Term
| what is the roof for the medulla and pons? |
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Definition
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Term
| what is the roof for the midbrain? |
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Definition
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Term
| what is the roof for the hypothalamus/thalamus? |
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Definition
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Term
| what ventricular system layer correlates w/the medulla and pons? |
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Definition
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Term
| what ventricular system layer correlates w/the midbrain? |
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Definition
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Term
| what ventricular system layer correlates w/the diencephalon? |
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Definition
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Term
| what does the tegmentum refer to? |
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Definition
| the core of the brainstem, includes the RAS and locus coeruleus (maintains consciousness). pathology here = failure of cardiovascular-respiratory fxn or coma. |
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Term
| where do the corticospinal pathways head? corticobulbar? |
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Definition
| spinal: to the rest of the body. bulbar: w/in the head. |
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Term
| what is the basic dorsal -> ventral pattern of organization in the brain stem? |
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Definition
| roof, ventricular system, tegmentum (CN nuclei), and cortico-efferent pathway |
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Term
| what do the white areas on transverse spinal sections represent? dark? |
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Definition
| white: neurons. dark: axons. |
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Term
| what are characterizes the dorsal columns in a spinal cord transverse section? |
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Definition
| these lead up to the medial lemniscus = sensation of fine touch and proprioceptive information. the gracile nucleus is medial to the cuneate nucleus; its neurons receive afferent input from dorsal root ganglion sensory neurons subserving the lower trunk and limbs, while neurons of the cuneate nucleus receive connections from dorsal root neurons innervating the upper body. neurons of the dorsal column nuclei send axons that form the internal arcuate fibers, decussating (crossing to the opposite side) to form the medial lemniscus, ultimately synapsing with third-order neurons of the thalamus. |
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Term
| what are characterizes the lateral corticospinal tract in a spinal cord transverse section? |
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Definition
| these terminate on lamina 9 neurons in gray matter, primarily at cervical and lumbosacral enlargements and the pathway involves motor control of distal the parts of extremities. |
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Term
| what are characterizes the rubrospinal tract in a spinal cord transverse section? |
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Definition
| this is in the same area as the lateral corticospinal tract, but a little more ventral and smaller - responsible for more proximal musculature of axial skeleton - terminate on lamina 8 neurons. |
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Term
| what are characterizes the anterolateral/spinothalamic tract in a spinal cord transverse section? |
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Definition
| located in front of the ventral horns, this carries simple touch, pain and temperature to the brainstem - but first, the axons of the tract cells immediately cross over (decussate) to the other side of the spinal cord via the anterior white commissure. |
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Term
| what is at the place of the spinal dorsal columns in the medulla? |
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Definition
| the nucleus gracilis and nucleus cuneatus (2nd neurons in this pathway). at this level, these pathways cross to form the medial lemniscus. |
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Term
| what characterizes what goes on w/the pyramids in the medulla? |
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Definition
| they come down from the motor cortex and (70-90%) cross over here to form the lateral funiculus and ultimately the lateral corticospinal tract. this 3-5 mm zone of decussation has the most risk for neurologic damage (quadriplegic from subluxation). |
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Term
| where is the anterolateral/spinothalamic system found in the medulla? |
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Definition
| on the lateral side of the structure, just medial of the border (occupied by the posterior spinocerebellar tract). these are ascending 2nd neurons which have already decussed (through ventral white commissure) - and carry pain/temperature information. |
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Term
| where are the spinal nucleus of the trigeminal and spinal tract of the trigeminal located? |
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Definition
| between the dorsal columns and anterolateral tract of the spinal cord. the spinal nucleus of the trigeminal is more medial and the spinal tract of the trigeminal is more lateral. the trigeminal nuclei essentially function as the somatosensory (proprioception, 2 point touch, pain and temperature, vibration) dorsal horns in the spinal cord - but just for the face. this has some clinical application where pathology in the heart can refer to the jaw. |
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Term
| what characterizes the dorsal columns in the lower medulla? |
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Definition
| the nucleus gracilus and cuneatus decuss to the midline and form the medial lemniscus at this level |
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Term
