Pyramidal

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Pyramidal Extrapyramidal system

• Lect. Thawatchai Lukseng
• M.Sc. (Physiology)
• School of AHS PH, Walailak University

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Objectives

• ???????????????????????????? Pyramidal system ???
  extrapyramidal system ???
• ?????????????????????????????????????????
  Pyramidal system ??? extrapyramidal system ???
• ????????????????? Upper motor neuron ??? Lower
  motor neuron ???
• ????????????????????????????????????????

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Introduction
The brain
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Brodmann area
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Homunculus
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Introduction
The spinal cord
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• Upper motor neuron (UMN)
• Lower motor neuron (LMN)

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• Upper motor neuron A neuron that starts in the
  motor cortex of the brain and terminates within
  the medulla or within the spinal cord. Damage to
  upper motor neurons can result in spasticity and
  exaggerated reflexes. There is no standard
  laboratory test for upper motor neuron disease.
• (from http//www.medterms.com/script/main/art.as
  p?articlekey33870 )

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Upper Motor Neurons

• Are entirely within the CNS.
• Originate in
• Cerebral cortex
• Cerebellum
• Brainstem
• Form descending tracts

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UMN Classification

• Classified according to where they synapse in the
  ventral horn
• Medial activation system
• Innervate postural and girdle muscles
• Lateral activation system
• Associated with distally located muscles used
  for fine movements
• Nonspecific activating system
• Facilitate local reflex arcs

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• Lower motor neuron A nerve cell that goes from
  the spinal cord to a muscle. The cell body of a
  lower motor neuron is in the spinal cord and its
  termination is in a skeletal muscle. The loss of
  lower motor neurons leads to weakness, twitching
  of muscle (fasciculation), and loss of muscle
  mass (muscle atrophy).

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Lower Motor Neurons

• Begin in CNS.
• From anterior horns of spinal cord.
• From brainstem cranial nerve nuclei.
• Made up of alpha motor neurons.
• Make up spinal and cranial nerves.

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Upper Lower motor neuron syndrome
UMNS LMNS
Lesion CNS CNS PNS
Signssymptoms Hyperreflexia Hyporeflexia
Hypertonia Hypotonia
Spastic paralysis Flaccid paralysis
Babinski sign Fasciculation
Clonus Muscle atrophy
Clasp- knife response
Damaged structures UMN in cortex, Pathways in the brain or spinal cord Alpha-motor neuron in brainstem spinal cord, or cranial nerve or spinal nerve
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Pyramidal and Extrapyramidal system
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Pyramidal and extrapyramidal system

• Pyramidal system
• Corticobulbospinal tract
• Corticospinal tract
• Bulbospinal tract
• Extrapyramidal system
• Basal ganglia, red nucleus, substantia nigra,
  reticular formation, cerebellum

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Pyramidal system

• Corticobulbospinal tract
• Pyramidal cell in layer III and V of motor area
• 30 from primary motor cortex (area 4)
• 30 from area 6 (supplementary motor area,
  premotor cortex)
• 40 from somatosensory cortex (area 3,1,2),
  parietal cortex area 5,7 and anterior cingulate
  area 24

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• Corticobulbospinal tract
• Corona radiata ? posterior limb of internal
  capsule ? ventral of midbrain?cerebral peduncles
• At medulla ? medullary pyramids

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• Most of the cortico-spinal fibers (about 80)
  cross over to the contralateral side in the
  medulla oblongata (pyramidal decussation). Those
  that cross in the medulla oblongata travel in the
  lateral corticospinal tract.
• 10 enter the lateral corticospinal tract on the
  same side
• The remainder of them (10) cross over at the
  level that they exit the spinal cord, and these
  travel in the anterior corticospinal tract.

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Corticospinal Tract Divisions

• Lateral corticospinal tract
• Made up of corticospinal fibers that have
  crossed in medulla.
• Supply all levels of spinal cord.
• Anterior corticospinal tract
• Made up of uncrossed corticospinal fibers that
  cross near level of synapse with LMNs.
• Supply neck and upper limbs.

