Cranial nerves in reptiles, birds, and mammals – origin, nature and functions
The brain of reptiles, birds, and mammals is connected to twelve pairs of cranial nerves. Out of these spinal accessory and hypoglossal (XI and XII) are’ not present in fishes. Following is a table of cranial nerves of a mammal with their branches.
| Name with main branches |
Origin from brain |
Distribution | Nature | |
| Olfactory | Olfactory lobe | Olfactory epithelium | Sensory | |
| Optic | Optic thalamus | Retina of eye | Sensory | |
| Oculomotor (Four) | Crura cerebri of mid brain | inferior oblique, inferior rectussuperior rectus, inferior rectus, iris, ciliary body | Motor | |
| Superior oblique eye muscles | ||||
| Trochlear (Pathetic) | Midbrain | Superior oblique eye muscles | Motor | |
| Trigeminal | Pons Varolii | Mixed | ||
| V1 Ophthalmic | (side of medula) | Eye, eyelids, snout | Sensory | |
| V2 Maxillary | Upper jaw, vibrissae | Sensory | ||
| nose, lower eyelid | ||||
| V3 Mandibular | Lower jaw and lip, external ear, tongue | Mixed | ||
| Abducens | Pons Varolii (ventral side of medulla) | External rectus muscle of eyeball | Motor | |
| VII | Facial | Pons Varolii | ||
| (side of medula) | ||||
| V111 Palatine | Palate | Sensory | ||
| VII2 Chorda tympani | Tongue, salivary glands, taste buds. | Sensory | ||
| V113Hyomondibular | Lower jaw, neck, pinna, hyoid | Mixed | ||
| Auditory | Medulla | Sensory | ||
| II1 Vestibular | Internal ear | Sensory | ||
| “ | Vl12 Cochlear | Cochlea | Sensory | |
| Glosopharyngeal | Medulla | |||
| X1 Lingual | Tongue, pharynx, salivary glands | Mixed | ||
| X2 Pharyngeal —- | Pharynx, salivary glands | Mixed | ||
| Vagus | Posterior part of medulla | |||
| X1 Anterior laryngeal | Cricoid, thyroid muscles of larynx | Motor | ||
| X2 Recurrenl laryngeal | All muscles of Larynx | Motor | ||
| X3 Cardiac depressor | Heart | Motor | ||
| X4Pneumogastric | Lungs, esophagus, stomach, ileum | Sensory & Motor | ||
| Spinal accessory | Medulla | Pharynx, larynx, neck, shoulder | Motor | |
| Hypoglossal | Medulla | Neck and tongue | Motor |
Functions:
- Oelfactory nerve is concerned with the sense of smell.
- Optic nerve is concerned with vision
- Oculomotor nerve is concerned with eyelids, eyes, adjustments of light entering the eyeball, focusing of the lens, movement of eyeball.
- Trochlear nerve is concerned with movement of eyeball.
- Trigeminal nerve is concerned with condition of facial muscles (sensory). Its ophthalmic branch is sensory and concerned with eyes, tear glands, scalp, forehead, and upper eyelids. Its maxillary branches are concerned with upper teeth, upper gum, upper lip, lining of the palate, and skin of the face (sensory). The mandibular branches connect to scalp, skin of lower jaw, lower gum and teeth and lower lip.
- Abducens nerve connects to external rectus muscle and moves the eyeball.
- Facial nerve is concerned with face muscles (sensory), taste receptors of anterior tongue (sensory), and facial expression, tear glands, and salivary glands (motor).
VIII Auditory or Vestibulocochlear nerve, its vestibular branche is concerned with equilibrium, and cochlear branch with hearing.
- Glossopharyngeal nerve connects to pharynx, tonsils, posterior tongue, and carotid arteries (sensory), pharynx and salivary glands (motor).
- Vagus nerve is concerned with speech, swallowing, heart and visceral organs in the thorax and abdomen (motor. pharynx, larynx, esophagus, and visceral organs (sensory).
Xl. Accessory spinal nerve Its cranial branch connects to soft palate, pharynx and larynx, while its spinal branch supplies neck and back.
XII. Hypoglossal nerve connects to tongue muscles, and controls tongue movements.
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