| what characterizes the pyramids in the lower medulla? |
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Definition
| these are located in the ventral position and represent the descending corticospinal pathway (most of corticobulbar fibers have already synapsed on CN nuclei) |
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Term
| what characterizes the anterolateral system in the lower medulla? |
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Definition
| ascending pain/temp signals have already decussed and are in the lateral edge of of the transverse section |
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Term
| what characterizes the spino-cerebellar tract in the lower medulla? |
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Definition
| this is the most lateral aspect of the transverse section and represents movement dorsally into the enters inferior cerebellar peduncle to go to the target cerebellum |
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Term
| what characterizes the olive in the lower medulla? |
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Definition
| this protrusion on the ventro-lateral surface of the medulla represents the inferior-olivary nucleus which projects into the cerebellar hemispheres (telling cerebellum exactly what it is that the person wants to do with voluntary motor system). |
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Term
| what characterizes the nucleus ambiguus in the lower medulla? |
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Definition
| the nucleus ambiguus is the LMN nucleus for the vagus nerve and contains innervations for the larynx, pharynx, palate. this is located just medial to the ALS tract (which is medial to the spinocerebellar tract). these neurons have axons that exit brainstem at post olivary sulcus and join other fibers of vagus nerve. |
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Term
| what characterizes the hypoglossal nucleus in the lower medulla? |
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Definition
| this is located most medially in the center of the medulla (dorsal to medial longitudinal fasiculus) and contains the hypoglossal LMN which innervate the intrinsic (articulation) and extrinsic (gross movement) muscles of tongue |
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Term
| what characterizes the medial longitudinal fasiculus in the lower medulla? |
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Definition
| this is located medially (ventral to the hypoglossal nucleus) and contains CN3,4,6 - which are responsible for coordinating activity of the EOM. the purpose of this major descending tract through the brainstem is to coordinate eye movement w/the upper part of the cervical spinal cord. |
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Term
| what are the 2 major brainstem syndromes associated w/the mid/upper medulla? |
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Definition
| lateral medullary syndrome (problems w/pain and temperature = *wallenbergs) and medial medullary syndrome (problems w/the dorsal column: medial lemniscus syndrome) |
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Term
| what characterizes the medial lemniscus in the mid/upper medulla? |
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Definition
| the dorsal column has completely crossed over = medial lemniscus pathway in the most medial and ventral part of the mid/upper medulla. the raphe nuclei are included here and are part of the RAS. |
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Term
| what characterizes the pyramids and ALS in the mid/upper medulla? |
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Definition
| they are in the same position as the lower medulla - pyramids ventral and medial, ALS: lateral (major separation of medial leminiscus and ALS) <- *where the medial and lateral medullary syndromes derive. |
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Term
| what characterizes the inferior cerebellar peduncle in the mid/upper medulla? |
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Definition
| this large myelinated bundle sits in the upper dorsal and lateral portion of the mid/upper medulla and represents the major input to the cerebellum. at this point, the spino-cerebellar pathway has completely entered the inferior cerebellar peduncle and is also joining axons arising from the olivary nuclei. |
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Term
| what characterizes the dorsal lateral nuclear complex in the mid/upper medulla? |
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Definition
| this contains the cochlear and vestibular nuclei |
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Term
| what characterizes the spinal nucleus and trigeminal tract in the mid/upper medulla? |
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Definition
| these sit just medial/ventral to the inferior cerebellar peduncle - their exit/entrance is at the level of the pons and therefore afferent sensory fibers that come into pons will descend in brainstem – through pons and into medulla to synapse on neurons. |
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Term
| what characterizes the olive and inferior olivary nucleus in the mid/upper medulla? |
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Definition
| in the same ventro/lateral position as the lower medulla, but less protuberant |
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Term
| what characterizes the nucleus ambiguus in the mid/upper medulla? |
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Definition
| located ventro/medially to the trigeminal nucleus |
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Term
| what characterizes the hypoglossal nucleus in the mid/upper medulla? |
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Definition
| still medial, but completely dorsal |
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Term
| what characterizes the dorsal motor nucleus of vagus in the mid/upper medulla? |
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Definition
| this lies just medial to the hypoglossal nucleus and innervates the thoracic viscera down to the L colic flexure. |
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Term
