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Major divisions of the nervous system
Central nervous system (CNS)
Peripheral nervous system (PNS)
Somatic (cerebrospinal) nervous system
Visceral (autonomic) nervous system (ANS)
- sympathetic division
- parasympathetic division
Satisfactory criterion for this is found only in the PNS. In the CNS we cannot easily make
difference between the somatic and autonomic nervous systems.
Cranial cavity
Vertebral canal
external layer of dura mater
No free epidural space!
epidural space
dura mater
internal layer of dura mater
subdural space
subdural space
arachnoid mater
arachnoid mater
subarachnoid space
subarachnoid space
pia mater
pia mater
The meninges
Three membranes called meninges envelop the nervous system. At the CNS level they are easily recognized as dura
mater (pachymeninx), arachnoid mater and pia mater (the last two forming together so-called leptomeninges). At
the level of the PNS these membranes continue as the sheaths of peripheral nerves and ganglions.
The dura mater is the outermost and thickest of all meninges. It lines the cranial cavity and the vertebral canal and
provides support and protection for the nervous system within. It is made of two layers. The external layer serves as
the internal periosteum for bones that built the walls of the cranial cavity and vertebral canal. The internal layer may
be a separate structure (as it is in the vertebral canal) or may fuse with external layer (as in the cranial cavity). The
real space existing in the vertebral canal between the two layers of the spinal dura mater is called epidural
(extradural) space and it contains blood vessels and roots of spinal nerves bathed in fatty tissue. The remnants of
epidural space in the cranial cavity are only seen as dural sinuses, trigeminal cavity and pituitary cavity. There is
no free epidural space in the cranial cavity in a healthy individual. In pathologic condition however, this space may
form again when some contents, especially blood flowing out of torn meningeal arteries, will set the two dural layers
apart.
The internal layer of cranial dura mater in some places makes infoldings that protrude into the cranial cavity and
divide it into smaller compartments. These infoldings include the cerebral falx, the tentorium cerebelli and the
cerebellar falx. The two falxes are oriented sagittally and they intervene between the hemispheres (cerebral or
cerebellar, respectively). The tentorium cerebelli separates the cerebral hemispheres (occipital lobes) from the
cerebellum. The tentorium is attached to the grooves of the transverse and superior petrosal venous sinuses and to the
posterior and anterior clinoid processes. It divides the cranial cavity into supratentorial and infratentorial
compartments. Anteriorly the tentorium is notched to allow the brainstem to pass between the supratentorial and
infratentorial compartments. The supratentorial compartment is further partially divided into two halves by the falx
cerebri. Each half houses one cerebral hemisphere. Below the cerebral falx the telencephalon impar passes to connect
the two hemispheres. The falx cerebelli is not so prominent and it only marginally separates the cerebellar
hemispheres. In addition the internal layer of cranial dura roofs the trigeminal cavity and it also passes above the
pituitary gland as the so-called sellar diaphragm (diaphragma sellae). The pituitary stalk pierces sellar diaphragm
centrally.
The meninges - continued
The arachnoid mater is a delicate membrane, which lines internal surface of the dura mater. It is pressed to the dura
but does not fuse with it. Between the two membranes there is a capillary (hair-like) space moistened with the tissue
fluid. This space is called the subdural space or cavity. It can become the true space if something (e.g. blood) will
accumulate within. Near the dural sinuses and some veins the arachnoid forms many specialized organs, which serve
as the sites of evacuation of the cerebrospinal fluid into the venous blood. These are called arachnoid granulations
(granulations of Pacchioni).
The pia mater grows together with the tissue of the nervous system. It is very thin but functionally important
envelope. It surrounds the vessels, which penetrate the nervous tissue giving them a bit of support. At some places it
invaginates deeply in the internal spaces (ventricles) of the brain and takes part in forming the choroid plexuses (the
organs which produce the majority of the cerebrospinal fluid).
The capacity of the dural envelope is greater than the volume of the nervous system. As pia mater shapes on the
nervous system and arachnoid mater shapes on the dura mater, there is quite a distance between them. This space is
filled with the cerebrospinal fluid and forms the subarachnoid space or cavity. At some places this space is
especially broad and constitutes the subarachnoid cisterns. Through the subarachnoid space tiny fibers of arachnoid
mater run, connecting it with pia mater. There are cerebral vessels and roots of cranial nerves suspended in the
cerebrospinal fluid in the subarachnoid space.
