Brain Stem IBrain Stem I

Basic NeuroscienceBasic Neuroscience

James H. Baños, Ph.D.James H. Baños, Ph.D.QuickTime™ and a

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OverviewOverview

Major external featuresMajor external features Transverse sectionsTransverse sections Pathways: The big FourPathways: The big Four Neurotransmitter nucleiNeurotransmitter nuclei

Major Brain Stem Major Brain Stem ActivitiesActivities

ConduitConduit Ascending and descending pathwaysAscending and descending pathways

Integrative functionsIntegrative functions Complex motor patternsComplex motor patterns Respiratory and cardiovascular activityRespiratory and cardiovascular activity Regulation of arousal and level of Regulation of arousal and level of

consciousnessconsciousness Cranial Nerve functionsCranial Nerve functions

Major External Major External FeaturesFeatures

Brain StemBrain Stem

Midbrain

Pons

Medulla

MidbrainMidbrain

Cerebral PedunclesCerebral Peduncles Interpeduncular cisternInterpeduncular cistern

Origin of CN III -- Oculomotor NerveOrigin of CN III -- Oculomotor Nerve

Corpora QuadrigeminaCorpora Quadrigemina Superior ColliculiSuperior Colliculi Inferior ColliculiInferior Colliculi

MidbrainMidbrainCorporaquadrigemina

Cerebralpeduncles

Interpeduncularcistern

CN III

PonsPons

Cerebellar PedunclesCerebellar Peduncles Superior (Dives under the colliculi)Superior (Dives under the colliculi) Middle (Bridge of the pons)Middle (Bridge of the pons) Inferior (inferior/medial to middle)Inferior (inferior/medial to middle)

Floor of the 4th VentricleFloor of the 4th Ventricle

PonsPons

PonsPons

Middle cerebellar peduncle

PonsPons

Middle cerebellar peduncle

Inferior cerebellar peduncles

Superior cerebellar peduncles

PonsPons

4th Ventricle4th Ventricle Inflow from aqueduct of Inflow from aqueduct of

SylviusSylvius Sulcus limitansSulcus limitans

MedullaMedulla

PyramidsPyramids Pyramidal decussationPyramidal decussation Inferior oliveInferior olive Obex (inferiormost point of the 4th Obex (inferiormost point of the 4th

ventricle)ventricle)

MedullaMedulla

Pyramids

Obex

Inferior olive

MedullaMedulla

Inferior Olive

Pyramids

Transverse Transverse SectionsSections

Transverse SectionsTransverse Sections

But first…a word about orientation…But first…a word about orientation…

Clinical Anatomical

MidbrainMidbrain

Cerebral pedunclesCerebral peduncles Substantia nigraSubstantia nigra Red nucleusRed nucleus

MidbrainMidbrain

Cerebral peduncles

Myelin Stained

MidbrainMidbrain

Substantia nigra

MidbrainMidbrain

Red Nucleus

MidbrainMidbrain

Colliculi

MidbrainMidbrain

Substantia nigra

MidbrainMidbrain

Substantia nigra

Red nucles

PonsPons

4th ventricle4th ventricle Pontine nucleiPontine nuclei Locus ceruleusLocus ceruleus

PonsPonsPontine nuclei

4th vent

Locus ceruleus

PonsPons

Locus ceruleus

PonsPons

4th ventricle4th ventricle Pontine nucleiPontine nuclei Locus ceruleusLocus ceruleus

PonsPons

4th ventricle

Middle cerebellar peduncle

Sulcus Limitans

PonsPons

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Rostral MedullaRostral Medulla

PyramidsPyramids Inferior OliveInferior Olive

Rostral MedullaRostral Medulla

PyramidsInferior olive

Caudal MedullaCaudal Medulla

Sensory nucleiSensory nuclei Nucleus GracilisNucleus Gracilis Nuclues CuneatusNuclues Cuneatus

Pyramidal decussationPyramidal decussation

Caudal MedullaCaudal Medulla

Nucleus cuneatusNucleus gracilis

Tectum and TegmentumTectum and Tegmentum

Tectum and TegmentumTectum and Tegmentum

TectumTectum Area posterior to the ventricular spaceArea posterior to the ventricular space Only prominent in the midbrainOnly prominent in the midbrain

Superior and inferior colliculi (“tectal Superior and inferior colliculi (“tectal plate”)plate”)

Tectum and TegmentumTectum and Tegmentum

Tectal Plate

Tectum and TegmentumTectum and Tegmentum TegmentumTegmentum

Area anterior to the ventricular space (but not Area anterior to the ventricular space (but not everything anterior)everything anterior)

This is the embryologically oldest areas of the This is the embryologically oldest areas of the brainstembrainstem

Area anterior to the tegmentum “added on” Area anterior to the tegmentum “added on” during developmentduring development

Big Four Big Four PathwaysPathways

Remember the Big Four?Remember the Big Four?

