Ascending, descending, and medulla oblongata is important anatomical structures for coordinations in physiology, embryology, and psychological activities in humans

1. Ascending and descending tracts
Obaje Godwin Sunday
Department of Anatomy
Alex Ekwueme Federal University Ndufu
Alike, Ebonyi State, +2348068638121

2. Characteristics of ascending tract
• Made up of 3 neurons (1st, 2nd, and 3rd
order)
• The posterior column is called
spinothalamic tract
• Receptors are exteroceptive or
proprioceptive from the origin

3. Characteristics of ascending tract
• Terminates at the Brodmann areas(3,1,2),
which is the primary sensory area in the
cerebral areas
• 1st order neuron located outside the CNS,
somewhere in the dorsal root ganglion of
spinal cord or in the sensory ganglia of
cranial nerves
• Except; trigeminal nerve whose 1st order
neuron in the midbrain

4. What Brodman areas look like

5. Characteristics of ascending tract
• 2nd order neurons located in the spinal
cord or medulla oblongata
• 2nd order neurons crossed to the
opposite (contralateral) in the cerebral
cortex
• 3rd order neurons located in the ventral
posterior side of thalamus

6. Characteristics of ascending tract
• Information is carried from the
environment and to the brain for
interpretation (cerebral cortex)
• Spinocerebellar Tract (SCT) is the
ascending tract when it reaches the
cerebellum
• It has two neurons to reach the
cerebellum

7. Characteristics of ascending tract
• 1st order neuron of SCT is located outside
CNS, probably in the dorsal root ganglion
of spinal cord or ganglia of cranial nerves
• Originated from the proprioceptive
receptors
• Terminated in the cerebellum

8. Characteristics of ascending tract
• 2nd order neuron of SCT is located outside
CNS, in the ganglia of spinal cord or medulla
oblongata
• Representation is ipsilateral in the cerebellum
• Carry postural and equilibrium movements

9. Characteristics
• Light touch and pressure, tickle, and itch ant.
Spinothalamic tract
• Pain and temperature by lat. Spinothalamic
tract
• Consciousness, fine touch, and two point
discrimination by fasciculi gracilis and
cuneatus
• Unconsciousness proprioception by ant and
post spinocerebellar tracts

10. Posterior column tract

11. Lateral spinothalamic tract

12. Spinocerebellar tract

13. Descending
tract

14. Characteristic features
• Involve 2 neurons ( upper and lower
motor neurons)
• The motor neurons located in the
anterior horn of spinal cord and motor
nuclei of cranial nerves are referred to
as lower motor neurons

15. Characteristic features
• The neurons present in the various parts
of the brain which influence the activity
of lower motor neurons are referred to
as upper motor neurons
• The control is usually contralateral.

16. Characteristic features
• Descending tracts arising from motor
and premotor area of cerebral cortex
constitute pyramidal tracts (lateral and
anterior corticospinal tracts)

17. Characteristic features
• All other descending tracts
pathways having their origin in
subcortical areas are referred
to as extrapyramidal
tracts (tectospinal, rubrospinal,
reticulospinal, olivospinal and
vestibulospinal)

18. Sensations
• Skilled voluntary movement by
corticospinal tract (pyramidal), ant and
post corticospnal
• Extrapyramidal
• Tectospinal tract for spinovisual reflexes
like head and neck movements while
eyes closed

19. Sensations
• Rubrospinal srrves as facilitators for
flexors and inhibitors for extensors
• Vestibulospinal tract for postures and
balancing

20. Sensations
• Reticulospinal tract (medial) serves as
facilitatory to extensor muscles
• Reticulospinal tract (lat) serves as
facilitatory to flexor muscles

21. Corticospinal tract

22. Differences between UMN and LMN
Features UMN LMN
Paralysis Type Spastic Flaccid
Muscle Tone Increased Decreased
Muscle atrophy Absent Present
Tendon reflexes Exaggerated Diminished
Babinski’s sign Present Absent

23. What happens in CST injuries/paralysis? A solution has come from Prof Liu in Hong Kong

24. Babinski’s sign
Dorsiflexion of great toe with fanning of
lateral toes on scratching lateral aspect of
plantar surface of foot
In healthy/normal adults the toes are
planter flexed

25. As soon as your baby’s
born, you’ll notice their
primitive reflexes —
although you might not
know them by name.
Palmar grasp reflex
Plantar reflex
Sucking reflex
Rooting reflex
Stepping reflex

26. OBLONGATA
Medulla

27. Characteristics
• Is the lowermost part of the brainstem
(other parts are pons and midbrain)
• Continuous below with the spinal cord
and above with pons.

