L04 - Brainstem Flashcards by Max Kam

What are the boundaries of the brainstem (anterior and posterior)

Anterior = Optic tract (sup.), C1 spinal nerve (inf.)

Posterior = Superior colliculus (sup.), C1 spinal nerve (inf.)

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3 major functions of the brainstem.

1) Passed through by all ascending, descending pathways
2) Where nuclei of most cranial nerve are located (e.g. 5 senses, facial expression)
3) Where many important life centers (reticular formation) are located, e.g. heartbeat, breath, blood pressure, ascending activating system, blood pH

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What are the main regions of the brainstem

Diencephalon

Midbrain

Pons

Medulla oblongata

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List some major external structures of Diencephalon.

Thalamus

Lateral and Medial geniculate body

Pineal gland Optic tract

Mammillary body

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List some major external structures of Midbrain.

Superior colliculi + Inferior colliculi = Corpora quadrigemina

Superior and inferior cerebral peduncle

Trochlear nerve

Oculomotor nerve

Interpenducular sulcus

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List some major external structures of Pons.

Superior, middle and inferior cerebellar peduncle

Medial eminence

Rhomboid fossa of 4th ventricle

Hypoglossal and Facial trigone

CN V, VII, VIII

Basilar sulcus (ant.) Median sulcus, Stria medullares, Sulcus limitans (post.)

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List some major external structures of Medulla oblongata

Olive Pyramid (+ decussation of pyramid at inf. border)

Cuneate fasciculus

Gracile fasciculus

CN IX, X, XI, XII

Anterior median fissure

Posterior median fissure

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List all the cranial nerves found in midbrain.

CN 2-4

Optic tract

Oculomotor nerve

Trochlear nerve

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List all the cranial nerves found in Pons

CN 5 - 8

Trigeminal nerve

Facial nerve

Abducens nerve

Vestibulocochlear nerve

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List all the cranial nerves found in Medulla oblongata

CN9 - 12

Glossopharyngeal nerve

Vagus nerve

Accesory nerve

Hypoglossal nerve

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Which cranial nerve separates midbrain and pons.

Oculomotor nerve

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Which cranial nerves separate pons and medulla oblongata?

CN VI, VII, VIII

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What pathways go through the medulla oblongata?

Dorsal: Dorsal - Medial Lemniscus tract (ascending sensory)

Ventral: Corticospinal tract (descending motor)

Middle: Reticular formation

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List the internal structures found at the inferior medulla oblongata.

Dorsal:

Nucleus Gracilis (lower limb sensory) + fasciculus
Nucleus Cuneatus (upper limb sensory) + fasciculus
Nucleus of Trigeminal nerve
Internal arcuate fibers (decussation for Dorsal Column Medial Lemniscal pathway)

Ventral:

Anterior gray column
Medullary pyramids + pyramidal decussation

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List the internal structures found at the middle medulla oblongata.

Dorsal:

Nucleus Gracilis. Nucleus Cuneatus
Nucleus of trigeminal nerve
Nucleus of Hypoglossal nerve

Ventral:

Inferior olivary nucleus (hearing)
Medial meniscus (relay mechanical sensory info from nucleus gracilis and cuneatus to thalamus)
Corticospinal tract

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List the internal structures found at the superior medulla oblongata.

Dorsal:

Vestibular nucleus
Vagus nucleus
Trigeminal nerve
Ambiguus nucleus (IX, X, XI)
Inferior cerebellar peduncle
Reticular formation (moved from middle to post)
Spinothalamic tract (lateral)

Ventral:

Medial lemniscus (Dorsal Column Medial Lemniscal pathway)
Corticospinal tract
Inferior olivary nucleus

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List the internal structures found at inferior pons.

Dorsal:

Abducens nucleus - Facial nerve
Middle cerebellar peduncle
Reticular formation
Medial lemniscus (DMLT)

Ventral:

Corticospinal tract
Pontine nucleus >> pontocerebellar fibers >> Middle cerebellar peduncle

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List the internal structures found at superior pons.

Dorsal:

Superior cerebellar peduncle
Medial lemniscus

Lateral: Pontine nucleus

Middle: Trochlear nucleus Reticular formation

Anterior: Corticospinal tract (antero-lateral, scattered between pontocerebellar fibers from pontine nucleus)

List the structures found at the midbrain. (Tectum and different areas of Tegmentum)

Tectum (dorsal):

Superior and inferior colliculus

Tegmentum (posterior):

Cerebral aqueduct + Periaqueductal gray
Oculomotor nucleus

Tegmentum (middle):

Medial lemniscus - Reticular formation - Red nucleus (motor) - Cerebral peduncle

Tegmentum (anterior):

Corticospinal tract (lateral) - Oculomotor nerve* (through interpeduncular fossa) - Substantia nigra (controls basal ganglia)

Functions of the Medulla Oblongata?

