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RESPIRATORY REFLEXES

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RESPIRATORY REFLEXES

RESPIRATORY REFLEXES
  • Respiratory rhythm is altered reflexly.
  • Occurs in response to metabolic signals & other stimuli.

MAJOR RESPIRATORY REFLEXES:

  • Hering-Breuer inflation reflex.
  • Hering-Breuer deflation reflex.
  • Irritant receptors.
  • J-reflex/J-receptors.
  • Head’s paradoxical reflex.
  • Afferent from proprioceptors.

1. HERING-BREUER INFLATION REFLEX:

  • Mediated by pulmonary stretch receptor.

Mechanism:

  • Lung inflation above particular volume results in,
  • Reflex inhibition of inspiration.
  • Initiation of expiration.

Major actions:

  • Limits tidal volume.
  • Increases respiratory frequency.
  • Prevents lung hyperinflation.
2. HERING-BREUER DEFLATION REFLEX:
  • Rapid lung deflation initiates prolonged inspiration (reflex hyperpnea).
3. IRRITANT RECEPTORS:
  • Respiratory tract mucosa contains rapidly adapting “Irritant receptors”.

– Responds to noxious gases, cigarette smoke, inhaled dust, cold air, etc.

  • Information from irritant receptors conveyed to CNS by vagal afferent fibers.

– Nerve stimulation causes reflex bronchoconstriction, cough & increased mucus secretion.

4. “J-REFLEX”/”J-RECEPTORS”:
  • J- receptors – 

– Sensory nerve endings of non-myelinated (type – C) afferent fibers in vagus nerve.

  • “J” refers to “Juxtacapillary”.

– Juxta-position to pulmonary capillaries,

– In alveolar interstitium.

Stimulating factors:
  • Increased in alveolar interstitial fluid → Interstitial edema.
  • Alveolar capillaries engorged

– As in CHF/pulmonary microemboli.

  • Stimulation reflexly causes,

– Severe tachypnea

– Bronchoconstriction

– Hypotension.

– Bradycardia.

Major stimulating factor:
  • Increased pulmonary capillary pressure.

– Eg: Especially during exercise at high altitude.

Effect of stimulation:
  • Produces tachypnea → Leading to dyspnea.

Inhibits stretch reflex in skeletal muscles → Inhibits exercise.

  • Protecting from pulmonary edema precipitation.
5. HEAD’S PARADOXICAL REFLEX:
  • Lung inflation further induces inflation.

Functions:

  • Physiological role of Head’s reflex is uncertain.
  • Play a role in initiating respiration at birth.

– Fetus is delivered with empty lungs.

– First breath doesn’t fill lungs completely.

– Each inflation promotes further inflation, facilitating lung filling.

6. AFFERENT FROM PROPRIOCEPTORS:

  • Proprioceptive afferent impulses from muscles & joints → Stimulate inspiratory neurons,

– Hence, increase pulmonary ventilation during exercise.

Exam Important

RESPIRATORY REFLEXES
1. HERING-BREUER INFLATION REFLEX:
  • Limits tidal volume.
  • Prevents lung hyperinflation.
2. “J-REFLEX” (“J-RECEPTORS”):
  • “J” refers to “Juxtacapillary” 

– Juxtaposition to pulmonary capillaries in alveolar interstitium.

Major stimulating factor:
  • Increased pulmonary capillary pressure.

– During exercise, especially at high altitude.

3. HEAD’S PARADOXICAL REFLEX:
  • Lung inflation further induces inflation.
4. AFFERENT FROM PROPRIOCEPTORS:
  • Impulses from muscles & joints → Stimulate inspiratory neurons,

– Hence, increased pulmonary ventilation during exercise.

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