Download Brainstem (II)

Brainstem (II)
李立仁 副教授
解剖學暨細胞生物學科
[email protected]
Brainstem (II)
Long tracts in the brainstem
Corticospinal tract (voluntary movement)
The posterior column-medial lemniscus system
(touch and proprioception)
Anterolateral system (pain and temperature)
Spinocerebellar tract (proprioception)
Brainstem (II)
Long tracts in the brainstem
Corticospinal tract (voluntary movement)
Projecting fibers
carrying commands for
initiation of voluntary
movements originated
from motor, premotor,
supplementary motor
and somatosensory
cortices descend
through the internal
capsule, cerebral
peduncle and basal
pons in company with
corticopontine and corticobulbar fibers.
Brainstem (II)
Long tracts in the brainstem
Corticospinal tract (voluntary movement)
Corticospinal axons continue into
the pyramids of the medulla.
At the spinomedullary junction,
most corticospinal fiber decussate
(pyramidal decussation) to form
the lateral corticospinal tract.
Those do not cross in the pyramidal
decussation continue into the
smaller anterior corticospinal
tract that typically crosses in the
spinal cord before terminating.
Brainstem (II)
Long tracts in the brainstem
The posterior column-medial lemniscus system
(touch and proprioception)
Large-diameter afferents with soma in the DRG
(1st order), conveying information about position
and movement of limb and the details of tactile
stimuli, enter the spinal cord and ascend through
the ipsilateral posterior funiculus (column) and
terminates in the ipsilateral posterior column
nuclei (nuclei gracilis and cuneatus).
Axons from these nuclei (2nd order neurons) cross
the midline as part of the internal arcuate fibers
at the level of midmedulla (sensory decussation)
and ascend to the ventral posterolateral nucleus
(VPL) of the thalamus.
3rd order neurons in VPL projects to primary somatosensory cortex in
postcentral gyrus.
Brainstem (III) Cranial nerves and nuclei
Main trigeminal sensory nucleus (V)
Central processes of primary afferents
with cell bodies in the trigeminal ganglion
(1st order) terminate in the main sensory
nucleus of the trigeminal nerve.
Axons of 2nd neurons cross the midline,
join the medial lemniscus, and ascend to
the ventral posteromedial nucleus (VPM)
of the thalamus.
3rd neurons in VPM in turn project to the
face area of the postcentral gyrus.
Touch and proprioception of face
Somatic sensory nerves
Brainstem (II)
Anterolateral system
(pain and temperature)
Small-diameter afferents with
cell body in the dorsal root
ganglion (1st order), conveying
pain and temperature (and tactile)
information, enter the spinal
cord in the lateral division of each
dorsal root and terminate on the
tract cells in the posterior horn.
Axons of 2nd neurons cross and
join the spinothalamic tract
(somatotopic arranged), then
ascend to the ventral
posterolateral nucleus (VPL) of
the thalamus.
Long tracts in the brainstem
Brainstem (II)
Long tracts in the brainstem
Spinocerebellar tract (proprioception)
Lower limb and trunk:
Posterior spinocerebellar tract
Primary afferents (1st order) terminate on the
interneurons (2nd order) in
the dorsal horn (Clarke's
nucleus) on the same side.
Projecting axons (2nd order)
ascend without crossing
and form synapses in
cerebella by way of
inferior cerebellar peduncle.
Brainstem (II)
Long tracts in the brainstem
Spinocerebellar tract (proprioception)
Upper limb and neck:
Spinocuneocerebellar tract
From above T1, primary afferents
enter the fasciculus cuneatus
directly and terminate on neurons
in the accessory cuneate nucleus
(2nd order).
Projecting axons (2nd order) enter
into the ipsilateral cerebellum via
the inferior cerebellar peduncle.
Brainstem (II)
Neurochemistry of the brainstem
“Out of billions of neurons in the human brain, relatively few
appear to contain biogenic amines – such cells number only in
the thousands……many of the cells containing these transmitters
are clustered together in a discrete region of the brain, the
brainstem.”
-- Nicholls et al., From Neuron To Brain
Glutamate is the most common excitatory transmitter in neurons
throughout the brain.
