14. Brainstem
Performs spinal cord-like functions for the head
Contains LMN for head muscles
Initial processing of general afferent information
concerning head
15. Conduit function
the only way for ascending tracts to reach the
thalamus or cerebellum, or for descending
tracts to reach the spinal cord, is by passing
through the brainstem.
16. Ascending tracts reach thalamus and
cerebellum
Descending tracts reach spinal cord
Many tracts do not run through straight-
frequent involvement of relay nuclei
19. Cranial nerve functions
Cranial nerves are head’s equivalent of spinal
nerves
Involved in olfaction, sight, hearing,
equilibrium and taste
Olfactory → telencephalon
Optic → diencephalon
20. The rest project to or emerge from brainstem
Collection of sensory and motor nuclei
related to cranial nerve function at various
levels in brainstem
21. Integrative function
Complex motor patterns
Regulation of cardiovascular and respiratory
activity
Some regulation of consciousness [function
of reticular formation in central core of
brainstem]
22. Much of this is accomplished by the reticular
formation, which forms the central core of
the brainstem
23. Medulla
The medulla is vaguely scoop .The "handle"
corresponds to the caudal or closed portion,
containing a central canal continuous with that
of the spinal cord.
The open portion of the scoop corresponds to
the rostral or open medulla, in which the central
canal expands into the fourth ventricle.
24. The apex of theV-shaped caudal fourth
ventricle, where it narrows into the central
canal, is called the obex
The longitudinal grooves on the surface of
the spinal cord continue into the medulla,
more clearly at some levels than at others.
25. They divide the surface of the caudal medulla
and part of the rostral medulla into a series of
columns that completely encircle it
The anterior median fissure is briefly
interrupted by the pyramidal decussation at the
junction between spinal cord and brainstem, but
then it continues rostrally to the edge of the
pons, separating the two pyramids
26.
27.
28.
29.
30. The pons
Pons is the Latin word for "bridge," and this
portion of it (called the basal pons) looks like a
bridge interconnecting the two cerebellar
hemispheres.
It is not, however, a direct interconnection.
Rather, many of the fibers descending in each
cerebral peduncle synapse in scattered nuclei of
the ipsilateral half of the basal pons.
31. These nuclei in turn project their fibers across
the midline, after which they funnel into the
middle cerebellar peduncle (brachium
pontis) and finally enter the cerebellum
42. The Internal Structure of the Brainstem Reflects
Surface Features and the Position of Long Tracts
The corticospinal and spinothalamic tracts have
consistent locations throughout the brainstem
The three major longitudinal pathways
(corticospinal tract, poterior columns, and
spinothalamic tract) can be followed
systematically through the brainstem
43. Two of the three stay in more or less the
same location throughout the brainstem.
Corticospinal fibers travel in the most ventral
part of the brainstem, traversing the cerebral
peduncle, basal pons, and medullary
pyramid.
At the spinomedullary junction, most of the
fibers in the pyramids decussate and form the
lateral corticospinal tracts
44.
45. The spinothalamic tract at all levels of the
brainstem is in or near the anterolateral
corner of the tegmentum, similar to its
position in the spinal cord.
The posterior columns terminate in the
posterior column nuclei (nucleus gracilis and
nucleus cuneatus) of the medulla
46. Locations of the corticospinal tract, medial lemniscus,
spinothalamic tract, and reticular formation in the caudal and
rostral medulla (A, B), caudal pons and midpons(C, D) and caudal
and rostral midbrain (E, F)
47. Efferent fibers from these nuclei decussate in
the medulla to form the medial lemniscus,
which reaches the thalamus
48.
49.
50.
51.
52.
53. Major midline decussations
The term decussation refers to the
intersection of matching fiber pathways as
they cross the midline on their way to or from
the brain.
Two major sensory decussations are those of
the spinothalamic pathway in the spinal cord
and the posterior column-medial lemniscal
pathway in the medulla oblongata.
54. A major cerebellar decussation is that of the
dentatothalamic tract in the midbrain.
The pyramidal, motor decussation is in the
medulla oblongata and contains corticospinal
fibers crossing to the contralateral side of the
spinal cord.
All four are brought into play by simply
clicking on a mouse
61. In the thoracic region of the developing spinal
cord, four distinct cell columns can be
identified in the gray matter on each side
In the basal plate, the general somatic efferent
column supplies the striated muscles of the
trunk and limbs.
62. The general visceral efferent column contains
preganglionic neurons of the autonomic
system.
In the alar plate, the general visceral afferent
column receives afferents from thoracic and
abdominal organs.
A general somatic afferent column receives
afferents from the body wall.
63.
64. In the brainstem, these four cell columns can
be identified
they are fragmented
not all contribute to each cranial nerve
66. General somatic efferent
(GSE) column.
Supplies the striated musculature of the orbit
(via the oculomotor, trochlear, and abducens
nerves) and tongue (via the hypoglossal nerve).
67. General visceral efferent
(GVE) column
Gives rise to the cranial parasympathetic
system
The target ganglia are the ciliary,
pterygopalatine, otic, and submandibular
ganglia in the head, and the vagal ganglia in
the thorax and abdomen
69. General somatic afferent
column.
Receives from skin and mucous membranes,
mainly in trigeminal nerve territory whose
most important components are
1. the skin and mucous membranes of the
oronasofacial region
2. the dura mater.
70. Three additional cell columns serve
pharyngeal arch derivatives and the inner ear.
71. Special visceral efferent
column
To pharyngeal arch musculature of face, jaws,
palate, larynx, and pharynx (via facial,
trigeminal, glossopharyngeal, vagus, and
cranial accessory nerves).
These striated muscles have visceral
functions in relation to food and air intake
(hence, visceral).