| what characterizes the nucleus and tract of the solitarius in the mid/upper medulla? |
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Definition
| this is located medial to the inferior cerebellar peduncle and dorsal to the trigeminal nucleus and contains afferent fibers coming back from vagally innervated thoracic/GI organs which is coordinated w/the dorsal motor nucleus (there is no voluntary control over this communication). |
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Term
| what is the floor of the 4th ventricle called? |
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Definition
| the emetic center (no BBB) which stimulates the dorsal motor nucleus (which then communicates w/the nucleus ambiguus) of the vagus if noxious substances are detected. |
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Term
| where are the axons rising from the hypothalamus (ultimate controller of ANS) and descending to the autonomic centers in the spinal cord found in the mid/upper medulla? |
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Definition
| just lateral to the trigeminal nucleus. these are rather diffuse, but may be the cause of horner's syndrome w/a lateral medullary lesion. horner's syndrome is not diagnostic - it may be the result of a tumor in the chest impinging on the sympathetic system. |
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Term
| what characterizes the hypoglossal nucleus in the mid/upper medulla? |
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Definition
| it is located medially and most dorsally, but its axons run ventrally (beneath the floor of the 4th ventricle) and exit between the pyramids and olive. any lesion along this path from the nucleus will = paralysis of the tongue. |
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Term
| what would be the effect of crossed findings/alternating hemiplegia due to a unilateral medial lesion in the mid/upper medulla? |
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Definition
| contralateral loss of dorsal column medial lemniscus (proprioception/fine touch/proprioception) and contralateral loss of corticospinal tract (neither have crossed over yet) = *UMN involvement*. ipsilateral CN *LMN* involvement. |
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Term
| what is the blood supply to the medulla? |
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Definition
| penetrating branches from the vertebral arteries. |
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Term
| what characterizes the medial lemniscus in the pons? |
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Definition
| it is still midline, but is starting to flatten and come horizontally. |
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Term
| what characterizes the ALS in the pons? |
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Definition
| still lateral, but moving medially, towards the medial leminiscus |
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Term
| what characterizes the trigeminal nucleus in the pons? |
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Definition
| the motor nucleus of the trigeminal has its LMN at the level of the pons and innervates the muscles of mastication, tensor palatini and tympani, anterior belly of digastric, myelohyoid. it is also the principle nucleus associated w/conscious proprioception, 2 point touch, vibration modalities carried by trigeminal. |
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Term
| what characterizes the medial longitudinal fasiculus in the pons? |
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Definition
| this is located just under the 4th ventricle and contains the CN6 nucleus - major pathways for coordination of CN6 w/trochlear and oculomotor as it ascends. |
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Term
| what characterizes the middle cerebellar peduncle in the pons? |
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Definition
| this comes off laterally and is the major input from the pons to the cerebellum |
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Term
| what characterizes the pontine nuclei in the pons? |
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Definition
| these are located in the ventral portion of the pons and relay descending cortical fibers to the cerebellum - these are *crossing fibers, meaning they will go contralaterally to the opposite middle cerebellar peduncle. thus, lesions (hemorrhage, tumors, abscess ) here (pons) will likely have bilateral impact. |
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Term
| what is locked in syndrome? |
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Definition
| this occurs due to pontine damage, where both cortical efferent pathways are taken away, including any CN below this level = cannot speak, but the center of consciousness is spared even though the pt cannot move or communicate |
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Term
| what is the blood supply to the pons? |
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Definition
| the basilar artery. (vertebro-basilar jxn is at jxn of medulla and pons) |
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Term
| where are the cortical efferent fibers in the pons? |
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Definition
| buried in the pontine eminence: very distinct and contained within a bundle – will appear on ventral surface after we go from pons to medulla – which will be the pyramids |
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Term
| where is the CN6 nucleus in the pons? |
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Definition
| dorsal and lateral to the medial longitudinal fasiculus. axons exiting from this nucleus take a course similar to the hypoglossal nerve (through the tegmentum) and exit the ventral surface of the brainstem. |
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Term
| what characterizes the nucleus and path of CN7 in the pons? |
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Definition
| the facial nucleus sits between the trigeminal nucleus and the ALS and sends its efferent axons back around the abducens nucleus dorsally behind it, which loop around that nucleus then pass back past its own CN7 nucleus, between the trigeminal nucleus laterally and the ALS medially and out the ventral lateral surface (the cerebellar pontine angle). parasympathetic axons from the salivatory nuclei also travel w/CN7. |
