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 pyramidal system and extra-pyramidal system

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Difference between pyramidal system and extra-pyramidal system 


Topics
Pyramidal system
Extrapyramidal system
Phylogeny
Present in mammal and achieving its greatest development in man
Phylogentically it is older than pyramidal system
Brodman’s area
Brodman’s area 4
Brodman’s area 6
Component
Pyramidal cells in the primary motor area 4, premotor area 6 , primary sensory are 3,1,2
Premotor area  corpus striatum , globus pallidus, tectum, red nucleus , reticular formation , vestibular nuclei and neocerebellum
Crossing of nerve fibres
80% cross in medulla and 20% cross in spinal cord
Most of the extrapyramidal tract cross except vestibulospinal
Function
Responsible for non-postural, precise movements of small muscles involved in skillful activity
Responsible for gross postural movements involving large groups of muscles
Pathways
Connected directly to lower motor neuron
Connected indirectly to lower motor neuron
Effects of lesion
No increase in muscle tone
Muscle tone increase (rigidity: lead pipe)  
Reflexes
Brisk
Normal
Power
Diminish
Usually not affected
Planter movement
Planter extensor
Flexor
Cortical fibres
Arise predominantly in primary motor area (Brodman’s area 4 )
Arise predominantly in premotor area (Braodman’s area 6)
Subcortical centres & basal ganglia
Play no role in pyramidal system
Play a key role in extrapyramidal system 
Involuntary movement
Absent
Present


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