Respiration Flashcards
What is compliance?
C= change in volume/ change in pressure
Measure of elasticity, low in pulmonary fibrosis, high in emphysema
What are special properties of the fluid lining the lungs?
Pulmonary surfactant- reduced surface tension in the alveoli
What mechanical factors affect airway resistance?
- Mucus secretion
- Constriction of the bronchiolar smooth muscle
- Oedema of bronchiolar tissue
- Lung volume
What chemical factors affect airway resistance?
Endogenous= histamine, serotonin, catecholamines Exogenous= sterioids, irritant chemicals
What chemical factors affect airway resistance?
Endogenous= histamine, serotonin, catecholamines Exogenous= steroids, irritant chemicals,sympathomimetics
What happens to the external and internal intercostal muscles, ribs, diaphragm and volume of the thorax before inspiration occurs?
EIs contract, IIs relax Ribs pulled upwards and outwards Diaphragm contracts Volume of thorax increases Atmospheric pressure is greater than intrapulmonary pressure
What happens to the external and internal intercostals muscles, ribs, diaphragm and volume of the thorax before expiration occurs?
EIs relax, IIs contract Ribs pulled inwards and downwards Diaphragm relaxes Volume of thorax decreases Intrapulmonary pressure is greater than atmospheric pressure
Which 2 factors cause intrapleural pressure to always be negative?
- Elasticity of the lungs- lungs pull away from thoracic wall
- Elasticity of thoracic wall- wall tends to pull away from lungs
What are the inflation factors which need to be overcome for inspiration to occur?
- Elastic recoil of lung tissue
- Surface tension in alveoli
- Airways resistance
What is pulmonary surfactant?
Surfactant produced by type 2 pneumocytes which lowers surface tension- making alveoli stable against collapse
What are characteristics of emphysema?
- Chronic overinflation of the alveoli
- Airways are flimsy and less able to resist collapse
- Elasticity of lungs impaired
- Obstructive pulmonary disease
What is airflow?
Airflow is proportional to the pressure gradient and inversely proportional to resistance
What are the main characteristics of the 3 flow types
- Laminar
- uniform speed and direction - Turbulent
- irregular currents and vortices develop - Transitional flow
- high number of bifurcations disrupt flow, creating eddies (swirling)
What determines the type of flow?
The Reynolds number
Re smaller than 1000= laminar
Re greater than 1500= turbulent
As you move towards the alveoli what happens to the:
- Total cross sectional area
- Reynolds number
- Velocity of air
- Ventilation
- Perfusion
- Increases
- Decreases
- Decreases
- Increases
- Increases
What type of disease is asthma?
Obstructive disease (atropic and non-atropic triggers)
What are 2 characteristics of an asthmatics spirometry reading
Decreased FEV1
Unaltered FVC
What causes asthma? (in regards to theN.S)
Increased parasympathetic activity
dysfunctional M2 receptors
causes an increase in basal tone and muscular constriction in response to irritants
What are the 3 general treatments of asthma?
1.B2 adrenergic agonists- short term= salbutamol long term= salmeterol 2.Anticholinergics block the effect of Ach e.g tiotropium bromide 3.Glucocorticoids anti inflammatory actions
What does parasympathetic control of respiration involve?
Ach released from vagus nerve
M3 activation-> Gq pathway-> muscular contraction
Ach that binds to M2-> inhibits further release of Ach- NEGATIVE FEEDBACK
What does sympathetic control of respiration cause?
NA released
B2 adrenoreceptors-> activation of Gs pathway->relaxation
What generates the basic respiratory rhythm?
Centres in the medulla
What does the dorsal respiratory group control?
Quiet inspiration
What does the ventral respiratory group control?
Forced inspiration and expiration
Where does the medulla get inputs from?
PONS, vagus nerve etc.
What does the pneumotaxic centre of the PONS do?
Increases the rate of breathing by shortening inspirations
What does the apneustic centre of the PONS do?
Increases the depth and decreases the rate of breathing by prolonging inspirations
What is the name of the reflex which gives the medulla information about the inflation of the lungs
Hering-Breur reflex
How do the stretch receptors in the lung decrease the rate of inspiration?
They signal to the vagus nerve-> vagus nerve inhibits inspiratory centres-> inspiratory centre signals via phrenic nerve-> affects diaphragm
What is the main stimulus for peripheral chemoreceptors?
Hypoxia
What is the main stimulus for central chemoreceptors?
Hypercapnia
What does cranial nerve 12 supply?
The chest and diaphragm
What does activity in the cranial nerve 12 match?
Activity in the pre-botzinger complex (cluster of neurons in the VRG)
What are the 3 types of breathing?
- Eupnea
- Sigh
- Gasp- with the help of the PONS
What are the 2 p.b.c cell types?
- Pacemaker
2. Non-pacemaker
What two types of activity do pacemaker cells demonstrate?
Bursting= summation of A.Ps, linked to contraction of muscles Spiking= basic rhythm
What pathway stimulates smooth muscle contraction?
Gq pathway
- Gq alpha subunit stimulated-> activates phospholipase C
- PLC cleaves PIP2 (phospholipid) releasing DAG and then IP3
- Dag stimulates PKC- stimulates Cav channels in membrane- calcium into cell- MLCphosphatase is inhibited
- IP3 is released into the cytosol, binds to IP3 receptors(in the E.R)-> opening calcium channels
- Calcium binds to calmodulin
- Calcium-calmodulin complex interacts and activates MLCK -> muscle contraction
What pathway stimulates smooth muscle relaxation?
Gs pathway
- Activated Gs subunit (by GTP binding) stimulates adenylate cyclase
- Adenylate cyclase catalyses the conversion of ATP to cAMP
- cAMP stimulates PKA
- PKA phosphorylates IP3 receptors (and MLCK)- reducing their sensitivity to IP3 binding
- MLCK inhibited= muscle relaxation
What is the Gi pathway?
Pathway that inhibits muscle relaxation
Gi inhibits adenylate cyclase and thus the production of cAMP
Opposes the Gs pathway
What occurs in the PBC?
Primary site of rhythm generation
