Lundy-Ekman Chapters 14, 15 and 16 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 Ventral 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 : anterior Tegmentum : posterior Tectum: only in midbrain, roof over cerebral aqueduct

Basilar region Predominantly motor structures Descending tracts Motor nuclei: pons, substantia nigra Pontocerebellar axons

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 Reflexive control of eye movements Movements of head

Caudal Medulla

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) Red nucleus Cortico- bulbar, spinal and pontine tracts 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 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 Smell Vision Taste Vestibular

Three main functions Motor innervation to muscles of face, eyes, tongue, jaw and two neck muscles. Somatosensory information from skin and muscles of face and TMJ, and special sensory information (olfactory, visual, auditory, vestibular, taste, and visceral sensations) 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 Neurotransmitter: ACh

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 Coma – loss of consciousness, unarousable, not reversible by strong stimuli Stupor – only arousable by strong stimuli Sleep – temporary, physiological loss of consciousness – arousable by environmental stimuli

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