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Corticobulbar Tract

• Innervates the head
• Most fibers terminate in reticular formation near
  cranial nerve nuclei.

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• Whichever of these two tracts it travels in, a
  cortico-spinal axon will synapse with another
  neuron in the ventral horn.
• This ventral horn neuron is considered a
  second-order neuron in this pathway, but is not
  part of the corticospinal tract itself.

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• Pyramidal system
• Corticospinal tract
• -CS fibers decusate (80)
• -CS fibers cross in the pyramids of the medulla
• Corticobulbar fibers terminate on the motor areas
  of the brain stem to regulate speech, tongue and
  head movement.

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Corticospinal Corticobulbar tract
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About Corticobulbar tract
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Corticobulbar tr.
Corticobulbar tr.
Facial n.
Facial n.
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Related disorders

• Terminology
• Paralysis? Total loss of muscle function
• Plegia ? another word for paralysis e.g.
  hemiplegia
• Paresis ? weakness or partial loss of muscle
  function
• Apraxia ? disorder of motor activity that
  consists of inability to perform a purposeful
  movement

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Related disorder (2)

• Middle cerebral artery (MCA) occlusion
• MCA are also called the artery of stroke
• MCA supplies most of the lateral surface of the
  cerebral hemisphere (the frontoparietal
  somatosensory cortex)
• Infarcts in its territory result in contralateral
  hemiparesis

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Upper motor neuron syndrome (UMNS)

• ??????? pyramidal tract ???????
  ?????????????????????????????????????
• Pyramidal tract ???? Myelinated nerve fibers
  ????????????????????? demyelinating disease
  ???????
• Multiple sclerosis (MS)
• Amyotrophic lateral sclerosis (ALS)

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Upper motor neuron syndrome (UMNS)

• ???????????? ??????
• Abnormal of voluntary movement
• Hypertonia
• Hyperreflexia
• Babinski sign

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Internal Capsule

• Near the basal ganglia, the pyramidal tract forms
  the central body (genu) of the internal capsule.

Internal capsule and neighboring basal ganglia
often injured by small strokes.
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Capsular stroke

• ??????? internal capsule
• affect corticospinal corticobulbar tract
  ????????? internal capsule
• ???????????????????????????????? ________________
  ??????????????????????? ____________ ????
  __________________
• ?????????????????????????????????????????????
  ?????????????????????????? ____________________
  tract

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Capsular stroke (???)

• ???? hypertonia
• spastic hemiplegia
• Hyperreflexia
• Clasp knife response
• Clonus
• Babinski sign

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??? Corticospinal tract

• ??? axon ?? synapse ??? LMN ?????????????????
• ???????? 2 tracts ???
• Ventral (anterior) corticospinal tract (10)
• ????????????????????
• ??????????????????????????????????
• ????????????????????????????
• Lateral corticospinal tract (90)
• ?????????????????
• ?????????????????????????
• ???????????????????????????????????

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??? Corticobulbar tract

• ?????????????????????????????????? ? ???? motor
  ???????
• ?????????????? brainstem ????????????????? motor
  nuclei ??????????????????????????????????
• ??????????????? ??????? ???????????
  ???????????????????????

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Upper Lower motor neuron syndrome
UMNS LMNS
Lesion CNS CNS PNS
Signssymptoms Hyperreflexia Hyporeflexia
Hypertonia Hypotonia
Spastic paralysis Flaccid paralysis
Babinski sign Fasciculation
Clonus Muscle atrophy
Clasp- knife response
Damaged structures UMN in cortex, Pathways in the brain or spinal cord Alpha-motor neuron in brainstem spinal cord, or cranial nerve or spinal nerve
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Extrapyramidal System

• Includes descending motor tracts that do not pass
  through medullary pyramids or corticobulbar
  tracts.
• Includes
• Rubrospinal tracts
• Vestibulospinal tracts
• Reticulospinal tracts
• Tectospinal tract

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