Respiratory Flashcards
What makes up the respiratory pump?
Collection of thorax, muscle, nerves, airways and pleura involved in respiration
What muscles are involved in inspiration?
- Diaphragm
- External intercostal
When are accessory muscles used in respiration and name some
During laboured breathing i.e. asthma attack or exercise.
- Scalene muscle: In neck, lifts ribs.
- Sternocleidomastoid muscle: Sternum and clavicle to mastoid process, lifts ribs
- Trapezius: In shoulders, pulls scapula to expand thorax
Describe inspiration
- Diaphragm contracts and moves down
- External intercostal muscles contract to lift rib cage
- Causes increase volume so decrease in pressure
- Pleural cavity decreases in pressure, increasing transpulmonary pressure
- When alveolar pressure < atmospheric pressure, air moves into lungs
Describe expiration
- Passive process due to lungs’ elasticity
- Diaphragm and external intercostal muscles relax, diaphragm moves up, rib cage moves back down
- Causes decrease in volume so increase in pressure of thorax
- Pressure increases in pleural cavity, so decreases in tranpulmonary.
- When alveolar pressure > atmospheric pressure, air moves out of lungs.
Which nerves are involved in respiration?
- Motor:
Phrenic (C3, 4, 5) for diaphragm
Thoracolumbar nerve roots for external intercostal
Describe the pleura of the lungs
- Parietal pleura on outside
- Visceral pleura on inside
- Pleural cavity filled with fluid in between
Describe the role of the pleura in respiration
- Lubrication for smooth movement when expanding/relaxing
- Decrease pressure in inspiration to increase transpulmonary pressure
- Increase pressure in expiration to decrease transpulmonary pressure
What respiratory sensors are in the pons?
Pneumotaxic centre, apneustic centre
What respiratory sensors are in the medulla?
Dorsal respiratory groups and ventral respiratory groups
What is the role of the pneumotaxic centre?
Inhibits apneustic centre to promote expiration
What is the role of the apneustic centre?
Stimulates DRG
What is the role of the dorsal respiratory groups?
Fires in bursts to cause respiratory muscle contraction. When stops = passive expiration
What is the role of the ventral respiratory groups?
Active in forced breathing. Initially stimulated when DRG activates accessory muscles, then VRG takes over at this point.
What do peripheral chemoreceptors respond to?
- Hypoxia (decreased pO2)
- Hypercapnia (increased pCO2)
- Some detect pH of blood
What are the sensors in the upper airway and where are they found?
- Nose, nasopharynx, larynx: Chemo and mechanoreceptors
- Pharynx: Receptors activated by swallowing (to stop respiration)
Where are slowly adapting stretch receptors (SASR) found?
Smooth muscle of airways
What are slowly adapting stretch receptors (SASR) activated by?
Lung distension
What is the response of slowly adapting stretch receptors (SASR) when activated?
Inhibition of respiration
Where are rapidly adapting stretch receptors (RASR) found?
Between airway epithelial cells
What are rapidly adapting stretch receptors (RASR) activated by?
- Lung distension
- Irritants
What is the response of rapidly adapting stretch receptors (RASR) when activated?
Bronchoconstriction
What are C fibres J receptors activated by?
Increase in interstitial fluid
What response do C fibres J receptors have when activated?
- Rapid, shallow breathing
- Bronchoconstriction
What has a larger effect on respiratory drive?
- pCO2
Describe gas exchange at alveoli
- O2 rich air is breathed in and travels down to alveoli
- O2 from alveoli diffuses into blood of capillaries surrounding alveoli (as this blood has low O2 conc.)
- CO2 from blood diffuses into alveoli (as they have a low CO2 conc.) to be expired
What are the 7 layers the oxygen must pass through?
- Alveolar epithelium
- Interstitial fluid
- Capillary endothelium
- Plasma layer in capillary blood flow
- RBC membrane
- RBC cytoplasm
- Hb binding site
What is perfusion?
Blood supply to the lungs
What is a V/Q mismatch?
Perfusion of blood in capillaries doesn’t match ventilation of alveoli
What is anatomical dead space?
Volume of inhaled air that doesn’t reach alveoli before expiration
What is physiological dead space?
Volume of inhaled air which does not undergo exchange due to a V/Q mismatch meaning alveoli are too poorly perfused
What does the steep drop on the oxygen dissociation curve mean?
That a small drop if pO2 means a large amount of O2 can be unloaded from Hb for respiring tissue
What causes the oxygen dissociation curve to shift right?
Increased temperature or pH
What causes the oxygen dissociation curve to shift left?
Decreased temperature or pH
What does it mean if the oxygen dissociation curve shifts left?
Tighter binding so less readily dissociates
What does it mean if the oxygen dissociation curve shifts right?
Decreased affinity for O2, so dissociates more readily
What is Bohr’s Law?
An increase in pH/[H+] will cause an oxygen dissociation curve to shift to the right and therefore have a decreased affinity for O2, so dissociates more readily.
What is Boyle’s Law?
