Brainstem part 1 Flashcards Preview

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Flashcards in Brainstem part 1 Deck (89):
1

Brainstem (parts)

midbrain, pons, medulla

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Brainstem (what does it do)

~Tracts interconnect cerebrum, spinal cord, & cerebellum
~cranial nerves & nuclei
~reticular formation

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External features of brainstem

Ventral and dorsal structures

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Ventral external structures- medulla

~ventral median sulcus
~pyramids
~pyramidal decussation
~olive

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Ventral external structures- pons

~basilar sulcus
~middle cerebellar peduncle

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Ventral external structures- midbrain

~cerebral peduncles
~interpeduncular fossa
~mammillary bodies

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Dorsal external structures- medulla

~gracile tubercle
~cuneate tubercle
~obex

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Dorsal external structures- pons

~4th ventricle
~middle and superior cerebellar peduncles

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Dorsal external structures- midbrain

~corpora quadrigemina

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Ventral median sulcus

~an indentation that runs the length of the medulla along the middle of the ventral surface of the medulla
~if the continuation of similar feature on the spinal cord

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Pyramids

~lying on both sides of the ventral median sulcus
~corticospinal pathways running along the ventral surface of the medulla

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Pyramidal decussation

~about 90% of the fibers of the corticospinal tract cross or decussate at the caudal end of the medulla
~it is seen as a disappearance of the ventral median sulcus

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Olive

~two bulges just lateral to the pyramids
~are due to a large nucleus called inferior olivary nucleus

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Basilar sulcus

~a shallow groove where basilar artery runs up the middle of the pons

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Middle cerebellar peduncle

~two large fiber tracts come off the pons laterally
~are entry of pontocerebellar fibers into the cerebellum

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Cerebral peduncle

~motor pathways between cerebrum and brainstem

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Interpeduncular fossa

~between the two cerebral peduncles

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Mammillary bodies

~within the interpeduncluar fossa
~are actually not part of the midbrain, but are the mort posterior part of hypothalamus

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Gracile tubercle

~nucleus gracilis of dorsal column pathway
~on the dorsal surface of the medulla

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Cuneate tubercle

~nucleus cuneatus of dorsal column pathway
~on the dorsal surface of the medulla

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Obex

~caudal end of 4th ventricle
~between the gracile tubercle

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4th ventricle

~forms much of the dorsal surface of the pons

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middle and superior cerebellar peduncles

~the 4th ventricle is lateral framed n the middle and superior cerebellar peduncles
*an inferior peduncle can sometimes be seen just rostral and dorsolateral to the olive

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corpora quadrigemina

~a four paired structure (sometimes referred to as midbrain tectum)
~2 superior colliculi and 2 inferior colliculi

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Descending tracts

(Motor based)
~Corticospinal
~Corticobulbar
~reticulospinal
~vestibulospinal
~tectospinal
~rubospinal

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Descending tracts beginning in the cerebral cortex

Corticospinal & Corticobulbar

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Descending tracts beginning in the brainstem

reticulospinal, vestibulospinal, tectospinal & rubrospinal

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Corticospinal (Descending tract)

the tract the begins in the cerebral cortex and ends in the spinal cord

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Corticospinal (Descending tract)

the tract the begins in the cerebral cortex and ends in the brains stem

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reticulospinal (descending tract)

the tract that begins in the reticular formation and ends in the spinal cord

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vestibulospinal (descending tract)

the tract that begins in the vestibular nuclei and ends in the spinal cord

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tectospinal (descending tract)

the tract the begins in the midbrain tectum and ends in the spinal cord

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rubrospinal (descending tract)

the tract the begins in the red nucleus and ends in the spinal cord

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Ascending Tracts

(sensory)
~Medial lemniscus pathway
~spinothalamic
~spinocerebellar
~trigeminothalamic tracts

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Dorsal column-medal lemniscus pathway (ascending pathway)

