Brainstem Anatomy and Reticular Formation Flashcards
1
Q
3 broad functions of the BS
A
- conduit: info goes to cortex and SC thru BS (white matter tracts up and down)
- CN: heads version of spinal nerves, but also nerves for taste, equilibrium, eye mm, etc
- integrative fnctn: complex motor patterns, cardioresp control, reflexes (RF is central core in BS)
2
Q
3 divisions of BS
A
- midbrain
- pons
- medulla
3
Q
main fiber tract locations in BS
A
- 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)
4
Q
tegmentum
A
tissue anterior to ventricle, “business end” has CN nuclei
5
Q
tectum (“roof”)
A
tissue posterior to ventricle
6
Q
“stuff” added to anterior surface in each section
A
- rostral medulla: pyramid, inferior olivary nucleus
- superior pons: basal bons
- midbrain: cerebral peduncle
7
Q
key landmarks in medulla
A
- pyramidal decussation: sep by ant med fissure
- olive: bulge created by inf olivary nucleus
- posterior columns: of SC continue into medulla
- fasciculous cuneatus: extends to cuneate tubercle, site of nucleus cuneatus
- fasciculous gracilus: extends to gracile tubercle, site of nucleus gracilus
- rootlets of CN IX and X: emerge from post olivary sulcus
- rootlets of CN XII: exit via preolivary sulcus
8
Q
caudal vs rostral medulla
A
caudal=closed end
rostral=open end (central canal, 4th ventricle)
9
Q
obex in medulla
A
apen of 4th ventricle where it narrows to central canal
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
11
Q
middle cerebellar peduncle
A
- in pons
- major cerebellar input pathway
- AKA brachium pontis
12
Q
key landmarks in pons
A
- CN V: enters at mid pons level thru MCP
- CN VI: exits BS at pontomedullary jnctn near midline
- CN VIII: exits lat to VII @ pontomed jnctn, med part=vestibular, lat part=cochlear
- CN VII: exits lat to VI @ pontomed jnctn, motor root=larger, more medial
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
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
15
Q
landmarks in midbrain
A
- cerebral aqueduct
- inf brachium: asc auditory path
- CN III: lower motor neursons for extraocular mm and contain pregang parasymp neurons that control sphincter and ciliary mm nucleus=rostral
- CN IV: caudal, leaves dorsal pt of BS (only one!) just below inf colliculus in sup oblique m
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
17
Q
superior colliculus
A
- grey matter in tectum of rostral midbrain
- directs visual attention and controls eye movement
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
19
Q
location and fnctn of somatic sensory CN nuclei
A
- dorsal
- mechanoreceptors
- pain and temp,
20
Q
location and fnctn of visceral sensory CN nuclei
A
- dorsal
- GI tract, BVs
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
BS blood supply
- vertebral-basilar system
- ant and med BS supplied by perforating brs
- circumferential aa supply lat BS and cerebellum
26
reticular formation
- 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
3 longitudinal zones of RF (med -> lat)
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
tracts from RF for movement
2 reticulospinal tracts
- medial: pons, ipsilateral, descends near MLF and in ant funiculus
- lateral: medulla, descend bilaterally, in lateral funiculus
29
RF and movement
- 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
RF and pattern generators
rhythmic motor patterns
1. gaze centers (midbrain = vert, pons = horiz)
2. mastication (supratrigem nucleus (pons))
3. locomotion, HR, resp, swallowing, wom (medulla)
31
bruxism
- stereotyped movement disorder
- tooth grinding/clenching
- normal sleep = mm in atonia, bruxism mm = cocontracted
32
peripheral causes theory of bruxism
- malocclusion results in premature and 1 sided contraction
- jaw movements continue in attempt to reach resting position
- based on clinical observation and Tx
33
central causes theory
- sleep related dysfunctions
| - input to supratrigem nucleus may be from basal gang, lat hypothalamus, central nucleus of amygdala
34
RF and pain pathway transmission
- RF is key in suppressing/facilitating pain based on circumstance
- periaqueductal grey is central to pain suppression
35
how does PAG suppress pain?
- 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
autonomic reflex circuitry and RF
- 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
arousal and consciousness and RF
- 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
neurochemical composition of RF nuclei w/ diffuse projection
- diffusely distributed connections and extensively blanket cortex and other areas
- BS: norepi, dopamine, serotonin
- hypothalamus: histamine containing neurons
- telencephalon: Ach
39
where are NE noradrenergic neurons located
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
locus ceruleus
- 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
clinical depression
- 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
panic disorder
increased NE
43
locations of dopaminergic neuron in midbrain
1. substantia nigra (putamen and caudate)
| 2. ventral tegmental area (limbic system)
44
dopaminergic projections and fiber types
1. nigrostriatal fibers for motor activity, from sub nigra
| 2. mesocortical fibers for organized thinking and planning from vent tegmental area
45
schizophrenia and dopamine
- disorganized thinking (frontal lobe)
- hallucinations (limbic/temporal)
- decreased dopamine in prefrontal cortex = social withdraw
- increased dopamine in limbic system = hallucinations
46
serotonin 5-HT neuron locations
-serotonergic neurons located at all BS levels in raphe
47
where do midbrain raphe nuclei for serotonin go?
to all regions of cortex
- attn: inhibition of distracting stimula
- hypothalamus: day/night cycle
48
where do medullary raphe nuclei for serotonin go?
to SC
| -pain supression (nucleus raphe magnus)
49
clinical depression and serotonin
SSRI
50
serotonin related issues
- decreased: high carb consumption, binge eating
- increased: compulsiave behavior, anorexia nervosa
*drugs that increase sero treat depression and anxiety