House discerte nuclei (i.e. CN 5, 9 - 12) in internal gray matter
Connect with spinal cord via ascending DCML, spinothalamic and descending corticospinal tracts
regulates: heart rate, blood vessel diameter, respiration, swallowing, vomiting, hiccupping, coughing, sneezing
Pyramid and Olive functions

Function of pyramids in Medulla Oblongata?

descending nerve tracts on the anterior surface.

Inferiorly fibers decussate; thus each half of the brain controls the opposite half of the body

Function of olives in Medulla Oblongata?

rounded; protrude from anterior surface.

regulate balance, coordination, modulation of sound from inner ear

Function of Pons?

Host fiber tracts to connect with cerebellum
House Pontine nuclei + Cranial nerve V-IX
Sleep and Respiratory center
House ascending and descending fibers

Function of midbrain tectum?

2 superior colliculi involved in visual reflexes (receive information from inferior colliculi, eyes, skin, cerebrum)

2 inferior colliculi involved in hearing

Function of midbrain tegmentum?

House nerve tracts: - Ascending tracts (e.g. spinal and medial lemniscus from spinal cord to brain) - Descending: cerebral peduncles from cerebrum through brainstem to spinal cord

Function of midbrain red nuclei and substantia nigra?

– Red nuclei of tegmentum: aid in unconscious regulation and coordination of motor activities – Substantia nigra: pigmented with melanin; interconnected with basal nuclei of the cerebrum (motor)

Outline the outflow of Corticospinal tract through the brain stem.

Motor cortex \>\> Cerebral peduncle in midbrain \>\> Pyramids in medulla oblongata \>\> pyramidal decussation \>\> Lateral corticospinal tract + Anterior corticospinal tract

Define reticular formation.

Diffusely interconnected neurons in brainstem (vs. more distinct nuclei associated with cranial nerves)

Function of reticular formation?

- INTEGRATE INFO: sensory, visceral, limbic, and motor functions, and project throughout the CNS - MODULATE FUNCTIONS: autonomic regulation of vital organ system, behavior, somatic motor activities, sleep cycles, alertness, pain modulation

What are the 4 types of reticular formation?

Ascending reticular activating system (ARAS): - Norepinephrine system - Serotonin system - Ach system - Dopamine system

Outline the basic functions of the 4 types of reticular formation?

- Norepinephrine system = Alertness, fight or flight - Serotonin system = Mood and emotions - Pontine- Ach system = wakefulness - Dopamine system = habitual and working memory + incentive emotion

Wakefulness is maintained by neuronal activity in which parts of the brain?

maintained by _cholinergic neuronal activity_ in 2 main arousal centers (Ach): 1. Brainstem: supplies acetylcholine for thalamus, brainstem 2. Forebrain: supplies acetylcholine for cerebral cortex

Pathology of Wallenberg syndrome?

Occlusion of the posterior inferior cerebellar artery supplying the LATERAL aspect of the medulla

What internal structures of the brainstem are affected by Wallenberg syndrome?

Affect lateral medulla: - CN V, IX, X - Spinothalamic tract - Ambiguus nucleus - Sympathetic nerve

Damage to CN V in Wallenberg syndrome causes what symptoms?

ipsilateral analgesia, thermoanesthesia

Damage to Spinothalamic tract in Wallenberg syndrome causes what symptoms?

contralateral analgesia, thermoanesthesia below neck

Damage to ambiguus nucleus in Wallenberg syndrome causes what symptoms?

ipsilateral paralysis in palatal, laryngeal muscles

Damage to sympathetic nerves in Wallenberg syndrome causes what symptoms?

Horner's syndrome Drooping eyelids, reduced pupil size

Pathology of Medial Medullary Syndrome?

Occlusion of the branches of vertebral artery supplying the MEDIAL aspect of the medulla

What internal structures are affected in Medial Medullary Syndrome?

- Medial lemniscus - Corticospinal tract - CN XII

Contralateral impaired sensations of position and movement and tactile discrimination seen in Medial Medullary Syndrome is due to damage to what?

Medial lemniscus, damage DCML pathway

Contralateral hemiparesis seen in Medial Medullary Syndrome is due to damage to what?

Corticospinal tract

Damage to CN XII in Medial Medullary Syndrome causes what symptoms?

Ipsilateral paralysis of tongue muscles with deviation to the paralyzed side when tongue is protruded

Degeneration of which brainstem region causes Parkinsonism?

Substantia nigra in Midbrain