Respiratory protective reflexes help protect the lungs and airways from foreign particles. The cough reflex clears irritants from the respiratory tract through forced expiration. Coughing is triggered by irritation in the respiratory tract or other areas. Sneezing is also a protective reflex triggered by nasal irritation that forcibly expels irritants. Swallowing reflex arrests breathing temporarily during eating to prevent choking. These reflexes help maintain a clear airway during breathing and swallowing.

1. Protective reflexes

2. RESPIRATORY PROTECTIVE REFLEXES
• Respiratory protective reflexes are the reflexes
that protect lungs and air passage from
foreign particles.
• Respiratory process is modified by these
reflexes in order to eliminate the foreign
particles or to prevent the entry of these
particles into the respiratory tract.
• Following are the respiratory protective
reflexes:

3. COUGH REFLEX
• Cough is a modified respiratory process
characterized by forced expiration. It is a
protective reflex and it is caused by irritation
of respiratory tract and some other areas
such as external auditory canal

4. Causes
• Cough is produced mainly by irritant agents. It
is also produced by several disorders such as
cardiac disorders (congestive heart failure),
pulmonary disorders (chronic obstructive
pulmonary disease (COPD) and tumor in
thorax, which may exert pressure on larynx,
trachea, bronchi or lungs.

5. Mechanism
• Cough begins with deep inspiration followed
by forced expiration with closed glottis. This
increases the intra pleural pressure above 100
mm Hg.
• Then, glottis opens suddenly with explosive
outflow of air at a high velocity. Velocity of the
airflow may reach 960 km/hour.
• It causes expulsion of irritant substances out
of the respiratory tract.

6. Reflex Pathway
• Receptors that initiate the cough are situated in
several locations such as nose, paranasal sinuses,
larynx, pharynx, trachea, bronchi, pleura,
diaphragm, pericardium, stomach, external
auditory canal and tympanic membrane.
• Afferent nerve fibers pass via vagus, trigeminal,
glossopharyngeal and phrenic nerves. The center
for cough reflex is in the medulla oblongata.
• Efferent nerve fibers arising from the medullary
center pass through the vagus, phrenic and spinal
motor nerves.
• These nerve fibers activate the primary and
accessory respiratory muscles.

7. SNEEZING REFLEX
• Sneezing is also a modified respiratory process
characterized by forced expiration. It is a protective
reflex caused by irritation of nasal mucous membrane.
Causes
• Irritation of the nasal mucous membrane occurs
because of dust particles, debris, mechanical
obstruction of the airway and excess fluid
accumulation in the nasal passages.
Mechanism
• Sneezing starts with deep inspiration, followed by
forceful expiratory effort with opened glottis resulting
in expulsion of irritant agents out of respiratory tract.

8. Reflex Pathway
• Sneezing is initiated by the irritation of nasal mucous
membrane, the olfactory receptors and trigeminal
nerve endings present in the nasal mucosa.
• Afferent nerve fibers pass through the trigeminal and
olfactory nerves. Sneezing center is in medulla
oblongata. It is located diffusely in spinal nucleus of
trigeminal nerve, nucleus solitarius and the reticular
formation of medulla.
• Efferent nerve fibers from the medullary center pass
via trigeminal, facial, glossopharyngeal, vagus and
intercostal nerves. These nerve fibers activate the
pharyngeal, tracheal and respiratory muscles.

9. SWALLOWING (DEGLUTITION) REFLEX
• Swallowing reflex is a respiratory protective reflex
that prevents entrance of food particles into the
air passage during swallowing.
• While swallowing of the food, the respiration is
arrested for a while. Temporary arrest of
respiration is called apnea. Arrest of breathing
during swallowing is called swallowing apnea or
deglutition apnea.
• It takes place during pharyngeal stage, i.e. second
stage of deglutition and prevents entry of food
particles into the respiratory tract.