein so no blood flows through
In Middle: Pa>PA>Pv
The pressure in arteries is now greater than PA so the vessel can open
At Bottom: Pa>Pv>PA
The alveoli pressure is lowest compared to Pa and Pv
97
Which part of the lung has the most O2 before taking another breath
The top because the blood flow is poor so much of the O2 it had before hasn’t been taken away yet
98
What is perfusion (Q)
The amount of blood going to lungs -> cardiac output: SV * HR
99
What is the ideal ventilation- perfusion ratio (V:Q) and what is it in real life
If we had uniform perfusion and ventilation across the lung, V:Q would be 1 but actually its 0.85 due to uneven blood flow across the lung
100
How do you find ventilation for ventilation perfusion ratio
Minute ventilation: Vt*f
Then Alveoli minute ventilation: (Vt -Deadspace)*f
101
What is pulmonary hypertension and how does it affect ventilation
This is failure of the right heart which leads to hypoxia in the lungs which leads to vasoconstriction
102
What are the Factors regulating the movement of Gas across the respiratory surface (alveolar membrane) (from alveoli to blood)
Area of the lungs
Thickness of alveolar membrane
Partial pressure differential across tissue of the gases
involved (O2 and CO2)
Solubility of gas in blood
Molecular weight in gas
103
How does Area help regulate movement of gas across the respiratory surface
Lots of small alveoli are packed into the same area to increase SA to huge area which increases gas exchange.
104
How does Thickness of tissue help regulate movement of gas across the respiratory surface
Small distance for diffusion increases rate of gas exchange. There is a thickness of only 0.5 um tissue thickness between air and blood.
105
How does Partial pressures of gas help regulate movement of gas across the respiratory surface
The pressure difference for O2 to go to the blood is 60 so big driving force and the pressure difference for CO2 to go from the blood to air is 6 so small driving force
106
What is the limitation of rate of O2 and N2O you can uptake across the alveoli membrane
The amount of O2 you can take up is dependent on blood flow (perfusion) which is proportional to rate of uptake because the rate of diffusion is very quick so the Haemoglobin is already saturated pretty quick
107
How does solubility of gas in blood and molecular weight of gas affect movement of gas across respiratory surface
Solubility more important than MWt of gas.
CO2 is 25x more soluble than O2 in blood (so quicker get into the blood) but CO2 is released from haemoglobin slower than O2 so this balances the movement of gases across the alveolar membrane
108
What are the two pulmonary circulations
1st is to the alveoli to collect oxygen,
2nd is to the tracheobronchial tree.
109
Describe the path of the Tracheobronchial tree circulation: receives, feeds, drains
The tracheobronchial tree receives blood from the systemic circuit as its artery comes from the aorta and this feeds the trachea bronchi and bronchioles. It drains by two veins, one going back to the right side of the heart for reoxygenation and the other an anatomical shunt into the left side of the heart, contaminating the freshly oxygenated blood.
110
Compare the pressure in the pul. artery, pul. capillaries and left atrium
~22 from the Pul. Artery, still pulsatile but dampening as vessels get smaller
~6 at Pul. Capillaries and now smooth laminar flow
~4 at Left Atrium so overall nice pressure gradient is maintained
111
Compare the relationship between pressure and resistance in the Pulmonary circuit and the Systemic circuit. What accounts for this difference.
In the Systemic circuit, if the resistance decreases, then the pressure will decrease
However in the pulmonary circuit, if the resistance if the resistance decreases the pressure will increase.
This is because an increase in pressure will cause distension and recruitment of capillaries which ends up reducing resistance
112
What is pulmonary Oedema caused by specifically
left heart failure causing congestion in the pulmonary veins as it can’t bail out the blood, therefore increasing the pressure and leading to fluid leaking out and breathlessness (dyspnoea).
113
How is the diffusion of a volume of gas affected by lung area, gas density, (pressure differential) and thickness of the alveolar membrane
Diffusion is proportional to lung area, gas density, and (pressure differential)
and Inversely proportional to thickness of the alveolar membrane
114
What is the limitation of rate of CO you can uptake across the alveoli membrane
The rate that it is uptaken in the blood is diffusion limited by its really long time to diffuse and bind the haemoglobin but that means that its hard to get off.
