Some aspects of upper respiratory tract reflexes

Area of Science:

• Physiology
• Neuroscience

Background:

• Respiratory and cardiovascular reflexes can be initiated from nasal and laryngeal receptors.
• Carotid body chemoreceptors normally induce hyperpnoea and bradycardia during asphyxia.

Purpose of the Study:

• To investigate the effects of cigarette smoke on nasal receptors and laryngeal nerve stimulation on cardiorespiratory reflexes in anesthetized dogs.
• To determine how laryngeal receptor stimulation influences carotid body reflexes during asphyxia.

Main Methods:

• Eliciting respiratory and cardiovascular reflexes in anesthetized dogs.
• Administering cigarette smoke to the nose.
• Stimulating the laryngeal nerve.
• Inducing asphyxia to activate carotid body chemoreceptors.

Main Results:

• Nasal cigarette smoke induced reflex apnoea, bradycardia, and vasoconstriction.
• Laryngeal nerve stimulation resulted in reflex apnoea, bradycardia, and limb vasoconstriction.
• Laryngeal receptor stimulation inhibited the respiratory reflex and enhanced the cardio-inhibitory reflex from carotid bodies during asphyxia, leading to temporary cardiac arrest.

Conclusions:

• Nasal and laryngeal stimulation can evoke significant cardiorespiratory responses.
• Laryngeal reflexes can override normal respiratory responses to asphyxia and potentiate cardiac inhibition, with potential clinical implications.