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Anatomy II: Exam I > Brainstem Anatomy and Reticular Formation > Flashcards

Brainstem Anatomy and Reticular Formation Flashcards

1
Q

3 broad functions of the BS

A
  1. conduit: info goes to cortex and SC thru BS (white matter tracts up and down)
  2. CN: heads version of spinal nerves, but also nerves for taste, equilibrium, eye mm, etc
  3. integrative fnctn: complex motor patterns, cardioresp control, reflexes (RF is central core in BS)
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2
Q

3 divisions of BS

A
  1. midbrain
  2. pons
  3. medulla
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3
Q

main fiber tract locations in BS

A
  1. corticospinal tract: anterior (starts at cortex, ends in SC)
    ascending- 2. spinothalamic tract: anterolateral (merge w/ med lemn go w/ thalamus)
    ascending- 3. med lemniscus: variable location (2 pt descrimination)
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4
Q

tegmentum

A

tissue anterior to ventricle, “business end” has CN nuclei

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5
Q

tectum (“roof”)

A

tissue posterior to ventricle

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6
Q

“stuff” added to anterior surface in each section

A
  • rostral medulla: pyramid, inferior olivary nucleus
  • superior pons: basal bons
  • midbrain: cerebral peduncle
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7
Q

key landmarks in medulla

A
  1. pyramidal decussation: sep by ant med fissure
  2. olive: bulge created by inf olivary nucleus
  3. posterior columns: of SC continue into medulla
  4. fasciculous cuneatus: extends to cuneate tubercle, site of nucleus cuneatus
  5. fasciculous gracilus: extends to gracile tubercle, site of nucleus gracilus
  6. rootlets of CN IX and X: emerge from post olivary sulcus
  7. rootlets of CN XII: exit via preolivary sulcus
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8
Q

caudal vs rostral medulla

A

caudal=closed end

rostral=open end (central canal, 4th ventricle)

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9
Q

obex in medulla

A

apen of 4th ventricle where it narrows to central canal

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10
Q

basal pons

A
  • bulge on ant surface
  • site of many neurons receiving axons from cerebral cortex
  • pontine neurons send axons across pons midline, collect laterally, create middle cerebellar peduncle
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11
Q

middle cerebellar peduncle

A
  • in pons
  • major cerebellar input pathway
  • AKA brachium pontis
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12
Q

key landmarks in pons

A
  1. CN V: enters at mid pons level thru MCP
  2. CN VI: exits BS at pontomedullary jnctn near midline
  3. CN VIII: exits lat to VII @ pontomed jnctn, med part=vestibular, lat part=cochlear
  4. CN VII: exits lat to VI @ pontomed jnctn, motor root=larger, more medial
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13
Q

superior cerebellar peduncle

A
  • in pons
  • “brachium conjunctivum”
  • roof of 4th ventricle
  • emerge from cerebellum
  • moves to midline entering BS near pons/midline
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14
Q

lateral lemniscus

A
  • in rostral pons
  • band of fibers covering superior cerebellar peduncle in rostral pons
  • point of ascending auditory path, terminating in inf colliculus
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15
Q

landmarks in midbrain

A
  1. cerebral aqueduct
  2. inf brachium: asc auditory path
  3. CN III: lower motor neursons for extraocular mm and contain pregang parasymp neurons that control sphincter and ciliary mm nucleus=rostral
  4. CN IV: caudal, leaves dorsal pt of BS (only one!) just below inf colliculus in sup oblique m
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16
Q

inferior colliculus

A
  • grey matter in tectum of caudal midbrain
  • major pt of auditory system, receives input from lat lemn, output goes thru inf brachium to med geniculate nucleus in thalamus
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17
Q

superior colliculus

A
  • grey matter in tectum of rostral midbrain

- directs visual attention and controls eye movement

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18
Q

cerebral peduncles

A

large bundles on white matter at base of midbrain

-contain tight packed fibers from cerebral cortex on way to BS and SC

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19
Q

location and fnctn of somatic sensory CN nuclei

A
  • dorsal
  • mechanoreceptors
  • pain and temp,
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20
Q

location and fnctn of visceral sensory CN nuclei

A
  • dorsal

- GI tract, BVs

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21
Q

location and fnctn of visceral motor CN nuclei

A
  • ventral

- preganglionic autonomic

22
Q

location and fnctn of somatic motor CN nuclei

A
  • ventral

- innervate skeletal m

23
Q

what separates motor/sensory nuclei in SC and BS

A

sulcus limitans

24
Q

special CN fnctns

A
  • special sensory: hearing, equilibrium
  • branchial motor: innervate mm derived embryologically from pharyngeal arches

*there are 6 types of nerve fibers in BS but no nerve has all 6 fibers

25
Q

BS blood supply

A
  • vertebral-basilar system
  • ant and med BS supplied by perforating brs
  • circumferential aa supply lat BS and cerebellum
26
Q

reticular formation

A
  • phylogenetically old
  • central core of BS, extends into cerebrum as hypothalamus
  • imp for regulation of posture, stereotypic motor behaviors, internal environment, pain, sleep and wakefullness, emotional tone
27
Q