Gamma-aminobutyric acid (GABA) is nearly a ubiquitous inhibitory
neurotransmitter.
Brainstem (II)
Neurochemistry of the brainstem
Brainstem (II)
Neurochemistry of the brainstem
Norepinephrine (noradrenaline)
by neurons only found in pons and medullary tegmental regions.
- Locus ceruleus (blue spot) near the floor of the 4th ventricle
-- project mainly to cerebral cortex
-- silent during sleep, active during wakefulness
-- form part of the ascending reticular activating system
- Reticular formation in the lateral part of medulla
-- send fibers to spinal cord
- Solitary nucleus and dorsal motor nucleus of vagus
Brainstem (II)
Neurochemistry of the brainstem
Norepinephrine (noradrenaline)
innervates the entire CNS
- ascending fibers to thalamus, hypothalamus, limbic
forebrain and cerebral cortex (SI)
- descending fibers to brainstem, cerebellum and spinal cord
Brainstem (II)
Neurochemistry of the brainstem
Dopamine
used by neurons mostly located in the midbrain
- compact part of substantia nigra (SNc)
- ventral tegmental area (VTA)
involved in the initiation of movement
cf. Parkinson’s disease
also involved in motivation and cognition
cf. drug addiction and schizophrenia
Brainstem (II)
Neurochemistry of the brainstem
Dopamine
projecting fibers are grouped into three bundles
- nigrostriatal (mesostriatal) afferents: SNc to caudate
nucleus and putamen)
- mesolimbic afferents: VTA to limbic structures ex.
amygdala and hippocampus
- mesocortical afferents: VTA to cerebral cortex (frontal)
Brainstem (II)
Neurochemistry of the brainstem
Serotonin (5-HT)
used by neurons in the raphe nuclei throughout the BS
- rostral raphe nuclei project to forebrain (sensory and limbic)
- caudal raphe nuclei project to brainstem and spinal cord and
may modulate thetransmission of pain
- form part of the ascending reticular activating system
- target of antidepressants
Brainstem (II)
Neurochemistry of the brainstem
Acetylcholine
used as neurotransmitter by some
neuron groups in the RF, motor and
preganglionic autonomic neurons
involved in sleep-wakefulness
control
Brainstem (II)
Reticular formation
A diffusely organized area in the central portion of the
brainstem)
Caudally, RF is continuous with the intermediate gray
matter of the spinal cord.
Rostrally, RF continues into the intralaminar nuclei of the
thalamus.
Brainstem (II)
Four major
groups :
Precerebellar
reticular nu.
coordination of
muscle contraction
Raphe (median) and
catacholamine nu.
sleep-alertness
pain modulation
Brainstem (II)
Central (medial)
reticular nu.
eye movement
conscious state
Lateral reticular nu.
respiratory and
circulatory system
feeding
Brainstem (II)
Functions of reticular formation
Control of movement
Spinal motor neurons are influenced
(in addition to the corticospinal
pathway) by reticulospinal pathways.
Reticulospinal neurons receive
collaterals from spinoreticular fibers
and spinothalamic fibers and inputs
from red nucleus, cerebellum and
somatosensory as well as motor
cortices.
The reticulospinal tracts carry
descending motor commands
generated within RF.
Reticular formation
Brainstem (II)
Functions of reticular formation
Modulates pain transmission
Neurons in the periaqueductal
gray (PAG) receives collaterals of
spinothalamic (pain-conducting)
fibers and projects to the raphe
nuclei (particularly nucleus raphe
magnus) in the RF.
Neurons in these areas in turn
send afferents to the superficial
laminae of the posterior horn,
suppressing the transmission of
pain information received by
spinothalamic neurons.
Reticular formation
Brainstem (II)
Reticular formation
Functions of reticular formation
Controls the arousal and consciousness
Neurons in RF collect multiple sensory information and send
ascending projections to diencephalon and telencephalon.
This pathway collaborates
with monoamine-containing
reticular projections form
the ascending reticular
activating system (ARAS)
that continuously send
signals to sustain cerebral
activities and consciousness.
Brainstem (II)
Reticular formation
Functions of reticular formation
Controls the arousal and consciousness
The ascending reticular activating system also works together
with histaminergic and cholinergic projections from
hypothalamus and basal forebrain regulate the sleep-awake cycle.
