Receptors and autonomic regulation of airways

Question 1

Where are peripheral chemoreceptors located? In intimate with what?

Answer 1

High in the neck at the bifurcation of the common carotid arteries and on the aortic arch= carotid and aortic bodies.
Arterial blood

Question 2

Peripheral chemoreceptors are composed of specialised receptor cells stimulated by what? What cells are located here and on hypoxia do what? Provide synaptic input to what?

Answer 2

Decrease in arterial partial pressure of oxygen and increase in arterial H+ conc.
Released stored neurotransmitters that stimulate the carotid sinus nerve.
Medullary inspiratory neurons

Question 3

Peripheral chemoreceptors fire when O2 comes close to what value? Haemoglobin what % saturated? Also doesn’t occur when?

Answer 3

60mmHg. 90%.

With CO in the blood- does not affect amount of O2 dissolved in blood/ diffusion capacity of the lung.

Question 4

Where are central chemoreceptors located? Provide excitatory synaptic input to what? Stimulated by what?

Answer 4

In the medulla
The medullary inspiratory neurons
Increase in H+ conc of CSF in brain (CO2 diffuses readily and blood partial CO2 pressure can influence CSF pH enabling detection of H+ changes)

Question 5

Reflex mechanisms controlling ventilation prevent small increases in arterial partial CO2 pressure compared to what? Ventilatory drive extremely sensitive to what?

Answer 5

To a much greater degree than they prevent equivalent decrease in arterial partial O2 pressure
Changes in arterial partial CO2 pressure of blood entering brain

Question 6

Central chemoreceptors account for what % of increased ventilation?

Answer 6

70% compared to peripheral chemoreceptors

Question 7

The nose, nasopharynx and larynx contain what receptor types? Stimulation does what?

Answer 7

Chemo and mechanical receptors- some appear to sense and monitor flow.
Inhibit the medullary respiratory centre.

Question 8

Pharynx has receptors activated by what action? Respiratory activity stops when?

Answer 8

Swallowing

During swallowing to protect against risk of aspiration of food/liquid

Question 9

Where are parasympathetic ganglia located in relation to their targets? What about sympathetic ganglia?

Answer 9

Near to with short post-ganglionic nerves.

Near the spinal cord with longer post- ganglionic fibres.

Question 10

Bronchconstrictor response controlled by what NS?

Answer 10

Parasympathetic- vagus nerve neurons terminate in parasympathetic ganglia in airway wall

Question 11

Neurotransmitter in parasympathetic NS innervating vasculature, glands and airways in lungs? Interacts with what receptors?

Answer 11

ACh
Muscarinic (M3) cholinergic receptors on muscle to provide intrinsic muscle tone

Question 12

Neurotransmitter in sympathetic NS? Innervates lung via what? Innervates what?

Answer 12

Noradrenaline
Sympathetic trunk
Vasculature and glands- not the airways

Question 13

Noradrenaline is released where to? Releases what? Binds to what receptors on muscles of airways? Leads to what process?

Answer 13

Adrenal glands– adrenaline released from adrenal medulla– binds to beta-2-adrenareceptors– bronchodilator.

Question 14

Neurons releasing ACh called what? Degenerate in what disease?

Answer 14

Cholinergic receptors

Alzeimer’s disease

Question 15

Nicotinic receptor responds to what neurotransmitters? Stimulated by what NS? Found where? Has ligand-gated channel permeable to what ions?

Answer 15

ACh and nicotine
Para and sympathetic but mainly parasympathetic
In post-ganglionic neurons and neuro-muscular junction
Na+ and K+ ions- opening results in depolarisation

Question 16

Neurons that released Nad are called what?

Answer 16

Adrenergic receptors

Question 17

Drugs that inhibit bronchoconstriction blocks what receptor? Called what?Used in what conditions?

Answer 17

M3 receptor= anti-cholinergic/ anti-muscarinic.

Asthma and COPD

Question 18

Drugs acting as bronchodilators? Pros of LAMAs compared to ipratropium?

Answer 18

LAMAs and ipratropium- LAMAs more widely used, long duration, reduce acute attacks and regulates mucus production too.

Question 19

How does activation of beta-2 receptors on airway smooth muscle cause relaxation? Dip in what hormone in morning causes common asthma attacks?

Answer 19

Activates adenylate cyclase, raising cyclic AMP.

Cortisol

Question 20

What two drug types are beta-2 agonists and assist in bronchodilator? Given with what in asthma? Not given with steroids in what condition?

Answer 20

SABAs and LABAs (short-acting and long-acting beta-2 agonists)
Steroids
COPD

Question 21

What is affinity in relation to receptors? Shown by what 2 things?

Answer 21

The degree to which a particular messenger binds to its receptor.
Antagonists and agonists.