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Term
| what does the midbrain isthmus function as? what kind of damage can occur here? |
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Definition
| a transitional level between the midbrain and pons. this is a critical site as it is involved w/the center of consciousness and so many important structure pass through it. herniation of the medial surface of the temporal lobe = uncal herniation can lead to loss of the ascending pathway from locus ceruleus and RAS – producing a loss of consciousness and even perhaps a coma in individual. |
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Term
| what characterizes the medial leminiscus and ALS in the midbrain isthmus? |
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Definition
| the medial lemniscus is now perpendicular to its original position and reaches laterally to form a 90 degree angle w/the ALS which is dorsolateral. |
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Term
| what characterizes the pontine nuclei and corticospinal pathway in the midbrain isthmus? |
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Definition
| these sit ventromedially in the midbrain isthmus, with the corticospinal pathway just behind the pontine nuclei. |
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Term
| what characterizes the medial longitudinal fasiculus in the midbrain isthmus? |
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Definition
| it is dorsomedial and just dorsal behind the locus ceruleus (responsible for ascending NE projection to cerebral hemispheres). |
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Term
| what is the roof structure in the midbrain isthmus? |
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Definition
| the cerebellum. here the 4th ventricle has narrowed and become the cerebral aqueduct. |
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Term
| what is the roof and ventricular component of the midbrain - inferior colliculus? |
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Definition
| roof: tectum, ventricular component: cerebral aqueduct (surrounded by periaqueductal grey - contains endogenous opiate containing neurons + association w/the hypothalamus descending pathway). |
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Term
| where are the medial leminiscus and ALS in the midbrain - inferior colliculus? |
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Definition
| the medial leminiscus cuts the section in half coronally and forms a 90 degree angle with the ALS which is a lateral lie reaching back dorsally. |
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Term
| what characterizes the superior cerebellar peduncle in the midbrain - inferior colliculus? |
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Definition
| this is medial, just dorsal to the medial lemniscus and is the major output from the cerebellum. |
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Term
| what characterizes the red nucleus in the midbrain - inferior colliculus? |
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Definition
| this is medial, between the medial lemniscus and superior cerebellar peduncle and gives rise to the rubrospinal pathway (this, the main route for the mediation of voluntary movement is responsible for large muscle movement such as the arms and the legs as well as for fine motor control. it facilitates the flexion and inhibits the extension in the upper extremities) |
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Term
| what characterizes the pontine nuclei and corticospinal pathway in the midbrain - inferior colliculus? |
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Definition
| these sit ventromedially in the midbrain - inferior colliculus, with the corticospinal pathway just behind the pontine nuclei. |
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Term
| what characterizes the medial longitudinal fasiculus in the midbrain - inferior colliculus? |
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Definition
| this sits ventrally under the cerebral aqueduct - between which is the trochlear nucleus, which sends its innervation to the superior oblique **dorsally and contralateral** (only CN to go dorsal/contralateral) |
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Term
| what characterizes the inferior colliculus in the midbrain? |
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Definition
| this sits most dorsal and lateral and acts as the relay for information coming from the cochlea. neurons from the inferior colliculus project primarily through medial longitudinal fasciculus to muscle in neck and upper part of trunk - allowing coordination of movement w/sound. |
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Term
| what is the roof structure at the top of the midbrain? ventricle? |
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Definition
| the superior colliculus and cerebral aqueduct. |
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Term
| what characterizes the cerebral peduncle in the midbrain - superior colliculus? |
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Definition
| it contains virtually all the corticospinal and corticobulbar fibers and forms large ventrolateral protrusions |
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Term
| what characterizes the medial lemniscus and ALS in the midbrain - superior colliculus? |
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Definition
| these form a right angle on the lateral edge with the ALS more dorsal |
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Term
| what characterizes the medial longitudinal fasiculus in the midbrain - superior colliculus? what nucleus is directly above it? what characterizes this nucleus? |
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Definition
| medial and directly under the cerebral aqueduct. directly above the medial longitudinal fasiculus is the oculomotor nucleus which sends out the axons for CN3 through the ventral surface of the brainstem, between the cerebral peduncles and through the tegmentum. this is also where the basilar artery branches into the superior cerebellar and posterior cerebral arteries - compression by aneurysms will be manifested in control by the eye. the oculomotor nucleus is composed of the LMN for the EOM and the edinger-westphal nucleus (parasymp neurons - synapse in the ciliary ganglion and have effect on smooth muscle that controls the shape of lens and smooth muscle that is responsible for constriction of pupils). |
