L04 - Brainstem Flashcards
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.)
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
What are the main regions of the brainstem
Diencephalon
Midbrain
Pons
Medulla oblongata
List some major external structures of Diencephalon.
Thalamus
Lateral and Medial geniculate body
Pineal gland Optic tract
Mammillary body
List some major external structures of Midbrain.
Superior colliculi + Inferior colliculi = Corpora quadrigemina
Superior and inferior cerebral peduncle
Trochlear nerve
Oculomotor nerve
Interpenducular sulcus
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.)
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
List all the cranial nerves found in midbrain.
CN 2-4
Optic tract
Oculomotor nerve
Trochlear nerve
List all the cranial nerves found in Pons
CN 5 - 8
Trigeminal nerve
Facial nerve
Abducens nerve
Vestibulocochlear nerve
List all the cranial nerves found in Medulla oblongata
CN9 - 12
Glossopharyngeal nerve
Vagus nerve
Accesory nerve
Hypoglossal nerve
Which cranial nerve separates midbrain and pons.
Oculomotor nerve
Which cranial nerves separate pons and medulla oblongata?
CN VI, VII, VIII
What pathways go through the medulla oblongata?
Dorsal: Dorsal - Medial Lemniscus tract (ascending sensory)
Ventral: Corticospinal tract (descending motor)
Middle: Reticular formation
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
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
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
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
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):
- Brainstem: supplies acetylcholine for thalamus, brainstem
- 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
