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Brain Stem I. Basic Neuroscience James H. Baños, Ph.D. Overview. Major external features Transverse sections Pathways: The big Four Neurotransmitter nuclei. Major Brain Stem Activities. Conduit Ascending and descending pathways Integrative functions Complex motor patterns
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Brain Stem I Basic Neuroscience James H. Baños, Ph.D.
Overview • Major external features • Transverse sections • Pathways: The big Four • Neurotransmitter nuclei
Major Brain Stem Activities • Conduit • Ascending and descending pathways • Integrative functions • Complex motor patterns • Respiratory and cardiovascular activity • Regulation of arousal and level of consciousness • Cranial Nerve functions
Midbrain Pons Medulla Brain Stem
Midbrain • Cerebral Peduncles • Interpeduncular cistern • Origin of CN III -- Oculomotor Nerve • Corpora Quadrigemina • Superior Colliculi • Inferior Colliculi
Midbrain Corpora quadrigemina CN III Cerebral peduncles Interpeduncular cistern
Pons • Cerebellar Peduncles • Superior (Dives under the colliculi) • Middle (Bridge of the pons) • Inferior (inferior/medial to middle) • Floor of the 4th Ventricle
Pons Middle cerebellar peduncle
Pons Superior cerebellar peduncles Middle cerebellar peduncle Inferior cerebellar peduncles
Pons • 4th Ventricle • Inflow from aqueduct of Sylvius • Sulcus limitans
Medulla • Pyramids • Pyramidal decussation • Inferior olive • Obex (inferiormost point of the 4th ventricle)
Medulla Obex Pyramids Inferior olive
Medulla Inferior Olive Pyramids
Transverse Sections • But first…a word about orientation… Anatomical Clinical
Midbrain • Cerebral peduncles • Substantia nigra • Red nucleus Midbrain = Mickey
Midbrain Myelin Stained Cerebral peduncles
Midbrain Substantia nigra
Midbrain Red Nucleus
Midbrain Colliculi
Midbrain Substantia nigra
Midbrain Red nucles Substantia nigra
Pons • 4th ventricle • Pontine nuclei • Locus ceruleus
Pons Pontine nuclei 4th vent Locus ceruleus
Pons Locus ceruleus
Pons • 4th ventricle • Pontine nuclei • Locus ceruleus
Pons 4th ventricle Sulcus Limitans Middle cerebellar peduncle
Rostral Medulla • Pyramids • Inferior Olive
Rostral Medulla Pyramids Inferior olive
Caudal Medulla • Sensory nuclei • Nucleus Gracilis • Nuclues Cuneatus • Pyramidal decussation
Caudal Medulla Nucleus cuneatus Nucleus gracilis
Tectum and Tegmentum • Tectum • Area posterior to the ventricular space • Only prominent in the midbrain • Superior and inferior colliculi (“tectal plate”)
Tectum and Tegmentum Tectal Plate
Tectum and Tegmentum • Tegmentum • 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
Remember the Big Four? Corticospinal tract Dorsal Columns Spinothalamic tract Spinocerebellar tracts
Big Four Pathways • Corticospinal tract • Descending motor • Spinothalamic tract • Ascending pain/temperature • Dorsal columns/Medial lemniscus • Ascending somatosensory and conscious proprioception • Spinocerebellar tracts • 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 • Major neurotransmitter nuclei • Reticular formation (not really a “nucleus” but acts like a group of nuclei) • Nuclei associated with cranial nerves
Raphe Nuclei • Ridge of cells along the midline in the center of the brainstem • Multiple nuclei • Caudal • projections to the spinal cord and other parts of the brainstem • Rostral • projections to multiple cortical areas
Raphe Nuclei • Major serotonin nuclei • Technically part of the reticular formation • Complex reciprocal relationships with multiple areas • Ascending pathways involved in many neurobehavioral phenomena • Mood • Sleep • Feeding/satiety • Descending pathways modulate spinal cord function • Pain
Locus Ceruleus • Major norepinephrine nucleus • Dorsal wall of the rostral pons • Projects to • Spinal cord • Brain Stem • Cortex