Question 22

What is efficacy? High efficacy agonist results in what? Low efficacy agonist results in what? Antagonist results in what?

Answer 22

How well a ligand activates a receptor.
Large change in receptor shape when bound
Small change in receptor change when bound
No conformational change to receptor shape when bound

Question 23

Examples of SABAs? Lasts for how long?

Examples of LABAs? Lasts for how long?

Answer 23

Salbutamol and terbutaline
4 hours
Salmeterol and formoterol
12 hours

Question 24

Example of short acting muscarinic antagonists?

Long acting?

Answer 24

Ipratropium

Tiotropium

Question 25

Where are slowly adapting stretch receptors (SASR'S) found? What do they do? Activated by what?

Answer 25

In airway smooth muscle. Maintain a persistent/ slowly decaying receptor potential during constant stimulus initiating action potentials in afferent neurons for the duration of the stimulus. By lung distension

Question 26

What feature do SASR'S have? High activity does what? If initiation is maintained what happens?

Answer 26

They are myelinated. Inhibits further inspiration, thus beginning expiration. They slowly adapt to low frequency firing.

Question 27

Where are rapidly adapting stretch receptors (RASR'S) found? What do they do? Activated by what?

Answer 27

Between airway epithelial cells. Generate a receptor potential and action potentials at the onset of a stimulus but very quickly cease responding. Lung distension and irritants.

Question 28

Two types of pulmonary stretch receptors?

Answer 28

Slowly adapting and rapidly adapting stretch receptors.

Question 29

Feature of RASR'S? Produce what? | High activity causes what? Might be involved in what?

Answer 29

They are myelinated. Brief burst of activity. Bronchoconstriction. The cough reflex

Question 30

Where are C-fibre J receptors found? What are they stimulated by? Can happen when?

Answer 30

In the capillary walls or the interstitium of the lungs. By an increase in lung interstitial pressure caused by collection of fluid in the interstitium. During vascular congestion caused by pulmonary embolism/ left ventricular heart failure and strenuous activity.

Question 31

Activity of J receptors results in what? Neural input from J receptors gives rise to what?

Answer 31

``` Rapid breathing (tachypena), shallow breathing, bronchoconstriction, cardiovascular depression and a dry cough. Sensations of pressure in the chest and dyspnea- laboured/ difficult breathing. ```

Question 32

Most common form of hypoxia? 4 most common causes?

Answer 32

Hypoxemia- arterial partial O2 pressure is reduced. 1) Hypoventilation 2) Diffusion impairment 3) Shunting 4) Ventilation- perfusion mismatch

Question 33

What does hypoventilation result in? Failure to do what adequately? Caused by what?

Answer 33

Increased arterial partial CO2 pressure. Failure to ventilate alveoli. Muscular weakness, obesity and loss of respiratory drive.

Question 34

Diffusion impairment results from what? Caused by what?

Answer 34

Thickening of alveolar membranes or decrease in SA- blood and alveolar partial O2 pressures fail to equilibrate. Pulmonary oedema, anemia, interstitial fibrosis(between alveolus and capillaries, connective tissue thickened.)

Question 35

What is shunting? Can also occur where?

Answer 35

Mixed venous blood to bypass ventilated alveoli in passing from right side of heart to left side e.g. ventricular septal defect (VSD) In bronchial arteries- venous blood perfuses unventilated alveoli.

Question 36

Most common cause of hypoxemia? Occurs in what? What occurs to arterial partial CO2 pressure? Caused by what?

Answer 36

Ventilation- perfusion mismatch. COPD and other lung disease. May be normal/ increased. A pulmonary embolus, asthma, pneumonia and pulmonary oedema.

Question 37

What is hypercapnia? Caused by what? Sometimes caused by what?

Answer 37

CO2 retention and increased arterial partial CO2 pressure. Hypoventilation. Ventilation-perfusion mismatch

Question 38

Partial CO2 and O2 pressures in type 1 respiratory failure? Most common cause of type 1?

Answer 38

Low pO2 and low/ normal pCO2. | Pulmonary embolism-- hypoxia.

Question 39

Partial CO2 and O2 pressure in type 2 respiratory failure? Cause of type 2?

Answer 39

Low pO2 but high pCO2. | Hypoventilation

Question 40

Two circulations in lungs? Pulmonary receives what % of cardiac output? Bronchial receives % of left ventricular output?

Answer 40

Pulmonary and bronchial. 100% 2%

Question 41

Vessel wall thickness in pulmonary circulation? Muscularisation and redistribution?

Answer 41

Thin. Minor muscularisation and no need for redistribution.

Question 42

Vessel wall thickness in systemic circulation? Muscularisation and redistribution? Pressure difference between systemic and pulmonary?

Answer 42

Thick. Significant muscularisation and redistribution is required. Systemic is much higher.