~begins the spinal nerves primary afferent and ends in cerebral cortex
~the tract does relay (synapse) twice between when it enters the spinal cord and reaches the cerebral cortex

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Ascending tracts that pass through the brainstem

spinothalamic, spinocerebellar & trigeminothalamic tracts

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spinothalmic (ascending tract)

going from the spinal cord to the thalamus

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spinocerebellar (ascending tract)

going from the spinal cord to the cerebellum

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trigmiothamic (ascending tract)

going from the trigeminal (cranial nerve V) to the thalamus

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There are many nuclei within the brainstem that serve the _____

cranial nerves

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The cranial nerves and their nuclei have 3 functions:

sensory, motor, autonomic (parasympathetic)

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Cranial Nerve I

Olfactory
~not end in brainstem

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Cranial Nerve II

Optic
~not end in brainstem

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Cranial Nerve III

Oculomotor

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Cranial Nerve IV

Trochlear

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Cranial Nerve V

Trigeminal

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Cranial Nerve VI

Abducens

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Cranial Nerve VII

Facial

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Cranial Nerve VIII

Vestibulocochlear

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Cranial Nerve IX

Glossopharyngeal

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Cranial Nerve X

Vagus

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Cranial Nerve XI

Spinal accessory

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Cranial Nerve XII

Hypoglossal

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Cranial Nerve V (details)

~there are three pairs of nuclei associated with the Trigeminal Nerve (Spinal, Chief, Mesencephalic Nerve)
~all three are dorsal and lateral located in medulla, pons, and midbrain

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Cranial Nerve V- Spinal Nucleus

~dorsal lateral medulla
~receives and relays pain and temperature sensation from the face

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Cranial Nerve V- Chief Sensory Nucleus

~dorsal lateral pons
~receives and relays touch and pressure sensations from the face

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Cranial Nerve V- Mesencephalic Nucleus

~dorsal lateral midbrain
~receives and relays proprioception sensation from face muscles

58

Cranial Nerve VII (details on Gustatory Nucleus)

(Cranial Nerve VII have a single sensory nucleus- the Gustatory Nucleus)
~dorsal and medially at pontomedullary junction
~transmits taste sensation from anterior 2/3 of tongue
~Gustatory Nucleus also receives taste sensation from CN IX (glossopharyngeal) and X (vagus)

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Cranial Nerve VIII (details)

the vestibulocochlear nerve (CN VIII) ends on 6 pairs of nuclei
~2 cochlear nuclei (auditory)
~4 vestibular nuclei
~nuclei are all on the dorsal surface of pons and ponto-medullary junction

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Sensory Nuclei of the Brainstem

~Gustatory Nucleus (input from CN VII, IX, and X)
~Nucleus Solitarius (input from CN IX and X)

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Nucleus Solitarius

~located on the dorsal & medial medulla
~receives input from the high pressure barorecptors of the carotid sinus (CN IX) and aorta (CN X)
~these inputs are involved in cardiovascular regulation

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Cranial Nerves that have sensory functions

CN I, II, V, VII, VIII, IX, X
(olfactory, optic, trigeminal, facial, vestibulocochlear, glossopharyngeal, vagus)

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Cranial Nerves that have motor functions

CN II, IV, V, VI, VII, IX, X, XI, XII
(oculomotor, trochlear, trigeminal, abducens, facial, glossopharyngeal, vagus, spinal accessory, hypoglossal)

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Oculomotor Nucleus

~located on the medial and dorsal midbrain
~contains motor neurons whose axons for the CN III
~these motor axonsinnervates the medial, superior, and inferior rectus muscle and inferior oblique muscle and the levator palpebrae

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Trochlear Nucleus

~medial and dorsal midbrain
~has axons that give rise to the CN IV
~innervation of the superior oblique muscle of eye

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Abducens Nucleus

~medial dorsal aspect of the caudal pons
~has axons that form the CN VI
~innervated the lateral rectus muscle of the eye

