Tongue, pharynx & reflexes

Tongue muscles and their four separate innervations, the swallowing muscles, the oculocardiac reflex, and the eye-drop colour code.

Tongue muscles

Intrinsic muscles change the SHAPE of the tongue; extrinsic muscles change its POSITION. That single split organises the whole topic.

Intrinsic — shape	Action	Extrinsic — position	Action
Superior longitudinal	Shortens, turns tip up	Genioglossus	Protrudes
Inferior longitudinal	Shortens, turns tip down	Hyoglossus	Depresses
Transverse	Narrows and lengthens	Styloglossus	Retracts
Vertical	Flattens and broadens	Palatoglossus	Elevates

Motor to all tongue muscles: hypoglossal nerve (CN XII) — EXCEPT palatoglossus, which is supplied by the vagus (CN X).
Sensation, anterior ⅔: lingual nerve (a branch of the mandibular division of the trigeminal, CN V₃).
Taste, anterior ⅔: chorda tympani (facial nerve, CN VII), travelling with the lingual nerve.
Sensation AND taste, posterior ⅓: glossopharyngeal nerve (CN IX).

Genioglossus is the muscle that protrudes the tongue and holds it forward off the posterior pharyngeal wall.
Loss of its tone under anaesthesia or sedation is the principal cause of upper airway obstruction — and why a jaw thrust works.

All muscles of swallowing are supplied by the vagus and the accessory nerve (via the pharyngeal plexus) — EXCEPT stylopharyngeus, which is supplied by the glossopharyngeal nerve (CN IX).
That gives a neat pair of exceptions to remember together: palatoglossus is the tongue exception (vagus), and stylopharyngeus is the pharynx exception (glossopharyngeal).
Sensory supply of the pharynx is largely glossopharyngeal — which is why a glossopharyngeal nerve block abolishes the gag reflex for awake fibreoptic intubation.

Afferent limb: short ciliary nerves → ophthalmic division of the trigeminal nerve (V₁) → ciliary ganglion → trigeminal nucleus.
Efferent limb: vagus nerve (CN X) → bradycardia, and potentially asystole.
Triggered by traction on the extraocular muscles (classically the medial rectus during squint surgery), by pressure on the globe, or by a retrobulbar block.
Management: stop the surgical stimulus first, ensure adequate depth of anaesthesia and oxygenation, then give an antimuscarinic (atropine or glycopyrrolate). Consider infiltration of the muscle.
It fatigues with repeated stimulation, which is why it often settles after the first episode.
Remember it as "five and dime" — CN V afferent, CN X efferent.

A standardised cap colour scheme, and an easy mark if it appears.

Cap colour	Class	Example
Red	Mydriatics / cycloplegics	Tropicamide, cyclopentolate, atropine
Blue	Beta blockers	Timolol — systemic absorption can cause bradycardia and bronchospasm
Green	Miotics (cholinergic)	Pilocarpine
Purple	Adrenergic agonists	Brimonidine, apraclonidine (α₂ agonists)

Timolol drops are systemically absorbed and can cause bradycardia, bronchospasm and heart block — relevant in asthmatics and in patients already on beta blockade.
Phenylephrine drops can cause significant hypertension, particularly in children.
Topical drops bypass first-pass metabolism via the nasolacrimal duct, so systemic effects are more marked than the small volume suggests.

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