115
Where is haemoglobin blood.
It is kept in a RBC, because it can be concentrated without affecting viscosity of the blood.
116
What are the ways that O2 is transported in blood and which is the majority
Binds with haemoglobin (majority)
2. Dissolves in solution
117
How does haemoglobin molecule bind O2
Haemoglobin has an 4 x a and B polypeptide chains containing a haem (fe2+) moiety in a chain.
The binding of O2 has cooperative allosteric effect where it twists the haem moiety to make next site more exposed to O2 for binding. (Speeds up as more O2 binds)
118
What does the Oxygen dissociation curve tell us about the binding of haemoglobin. What are the main features of the graph
Main features :
% oxygen saturation: (4 O2 = 100%) on the y. and partial pressure of O2 on the x.
There is a sigmoidal relationship due to cooperative binding
119
In the systemic veins, what is the PO2 and what does this mean for saturation of Haem compared to when its in the systemic arteries.
In Systemic veins the PO2 is low: 40 mmHg. This means that Haem has less affinity to take up O2. This encourages release
In the Systemic arteries/ alveoli
PO2 is high: 100 mmHG.
This means haem has higher affinity for binding O2.
This encourages O2 uptake
120
Why does Hb Affinity for O2 change as you go from Lungs to Veins
The tissues are more acidic because there is more CO2 going to Carbonic acid-> H+. This means that Hb has less affinity.
Whereas at lungs there is less CO2, so higher pH and O2 and is taken up and its max affinity restored.
121
What is the ratio of Carbon dioxide transported as bicarbonate in the plasma vs in red blood cells.
Where does the majority of bicarbonate come from in plasma vs RBC
70% transported in plasma to 30% RBC
Majority of the bicarbonate in plasma (60%) has originated from the RBC by help of enzyme then diffused out.
Majority in RBC (20%) is the rapidly forming bicarbonate
122
What is the difference between saturation and content of oxygen in blood
Saturation refers to the amount of O2 that the Hb can carry (1-4). It is not affected by volume of blood.
However the content of oxygen in the blood is affected by the amount of Hb present (volume of blood) and the saturation of that Hb as well.
123
What is the Bohr shift and what causes it
This is a shift in the oxygen dissociation curve to the right, meaning that Hb’s affinity for O2 is reduced for the same PO2, therefore promoting O2 release.
This is caused by increased metabolism products (at tissues)
: CO2, [H+] DPG, temperature.
124
What is the “opposite” Bohr shift and what causes it
This is a shift of the oxygen disassociation curve to the left, meaning the affinity for O2 is increased for the same PO2.
It is caused by : Decreased CO2, [H+], temperature, DPG. By making the Haem hs a higher affinity for O2. This sigmoidal relationship is moving depends on location of RBC
125
What shift does Fetal haemoglobin have on the oxygen dissociation curve and why is this important
Shift is to the left because it has higher affinity per PO2. This is important to help move O2 across the placenta from the mother’s haemoglobin to the foetus.
126
What shift does Myoglobin have on the oxygen dissociation curve and why is this important
It has big shift to the left, meaning that it has high affinity for O2 over a large range of PO2 and it only rlly dissociates when PO2 is really low so its a good storage of O2 for muscle.
127
What are the ways that CO2 is transported in blood - by most to least
Transported mainly in HCO3- (bicarbonate)
Combines to amine groups (on the heme molecule)
CO2 is dissolved in solution
Transported as H2CO3 and Co3- ions
(CO2 20x more soluble than O2 in blood )
128
How bicarbonate formed and what is the difference between rapidly and slowly forming.
CO2 + H2O is the limiting step -> forming carbonic acid which dissociates into bicarbonate and H+.
Rate limiting step makes rapid with carbonic anhydrase (in RBC) or slow without it.
