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Brain Stem I
Basic Neuroscience
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James H. Baños, Ph.D.
Overview
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Major external features
Transverse sections
Pathways: The big Four
Neurotransmitter nuclei
Major Brain Stem Activities
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Conduit
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Ascending and descending pathways
Integrative functions
Complex motor patterns
 Respiratory and cardiovascular activity
 Regulation of arousal and level of
consciousness
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Cranial Nerve functions
Major External
Features
Brain Stem
Midbrain
Pons
Medulla
Midbrain
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Cerebral Peduncles
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Interpeduncular cistern
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Origin of CN III -- Oculomotor Nerve
Corpora Quadrigemina
Superior Colliculi
 Inferior Colliculi
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Midbrain
Corpora
quadrigemina
CN III
Cerebral
peduncles
Interpeduncular
cistern
Pons
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Cerebellar Peduncles
Superior (Dives under the colliculi)
 Middle (Bridge of the pons)
 Inferior (inferior/medial to middle)
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Floor of the 4th Ventricle
Pons
Pons
Middle cerebellar peduncle
Pons
Superior cerebellar peduncles
Middle cerebellar peduncle
Inferior cerebellar peduncles
Pons
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4th Ventricle
Inflow from aqueduct of
Sylvius
 Sulcus limitans
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Medulla
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Pyramids
Pyramidal decussation
Inferior olive
Obex (inferiormost point of the 4th
ventricle)
Medulla
Obex
Pyramids
Inferior olive
Medulla
Inferior Olive
Pyramids
Transverse Sections
Transverse Sections
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But first…a word about orientation…
Clinical
Anatomical
Midbrain
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Cerebral peduncles
Substantia nigra
Red nucleus
Midbrain
Myelin Stained
Cerebral peduncles
Midbrain
Substantia nigra
Midbrain
Red Nucleus
Midbrain
Colliculi
Midbrain
Substantia nigra
Midbrain
Red nucles
Substantia nigra
Pons
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4th ventricle
Pontine nuclei
Locus ceruleus
Pons
Pontine nuclei
4th vent
Locus ceruleus
Pons
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Locus ceruleus
Pons
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4th ventricle
Pontine nuclei
Locus ceruleus
Pons
4th ventricle
Sulcus Limitans
Middle cerebellar peduncle
Pons
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Rostral Medulla
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Pyramids
Inferior Olive
Rostral Medulla
Pyramids
Inferior olive
Caudal Medulla
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Sensory nuclei
Nucleus Gracilis
 Nuclues Cuneatus
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Pyramidal decussation
Caudal Medulla
Nucleus cuneatus
Nucleus gracilis
Tectum and Tegmentum
Tectum and Tegmentum
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Tectum
Area posterior to the ventricular space
 Only prominent in the midbrain
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Superior and inferior colliculi (“tectal plate”)
Tectum and Tegmentum
Tectal Plate
Tectum and Tegmentum
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Tegmentum
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Area anterior to the ventricular space (but not
everything anterior)
This is the embryologically oldest areas of the
brainstem
Area anterior to the tegmentum “added on”
during development
Big Four Pathways
Remember the Big Four?
Corticospinal tract
Dorsal Columns
Spinothalamic tract
Spinocerebellar tracts
Big Four Pathways
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Corticospinal tract
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Spinothalamic tract
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Ascending pain/temperature
Dorsal columns/Medial lemniscus
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Descending motor
Ascending somatosensory and conscious proprioception
Spinocerebellar tracts
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Ascending unconscious proprioception
The Big Four -- Caudal Medulla
Lateral Cuneate Nucleus
Corticospinal tract
Medial Lemniscus
Spinothalamic tract
Spinocerebellar tracts
The Big Four -- Rostral Medulla
Corticospinal tract
Medial Lemniscus
Spinothalamic tract
Spinocerebellar tracts
The Big Four…err…three -- Pons
Corticospinal tract
Medial Lemniscus
Spinothalamic tract
The Big Three -- Midbrain
Corticospinal tract
Medial Lemniscus
Spinothalamic tract
Brain Stem Nuclei
Brain Stem Nuclei
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Major neurotransmitter nuclei
Reticular formation (not really a “nucleus”
but acts like a group of nuclei)
Nuclei associated with cranial nerves
Raphe Nuclei
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Ridge of cells along the midline in the
center of the brainstem
Multiple nuclei
Caudal
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projections to the spinal cord and other parts
of the brainstem
Rostral
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projections to multiple cortical areas
Raphe Nuclei
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Major serotonin nuclei
Technically part of the reticular formation
Complex reciprocal relationships with multiple
areas
Ascending pathways involved in many
neurobehavioral phenomena
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Mood
Sleep
Feeding/satiety
Descending pathways modulate spinal cord
function
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Pain
Locus Ceruleus
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Major norepinephrine nucleus
Dorsal wall of the rostral pons
Projects to
Spinal cord
 Brain Stem
 Cortex
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Locus Ceruleus
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Function
Arousal
 Modulation of stress responses
 Linked to
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Depression
 Anxiety
 Post-traumatic stress disorder
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Accounts for some of the psychiatric
symptoms in Parkinson’s Disease
Locus Ceruleus
Normal
Parkinson’s Disease
Substantia Nigra
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One of a few major dopamine center
Projects to the basal gangila
Function
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Modulation of movements
Major role in Parkinson’s Disease
NOT involved in psychiatric symptoms
Substantia Nigra
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Substantia Nigra
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Parkinson’s Disease
Normal
Nucleus Basalis of Meynert
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NOT in the brainstem, but important
Located in the basal forebrain
Major acetylcholine nucleus in the brain
Provides tonic stimulation to the
hippocampus
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Basal Forebrain
Nucleus Basalis of Meynert
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Major neurotransmitter associated with
Alzheimer’s Disease
Major medications for Alzheimer’s are
cholinesterase inhibitors
Coming Up…
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Reticular formation
Cranial nerves and their nuclei