Download Brainstem

Brainstem
Lundy-Ekman
Chapters 14, 15 and 16
Components of the Brainstem
• Midbrain
• Pons
• Medulla
• Rostrally – diencephalon
• Caudally – spinal cord
• Page 358 A and B (good pictures)
Midbrain structures
• Dorsal surface
– Tectum
• Superior colliculus
• Inferior colliculus
• Ventral surface
– Cerebral peduncles
– Interpeduncular fossa
Pontine Stuctures
• Cerebellar peduncles
– Superior cerebellar peduncle
– Middle cerebellar peduncle
– Inferior cerebellar peduncle
Medullary structures
• Pyramids
• Pyramidal decussation
Segments of the brainstem
• Basilar region
• Tegmentum
• Tectum
Basilar region
• Predominantly motor structures
Tegmentum
• Cranial nerve nuclei
• Reticular formation
• Ascending sensory tracts and sensory
nuclei
• Medial longitudinal fasciculus – fiber tract
that coordinates head and eye movements
Tectum
• Superior and inferior colliculi
• Pretectal area
Caudal Medulla
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Pyramids
Medial lemniscus
Dorsal column nuclei and tracts
Spinal trigeminal nucleus and tract
Inferior olivary nucleus
Rostral Medulla
• Note the cerebellar peduncles
Pons
• Corticobulbar, corticopontine, and
corticospinal tracts
• Pontine nuclei
• Pontocerebellar tract
– Cerebral cortetx  corticopontine tract 
pontine nuclei  pontocerebellar tract 
cerebellum
• Brachium pontis – Middle cerebellar
peduncle
Midbrain
• Cerebral peduncles (crus cerebri)
– Cortico- bulbar, spinal and pontine tracts
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Red nucleus
Substancia nigra
Medial lemniscus and spinothalamic tracts
Periaqueductal gray
Oculomotor nucleus
Tectum
Parkinson’s Disease
Sensory and Motor Organization of
the Brainstem
• Development lectures
• Brainstem – page 358
– Motor medial (GSE)
– Sensory lateral (SSA and GSA)
– Visceral (in between)
• Visceral motor medial
• Visceral sensory lateral
Overview of Cranial Nerves
• Arise from the brain
• Innervate the head and neck
• 12 pairs of cranial nerves
Location of Cranial Nerves
• Page 358
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Cerebrum – I
Diencephalon – II
Midbrain – III, IV
Pons – V
Pontomedullary border – VI, VII, VIII
Medulla – IX, X, XI, XII
Functions of Cranial Nerves
• Same overall functions as spinal nerves,
though a cranial nerve may not have all
categories of functions
– Motor
– Sensory
– Autonomic
• Some cranial nerves have special functions
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Smell
Vision
Taste
Vestibular
Three main functions
1. Motor innervation to muscles of face, eyes,
tongue, jaw and two neck muscles.
2. Somatosensory information from skin and
muscles of face and TMJ, and special sensory
information (olfactory, visual, auditory,
vestibular, taste, and visceral sensations)
3. Parasympathetic regulation of heart rate, blood
pressure, digestion, breathing, and some eye
muscles.
Lesions of Cranial Nerves
• Damage to cranial nerve in periphery (trauma,
inflammation)
– Ipsilateral deficits
• Damage to cranial nerve nuclei in CNS (stroke)
– Usually ipsilateral deficits
– Can help localize lesion in the brain
• Damage to upper motor neurons that control
cranial nerves (stroke)
– Usually do not see significant weakness due to
bilateral innervation of CN nuclei. (One significant
exception)
Consciousness
• Awareness of self and surroundings
– Regulate alertness, sleep and attention
Brain components
Reticular formation
• Ascending reticular activating system
(ARAS)
– Project to cerebral parts of consciousness
systems (basal forebrain, thalamus, cerebral
cortex)
• Basal forebrain – in telencephalon
• All regions must be intact for
consciousness
Basal forebrain
• Projects to widespread areas of cortex
• May contribute to:
– Modulation of level of awareness
– Sleep/wake cycle
• Neurotransmitter
• Damaged in Alzheimer’s disease
Consciousness Pathways
• RF neurons receive sensory info
• Multisynaptic transmission through RF
• Rostral RF (rostral pons and midbrain) project to
intralaminar nuclei of thalamus
• Intralaminar nucleus to widespread regions of
cerebral cortex
• Also direct pathways from RF to cerebral cortex
– Raphe – to cortex
– Locus ceruleus – to cortex and hypothalamus
Disorders of Consciousness
• To have a loss of consciousness
• Brainstem
– RF
– ARAS
• Cerebrum
– Hypothalamic/Thalamic activating systems
– Function of entire cerebral cortex
States of altered consciousness
• Coma
• Stupor
• Sleep
Locked-in state
• Not loss of consciousness – may appear
to have impaired consciousness
• Practically complete loss of voluntary
motor function
– Injury usually in ventral pons
– Loss of corticospinal, most corticobulbar
• Usually some sparing of eye movements
– Open eyes
– Some vertical movement of eyes