28. Characteristics
• Located in the posterior cranial fossa and
is related to clivus anteriorly and cerebellum
posteriorly.
• Separated from the cerebellum by the cavity
of fourth ventricle

29. Medulla oblongata

30. Medulla oblongata
• Function: Innervation to the viscera of
the head, thorax and abdomen, heart
rate. Involuntary actions like vomiting
and sneezing
• Nuclei: Cranial nerve nuclei (IX-XII):
inferior salivatory nucleus, spinal nucleus
of trig

31. Medulla oblongata
• Tracts: Corticospinal (pyramidal) tract,
cuneate fascicle, gracile fascicle, medial
lemnisci

32. Medulla oblongata
• Cone shaped neuronal mass, broad in
the upper part and narrow in the lower
part.
• It’s myelencephalon
• Approximately 3 cm in length

33. Medulla oblongata
• Divided into two part:
–Lower closed part: It has a central
canal
–Upper open part : In this part the
central canal widens and opens
dorsally to form the lower half of the
floor of fourth ventricle

34. Medulla oblongata

35. Medulla oblongata
• The ventral aspect of medulla oblongata
shows the following features
from medial to lateral:
• Anterior median fissure/sulcus in the
median plane (divides ventral aspect into
two symmetrical halves).

36. Medulla oblongata
• Pyramids: Elongated elevation produced
by underlying the corticospinal tract
• Anterolateral sulcus: Hypoglossal nerve
rootlets emerge along this sulcus

37. Medulla oblongata
• Olive: Oval elevation produced by
underlying Inferior olivary nucleus
• Posterolateral sulcus: Rootlets
of glossopharyngeal, vagus and cranial
part of accessory nerves emerge along
this sulcus from above downward

38. Medulla oblongata

39. Medulla oblongata
• Features of the dorsal surface of lower
closed part of medulla oblongata from
medial to lateral are:
• Posterior median sulcus: In the median
plane

40. Medulla oblongata
• Fasciculus gracilis (lowerpart) and
gracile tubercle (in the upper part):
gracile tubercle is produces by the
underlying nucleus gracilis, where the
axons comprising fasciculus gracilis
terminate

41. Medulla oblongata
• Fasciculus cuneatus (lowerpart) and
cuneate tubercle (in the upper part):
cuneate tubercle is produces by the
underlying nucleus cuneatus, where the
axons comprising fasciculus cuneatus
terminate.
• Inferior cerebellar peduncle: Connects
medulla to cerebellum.

42. Medulla oblongata

43. Dorsal surface of upper open part
of medulla oblongata
• Dorsal surface of upper part of medulla
forms the lower half of the floor of
fourth ventricle
• The transversely running stria medullaris
fibers separate the dorsal surface of
medulla from that of pons

44. Dorsal surface of upper open part of
medulla oblongata
• These fibers originate from arcuate
nucleus ( dislodged pontine nuclei) and
reach the cerebellum via inferior
cerebellar peduncle

45. Dorsal surface of upper open part of
medulla oblongata from medial to
lateral are:
• Median sulcus: in the median plane.
• Medial eminence: shows two triangular
areas, hypoglossal triangle above and
vagal triangle below, which overlie the
nucleus of hypoglossal nerve and dorsal
motor nucleus of vagus respectively

46. Dorsal surface of upper open part of
medulla oblongata from medial to
lateral are:
• Below the vagal triangle lies area
postrema ( chemoreceptor trigger zone
(CTZ) which trigger vomiting in response
to presence of emetic substances in the
blood). Area postrema is devoid of blood
brain barrier

47. Dorsal surface of upper open part of
medulla oblongata from medial to
lateral are:
• Sulcus limitans: separates medial
eminence from vestibular area.
• Vestibular area: inferior and
medial verstibular nuclei lie deep to this
area

48. Transverse sections of the medulla
oblongata at the level of pyramidal
decussation

49. Transverse sections of the medulla
oblongata at the level of sensory
decussation

50. Transverse sections of the medulla
oblongata at the level of olive (open part
of medulla)

51. The medulla oblongata is supplied by the
following arteries:
• Vertebral arteries.
• Anterior and posterior spinal arteries.
• Anterior and posterior inferior cerebellar
arteries.
• Basilar artery.

52. Applied Aspects
• Medial medullary syndrome
• It occurs due to injury to the
branches of anterior spinal
artery supplying the paramedian
region of medulla

53. Applied Aspects
• Following structures are affected:
• Hypoglossal nucleus
• Medial lemniscus
• Corticospinal tract (pyramid)

54. Medial medullary syndrome

55. The symptoms are as follows
• Contralateral hemiplegia (UMN Paralysis
• Ipsilateral paralysis of tonque muscles
(LMN Paralysis)
• Contralateral loss of conscious
proprioception of position and vibration

56. Lateral medullary syndrome
It occurs due to thrombosis of posterior
inferior cerebellar artery, which supplies a
wedge-shaped area on the dorsolateral
aspect of the medulla
The following structures are affected:
• Vestibular nucleus
• Inferior cerebellar peduncle

57. Lateral medullary syndrome
• Spinal nucleus and tract of trigeminal
• Nucleus ambiguus
• Reticular formation

59. For some of you who may
think that I have wasted
their time, please forgive
me. If you don’t like my face
help me watch this video to
the end
https://www.clutchprep.com/physiology/spinal-tracts-introduction-to-ascending-
and-descending-pathways