3 longitudinal zones of RF (med -> lat)

A
  1. raphe nuclei: “seam”, immediately adjacent to sagittal plane
  2. medial zone: alongside raphe, mix of large and small neurons, source of most ascending and descending projections
  3. lateral zone: prominent in rostral medulla and caudal pons, primarily involved in CN reflexes and visceral fnctn
28
Q

tracts from RF for movement

A

2 reticulospinal tracts

  • medial: pons, ipsilateral, descends near MLF and in ant funiculus
  • lateral: medulla, descend bilaterally, in lateral funiculus
29
Q

RF and movement

A
  • major alternative to corticospinal tract in regulating spinal motor neurons
  • influences spinal motor neurons directly
  • regulates spinal reflexes
  • reticulospinal tract neurons receive input from many areas
  • contains basic neural machinery for some complex pattern movements
30
Q

RF and pattern generators

A

rhythmic motor patterns

  1. gaze centers (midbrain = vert, pons = horiz)
  2. mastication (supratrigem nucleus (pons))
  3. locomotion, HR, resp, swallowing, wom (medulla)
31
Q

bruxism

A
  • stereotyped movement disorder
  • tooth grinding/clenching
  • normal sleep = mm in atonia, bruxism mm = cocontracted
32
Q

peripheral causes theory of bruxism

A
  • malocclusion results in premature and 1 sided contraction
  • jaw movements continue in attempt to reach resting position
  • based on clinical observation and Tx
33
Q

central causes theory

A
  • sleep related dysfunctions

- input to supratrigem nucleus may be from basal gang, lat hypothalamus, central nucleus of amygdala

34
Q

RF and pain pathway transmission

A
  • RF is key in suppressing/facilitating pain based on circumstance
  • periaqueductal grey is central to pain suppression
35
Q

how does PAG suppress pain?

A
  • receives pain info from spinomesencephalic fibers, get input from hypothalamus and cortex,
  • PAG-raphe-post horn of SC/spinal V nucleus

*opiates control pain by activating PAG raphe at multiple levels

36
Q

autonomic reflex circuitry and RF

A
  • lots of visceral infor reaches RF
  • responds to environ changes and projects to BS autonomic nuclei and SC
  • in/expiration rhythm in pons/medulla
  • HR and BP control in medulla
37
Q

arousal and consciousness and RF

A
  • RF projects to thalamus and cortex
  • midbrain and pons RF get input from multiple sensory modalities (pain, spinoreticular fibers)
  • project to thalamic intralaminar nuclei, which project diffusely to cortex (arouses bc sensory stim or demanding task)
  • maintain consciousness: bilat damage to RF results in coma (controlled by asc retic activating system
38
Q

neurochemical composition of RF nuclei w/ diffuse projection

A
  • diffusely distributed connections and extensively blanket cortex and other areas
  • BS: norepi, dopamine, serotonin
  • hypothalamus: histamine containing neurons
  • telencephalon: Ach
39
Q

where are NE noradrenergic neurons located

A
  1. medulla: solitary nucleus (memory ebhancement), ventrolateral medulla (pain reg to SC)
  2. rostral pons: locus ceruleus, vigilance and attention
    * active in attentive situation, decreased during sleep
40
Q

locus ceruleus

A
  • NE released in cortex from here, respond to novel environ stim, produces increased arousal and anticipation, facilitate attn to stim
  • released in trigem spinal nucleus and SC from ventrolat medulla and suppress incoming pain
41
Q

clinical depression

A
  • bc decreased NE, locus ceruleus neuron activity decreased
  • common in PD pts bc locus ceruleus neurons are lost
  • some drugs for dep increase rate on LC neuron fiting
42
Q

panic disorder

A

increased NE

43
Q

locations of dopaminergic neuron in midbrain

A
  1. substantia nigra (putamen and caudate)

2. ventral tegmental area (limbic system)

44
Q

dopaminergic projections and fiber types

A
  1. nigrostriatal fibers for motor activity, from sub nigra

2. mesocortical fibers for organized thinking and planning from vent tegmental area

45
Q

schizophrenia and dopamine

A
  • disorganized thinking (frontal lobe)
  • hallucinations (limbic/temporal)
  • decreased dopamine in prefrontal cortex = social withdraw
  • increased dopamine in limbic system = hallucinations
46
Q

serotonin 5-HT neuron locations

A

-serotonergic neurons located at all BS levels in raphe

47
Q

where do midbrain raphe nuclei for serotonin go?

A

to all regions of cortex

  • attn: inhibition of distracting stimula
  • hypothalamus: day/night cycle
48
Q

where do medullary raphe nuclei for serotonin go?

A

to SC

-pain supression (nucleus raphe magnus)

49
Q

clinical depression and serotonin

A

SSRI

50
Q

serotonin related issues

A
  • decreased: high carb consumption, binge eating
  • increased: compulsiave behavior, anorexia nervosa

*drugs that increase sero treat depression and anxiety

Anatomy II: Exam I (10 decks)

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