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Trigeminal Motor Nucleus

~dorsal aspect of the mid pons
~gives rise to the CN V
~innervates muscles of mastication

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Facial Motor Nucleus

~dorsal lateral aspect of the pontomedularly junction
~gives rise to CN VII
~innervates muscles of facial expression

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Nucleus Ambiguus

~dorsal lateral aspect of the medulla and pontomedullary junction
~gives rise to axons which for 3 cranial nerves (CN IX, X, XI)
these nerves innervate stylopharyngeus muscle (CN IX), the laryngeal and pharyngeal muscles (CN X and XI), and the muscles of the uvula (CN X)

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Accessory Nucleus

`extends up from the dorsal horn of the cervical spinal cord into the dorsal medial aspect of the caudal medulla
~forms the spinal portion of the CN XI
~axons from these lower motor neurons innervate the sternocleidomastoid and upper trapezius muscles

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Hypoglossal Nucleus

~dorsal and medial aspect of the rostral medulla
~lower motor nucleus of the CN XII
~axons from the hypoglossal nucleus innervate the muscle of the tongue

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Cranial Nerves with autonomic function

CN III, VII, IX, X
(oculomotor, facial, glossopharyngeal, vagus)

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Several nuclei have autonomic- parasympathetic functions

~Edinger-Westphal Nucleus
~Superior Salivatory Nucleus
~Inferior Salivatory Nucleus
~Dorsal Motor Nucleus

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Edinger-Westphal Nucleus

~dorsal medial midbrain
~part of the oculomotor nuclear complex (gives rise to axons which form part of the CN III)
~axons are the parasympathetic innervations of pupil and ciliary muscles of the eye which function constriction and accommodation of the lens for close vision

75

Superior Salivatory Nucleus

~dorsal medial pons
~gives rise to fibers in CN VII
~axons are parasympathetic efferent to lacrimal glands and to the submandibular and sublingual salivary glands

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Inferior Salivatory Nucleus

~dorsal medial medulla
~has axons that forms part of the CN IX
~provides parasympathetic efferent to parotid gland

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Dorsal Motor Nucleus

~dorsal medial medulla
~provides parasympathetic innervation via CN X (vagus nerve) to the thoracic and abdominal viscera

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Cranial Nerve I (are there any; if so, name of nucleus/I)

no cranial nerve nuclei

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Cranial Nerve II (are there any; if so, name of nucleus/I)

no cranial nerve nuclei

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Cranial Nerve III (are there any; if so, name of nucleus/I)

~Oculomotor (motor)
~Edinger-Westphal (autonomic)

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Cranial Nerve IV (are there any; if so, name of nucleus/I)

~Trochlear (motor)

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Cranial Nerve V (are there any; if so, name of nucleus/I)

~Nucleus of Spinal Tract (sensory)
~Chief Sensory (sensory)
~Mensencephalic (sensory)
~Trigeminal (motor)

83

Cranial Nerve VI (are there any; if so, name of nucleus/I)

~Aducens (motor)

84

Cranial Nerve VII (are there any; if so, name of nucleus/I)

~Gustatory (sensory)
~facial motor (motor)
~superior salivatory (automonic)

85

Cranial Nerve VIII (are there any; if so, name of nucleus/I)

~cochlear (2) (sensory)
~vestibular (4) (sensory)

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Cranial Nerve IX (are there any; if so, name of nucleus/I)

~solitary (visceral sensory)
~ gustatory (special sensory)
~nucleus ambiguous (motor)
~inferior salvatory (autonomic)

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Cranial Nerve X (are there any; if so, name of nucleus/I)

~Solitary (visceral sensory)
~Gustatory (special sensory)
~nucleus ambiguous (motor)
~ dorsal motor (autonomic)

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Cranial Nerve XI (are there any; if so, name of nucleus/I)

~accessory (motor)
~nucleus ambiguous (motor)

89

Cranial Nerve XII (are there any; if so, name of nucleus/I)

~hypoglossal (motor)