Lecture 11: Respiratory Reflexes

Question 1

What is the Hering-Brauer reflex?

Answer 1

A vagal reflex mediated by stretch receptors in the lungs. Lung inflation inhibits inspo drive. Weak reflex in humans, only really effective when anaesthetised

Question 2

What are slowly adapting receptors (SAR), describe their function:

Answer 2

• vagal afferents that respond to stretch on the smooth muscle of the bronchi
• they are myelinated nerves with B and Aδ fibres
• conduction velocity of 15-30m/s
• cause reduction in tidal volume and inspo time and bronchodilation

Question 3

What are rapidly adapting receptors (RAR), describe their function:

Answer 3

• vagal afferents that respond to stretch and irritants and are found in or near the epithelium of the lower respiratory tract
• response rapidly decreases with time
• measures the rate of inflation and deflation
• myelinated with a conduction velocity of 15-20m/s
• active during tidal breathing
• causes tachypnea, cough, hyperventilation and bronchoconstriction

Question 4

What are C fibre afferents?

Answer 4

• Pain fibres in the epithelium that respond to tissue damage and irritants (capsaicin)
• 2 types: bronchial and pulmonary (J receptors)
• slow conduction velocity 1m/s
• produce bronchoconstriction, brachycardia, initial apnea and later hyperpnea and cough

Question 5

How does capsaicin activate receptors?

Answer 5

Activate vallinoid receptor VR1 which is a TRP channel, activation causes a heat sensation