The document provides an overview of the brainstem's anatomy and function, detailing its components: midbrain, pons, and medulla oblongata, which manage vital functions and contain various tracts. It describes the extrapyramidal tracts responsible for involuntary bodily movements, including their origins, courses, terminations, and functions. Specific tracts such as the medial longitudinal fasciculus, vestibulospinal tracts, reticulospinal tract, tectospinal tract, rubrospinal tract, and olivospinal tract are explained regarding their roles in coordinating muscle tone, reflexes, and motor control.

1. EXTRAPYRAMIDAL
TRACTS
- Hitesh Rohit(3rd year BPT)

2. BASIC OF BRAINSTEM
• Brainstem=midbrain+pons+medulla oblongata
• It contains ascending and descending tracts between
brain and spinal cord.
• It contains many centers for regulation of vital
functions.

4. • Midbrain:-
• Made up of two parts:-1)Tectum and 2) Cerebral peduncles
• Tectum
• Superior Inferior
colliculus colliculus

5. • Cerebral peduncle includes:-
• 1)Basis pedunculi
• 2)Substantia nigra
• 3)Tegmentum that includes 3 decussations and red nucleus.
• Red nucleus:-
• Large oval or round mass of gray matter.
• Extends between the superior colliculus and hypothalamus.

7. • Functions of red nucleus:-
• Control of muscle tone
• Control of complex muscular movement
• Control of righting reflex
• Control of movement of eyeball
• Control of skilled movements.

8. • PONS:-
• It forms a bridge between medulla and midbrain.
• Functions:-
• Pons forms the pathway that connects cerebellum and
cortex.
• Pyramidal tract passes through the pons.
• Nuclei of V, VI, VII and VIII cranial nerves are located in pons.
• It contains vestibular nuclei.

9. • Medulla oblongata:-
• Lowermost part of brain.
• Situated below pons and is continued downward as spinal cord.
• It forms main pathway for ascending and descending tracts.
• It has many important centers that controls the vital functions.
1)Respiratory centers
2)Vasomotor center
3)Deglutition center
4)Vomiting center
5)sup. and inf. Salivary nuclei
6)Cranial nerve nuclei(V,VIII,X,XI and XII)
7) Vestibular nuclei (med,lat,sup,,inf)

11. • The reticular formation is a set of interconnected
nuclei that are located throughout the brainstem. It
is not anatomically well defined, because it includes
neurons located in different parts of the brain.

13. INTRODUCTION
• Descending tracts of spinal cord other than pyramidal
tracts are called “extrapyramidal tract”.
• They are responsible for the involuntary and automatic
control of all musculature, such as muscle tone, balance,
posture and locomotion

14. TYPES OF EXTRAPYRAMIDAL TRACT:-
• 1) Medial longitudinal fasciculus
• 2) Anterior vestibulospinal tract
• 3) Lateral vestibulospinal tract
• 4) Reticulospinal tract
• 5) Tectospinal tract
• 6) Rubrospinal tract
• 7) Olivospinal tract

15. MEDIAL LONGITUDINAL FASCICULUS
• Origin:- Fibers of this tract take origin from four
different areas in brainstem:
• i. Vestibular nuclei
• ii. Reticular formation
• iii. Superior colliculus
• iv. Interstitial cells of Cajal

16. • Course:-After entering the spinal cord from the brainstem, the
fibers of medial longitudinal fasciculus descend through
posterior part of anterior white column of the same side.
In the spinal cord, this tract is well defined only in upper cervical
segments. Below this level, the fibers run along with the fibers of
anterior vestibulospinal tract.

17. • Extent:- Fibers of this tract extend up to the upper cervical
segments of spinal cord.
• Termination:- Fibers of this tract terminate in anterior
motor neurons of the spinal cord along with fibers of
anterior vestibulospinal tract either directly or through
internuncial neurons.

19. • Function:- Medial longitudinal fasciculus helps in the
coordination of reflex ocular movements and the
integration of ocular and neck movements.
• Effects of Lesion:- Reflex ocular movements and reflex
neck movements are affected in the lesion of this tract

20. ANTERIOR VESTIBULOSPINAL TRACT
• Origin: Fibers of this tract arise from medial vestibular
nucleus in medulla oblongata. In fact, anterior
vestibulospinal tract is the extension of medial
longitudinal fasciculus. Most of the fibers are
uncrossed.
• Extent: Fibers run up to thoracic segments of spinal
cord.