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Term
| what characterizes the superior colliculus in the midbrain - superior colliculus? |
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Definition
| this is the most dorsal structure and is the relay center for vision = effect on muscles of neck and upper part of trunk so that the head will be turned toward visual stimuli |
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Term
| what characterizes the red nucleus in the midbrain - superior colliculus? |
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Definition
| this very dark large structure medial and ventral is the origin of the rubrospinal pathway (works closely with corticospinal pathway – more proximal musculature for position of extremities). one of the major inputs to the red nucleus is from the superior cerebellar peduncle. |
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Term
| what characterizes the substantia nigra in the midbrain - superior colliculus? |
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Definition
| this is located just medially from the superior cerebellar peduncle and contains dopaminergic neurons. |
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Term
| what would a unilateral lesion on the ventral surface of the midbrain result in? |
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Definition
| an alternating hemiplegia: effect on the descending corticospinal fibers (manifested contralaterally in the body) and the oculomotor nerve axons (ipsilaterally). |
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Term
| what are the three levels of the brainstem where alternating hemiplegia occurs? how can these be differentiated clinically? |
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Definition
| at the superior colliculi level of the midbrain, the level of the pons medullary junction, and the level of the medulla. at any of these levels, the corticospinal pathways would be contralaterally affected. if the eye was positioned down and out due to loss of control from C3, the lesion would be at the level of the superior colliculus in the midbrain. if the eye was deviated towards the midline, the lesion would be at the level of the pons medullary junction b/c the abducens nerve would be damaged. if the tongue was paralyzed on one side w/hemiplegia in the body on the other, the hypoglossal nerve in the medulla would be affected. |
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Term
| what is an example of central medulla syndrome? |
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Definition
| permanent deficits due to low medulla compression affecting the decussating corticospinal tracts and internal arcuate fibers of the dorsal column-medial lemniscus tract. |
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Term
| what is an example of medial medullary syndrome? |
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Definition
| alternating hemiplegia: ipsilateral tongue paralysis (tongue points towards side of the lesion), contralateral UMN hemiplegia, and contralateral DC/ML sensory loss - due to is a pathological change in the tissue supplied by median and paramedian penetrating arteries arising from the vertebral artery. **medial medullary syndrome will involve position/vibration/fine touch** |
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Term
| what is an example of lateral medullary syndrome (wallenberg)? |
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Definition
| mild hoarseness/inability to swallow: nucleus ambiguus. left horner's syndrome (ptosis, miosis, anhidrosis): entrapment phenomena of sympathetic chain in thorax and neck OR (as in this case) damage to the hypothalamo-spinal autonomic pathway in the dorsolateral region. nystagmus: damage to the vestibular nucleus (dorsolateral). decreased light touch on ipsilateral face: damage to trigeminal nucleus and ALS, both present laterally. ipsilateral soft palate paresis: damage to lateral vagus/nucleus ambiguus. ipsilateral ataxia: damage to dorsolateral inferior cerebellar peduncle. absent babinski/symmetric reflexes/other motor/sensory exams intact: medial lemniscus/ALS/intact corticospinal tracts. |
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Term
| what characterizes locked in syndrome? |
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Definition
| damage to the basilar pons = bilateral destruction of the longitudinal cortical efferent fibers, disconnecting the spinal cord (quadriplegia) as well as CN motor nuclei below this level (specifically 10, 11, and 12). impaired eye movement: damage to CN6 axons which extend out at this level. |
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Term
| what is millard-gubler (ventrolateral pons) syndrome? |
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Definition
| ipsilateral half of face seems ‘flat’ and does not appear to react to emotional changes + dry mouth: damage to CN7, which projects ventrally at this level before the parasympathetics split. slight weakness in abduction on the ipsilateral side: damage to abducens axons which project at this level. movements of extremities on contralaterally side show weakness w/increased reflex activity, present babinski, and opposition of thumb to digits - dramatically impaired: damage to corticospinal tract fibers found in the ventral pons. |
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Term
| what is weber (ventromedial midbrain) syndrome? |
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Definition
| ipsilateral eye does not adduct past the midline or move vertically at all; it does abduct normally: damage to CN3. contralateral babinski in extremities: corticospinal tracts damaged. right lower facial droop: damage to ventral corticobulbar tracts. contralateral pupil enlarges to 6 mm and does not react directly or consensually to light, whereas the ipsilateral pupil reacts normally: damage to parasympathetic portion of CN3. |
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