Major divisions of the brain
ontogenetic point of view
Encephalon - Brain
clinical point of view
Encephalon - Brain
(prosencephalon - forebrain)
telencephalon
cerebral hemispheres
telencephalon impar
diencephalon
cerebrum
cerebral hemispheres
telencephalon impar
thalamencephalon
hypothalamus
diencephalon (not included by some authors)
mesencephalon - midbrain
tectum of midbrain
cerebellum
cerebral peduncles
(rhombencephalon - hindbrain)
metencephalon
pons
cerebellum
brainstem
midbrain
pons
myelencephalon
medulla oblongata
medulla oblongata
Major divisions of the brain - continued
Diencephalon
thalamus
thalamencephalon
epithalamus
hypothalamus - includes subthalamus
Mesencephalon
tectum of midbrain
tegmentum
cerebral peduncles
cerebral crura
Specific sensory pathway:
1) - runs from receptors to cerebral cortex,
2) - conveys only one kind of sensation,
3) - uses as few neurons as possible.
Specific sensory pathways
Somatosensory pathways
convey information about somatic sensation
Somatosensory pathway of spinothalamic
(anterolateral) system
conveys pain, temperature and imprecise touch
information from trunk and limbs
Somatosensory pathway of posterior
funiculus/medial lemniscus system
conveys body movements and position,
pressure, vibration and precise touch
information from trunk and limbs
Somatosensory pathways of trigeminal
system
convey all somatic information from head
Olfactory pathway
conveys olfactory information
Visual pathway
conveys visual infomation
Auditory pathway
conveys auditory information
Gustatory pathway
conveys gustatory information
Vestibular pathway
conveys head movements and position
information
Lateral spinothalamic tract
Sensory ganglionic cells are the primary neurons. Their dendrites innervate pain and
temperature receptors and convey impulses running in spinal nerve towards the spinal
ganglion. In spinal ganglion the somata of these cells are found. Then the impulses are
conveyed by axons of sensory ganglionic cells. These small-diameter fibers enter the
spinal cord in posterior root and end synapsing with the cells of posterior horn.
Posterior horn cells are the secondary neurons. Their axons leave the posterior horn
and run through the white commissure toward the contralateral lateral funiculus. Then
they bend up and ascend through the whole length of spinal cord and brainstem to
reach the thalamus. In the spinal cord they run in anterior part of lateral funiculus. In
the brainstem they run through tegmentum (forming the so-called spinal lemniscus).
After arriving at thalamic level they end synapsing with the cells in ventral posterior
lateral nucleus (VPL).
Cells of VPL nucleus of thalamus are the tertiary neurons. Their axons ascend in the
posterior limb of internal capsule to get to the cortex. The bundle of these axons forms
the sensory radiation. The tertiary neurons end synapsing in the somatosensory cortex.
For the trunk and limb regions the cortex is in the posterior part of paracentral lobule
(lower limb) and superior (trunk) and middle (upper limb) parts of postcentral gyrus.
Lateral spinothalamic tract conveys pain and temperature sensations. It comprises three
neurons. Secondary neurons decussate in white commissure of spinal cord.
Decussation is called low, for the tract reaches the other side of the nervous system
almost at the level at which the primary neurons enter the spinal cord.
somatosensory
cortex
Lateral spinothalamic tract
III
neuron
sensory radiation
of posterior limb
of internal capsule
on the other side
cells of ventral posterolateral
(VPL) nucleus of thalamus
tegmentum
of brainstem
II
neuron
white commissure of
spinal cord
to
lateral funiculus
of spinal cord
decussation!
cells of posterior horn
of spinal cord
I
neuron
small-diameter fibers
of posterior root of
spinal nerve
cells of spinal ganglion
branches of
spinal nerve
carries pain and temperature information from
receptors
on the same side
Anterior spinothalamic tract
Sensory ganglionic cells are the primary neurons. Their dendrites innervate imprecise
touch receptors and convey impulses running in spinal nerve towards the spinal
ganglion. In spinal ganglion the somata of these cells are found. Then the impulses are
conveyed by axons of sensory ganglionic cells. These small-diameter fibers enter the
spinal cord in posterior root and end synapsing with the cells of posterior horn.
