Comparison between tract and nerve

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  Comparison between tract and nerve Nerve Nerve contain bundle of axons (nerve fibers) in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body. It is the most important part of peripheral nervous system Location: Peripheral nervous system. Structure: Made of axons, connective tissue layers (endoneurium: axon is surrounded by it , perineurium: bundle of axons are surrounded by it, epineurium: whole nerve trunk is surrounded by it), and blood vessels. It gets myelination by Schwann cell   Function: Carries sensory signals to the CNS (afferent) from peripheral part of body or motor signals carry from from the CNS (efferent) to target organs like skeletal muscle, cardiac muscle, smooth muscle or glands Example: Sciatic nerve, median nerve, except optic nerve (though optic nerve is technically part of CNS in develop...
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Difference between lesion of oculomotor, trochlear and abducent nerve

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 Lesion of nerves supply extraocular muscle

Nerve

Lesion

Oculomotor nerve lesion

down and abducted eye

Trochlear nerve lesion

Upward and adducted eye

Abducent nerve lesion

Adducted eye


'

The trochlear nerve innervation, functions of muscles and lesion

 

Innervation

Function

Lesion

Extraocular muscle

Superior oblique

 Intorsion (medial rotation), depression and abduction, respectively.

Trochlear nerve palsy results in upward deviation of the eye (hypertropia).

The abducent  nerve innervation, functions of muscles and lesion

 

Innervation

Function

Lesion

Extraocular muscle

Lateral rectus

 Abducts the eyeball.

Trochlear nerve palsy results in upward deviation of the eye (hypertropia).

Lesion of oculomotor nerve

The oculomotor nerve innervation, functions of muscles and lesion :

Lesion of this nerve make eye down and out

 

Innervation

Function

Lesion

Muscle of eyelid

Levator palpebrae superioris

raises the upper eyelid

Ptosis: Drooping of the eyelid due to weakness or paralysis of the muscle responsible for elevating the upper eyelid (levator palpebrae superioris).

Extra-ocular muscle

Superior rectus muscle

 

eye  rotates upward

Lateral strabismus/squint: due to paralysis of medial rectus and unopposed action of lateral rectus muscle which is supply by abducens  nerve

Diplopia on looking medially and superiorly.

 

Medial rectus muscle  

 

adducts the eye toward the nose

Inferior rectus muscle

rotates the eyeball down"

Inferior oblique

Extortion(lateral rotation) , elevation, and abduction.

Muscle of pupil

Sphincter papillae

Constriction of pupil (miosis)

Dilated pupil (mydriasis): Loss of pupillary constriction due to paralysis of the sphincter pupillae muscle, which is innervated by the oculomotor nerve.

Muscle alter curvature of lens

Ciliary  muscle

Contraction of this muscle relax suspensory ligament, so diameter of lens increase during near vision (accommodation)   

Loss of accommodation: due to paralysis of medial rectus, sphincter papillae and ciliaris muscles.


 




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