True about oculocardiac reflex –
**Core Concept**
The oculocardiac reflex is a physiological response that occurs when there is traction or pressure applied to the extraocular muscles, leading to a decrease in heart rate (bradycardia) and potentially even asystole. This reflex is mediated by the ophthalmic branch of the trigeminal nerve (V1) and the vagus nerve (CN X).
**Why the Correct Answer is Right**
The oculocardiac reflex involves the stimulation of the sensory fibers of the trigeminal nerve (V1), which then synapse in the brainstem with the vagus nerve (CN X). The vagus nerve then stimulates the sinoatrial (SA) node, leading to a decrease in heart rate. This reflex is often seen in patients undergoing eye surgery, particularly when the eyes are manipulated or the extraocular muscles are stretched.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the oculocardiac reflex is not exclusively associated with the sympathetic nervous system. While the sympathetic nervous system does play a role in regulating heart rate, the oculocardiac reflex is primarily mediated by the parasympathetic nervous system through the vagus nerve.
**Option B:** This option is incorrect because the oculocardiac reflex is not primarily mediated by the glossopharyngeal nerve (CN IX). While the glossopharyngeal nerve does play a role in regulating heart rate, the oculocardiac reflex is primarily mediated by the trigeminal nerve (V1) and the vagus nerve (CN X).
**Option C:** This option is incorrect because the oculocardiac reflex is not primarily associated with the carotid sinus. While the carotid sinus does play a role in regulating heart rate, the oculocardiac reflex is primarily mediated by the stimulation of the sensory fibers of the trigeminal nerve (V1).
**Clinical Pearl / High-Yield Fact**
The oculocardiac reflex is often seen in patients undergoing eye surgery, particularly when the eyes are manipulated or the extraocular muscles are stretched. This reflex can be prevented by avoiding traction or pressure on the extraocular muscles or by administering atropine to block the vagus nerve.
**Correct Answer:** C.