Posterior horn cells are the secondary neurons. Their axons leave the posterior horn
and run through the white commissure toward the contralateral anterior funiculus.
Then they bend up and ascend through the whole length of spinal cord and brainstem
to reach the thalamus. In the spinal cord they run in lateral part of anterior funiculus. In
the brainstem they run through tegmentum (adding to the spinal lemniscus). After
arriving at thalamic level they end synapsing with the cells in ventral posterior lateral
nucleus (VPL).
Cells of VPL nucleus of thalamus are the tertiary neurons. Their axons ascend in the
posterior limb of internal capsule to get to the cortex. The bundle of these axons forms
the sensory radiation. The tertiary neurons end synapsing in the somatosensory cortex.
For the trunk and limb regions the cortex is in posterior part of the paracentral lobule
(lower limb) and superior (trunk) and middle (upper limb) part of postcentral gyrus.
Anterior spinothalamic tract conveys imprecise touch sensations. It comprises three
neurons. Secondary neurons decussate in white commissure of spinal cord.
Decussation is called low, for the tract reaches the other side of the nervous system
almost on the level on which the primary neurons enter the spinal cord.
somatosensory
cortex
Anterior spinothalamic tract
III
neuron
sensory radiation
of posterior limb
of internal capsule
on the other side
cells of ventral posterolateral
(VPL) nucleus of thalamus
tegmentum
of brainstem
II
neuron
white commissure of
spinal cord
to
anterior funiculus
of spinal cord
decussation!
cells of posterior horn
of spinal cord
I
neuron
small-diameter fibers
of posterior root of
spinal nerve
on the same side
cells of spinal ganglion
branches of
spinal nerve
carries imprecise touch information from
receptors
Ascending tracts of posterior funiculus
Sensory ganglionic cells are the primary neurons. Their dendrites innervate receptors
of many kinds of discriminative sensations (limb position and movement, pressure,
vibration, precise touch) and convey impulses running in spinal nerve towards the spinal
ganglion. In spinal ganglion the somata of these cells are found. Then the impulses are
conveyed by axons of sensory ganglionic cells. These large-diameter fibers enter the
spinal cord in posterior root and reach posterior funiculus. In posterior funiculus they
bend up and ascend through the spinal cord to reach the medulla. Fibers from lower
part of the body form gracile fasciculus, fibers from upper part - cuneate fasciculus. In
medulla the fibers end synapsing with cells of gracile or cuneate nucleus, respectively.
Cells of gracile and cuneate nuclei are the secondary neurons. Their axons cross the
midline in lemniscal decussation and then ascend in the brainstem tegmentum, forming
the medial lemniscus. They run through the whole length of brainstem to reach the
thalamus. After arriving at thalamic level they end synapsing with the cells in ventral
posterior lateral nucleus (VPL).
Cells of VPL nucleus of thalamus are the tertiary neurons. Their axons ascend in the
posterior limb of internal capsule (adding to the sensory radiation) to get to the cortex.
The tertiary neurons end synapsing in the somatosensory cortex. For the trunk and limb
regions the cortex is in posterior part of the paracentral lobule (lower limb) and
superior (trunk) and middle (upper limb) part of postcentral gyrus.
Ascending tracts of posterior funiculus convey discriminative kinds of sensations.
They comprise three neurons. Secondary neurons decussate in lemniscal decussation.
Decussation is called high, for the tracts reach the other side of the nervous system on
the level of medulla, which is high above the level of primary neurons entrance.
Ascending tracts of posterior funiculus
III
neuron
somatosensory
cortex
sensory radiation
of posterior limb
of internal capsule
on the other side
cells of ventral posterolateral
(VPL) nucleus of thalamus
medial lemniscus
in tegmentum of
brainstem
II
neuron
lemniscal decussation
to
decussation!
cells of gracile and cuneate nuclei
fascicles of
posterior funiculus
of spinal cord
large-diameter fibers
of posterior root of
spinal nerve
I
neuron
on the same side
cells of spinal ganglion
branches of spinal nerve
carry discriminative information from
receptors
somatosensory
cortex
Trigeminothalamic tracts
II
neuron
on the other side
tegmentum
of brainstem
decussation!
