RESP - E. LUNG STRUCTURE AND FUNCTION-COVERED

Question 1

what is the role of the respiratory system

Answer 1

to ensure adequate intake of oxygen and removal of carbon dioxide

Question 2

how blood flow through lungs

Answer 2

• deoxygenated blood from heart picks up oxygen in alveoli and excretes carbon dioxide from blood into alveoli
• pulmonary vein takes oxygenated blood to heart to be pumped around body

Question 3

sympathetic nervous system

Answer 3

• fight or flight responses
• Noradrenaline acts at adrenoceptors in lungs
• Adrenaline released from adrenal glands

Question 4

parasympathetic nervous system

Answer 4

• rest and digest responses
• acetylcholine acts at muscarinic receptors

Question 5

adrenoceptors - alpha

Answer 5

• alpha1 ARs: vascular smooth muscles contraction
• alpha2 ARs: vascular smooth muscle contraction and pre-synaptic regulation of NA release

Question 6

adrenoceptors - beta

Answer 6

• beta1 ARs - contraction of heart
• beta2 ARs - airway smooth muscle relaxation
• beta3 ARs - skeletal muscle, adipose tissue

Question 7

muscarinic receptors

Answer 7

• M1: CNS, salivary glands, gastric glands
• M2: heart - contraction, GI smooth muscle contraction, CNS
• M3: salivary glands, smooth muscle of GIT and airways
• M4: CNS
• M5: CNS

Question 8

sympathetic pathway in airways

Answer 8

• circulates adrenaline from adrenal glands
• acts on B2-ARs on bronchial smooth muscle = relaxation
• inhibition of mediator release from mast cells
• B2-ARs on mucous glands to inhibit secretion so increased clearance of mucous

Question 9

parasympathetic pathway in airways

Answer 9

• release ACh
• activates muscarinic M3 receptors
• bronchoconstriction and increased mucous secretion

Question 10

sensory nerves in airways

Answer 10

• protective mechanism
• in control of cough reflex
• cause coughing, bronchoconstriction and increased mucous secretion
• unregulated in inflammation (increased)
• involved in exercise-induced asthma?
• involved in cold-induced asthma?

*no drugs to control sensory nerves
we want to dampen the effect down

Question 11

what is eupnoea

Answer 11

• normal breathing rhythm
• 1/3 air remains in main airways
• deeper breaths: more air passes into alveoli for gas exchange

Question 12

what is dyspnoea

Answer 12

• difficult breathing

Question 13

what is airway resistance

Answer 13

the opposition to airflow in respiratory tree (lungs)
- depends on friction and airway cross section

1. contraction of airway smooth muscle leading to constriction of airways
2. increased growth of smooth muscle (remodelling) reducing size of lumen (asthma, COPD) which increases resistance to airflow
3. excess mucous production which increases resistance to airflow (chronic bronchitis common in COPD)

Question 14

what is compliance

Answer 14

• indication of ability of lungs to stretch when breathing in

Question 15

what is elastance

Answer 15

• ability of lung to recoil to normal size when breathing out

Emphysema/COPD can lead to loss of elastance

Question 16

what is fibrosis

Answer 16

• caused by lung damage eg - after TB
  stiff lungs (with fibrosis) have low compliance and high elastic recoil (as difficult to stretch) - total lung capacity reduces

Question 17

control of breathing

Answer 17

• controlled though ANS
• build up of carbon dioxide (holding breath) is recognised by chemoreceptors in respiratory centres in brain stem and breathing is stimulated

Question 18

what is spirometry

Answer 18

• measure lung volume

Question 19

obstructive airway disease

Answer 19

• FEV1 decreases as air comes out slower
• FVC roughly the same if all air can be expelled
  compared to normal
  but FEV1:FVC ratio decreases

*hard for them to exhale all the air from their lungs

Question 20

restrictive airway disease

Answer 20

• FVC decreases
• FEV1 decreases
  but FEV1:FVC ratio is the same as normal

*fibrosis
*can’t fully fill their lungs with air

Question 21

peak flow meter

Answer 21

• small, hand-held device
• measures flow of air out of lungs
• PEF - peak expiratory flow: speed at which you breathe air out
  rises rapidly during forced expiration then drops
• constriction of airways reduce peak flow
• record in morning and evening

Question 22

respiratory acidosis

Answer 22

• reduction in lung function = impaired expiration of carbon dioxide
• build up of carbon dioxide leads to increased H+ conc and hence a drop in pH (acidosis)
• leads to increased breathing to limit hypoxia
• excrete more carbon dioxide, decrease carbonic acid in body and pH should rise

diabetes - build up of acids in body

Question 23

hyperventilation

Answer 23

• leads to loss of carbon dioxide and hence alkalosis (increase in pH)
• leads to inhibition of ventilation to limit hyperventilation

vomiting out acid from stomach - decrease in ventilation to decrease carbon dioxide input and decrease pH

Question 24

smoking

Answer 24

• causes 1/3 of all cancer deaths
• particulate matter and tar
  tar is the solid material inhaled and forms a sticky brown residue in lungs and airways