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Cranial NervesOriginates from brain (mainly brain

stem) and passes through foramina of skull

There are 12 pairs of cranial nervesThey have both name and number

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There are mixed cranial nerves, sensory cranial nerves

and motor cranial nerves

All motor cranial nerves contain a small number of sensory fibers

that is proprioceptive

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Olfactory nerve Olfactory nerve II The axons that makes

the olfactory nerve starts from nasal mucosa.

They make 20 small bundles of fibers that pierce the cribriform plate

Olfactory nerve carry the sense of smell

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Optic nerve IIOptic nerve II Axons start in retina They carry visual

information to brain. Most of the optic

tract fibers terminate in thalamus.(lateral geniculate nucleus)

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Occulomotor nerve IIIOcculomotor nerve III Starts from

occulomotor nucleus in the ventral part of the midbrain.

Extends to various external eye muscles

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Trochlear nerve Trochlear nerve IVIVOriginates from

the midbrain They go to the

superior oblique muscle of the eye

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Trigeminal nerve VTrigeminal nerve V It splits into three large

branches It makes ophtalmic

nerve, maxillary nerve, mandibular nerve

Carry sensory information from face and teeth

Its motor nerve controls mastication

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Abducence nerve VIAbducence nerve VIIts fibers originate from pons

and extends to the lateral rectus muscle of the eye.

This muscle abducts the eye.

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CN VICN VI

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Facial nerve VIIFacial nerve VII

Arise from the lower part of the pons. Innervates superficial muscles of face

and skull. Its autonomic fibers innervate the

submaxillary and sublingual salivary glands and lacrimal glands.

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Vestibulocochlear nerveVestibulocochlear nerve

Has two distinct divisions:Vestibular and cochlear

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Vestibular branchVestibular branch

Arise from semicircular canals in internal ear and terminates in pons medulla and cerebellum.

Its function is to maintain equilibrium.

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Cochlear branchCochlear branch Starts from the organ of corti and

terminate between medulla and pons. Conduct the sense of hearing. Its some times called auditory or

acoustic nerve.

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Glossopharyngeal nerveGlossopharyngeal nerve IX

It is a mixed nerve. Supplies the tongue and pharynx It also supplies the carotid sinus Its fibers extend to medulla.

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Vagus nerve Vagus nerve XX Contains sensory and motor fibers It has many widely distributed branches Sensory fibers supply, pharynx, larynx, pharynx, larynx,

trachea, heart, carotid body, lungs, trachea, heart, carotid body, lungs, bronchi, esophagus, stomach, small bronchi, esophagus, stomach, small intestine and gall bladderintestine and gall bladder

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motor fibers of vagus nereve

Are mainly autonomic. They controls muscles for swallowing Most of them are parasympathetic. They also go to pharynx, larynx,

thoracic organs and abdominal organs.

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Accessory nerve XIAccessory nerve XI

Is a motor nerveIs considered an

accessory nerve to vagus.It was formerly called the

spinal accessory nerve

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Hypoglossal nerve XIIThe motor fibers supplies the

muscles of the tongue It also have sensory

(proprioceptive) nerves.

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Divisions of Divisions of peripheral nervous peripheral nervous systemsystemSensory divisionSensory division

Motor divisionMotor division

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Somatic motor nervous system

Includes all the voluntary movements outside the CNS

The end motor neuron stimulates the effector muscle by means of acetylcholineacetylcholine

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Somatic reflexes A reflex is a predictable response to an

stimulus Based on the center of a reflex we have

cranial and spinal reflexes. We also have somatic reflexes and

autonomic reflexes

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Autonomic reflexesAutonomic reflexes Is either muscle contraction or glandular

secretion Cause Smooth or cardiac muscle

contraction or secretion of a gland

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Important somatic reflexesImportant somatic reflexes

Knee jerk reflexAnkle jerk reflexBabinski reflexCorneal reflexAbdominal reflex

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Knee jerk reflexKnee jerk reflex Is extension of lower leg in response to

tapping patellar tendon It is also a spinal cord reflex, segmental spinal cord reflex, segmental

reflex, stretch reflex, extensor reflex and reflex, stretch reflex, extensor reflex and deep tendon reflex.deep tendon reflex.

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Ankle jerk reflexAnkle jerk reflex

It is called achilles reflex Cause plantar flexion Its center is in the first and second

segment of the cord

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Babinski reflexBabinski reflexIs extension of great toeInfants show this reflex up

to 1 ½ yrsAfter that it is considered

abnormal

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Corneal reflexCorneal reflex Is blinking in response to touching the

cornea It is mediated by the ophtalmic branch

of fifth cranial nerve Centers in the pons and motors in

seventh cranial nerve

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Abdominal reflexAbdominal reflex Is drawing in of the abdominal wall in

response to stroking the side of the abdomen

Its center is in 9th to 12th spinal nerves In pregnancy it is abscent.

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