cells of ventral posteromedial
(VPM) nucleus of thalamus
to
III
neuron
sensory radiation
of posterior limb
of internal capsule
cells of sensory nuclei
of trigeminal nerve
roots of
cranial nerves
I
neuron
on the same side
cells of sensory ganglions
of cranial nerves
branches of
cranial nerves
carry somatosensory information from
receptors
gustatory
cortex
Gustatory pathway
II
neuron
on the other side
tegmentum
of brainstem
decussation!
cells of ventral posteromedial
(VPM) nucleus of thalamus
to
III
neuron
along with sensory
radiation of posterior
limb of internal capsule
cells of upper part
of solitary nucleus
roots of
cranial nerves
I
neuron
on the same side
cells of sensory ganglions
of cranial nerves
branches of
cranial nerves
carries taste information from
receptors
Visual pathway
visual cortex
optic radiation of
posterior limb of
internal capsule
IV
neuron
cells of lateral geniculate nucleus
(LGN) of thalamus
to
optic tract
optic chiasma
III
neuron
partial
decussation!
optic nerve
ganglion cells of retina
II
neuron
intraretinal
pathway
bipolar cells of retina
I
carries visual information from
neuron
rods and cones
Partial decussation of visual pathway
visual field defects
L
visual field
R
site of lession
1
optical apparatus of the eye
retina
optic nerve
2
optic chiasma
optic tract
3
lateral geniculate body
1 - blindness of left eye
optic radiation
2 - hemianopia heteronyma (bitemporalis)
3 - hemianopia homonyma (right)
visual cortex
Auditory pathway
III
neuron
II
neuron
acoustic radiation of
sublentiform part of
internal capsule
on both sides
cells of medial geniculate
nucleus (MGN) of thalamus
brachium of
inferior colliculus
partial
decussation!
lateral lemniscus
cells of different
nuclei of brainstem
to
IV
neuron
auditory cortex
lateral lemniscus
trapezoid body
on both sides
partial
decussation!
cells of cochlear nuclei
root of vestibulocochlear
nerve
I
neuron
bipolar cells of
spiral ganglion
on the same side
branches of cochlear part
of vestibulocochlear nerve
carries auditory information from
receptors
olfactory
cortex
Olfactory pathway
lateral olfactory stria
olfactory tract
mitral cells of
olfactory bulb
olfactory nerve
I
neuron
to
II
neuron
olfactory receptor cells
in mucous membrane
of nasal cavity
olfactory cilia
carries smell information from
! Olfactory pathway
receptors
has two neurons only
does not pass through thalamus
does not cross the midline
on the same side
Cortical areas
Projection areas - get information mainly from one lower center
or send information mainly to one lower center,
are interconnected with projection thalamic nuclei
Sensory areas
Somatosensory (somaesthetic) area
Visual area
Auditory area
Gustatory area
Olfactory area
Vestibular area
Motor area
Association cortical areas - exchange information mainly with other cortical areas
and also with many lower centers
Unimodal association areas - deal with one functional modality only
Multimodal association areas - deal with many functional modalities
Complexes of areas dealing with one functional modality =
projection area + unimodal association area
Sensory areas
Somatosensory complex
Projection somatosensory area - postcentral gyrus and posterior part of paracentral lobule
Association somatosensory area - superior parietal lobule
Visual complex
Projection visual area - calcarine sulcus and adjacent parts of cuneus and lingual gyrus
Association visual area - around (except anteriorly) the projection visual area extending into the
temporal and parietal lobes
Auditory complex
Projection auditory area - transverse temporal gyri and middle part of superior temporal gyrus
Association auditory area - superior temporal gyrus around the projection auditory area
Olfactory complex
Projection olfactory area - uncus
Association olfactory area - enthorhinal area
Projection gustatory area - opercular part of postcentral gyrus
Projection vestibular area - probably lower part of postcentral gyrus
Association unimodal
areas - probably in
superior parietal lobule
Motor areas
Motor complex
Primary projection motor area - precentral gyrus and anterior part of paracentral lobule
Supplementary projection motor area - posterior part of medial frontal gyrus
Association motor area - middle and posterior parts of frontal gyri on the superolateral surface
Frontal eye field - middle part of middle frontal gyrus
Motor (anterior) speech area (Broca’s area) - unpaired, only in dominant hemispheretriangular and opercular parts of inferior frontal gyrus
Multimodal association areas
Posterior association area - opercular part of the postcentral gyrus, inferior parietal lobule, posterior
parts of superior and middle temporal gyri
Sensory (posterior) speech area (Wernicke’s area) - unpaired, only in dominant hemisphere supramarginal and angular gyri and posterior parts of superior and middle temporal gyri
Anterior association area - anterior parts of frontal gyri and inferior surface of frontal lobe
Medial association area - cingulate and parahippocampal gyri
Pyramidal motor system
comprises two neurons
Upper motor neuron - cells of primary motor cortex
Lower motor neuron - motor cells of anterior horn of spinal cord or
cells of motor nuclei of cranial nerves
is functionaly connected with voluntary movements
Pyramidal motor tracts
Corticospinal tracts - related to the striated muscles innervated by spinal nerves
Lateral corticospinal
tract
Anterior corticospinal
tract
Corticonuclear tracts - related to the striated muscles innervated by cranial nerves
carries motor information from
motor cortex
cells of paracentral lobule and superior
and middle parts of precentral gyrus
corona radiata of
internal capsule
anterior part of posterior
limb of internal capsule
I
neuron
cerebral crus
longitudinal
fascicles of pons
to
pyramid
pyramidal decussation
lateral funiculus
of spinal cord
motor cells of anterior horn
of spinal cord
II
neuron
anterior root of
spinal nerve
branches of
spinal nerves
Lateral corticospinal tract
muscles
decussation!
