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