central nervous system:-pyramidal and extrapyramidal tracts and function

 Tracts/ pathways-

i)ascending pathway-from receptor CNS.

ii)Descending pathway.-from CNS to muscle.

i)ascending pathway-

pain pathway/lateral spinothalamic pathway.

b)dorsal spinothalamic pathway

c)ventral pathway

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ii)descending/pyramidal pathway

a)cortico-spinal tract

Touch pathway(dorsal spino thalamic tract)

fibers origin from meissner's corpuscle,merkel's disc

course:-

i)it enters the dorsal root of the spinal cord and travels along the dorsal column.

ii)1 st synapse occurs in medulla oblongata.

iii)nucleus of gracilius-from tract gall

    nucleus of cuneatus-from tract of burdach.

iv)the fitness  cross opposite side  in medulla oblongata,ascend up to thalamus where it relays.v)from thalamus 3rd order neuron arise and ascend 

   up to the cerebral cortex.

terminates:-

the fibers terminates in the sensory center- 3,1,2

sensation:-

fine touch,proprioception,vibration,or function,pressure,streognosis,localisation and 2 point discrimination.

Pain pathway/lateral spinothalamic tract:-\

Pain ;-Unpleasant subjective sensation due to nerve damage.

Cause:-trauma,spasm,inflammation

type:-

fastpain:-	Slow pain;-
15-30m/s(velocity)	Less than 2m/s
A delta fibers	C-unmyelinated fibers
Sharp and localise	Dull and diffused
Neo Lateral spinothalamic tract	Paleo lateral spinothalamic tract

Function:-

It Carries pain and a temperature sensation.

Origin;-

Free nerve endings

Course:-

First order neurons arise from free ending synapses arise at the dorsal root of the spinal cord.

2nd order neurons arise from  dorsal root crosses into the opposite side of the spinal cord right in front of the central canal lateral spinothalamic tract which ascends to the pons medulla and midbrain.

-in midbrain,it gives for reticular formation.

-2nd order neuron synapse in thalamus.

Termination:-3rd order neuron arise from thalamus and terminates in sensory cortex  area-3,1,2

Referred pain:-

Pain which originates from the visceral area but which felt somewhere skin.

Eg:-appendicitis -pain around umbilicus

-myocardial infarction-pain around left shoulder.

-dermatomal theory:-

i)Referred pain mechanism (Dermatomal rule)  Dermatomal rule - When pain is referred, it is usually to a structure that developed from the same embryonic segment or dermatome as the structure in which the pain originates. 

Convergence theory:-

1)the fiber from the viscera and skin. Where pain is felt is converged in the dorsal root of the spinal cord therefore the referred pain.

Phantom pain:-

Because of the law of projection of receptors even though the limb is not there i.e.,amputated pain is felt because the receptors are different along the way.

Gate control theory of pain:-

-endogenous mechanism of pain inhibition.The gate control theory of pain asserts that non-painful input closes the nerve "gates" to painful input, which prevents pain sensation from traveling to the central nervous system.

1)The spinal cord pain is inhibited by substantia gelatinosa of rolando.

2)By release of enkephalins and encephalins

Descending tract:-

-Information is carried from CNS to muscle /gland

-pyramidal/corticospinal tract.

Origin;-betz cells of cerebral cortex they are large cells

It is from area 4 and area 6,8,3,1,2

Course:-all the fibers from pain together in an internal capsule this is called corona radiata.

-fibers redistribute and descend to medulla oblongata.

Pyramidal demonstration occur at medulla

-80%of fiber descends down as the lateral cortico spinal tract and terminates in the anterior grey  horn .

-the remaining 20%of fibers  descends down as ventral corticospinal tract  and finally they are crossed at terminates in anterior grey horn

Termination:-

Anterior grey horn which forms LMN (lower motor neuron)innervates muscle and causes movement.

UMN:-IT IS PYRAMIDAL TRACT THAT ARISE FROM CEREBRAL CORTEX AND ENDS IN THE ANTERIOR GREY PART.

LMN:-IT IS ANTERIOR GREY HORN CELL THAT ARISE FROM SPINAL CORD AND INNERVATES THE MUSCLE.

UMN lesion	LMN lesion
hypertonia-spasticity	hyperplasia-flaccidity
Deep reflex-exaggerated	Deep reflex -loss
Superficial reflex-lost	Superficial reflex -loss
Babinkis sign positive	Atrophy of muscle
Not much atrophy

Hemiplegia:-

Cause:-damage to pyramidal tract at internal capsule.

Symptom-paralysis of the opposite half of the body.

Monoplegia:-

Cause:-injury at cerebral cortex

Symptom:-single limb is paralysed.

Quadriplegia:_

Cause injury to spinal cord at cervical level.

Symptom:-paralysis of  limb

Paraplegia;-

Cause:-injury to spinal cord at lower lumbar level.

Symptom€;-lower to limb are paralysed.

Extra pyramidal tract:-

1)Retrospinal tract-originating from red nucleus

2)vestibulospinal tract-origin from olivary nucleus

3)vestibulospinal tract:-origin from vestibular nucleus

)tectospinal tract:_originates from tectum

)retrospinal tract:-originates from reticular formate

Pyramidal tract	Extrapyramidal tract
Newer origin	Older origin
Afterbirth-formylated of nerve fiber- from one and half to two years its starts functioning	In foetus it causes movement before birth starts functioning
Meant for skilled movements	Gross movement
Voluntary movement occurs,has role in stretch reflex	Maintain posture and muscle tone

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