carries motor information from
motor cortex
cells of paracentral lobule and superior
and middle parts of precentral gyrus
corona radiata of
internal capsule
anterior part of posterior
limb of internal capsule
I
neuron
cerebral crus
longitudinal
fascicles of pons
to
pyramid
anterior funiculus
of spinal cord
white commissure
decussation!
motor cells of anterior horn
of spinal cord
II
neuron
anterior root of
spinal nerve
branches of
spinal nerves
Anterior corticospinal tract
muscles
carry motor information from
motor cortex
cells of lower part
of precentral gyrus
corona radiata of
internal capsule
I
neuron
genu of internal capsule
cerebral crus
to
(longitudinal
fascicles of pons)
tegmentum of brainstem
II
neuron
cells of motor nuclei
of cranial nerves
Corticonuclear tracts
roots and branches
of cranial nerves
muscles
partial
decussation!
Corticonuclear tract
is „duplicated” for most motor nuclei of cranial nerves, with the exception
of the lower part of motor facial nucleus and hypoglossal nucleus.
Motor nuclei of cranial nerves except the two mentioned above
receive crossed and uncrossed cortical fibers.
Lower part of facial motor nucleus and hypoglossal nucleus
receive only crossed cortical fibers.
Thalamic nuclei - anatomical classification
Median nuclei
Medial nucleus (medialis dorsalis nucleus)
Intralaminary nuclei
Anterior nucleus
Lateral nucleus
lateral dorsal nucleus
Dorsal nucleus
lateral posterior nucleus
pulvinar
Metathalamus
lateral geniculate body
medial geniculate body
ventral anterior nucleus
Ventral nucleus
ventral lateral nucleus
ventral posterior nucleus
posterior nuclei
Reticular nucleus
ventral posterior medial nucleus
ventral posterior lateral nucleus
ventral posterior inferior nucleus
Thalamic nuclei - functional classification
Specific nuclei - nucleus has precise topographical projection to
a limited region of the ipsilateral cortex and this cortical region
projects back topographically upon the nucleus
Relay nuclei - nucleus receives a major non-thalamic subcortical input
Sensory nuclei - nucleus is involved in sensory function
Motor nuclei - nucleus is involved in motor function
Limbic nuclei - nucleus is involved in limbic function
Association nuclei - nucleus receives their main subcortical input
from other thalamic nuclei
Nonspecific nuclei - nuclear connections with the cerebral cortex
are not of topographically reciprocal type
Sensory thalamic nuclei
spinothalamic tracts,
medial lemniscus
ventral posterior lateral
(VPL) nucleus
somatosensory cortex
(trunk and limbs areas)
trigeminothalamic tracts,
gustatory pathway
ventral posterior medial
(VPM) nucleus
somatosensory cortex
(head area)
optic tract
lateral geniculate nucleus
(LGN)
visual cortex
brachium of
inferior colliculus
medial geniculate nucleus
(MGN)
auditory cortex
Motor thalamic nuclei
globus pallidus, substantia
nigra (cerebellum)
ventral anterior (VA)
nucleus
premotor cortex
cerebellum (globus pallidus,
substantia nigra)
ventral lateral (VL)
nucleus
motor cortex
Limbic thalamic nuclei
amygdaloid body
part of medialis dorsalis
(MD) nucleus
orbitofrontal cortex
mamillary body
anterior nucleus (Ant)
cingulate cortex
Association thalamic nuclei
other thalamic nuclei,
visual pathway
collaterals
other thalamic nuclei
other thalamic nuclei,
hypothalamus
pulvinar (Pul)
parietal, occipital and