Pressure of a gas in a closed container is inversely proportional to the container’s volume. P1V1 = P2V2
What is Dalton’s Law?
Each gas in a mixture exerts its own force, as if the other gasses were not present.
P(total) = P1 + P2 + P3 etc
What is Henry’s Law?
The amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas when at equilibrium with the liquid
What is Laplace’s Law?
P = 2T/r
Where P = Pressure
T = Surface tension
r = Radius
of an alveolus
What is surface tension and where is it present?
Molecules at the surface of a liquid adhere closely together to form a ‘film’. Present on surface of alveoli.
Where is surfactant produced?
By type 2 pneumocytes (alveolar cella)
List 3 roles of surfactant?
- Reduce surface tension of alveoli to prevent collapse during expiration.
- Reduce surface tension to prevent air moving from smaller to larger alveoli (Laplace’s Law)
- Reduce surface tension to increase compliance of lungs (as can expand more easily)
What is the acid/base dissociation equation?
CO2 + H2O H2CO3 HCO3- + H+
What is the Henderson-Hasselbalch equation when applied to the blood?
pH = 6.1 + log ([HCO3-]/0.03*pCO2)
What must the ratio in the Henderson-Hasselbalch equation be equal to and why? What happens if it is not?
Must be equal to 1.3 to maintain optimum blood pH of 7.4. If changes = acidosis or alkalosis
What is hypoxia? List 2 causes.
Oxygen deficiency. Caused by V/Q mismatch or hypoventilation.
What is hypercapnia? List 3 causes.
Elevated CO2 levels. Caused by V/Q mismatch or increased CO2 production, hypoventilation.
What is peak expiratory flow (PEF)?
The maximum airflow that can be achieved during forced expiration
What is forced expiratory volume (FEV1)?
The maximum amount of air that can be forcibly expired within a second.
What is total lung capacity?
Total volume of air the lungs can hold.
What is vital capacity?
The maximum volume of air the can be expired after maximal inspiration.
What is functional residual capacity?
The volume of air remaining in lungs after passive expiration
What is expiratory reserve volume?
The additional volume of air that can be forcibly expired after tidal volume.
What is inspiratory reserve volume?
The additional volume of air that can be forcibly drawn in to lungs after normal tidal volume.
What is tidal volume?
The volume of air expired during passive expiration or taken in during normal inspiration.
What is residual volume?
The amount of air which will always remain in lungs, even after maximal expiration.
What is airway obstruction?
Impediment to inspiratory/ expiratory flow
What is airway restriction?
Diminished lung capacity (lungs restricted from full expansion)
What changes occur in an ageing lung?
- Decreased elastic recoil, compliance, immune function and gaseous exchange.
- Decreased response to hypoxia and hypercapnia
What additional changes occur at birth other than those mentioned in CV?
- Fluid forced out of lungs by birthing process
- Adrenaline increases surfactant production and so decrease in surface tension
- O2 is inhaled causing vasodilation of pulmonary arteries
Compare systemic and pulmonary arteries
Systemic - Thinner walls and minor muscularisation
Pulmonary - Thicker walls and significant muscularisation
What does O2 act as in systemic vessels?
Vasoconstrictor
What does O2 act as in pulmonary vessels?
Vasodilator
What does CO2 act as in systemic vessels?
Vasodilator
What does CO2 act as in pulmonary vessels?
Vasoconstrictor
Name another common vasodilator
Nitric oxide (NO)
What is hypersensitivity?
An undesirable reaction produced by the immune system.
Describe a type 1 hypersensitivity reaction
- Antigens interact with IgE bound to mast cells
- Histamine is released
- Leads to: capillary dilation, bronchonstriction, mucus secretion, itching etc
If there is a type 1 hypersensitivity reaction all over the body, what is this known as?
Anaphalaxis
What is the significance of Laplace’s Law?
Smaller alveoli = Greater pressure.
So air will move from smaller to larger alveoli, causing the smaller ones to collapse
What is intrinsic tone of the airways regulated by?
Parasympathetic nervous system
Describe the action of sympathetic nerves on airways
- Noradrenaline binds to Beta-2 adrenergic receptors
- Causes bronchodilation
- These are G-protein coupled
Describe the action of parasympathetic nerves on airways
- Acetylcholine binds to muscarinic M3 receptors
- Causes bronchoconstriction
- These are G-protein coupled
What are the 2 types of cholingeric receptors and what type of receptor complex do they form?
- Nicotinic: lignad-gated
- Muscarinic: G-protein coupled
What are the 2 types of adrenergic receptors and what type of receptor complex do they form?
- Alpha: G-protein coupled
- Beta: G-protein coupled
What is a shunt in terms of a V/Q mismatch?
When the alveoli are well perfused, but too poorly ventilated for gas exchange.
What nerve supplies the parasympathetic outflow in the lung?
Vagus
What nerve supplies the sympathetic outflow in the lung?
