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 supra-nuclear and infra-nuclear lesion of facial nerve

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Difference between supra-nuclear and infra-nuclear lesion of facial nerve
Supra nuclear lesion of facial nerve
Infra nuclear lesion of facial nerve
Central palsy
Peripheral palsy
Forehead intact bilaterally
Total facial palsy of one side
Tone maintain
Flaccid
No muscle atrophy
Muscle atrophy
Reflexes intact
No reflexes
Ataxia
No ataxia
Lesion is usually in internal capsule 
 The facial nucleus itself can be affected by infarcts of the pontine arteries. 
Damage of the pyramidal tracts
Damage to facial nerve in: - Internal acoustic meatus by a tumour - Middle ear by infection or operation - Facial canal by perineuritis, Bell’s palsy - Parotid gland by a tumour - Lacerations of the face
 Lesion is usually at stylomastoid foramen
Accompanied by hemiplegia on the same side as facial paralysis
Hemiplegia seen only in nuclear paralysis in lower pons, will be contralateral
Movements of the lower part of the face affected because the upper part of the face is under bilateral cortical control
Movements of the entire half of the face affected
Voluntary movements are affected, emotional expressions appear to be normal since different pathways are involved
Both voluntary and emotional movements are affected since it is final common pathway
Wrinkle present and eye can be close because upper part of frontalis and orbicularis oculi do not paralyzed due to bilateral innervations  
Wrinkle absent and eye cannot be close because  frontalis and orbicularis oculi are  paralyzed   

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