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31 Cards in this Set
- Front
- Back
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Rostrally, the midbrain becomes continuous with what structures?
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diencephalon and internal capsule
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Caudally, the medulla becomes continuous with what structure?
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Cervical spinal cord (this happens at the level of the foramen magnum)
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What two major components make up the midbrain?
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Tectum (aka quadrigeminal plate): Composed of superior and inferior colliculi
Cerebral peduncles: Composed of tegmentum (forms central part of midbrain beneath tectum and cerebral aqueduct), substantia nigra (lie ventral to the tegmentum), and crus cerebri (ventrolateral protrusions of the midbrain that contain large bundles of descending fibers) |
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What separates the tectum from the tegmentum in the midbrain?
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Cerebral aqueduct (this aqueduct connects the third and fourth ventricles)
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Where is the pons located?
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Ventral to the upper half of the fourth ventricle
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What two major components make up the pons?
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Tegmentum: continuous with the midbrain tegmentum, lies immediately ventral to the fourth ventricle
Basis pontis: lies ventral to the tegmentum |
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What are the two portions of the medulla?
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Open medulla: located rostrally, open to the fourth ventricle
Closed medulla: located caudally, closed to fourth ventricle (related to central canal) |
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What structure is attached dorsally to the brainstem?
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Cerebellum (connected to midbrain, pons, and medulla by superior, middle, and inferior cerebellar peduncles).
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What does a typical brain stem horizontal cross section consist of?
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-Nuclei associated with cranial nerves III-XII
-Nuclei involved in sensory, motor, and visceral systems -Ascending sensory, descending motor, and other fibers -Reticular formation (less well-defined groups of neurons and fibers located within central gray matter of brainstem) |
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Describe the dorsal brainstem
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Midbrain:
-superior/inferior colliculi -cranial nerve IV (pineal gland extends caudally over colliculi and posterior thalamus is visible) Pons: -Posterior pontine tegmentum -Cerebellar peduncles -Superior medullary velum -Stria medullaris: anatomic distinction between pons & medulla Medulla: -Fasciculi gracilis and cuneatus widen to form the gracile and cuneate tubercles -Obex marks separation between open/closed medulla -Inferior medullary velum |
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Describe the ventral brainstem
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Midbrain:
-crus cerebri -interpeduncular fossa -cranial nerves III and IV (IV starts dorsally) (may also see mammillary bodies and pituitary stalk of diencephalon and optic nerves, chiasm tracts) Pons: -basis pontis -cranial nerves V, VI, VII Medulla: -medullary pyramids (with decussation of the pyrammids at transition from medulla to spinal cord) -Olives (lateral to pyramids in upper 2/3 of medulla) -Cranial nerves VIII, IX, X, XII |
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Which cranial nerves are not attached to the brainstem?
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CN I (Olfactory): attached to forebrain
CN II (Optic nerve): projects from retina to LGN of thalamus CN XI (Spinal accessory nerve): attached to upper cervical spinal cord |
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Which cranial nerves are attached to the brainstem and what region are they attached to?
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Midbrain:
-CN III (Oculomotor) -CN IV (Trochlear) Pons: -CN V (Trigeminal) -CN VI (Abducens) -CN VII (Facial) Medulla -CN VIII (Vestibulocochlear) -CN IX (Glossopharyngeal) -CN X (Vagus) -CN XII (Hypoglossal |
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How are the cranial nerve nuclei organized?
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Into five functional columns. The nuclei of nine cranial nerves (I, II, & VIII nuclei concerned entirely with special senses) form five longitudinal columns of nerve cells that are roughly located from "medial" to "lateral" within each brainstem cross section within which they appear
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Describe the complexity of the cranial nerve nuclei organization
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-Each funcitonal column is discontinuous
-There are many types of columns to represent the motor, sensory, and visceral functions in the brainstem -Cross-sectional anatomy of the brain stem varies considerably from level to level -Each cranial nerve is associated with unique combination of cranial nerve nuclei |
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What are the five functional columns in the brainstem?