temporal association cortex
lateral posterior (LP)
nucleus
parietal association cortex
part of medialis dorsalis
medial temporal and
(MD) nucleus
prefrontal association cortices
Hypothalamic nuclei
pre-optic area
optic region
supra-optic nucleus
paraventricular nucleus
tuberal region
infundibular nucleus
subthalamus
mamillary region
mamillary nuclei
subthalamus
Function of better known hypothalamic nuclei
pre-optic region
belongs to the telencephalon on embryological grounds,
secretes factors controling pituitary production of gonadotropins,
demonstrates sexual dimorphism
optic region
supra-optic nucleus - secretes vasopressin (antidiuretic hormone, ADH)
paraventricular nucleus - secretes oxytocine
tuberal region
infundibular nucleus - secretes hormones which control the function
of anterior lobe of pituitary gland
mamillary region
mamillary nuclei - take their part in Papez’s circuit,
which is related to memory functions
subthalamus
subthalamic nucleus - belongs to the motor extrapyramidal system
Nuclei of cranial nerves
I, olfactory nerve
projection of telencephalon, no nuclei
II, optic nerve
projection of diencephalon, no nuclei
True cranial
nerves
M - motor
nucleus
S - sensory
nucleus
M - oculomotor nucleus
III, oculomotor
nerve
IV, trochlear
nerve
P - accessory oculomotor nucleus
(Westphal-Edinger nucleus)
M - trochlear nucleus
P - parasympathetic
nucleus
mesencephalic
tegmentum at the level
of superior colliculus
mesencephalic
tegmentum at the level
of inferior colliculus
V, trigeminal
nerve
M - trigeminal motor nucleus
midlevel of pontine tegmentum
S - mesencephalic nucleus
tegmentum in upper pons
and mesencephalon
S - pontine nucleus
midlevel of pontine tegmentum
S - spinal nucleus
VI, abducent
nerve
VII, facial
nerve
tegmentum in lower pons,
medulla and cervical spinal
cord
M - abducent nucleus
tegmentum of lower pons
M - facial motor nucleus
tegmentum of lower pons
S - sensory nuclei of
trigeminal nerve
as described above
S - upper (gustatory) part
of solitary nucleus
tegmentum of lower pons
P - superior salivatory nucleus
tegmentum of lower pons
VIII, vestibular
part of
vestibulocochlear
nerve
VIII, cochlear
part of
vestibulocochlear
nerve
S - vestibular nuclei
4 nuclei:
superior, inferior,
lateral and medial
tegmentum of lower
pons and medulla
S - cochlear nuclei
2 nuclei:
dorsal and ventral
tegmentum of
pontomedullary junction
M - ambiguus nucleus
tegmentum of medulla
S - sensory nuclei of
trigeminal nerve
as described above
(conscious somatic sensation)
IX, glossopharyngeal
nerve
S - upper (gustatory) part
of solitary nucleus
tegmentum of lower pons
S - lower part of
solitary nucleus
tegmentum of medulla
(nonconscious somatic
sensation)
P - inferior salivatory nucleus
tegmentum of
upper medulla
M - ambiguus nucleus
tegmentum of medulla
S - sensory nuclei of
trigeminal nerve
as described above
(conscious somatic sensation)
X, vagus
nerve
S - upper (gustatory) part
of solitary nucleus
tegmentum of lower pons
S - lower part of
solitary nucleus
tegmentum of medulla
(nonconscious somatic
sensation)
P - dorsal nucleus of vagus
tegmentum of medulla
M - nucleus ambiguus
tegmentum of medulla
XI, accessory
nerve, spinal part
M - spinal accessory
nucleus
upper cervical
spinal cord
XII, hypoglossal
nerve
M - hypoglossal nucleus
tegmentum of medulla
XI, accessory
nerve, cranial
part