Nerves which emerge from the brain region are
known as cranial nerves. Cranial nerves are completely different from spinal
nerves. Spinal nerves are those nerves which emerge from spinal cord segments.
Traditionally, there are twelve pairs of cranial nerves present in the human
body. The first and second pair of cranial nerve emerges from the region of
cerebrum and rest of ten pairs emerges from region of brainstem.
There are following twelve cranial nerves
present in the humans and non-human vertebrates:
1. Olfactory
2. Optic
3. Oculomotor
4. Trochlear
5. Trigeminal
6. Abducens
7. Facial
8. Auditory
or Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. Spinal
Accessory
12. Hypoglossal
Olfactory:
Olfactory is a purely sensory nerve and
originates from telencephalon. Olfactory nerves are present in anterior
olfactory nucleus and its major function is to transmit the sense of smell
received from the nasal cavity. It is located in olfactory foramen which is in
cribriform plate of ethmoid.
Optic:
Like olfactory, it is also a purely sensory nerve
and originates from diencephalon. Optic nerves are present in ganglion cells of
retina and it transmits signals which are visual from the retina present in the
eye to the human brain. It is located in a passage which is known as optic
canals.
Oculomotor:
Unlike the first two cranial nerves it is
mainly a motor. It can be easily understood by its name. It originates from two
type of nucleus one is oculomotor nucleus and the other one is Edinger-Westphal
Nucleus. Its major function is to innervate inferior oblique, superior medial
rectus, inferior rectus and levator palpebral superioris.
Trochlear:
It belongs to the family of oculomotor. It is
also motor like oculomotor. It mainly originates from dorsal aspect of midbrain
and it has trochlear nucleus present in the brain.
Trigeminal:
Unlike the other four cranial nerves,
trigeminal is both sensory and motor nerve. It originates from pons.
Abducens:
It is a mainly motor nerve and originates
from anterior margin of pons. Its nucleus is known as Abducens nucleus.
Facial: It is the most commonly
known cranial nerve. It acts as both sensory and motor nerve. It originates
from pons or cerebellopontine angle which is located above olive.
Auditory:
Auditory nerve is also known as
Vestibulocochlear or acoustic or auditory vestibular nerve.
Glossopharyngeal:
It functions as both sensory and motor nerve.
It originates from medulla. Its nucleus is known as ambiguous nucleus. Some of
the sensation received is also relayed to the brain and it is generally located
in jugular foramen of the brain.
Vagus:
Vagus also functions as sensory and motor
nerve. It originates from poster lateral sulcus which is present in medulla.
Its nucleus is known as ambiguous nucleus. The major function of Vagus is to
supply innervation known as branchiomotor to most of the pharyngeal muscles and
laryngeal muscles. Stylopharyngeus muscle is innervated by glossopharyngeal
Spinal
Accessory: Spinal accessory nerve is also known as
just accessory or cranial accessory nerve. In this paragraph, we will use the
word accessory for it. Accessory is mainly a motor nerve. As the name suggest
it originates from spinal roots and cranial roots.
Hypoglossal:
Hypoglossal nerve mainly functions as motor.
It originates from medulla and its nucleus is hypoglossal nucleus. The
important function of hypoglossal is to provide motor innervation to tongue and
motor. It doesn’t provide innervation to palatoglossus. Palatoglossus is
innervated by vagus nerve. It also innervates other glossal nerves. It plays
essential role in bolus formation, swallowing and articulation of speech. It is
found in hypoglossal canal.
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