Brainstem (II)
Blood supply of the brainstem
Vertebral-basilar system
Medulla oblongata
Anterior spinal a.
Posterior spinal a.
Posterior inferior
cerebellar a.
Brs. Vertebral a.
Pons
Brs. Basilar a.
Midbrain
Brs. Basilar a.
Superior cerebellar aa.
Posterior cerebral aa.
F
E
D
C
B
A
Brainstem (II)
General arrangement of
cranial nerve nuclei
(SA)
(VA)
Alar
plate
Basal
plate
(VE)
(SE)
Brainstem (II)
General Arrangement
Brainstem (II) Cranial nerve nuclei
General Arrangement
General
General somatic afferents (GSA) : from skin, skeletal muscles, joints and ligaments
General visceral afferents (GVA) : from visceral organ and blood vessels
General somatic efferents (GSE) : to skeletal muscles derived from myotomes
General visceral efferents (GVE) : to smooth and cardiac muscles and glands
Special
Special somatic afferents (SSA) : from visual and auditory organs
Special visceral afferents (SVA) : from visceral sense (taste and smell) organs
Branchial
Branchial efferents (BE) : to striated muscles derived from branchial arches
Brainstem (II) Cranial nerve nuclei
GSE (3, 4, 6, 12)
Oculomotor (III)
Trochlear (IV)
Abducens (VI)
Hypoglossal (XII)
GVE (3, 7, 9, 10)
Edinger-Westphal n. (III)
Sup. Salivatory nu. (VII)
Inf. Salivatory nu. (IX)
Dorsal nu. Vagus (X)
BE (5, 7, 9, 10, 11)
Trigeminal motor nu. (V)
Facial motor nu. (VII)
Nu. Ambiguus (IX, X)
Accessory nu. (XI)
General Arrangement
Brainstem (II) Cranial nerve nuclei
SSA (8)
Cochlear and vestibular
nuclei (VIII)
GSA (5, 7, 9, 10)
Main trigeminal
sensory nucleus (V)
Mesencephalic
trigeminal nucleus (V)
Spinal trigeminal
nucleus (V, VII, IX, X)
GVA/SVA (VA) (7, 9, 10)
Nu. Solitary tract
(VII, IX, X)
General Arrangement
Brainstem (II) Cranial nerve nuclei
Brainstem (II)
Cranial nerves and nuclei
Somatic motor nerves (3, 4, 6, 12) --- GSE
Oculomotor nerve (III) innervates four extra-ocular muscles
Trochlear nerve (IV) innervates superior oblique
Abducens nerve (IV) innervates lateral rectus
Hypoglossal nerve (XII)
innervates tongue muscles
Brainstem (II) Cranial nerves and nuclei
Oculomotor
nerve (III)
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Somatic motor nerves
Oculomotor nerve (III)
Supplies :
Levator palpebrae
superioris
Superior rectus
Medial rectus, inferior
oblique, inferior rectus
Brainstem (II) Cranial nerves and nuclei
Oculomotor nerve (III)
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Trochlear nerve (IV)
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Somatic motor nerves
Trochlear nerve (IV)
Supplies :
Superior oblique (SO4)
Brainstem (II) Cranial nerves and nuclei
Trochlear nerve (IV)
A unique cranial nerve that :
exit from the dorsal surface of the brain
all the lower motor neuron fibers decussate
longest intracranial course
smallest number of axons
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Abducens nerve (VI)
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Abducens nerve (VI)
Supplies :
Lateral rectus
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Abducens nerve (VI)
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Inter-nuclear connection
-- between abducens nucleus
and oculomotor nucleus
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Hypoglossal nerve (XII)
Somatic motor nerves
Brainstem (II) Cranial nerves and nuclei
Somatic motor nerves
Hypoglossal nerve (XII)
Hypoglossal trigone
Brainstem (II) Cranial nerves and nuclei
Somatic motor nerves
Hypoglossal nerve (XII)
Supplies :
intrinsic and most extrinsic tongue muscles of same side
If damaged :
Tongue is deviated
toward the side
of lesion.
Bilateral lesions of
hypoglossal nerve
cause difficulties in
eating & speaking