129
How does CO2 associate with amine groups on Hb
CO2 + R-NH2 -> R- NHCOO- + H+
Amine group loses an H to let COO join on.
130
What determines whether O2 is being taken up and CO2 being released by RBC or versa
The concentration of H+ which changes Hbs affinity for O2.
131
What is the chloride shift
During the process of CO2 entering the RBC to be converted to Bicarbonate, Chloride shift is how Cl- moves in the opposite direction to bicarbonate ion(-) as it moves in or out of RBC to maintain the electroneutrality.
132
How does Haemoglobin help to make a buffer in RBCs
Haemoglobins bind to H+ produced by the carbonic acid to stop the pH increasing and in doing so, reduces its affinity for O2, leading to release of O2.
133
What is the Haldane effect
This is the difference between the affinity of Hb for transporting CO2 in the venous blood vs the arterial blood.
There is an increase in Hb affinity for CO2 in venous blood which enhances the uptake of CO2 from tissues. Compared to PO2, if there is lower PO2 there will be a greater Hb affinity for CO2
134
Compare Hypoxia to Anoxia and Asphyxia
Hypoxia: low levels of O2
Anoxia: No O2
Asphyxia: Deprived of O2
135
How does blood gas levels control the rate and depth of breathing
Chemoreceptors detect the levels of gas (O2 and CO2) in the blood and send signals to the brain to control breathing
136
What 7 things stimulates peripheral chemoreceptors?
Hypoxia
Hypercapnia
combo of 1&2
Haemorrhage
Acidosis
Increased sympathetic activity
NaCn -> mimics removal of O2 by switching off ETC
137
Compare the response time of the peripheral chemoreceptors
vs central chemoreceptors
Peripheral has fast response time: within a breath
Central: has slow response time because the rate of producing H+ from CO2 is slow in CSF because not many carbonic anhydrase: `30 s
138
What stimulates central chemoreceptors to stimulate breathing
Increase of CO2 in the brain capillaries, is detected by nerves in the medulla oblongata by CO2 crossing the blood brain barrier into the Cerebrospinal fluid.
and forming bicarbonate (with limited carbonic anhydrase present compared to in RBC). The H+ ions from this reaction in the cerebrospinal fluid stimulate the central chemoreceptors in the medulla
139
Describe the main stages of the ventilatory response to Hypoxia (stimulated by addition of N2 to inhaled gas)
(peripheral chemoreceptors only)
As the PO2 is decreased, ventilation will reach 1. peak ventilatory response then
Depression in ventilation because in order to conserve O2 brainstem neural activity is reduced-> slowing of breathing
Apnoea: where there is last attempt to get O2 through gasp to auto resuscitate.
140
Describe features of the Ventilatory response to Hypercapnia. (both receptors) What contribution does receptors do
With only slight increase in PCO2 there is a very steep increase in minute ventilation.
Central does 80%, Peripheral 20%
141
What keeps you breathing through sleep
Central chemoreceptors provide a stimulus to breath and they are sensitive to CO2. This is Ondine curse.
142
The partial pressure of a gas (O2, CO2) is higher when the concentration of the gas in the blood is:
Why
higher. Ie PO2 is higher in the arteries than veins.
This is because the gas moves from a place of higher pressure to low pressure
143
What are the main features of the CO2 dissociation curve
It has ml/ L blood of CO2 on the y and PCO2 on the x.
The curve depends on the PCO2 and is linear over the physiological range, there is no measure of saturation as CO@ is very soluble in plasma.
144
What is hyper and hypo. What is capnia and ventilate
Hyper: high
Hypo: low
Capnia: CO2
Ventilate: breathing
145
What is Apnoea vs Dyspnoea
Apnoea : no breathing
Dyspnoea: sensation of breathlessness
146
What is the location and projection of peripheral chemoreceptor vs central chemoreceptor
Peripheral: is located in the bifurcation of the carotid artery (carotid body).
Projection: Sinus nerve that joins with the glossopharyngeal 9th cranial nerve to the medulla
Central: 3 chemosensitive regions on the ventral surface of medulla oblongata.