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1. Somatic Motor Column containing General Somatic Efferents (GSE) is most medial
2. Branchial Motor Column containing Special Visceral Efferents (SVE) is next 3. Visceral Motor Column containing General Visceral Efferents (GVE) is next 4. Visceral Sensory Column containing General Visceral Afferents (GVA) and Special Visceral Afferents (SVA) is next 5. Somatic Sensory Column containing General Somatic Afferents (GSA) is most lateral column |
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Describe the Somatic Motor Column (location, nuclei)
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-General Somatic Efferents
-Distributed in midbrain (III, IV), pons (VI), and medulla (XII) -III, IV, and VI nuclei supply the extrinsic muscles of the eye (however, NOT lower motor neurons -- no upper motor neuron connections) -XII supplies muscles of the tongue (neurons in this nucleus ARE lower motor neurons) -these somatic motor neuron nuclei are located nearest the midline in brainstem cross sections (represent continuation of anterior horn motor nerve cells of cord) |
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Describe the Branchial Motor Column (location, nuclei)
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-Special Visceral Efferents
-located in pons (motor nuclei of V and VII), medulla (nucleus ambiguus), and upper cervical spinal cord (lower motor neurons of XI) -These LOWER MOTOR NEURONS supply muscles that develop in association with the brancial arches and are concerned with facial expression, chewing, phonation, shrugging shoulders, turning head -Contain lower motor neuron cell bodies that are controlled by descending corticobulbar motor pathways (similar to XII in somatic motor column) |
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Describe the Visceral Motor Column (location, nuclei)
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-Longitudinal column of parasympathetic preganglionic neurons
-Distributed in midbrain (nucleus of Edinger-Westphal associated with III), the pons (lacrimal and superior salivatory nuclei), and medulla (inferior salivatory nuclei and dorsal motor nucleus of the vagus) -Innervates smooth muscles and glands of the head and also to thoracic and abdominal viscera (General Visceral Efferents) |
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Describe the Visceral Sensory Column (location, nuclei)
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-Consists of single nucleus in medulla (nucleus of the solitary tract)
-Receives general visceral afferents (GVA) from mouth, larynx, pharynx, thoracic, and abondominal visceral; receives special visceral afferents (SVA) of taste -receives sensory info from cranial nerves VII, IX, and X |
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Describe the Somatic Sensory Column (location, nuclei)
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-Long column of sensory relay neurons serving general somatic sensibilities from the head
-Extends from midbrain through the pons and medulla into the upper cervical spinal cord -Relays General Somatic Afferent (GSA) info from face, orbit, mouth, and nasal cavity and from meninges |
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What are the major descending tracts through the brainstem?
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Corticospinal tract:
-From primary motor cortex to ventral horn of spinal cord at all levels -Located ventrally in midbrain, pons, and open medulla -In lower medulla, 85% of fibers cross to opposite side to take up a more dorsal position in spinal cord Corticobulbar tracts: -Represent the upper motor neurons that innervate the somatic and brancial lower motor neurons of the brain stem -Follow same course as corticospinal fibers |
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What are the major ascending tracts through the brainstem?
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Medial lemniscus and spinal lemniscus
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What is the tract that runs through most of the brain stem and serves to coordinate eye movements and head position and gaze?
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Medial longitudinal fasciculus (MLF)
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What is the reticular formation?
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Consists of a substantial part of the brainstem gray matter in which groups of neurons and bundles of fibers have a net-like appearance
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Name structures in the rostral midbrain cross section (what structures are here but not in other cross sections?)
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NUCLEUS SUP. COLLICULUS
Cerebral aqueduct Periaqueductal gray OCULOMOTOR NUCLEUS (III) mlf e-w nucleus Spinothalamic tract Medial lemniscus substantia nigra crus cerebri (CS/CB fibers) vta RED NUCLEUS |
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Name structures in the caudal midbrain cross section (what structures are here but not in other cross sections?)
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NUCLEUS INF. COLLICULUS
Cerebral aqueduct Periaqueductal gray TROCHLEAR NUCLEUS (IV) mlf lateral lemniscus Spinothalamic tract Medial lemniscus substantia nigra crus cerebri (CS/CB fibers) decussation of superior cerebellar peduncles |
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Name structures in the mid pons cross section (what structures are here but not in other cross sections?)
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Superior cerebellar peduncle
Middle cerebellar peduncle 4th ventricle Pontine nuclei & basis pontis Medial lemnsicus and spinothalamic tract TRIGEMINAL NERVE (V) -- MOTOR & PONTINE NUCLEI mlf reticular formation |
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Name structures in the caudal pons cross section (what structures are here but not in other cross sections?)
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4th ventricle
Pontine nuclei & basis pontis Medial lemnsicus and spinothalamic tract TRIGEMINAL NERVE (V) -- SPINAL NUCLEUS/TRACT mlf FACIAL MOTOR NUCLEUS (VII) ABDUCENS NUCLEUS (VI) VESTIBULAR NUCLEI |
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Name structures in the rostral/open medulla cross section (what structures are here but not in other cross sections?)
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4th ventricle & choroid plexus
mlf, medial lemniscus, spinothalamic tract HYPOGLOSSAL NUCLEUS (XII) DORSAL MOTOR NUCLEUS OF VAGUS NERVE (X) VESTIBULAR NUCLEUS SOLITARY NUCLEUS/TRACT COCHLEAR NUCLEI NUCLEUS AMBIGUOUS INFERIOR OLIVARY NUCLEUS AND OLIVE PYRAMID |
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Name structures in the caudal/closed medulla cross section (what structures are here but not in other cross sections?)
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spinothalamic tract
spinocerebellar tracts medial lemniscus mlf PYRAMID NUCLEUS GRACILIS & FASICULIS GRACILIS NUCLEUS CUNEATUS AND FASICULIS CUNEATUS Trigeminal Nerve (V) -- spinal tract and nucleus Nucleus of solitary tract Hypoglossal nucleus (XII) Dorsal motor nucleus of X Internal arcuate fibers reticular formation |
