The pyramidal tract (corticospinal tract) originates from motor areas of the cerebral cortex and descends through the brainstem and spinal cord. It crosses to the opposite side and terminates on internuncial neurons which connect to motor neurons in the anterior horn of the spinal cord. The extrapyramidal tracts include the rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts and are involved in motor control. Lesions of the pyramidal tract can cause paralysis on the opposite side of the body.

3.  Tracts originating from the brain and
descending in to spinal cord
 These tracts are concerned with various
motor activities of body
 Two groups
› Pyramidal tract
› Extra pyramidal tract

4.  Aka corticospinal tract
 Contains axons of cell bodies present in
motor cortex of brain.
 Pyramidal cells of Betz
 Origin :-
 30% from primary motor cortex (Area 4)
 30% from premotor area and supplementary
motor cortex
 40% from the somatic sensory area

8.  The fibers descend as a part of corona
radiata
 Then pass through the posterior limb of
internal capsule
 Then downwards through the brainstem
 Forming pyramids in the medulla
 At the lower part of medulla 90% of the
fibers decussate in the midline to reach
opposite side
 Forming two separate tracts from here

11.  Constituted by crossed fibers
 Descends in the lateral white funiculus of
opposite side
 These fibers terminate in the internuncial
neurons of spinal grey matter.
 Internuncial neurons synapse with motor
neurons in anterior horn cells
 Some fibers end directly on the AH cells
 Axons of AH cells supply skeletal muscle
through spinal nerve

12.  Formed by the uncrossed pyramidal
fibers
 They descend thro ant white funiculi on
same side
 They reach only till mid thoracic region
 On reaching appropriate spinal segment
they cross to the opposite side
 Terminate in the same way as lateral
corticospinal tract

13.  In brainstem some fibres terminate in
motor nuclei of cranial nerve
 They cross to opposite side at various
levels of brainstem depending upon the
nuclei
 Which supply muscles of face

14.  Both the anterior and lateral
corticospinal tracts ultimately innevate
opposite side of the body
 i.e Fibres from the right lobe of cerebral
cortex terminate on the left AH cells

15.  UMN :- neurons giving origin to pyramidal
tract
 LMN :- AH cells along with their neuron
constitutes LMN

16.  Fibres of CS tract are unmyelinated at
birth
 Myelination begins at 2nd week after birth
and completes at 2years of age
 Contains large fibres and small fibres
 Large fibres disappear at old age
leading to shaky movements

17.  Cerebral cortex controls voluntary
movements of the body thro CS tract
 Lesion produce paralysis of concerned
muscle group
 Sends collateral to other motor control
systems like basal ganglia , cerebellum ..

18.  Descendings tracts other than pyramidal
tract are called extra pyramidal tracts
› Rubrospinal tract
› Vestibulospinal tract
› Reticulospinal tract
› Tectospinal tract
› Olivospinal tract
› Medial longitudinal fasciculus

22.  Origin:- arises from nucleus
magnocellularis or red nucleus in
midbrain
 Course :- fibres cross to the opposite side
in the lower part of tegmentum of
midbrain
 After that follows a course similar to
lateral CS tract
 Termination :- on the interneurons along
with CS tract

23.  Facilitates flexor muscles and inhibit
extensor muscles
 Red nucleus receives corticorubral fibres
from ipsilateral motor cortex
 Cortico-rubro-spinal tract acts as a
alternate route of pyramidal tract
 Reaches only upper three cervical
segments

27.  Lateral Vestibulospinal Tract:- origin from
lateral vestibular nucleus (deiter’s) at
lower pons
 fibres are somatotopically arranged in
this nucleus
 Course :- tract is uncrossed and lies in the
ant funiculi
 They terminate on alpha and gamma
motor neuron thro interneuron

30.  Vestibular nucleus receives afferents
from vestibular apparatus mainly from
utricle
 Adjustment of postural muscles to linear
acceleration
 Facilitates extensor muscles and inhibits
flexor muscle
 Maintenance of balance

31.  Fibres originates from medial vestibular
nucleus
 Descends thro the anterior funiculi and
mostly uncrossed
 Fibres ends in AH cells either directly or thro
interneuron
 Receives inputs from vestibular apparatus
mainly from semicircular canals
 Controls movements of head with respect
to auditory and visual stimuli .

32.  Two divisions
 Medial – pontine Reticulospinal tract
 Lateral – medullary Reticulospinal tract
 pontine Reticulospinal tract:- arises from
medial pontine reticular formation and
descends mostly uncrossed and
terminates in alpha & gamma motor
neurons in spinal cord thro interneurons

33.  Fibres orginates from medullary reticular
formation (gigantocellular) , descends
mostly uncrossed in the lateral funiculi
and terminates in same way as pontine
RS tract

35.  Reticular formation Receives afferents
from cortex
 Forming cortico-reticulospinal pathway
 Control of movements and muscle tone
 Also convey autonomic fibres from
higher center to spinal cord

36.  Pontine and medullary nuclei functions
opposite to one another in controlling
› Muscle tone
› Respiration
› Vascular caliber
› Antigravity muscles posture

37.  Fibres originates from superior colliculi
 Fibres cross the midline at tegmentum of
midbrain (dorsal tegmental decussation)
 And descends thro anterior funiculi
 Terminates in AH cells of upper cerviccal
levels
 Functions :- turning head and moving
arms in response to visual or other stimuli

38.  Originates from inferior olivary nucleus
 Descends uncrossed and terminates in
AH cells
 May control reflex muscle activity
 Tract is of doubtful existence

40.  Extends from midbrain downwards
 Fibres takes origin from
› Vestibular nuclei
› Reticular formation
› Superior colliculus
› Interstitial nucleus of cajal
› Posteriior commisure
› Has connection Cranial nerves 3, 4, 6, 7 , 8, 12
 AH cells of muscles of neck
 Function :- harmonius movement of eye
and neck

44.  Upper Motor Neuron paralysis :- paralysis
of UM neurons
 Lower Motor Neuron Paralysis :- paralysis
of LM neurons

47.  Monoplegia :- paralysis of all muscles of
one limb
 Hemiplegia :- paralysis of one half of
body
 Paraplegia :- paralysis of both lower
limbs
 Quadriplegia :- paralysis of all four limbs