21. • Course:- Fibers of this tract run down from medulla into
the anterior column of spinal cord along the periphery.
All the fibers are uncrossed.
• Termination:- Along with fibers of lateral
vestibulospinal tract, the fibers of this tract terminate in
anterior motor neurons directly or through internuncial
neurons.

23. LATERAL VESTIBULOSPINAL TRACT
• Origin:- Fibers of this tract take origin from the lateral
vestibular nucleus in medulla. This nucleus is also called
Deiter nucleus.
• Extent:- fibers of this tract are present throughout the
spinal cord.
• Course:- From Deiter nucleus, most of the fibers descend
Directly through lateral column. Very few fibers cross to

25. • Termination:- Fibers of this tract terminate in the anterior
motor neuron, either directly or via internuncial neurons.
• Functions :- vestibular nuclei receive impulses concerned with
muscle tone and posture from vestibular apparatus and
cerebellum.
Vestibular nuclei in turn convey the impulses to different parts
of the body through the anterior and lateral vestibulospinal
tracts.
Vestibulospinal tracts are concerned with adjustment of
position of head and body during angular and linear
acceleration.

26. • Effect of Lesion:- Adjustment of head and
body becomes difficult during acceleration
when the vestibulospinal tracts are affected by
lesion.

27. RETICULOSPINAL TRACT
• Origin:-
• Fibers of this tract arise from the reticular formation of
pons and medulla.
• Pontine reticular fibers are uncrossed (direct) and
descend in medial part of anterior column.
• Fibers from medullary reticular formation are
predominantly uncrossed and only few fibers are crossed.
• These fibers descend in lateral part of anterior column
and to some extend in the anterior part of lateral column.

29. • Extent:-Fibers of reticulospinal tract extend up to thoracic
segments.
• Termination:- Fibers of reticulospinal tract terminate in
gamma motorneurons of anterior gray horn through the
internuncial neuron.
• Functions:- Reticulospinal tract is concerned with control
of movements and maintenance of muscle
tone,respiration and diameter of blood vessels.
• Pontine and medullary fibers have opposite effects on
these functions, which are given in Table :-

30. Function
Pontine
reticular fibers
Medullary
reticular fibers
Control of voluntary
and reflex
movements
Facilitation Inhibition
Control of muscle
tone through
gamma motor
neurons
Facilitation Inhibition
On respiration Favor expiration Favor inspiration
On blood vessels Cause
vasoconstriction
Cause
vasodilation

31. • Effect of Lesion:- Lesion of reticulospinal tract
causes disturbances in respiration, blood pressure,
movements of body and muscle tone.

32. TECTOSPINAL TRACT
• Origin:- Nerve fibers of this tract arise from
superior colliculus of midbrain.
• Extent:-Tectospinal tract extends only up to
lower cervical segments.
• Course:- After taking origin from superior
colliculus, the fibers cross the midline in dorsal
tegmental decussation and descend in anterior
column.

34. • Termination:- Fibers of tectospinal tract terminate in the
anterior motor neurons of spinal cord, directly or via
internuncial neurons.
• Function:- Tectospinal tract is responsible for the movement
of head in response to visual and auditory stimuli.

35. RUBROSPINAL TRACT
• Origin:- Fibers of this tract arise from large
cells (nucleus magnocellularis) of red nucleus
in midbrain.
• Extent:- Nerve fibers of this tract appear in the
spinal cord only up to thoracic segments

37. • Course:- After arising from the red nucleus, the fibers cross the midline
in ventral tegmental decussation and descend into spinal cord through
the reticular formation of pons and medulla.
• Termination:-fibers of rubrospinal tract end in the anterior motor
neurons of the spinal cord via internuncial neurons.
• Function:-Rubrospinal tract exhibits facilitatory influence upon flexor
muscle tone.

38. OLIVOSPINAL TRACT
• Origin:- The nerve fibers of the olivospinal tract take
origin from the inferior olivary nucleus, which is present
in the medulla oblongata.
• Termination:-fibers of this tract terminate in the anterior
motor neurons of spinal cord.
• Function:-Functions of the olivospinal tract are not
known clearly.
• It is believed that this tract is involved in reflex
movements arising from the proprioceptors.

39. • Cross section of medulla oblongata

41. K. Bye