Sympathetic trunk
Describe hypoxic pulmonary constriction
When small arterioles constrict in low O2 levels to divert blood to areas of high O2, to avoid a V/Q mismatch
List the 3 ways in which CO2 is carried in blood
- Bound to Hb
- Dissolved in plasma
- As HCO3-
What does Pa mean?
arterial partial pressure
What does PA mean?
Alveolar partial pressure
What does PIO2 mean?
Partial pressure of inspired oxygen
What is the alveolar gas equation?
PAO2 = PiO2 - (PaCO2/R)
R = Respiratory quotient
Outline the process of acute inflammation and summarise its action
- Pathogen/tissue injury
- Vasodilation - exudate plasma (including antibodies)
- Biochemical cascade activated
- Migration of neutrophils
- Immediate onset, short lived, is resolved
Outline the process of chronic inflammation and summarise its action
- Persistent acute inflammation/ non-degradable pathogen
- Mononucleate cells migrate
- Delayed onset, lasts months/years, results in fibrosis/necrosis etc
Describe neutrophil function
1 - Receptors 2 - Activation 3 - Adhesion (by integrins) 4 - Migration 5 - Phagocytosis 6 - Kill bacteria (ROS/elastase etc)
What does necrosis result in?
Inflammation
What does apoptosis result in?
Phagocytosis
List 4 non-immune hot defence mechanisms
1 - Epithelial barriers
2 - Mucus
3 - Mucociliary escalator
4 - Coughing
What is the mucociliary escalator?
Cilia beat in directional waves to move mucus up the airways
Outline the process of coughing
- Lots of air inspired
- Epiglottis and vocal cords shut tightly to trap air in lungs
- Diaphragm and internal intercostal muscles contract - cause increase in pressure and so tracheal narrowing
- Epiglottis and vocal cords suddenly open wide.
- Pressure difference and tracheal narrowing: air expired and high flow rate.
What normally happens to airway epithelium after injury and why? What is it called when this goes wrong?
- Repair due to their plasticity.
- When this goes wrong, leads to pulmonary diseases
Describe the role of B lymphocytes in adaptive immunity
- Pathogenic cell recognised as non-self
- Antigen presentation
- Clonal selection
- Clonal expansion
- Copies differentiate into:
Memory B cells, plasma cells
What is the role of plasma cells?
Produce specific antibodies
Describe the role of T lymphocytes in adaptive immunity
- Virus leaves non-self antigens on surface of cell it has invaded.
- Clonal selection
- Clonal expansion
- Copies differentiate into:
Cytotoxic cells, helper T cells
What do helper T cells do?
Aid activation of cytotoxic cells and plasma cells by use of cytokines. Express CD4.
Where do B cells mature and migrate to?
Mature in bone marrow, move to spleen and lymph nodes.
Where do T cells mature?
Thymus
What happens during antigen presentation?
Cell ingests pathogen and displays its antigens using MHC
What are the 5 functions of adaptive immune response?
1 - Diversity - react to many pathogens 2 - Self-tolerance 3 - Recognition of pathogens 4 - Effector functions - elimination of pathogens 5 - Immunological memory
What is the significance of Boyle’s Law?
Relates to breathing mechanism - when volume of lungs/thorax increases during inspiration, pressure decreases.
What is the significance of Dalton’s Law?
Air will always have the same relative concentrations regardless of whether it is atmospheric or in the lungs etc.
What is the significance of Henry’s Law?
Implies that the amount of oxygen dissolving in the bloodstream (via capillaries) in proportional to the amount of oxygen in the air in alveoli.
Define type 1 respiratory failure
Hypoxia with no hypercapnia
Define type 2 respiratory failure
Both hypoxia and hypercapnia
Define forced vital capacity (FVC)
The maximum amount of air that can be expired after maximal inspiration, usually in 6 seconds.
How do you calculate FEV1%?
FEV1/FVC
What does an FEV1% of less than 70% indicate?
Airways obstruction
What are pattern recongnition receptors? What is their purpose?
- Part of innate immune system
- Recognise either PAMPs (pathogen-associated molecular patterns) or DAMPs (damage-associated molecular patterns)
- Allow us to recognise pathogens never seen before
Describe the Gells and Coombs classification of hypersensitivity
Type 1: Allergy - IgE mediated
Type 2: Cytotoxic - Ig bound to cell surface antigen
Type 3: Immune complex formed
Type 4: Delayed-response - mediated by T-cells
What are affinity and efficacy?
Affinity - Ability of drug to bind to receptor
Efficacy - Ability to illicit a response after binding
What is an antagonist?
Has affinity but no efficacy. Block agonists.
What is an agonist?
Has affinity and efficacy, binds to receptor and can illicit a response.
Why is it useful that increased pH and temperature shift the oxygen dissociation curve to the right?
Because more metabolically active tissues have a higher pH and temperature, and shifting the curve to the right means more oxygen is unloaded, which is needed by the tissue.
What does a low FVC always indicates?
Airway restriction
What is the rhythm generator?
Pacemaker cells which set the basal respiratory rate