Corticospinal tract

Dorsal Columns

Spinothalamic tract

Spinocerebellar tracts

Big Four PathwaysBig Four Pathways Corticospinal tractCorticospinal tract

Descending motorDescending motor Spinothalamic tractSpinothalamic tract

Ascending pain/temperatureAscending pain/temperature Dorsal columns/Medial lemniscusDorsal columns/Medial lemniscus

Ascending somatosensory and conscious proprioceptionAscending somatosensory and conscious proprioception Spinocerebellar tractsSpinocerebellar tracts

Ascending unconscious proprioceptionAscending unconscious proprioception

The Big Four -- Caudal MedullaThe Big Four -- Caudal Medulla

Corticospinal tract

Medial Lemniscus

Spinothalamic tract

Spinocerebellar tracts

Lateral Cuneate Nucleus

The Big Four -- Rostral MedullaThe Big Four -- Rostral Medulla

Corticospinal tract

Medial Lemniscus

Spinothalamic tract

Spinocerebellar tracts

The Big Four…err…three -- PonsThe Big Four…err…three -- Pons

Corticospinal tract

Medial Lemniscus

Spinothalamic tract

The Big Three -- MidbrainThe Big Three -- Midbrain

Corticospinal tract

Medial Lemniscus

Spinothalamic tract

Brain Stem Brain Stem NucleiNuclei

Brain Stem NucleiBrain Stem Nuclei

Major neurotransmitter nucleiMajor neurotransmitter nuclei Reticular formation (not really a Reticular formation (not really a

“nucleus” but acts like a group of “nucleus” but acts like a group of nuclei)nuclei)

Nuclei associated with cranial Nuclei associated with cranial nervesnerves

Raphe NucleiRaphe Nuclei

Ridge of cells along the midline in Ridge of cells along the midline in the center of the brainstemthe center of the brainstem

Multiple nucleiMultiple nuclei Caudal Caudal

projections to the spinal cord and other projections to the spinal cord and other parts of the brainstemparts of the brainstem

Rostral Rostral projections to multiple cortical areasprojections to multiple cortical areas

Raphe NucleiRaphe Nuclei

Major serotonin nucleiMajor serotonin nuclei Technically part of the reticular formationTechnically part of the reticular formation Complex reciprocal relationships with multiple Complex reciprocal relationships with multiple

areasareas Ascending pathways involved in many Ascending pathways involved in many

neurobehavioral phenomenaneurobehavioral phenomena MoodMood SleepSleep Feeding/satietyFeeding/satiety

Descending pathways modulate spinal cord Descending pathways modulate spinal cord functionfunction PainPain

Locus CeruleusLocus Ceruleus

Major norepinephrine nucleusMajor norepinephrine nucleus Dorsal wall of the rostral ponsDorsal wall of the rostral pons Projects toProjects to

Spinal cordSpinal cord Brain StemBrain Stem CortexCortex

Locus CeruleusLocus Ceruleus

FunctionFunction ArousalArousal Modulation of stress responsesModulation of stress responses Linked toLinked to

DepressionDepression AnxietyAnxiety Post-traumatic stress disorderPost-traumatic stress disorder

Accounts for some of the psychiatric Accounts for some of the psychiatric symptoms in Parkinson’s Diseasesymptoms in Parkinson’s Disease

Locus CeruleusLocus Ceruleus

Normal Parkinson’s Disease

Substantia NigraSubstantia Nigra

One of a few major dopamine centerOne of a few major dopamine center Projects to the basal gangilaProjects to the basal gangila FunctionFunction

Modulation of movementsModulation of movements Major role in Parkinson’s DiseaseMajor role in Parkinson’s Disease NOT involved in psychiatric NOT involved in psychiatric

symptomssymptoms

Substantia NigraSubstantia Nigra

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Substantia NigraSubstantia Nigra

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Parkinson’s Disease Normal

Nucleus Basalis of Nucleus Basalis of MeynertMeynert

NOT in the brainstem, but importantNOT in the brainstem, but important Located in the basal forebrainLocated in the basal forebrain Major acetylcholine nucleus in the Major acetylcholine nucleus in the

brainbrain Provides tonic stimulation to the Provides tonic stimulation to the

hippocampushippocampusQuickTime™ and a

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Basal Forebrain

Nucleus Basalis of Nucleus Basalis of MeynertMeynert

Major neurotransmitter associated Major neurotransmitter associated with Alzheimer’s Diseasewith Alzheimer’s Disease

Major medications for Alzheimer’s Major medications for Alzheimer’s are cholinesterase inhibitorsare cholinesterase inhibitors

Coming Up…Coming Up…

Reticular formationReticular formation Cranial nerves and their nucleiCranial nerves and their nuclei