Anatomical Basis of Sleep and Comas

Question 1

periaqeductal gray matter

• located where?
• has what anatomic relations?
• divided into what regions? based on what?

Answer 1

• location: around cerebral aqueduct (3rd ventricle) for its entire length
• relations: continuous with the periventricular gray matter (cortex surrounding 3rd ventricle)
• regions: control descneding pathways for
  
  • ventral - arousal, REM sleep
  • ventrolateral - arousal, REM sleep, pain modulation
  • lateral - pain modulation
  • dorsomedian - pain modulation

Question 2

what periaqeductal gray matter column function in arousal?

Answer 2

• ventral column
• ventrolateral coluomn

Question 3

which periaqeductal gray matter columns function in control of REM sleep?

Answer 3

• ventral column
• ventrolateral column

Question 4

which periaqueductal gray matter columns modulate pain?

Answer 4

• dorsomedian
• lateral
• ventrolateral

Question 5

basal forebrain

• location
• anatomic relations
• features

Answer 5

• location: portion of inferior frontal lobe that is
• relations:
  
  • rostral to the hypothalamus
  • joins the temporal & frontal lobes
• features: dominanted by the olfactory trigone, which:
  
  • is bordered
    
    • rostrally by the:
      
      • medial olfactory striae
      • lateral olfactory striae
    • caudally by the: the diagonal band of brcoa
  • contains the: anterior perforated substance

Question 6

the olfactory trigone is

• located where?
• defined by what borders?
• characterized by what features?

Answer 6

• location: basal forebrain
• borders:
  
  • rostrally: medial & lateral olfactory straie
  • caudally: diagonal band of broca
• contains: anterior perforated substance
  
  • groups of neurons with one especially prominent: basal nucleus of meynert
  • perforated by anterior cerebral artery

Question 7

what is the anterior perforated substance?

what is another name for it?

what features does it contain?

Answer 7

• aka substanita innomata
• a group of poorly defined neurons with in the olfactory trigone
• features:
  
  • perforated by anterior cerebral artery
  • contains the basal nucleus of meynert

Question 8

the basal nucleus of meynert

• is located where?
• has what role?
• is clinically relevant how?

Answer 8

• location: in the anterior perforated substance within the olfactory trigone
• role: sends widespread cholinergic projections throughout the
  
  • cerebral cortex -> general arousal
  • hippocampus -> neural plasticity & learning
    
    • in conjuction w/ diagonal band of broca
• clinical: damage to this nucleus leads to dementia (ex- altzeimers)

Question 9

what is the treatment for damage to the basal nucleus of meynert?

why?

Answer 9

• ACh
• this nucleus mediates arousal / learning & plasticity via widespared cholinergic projections

Question 10

what borders the hypothalamus

• superiorly
• rostrally
• cadually

Answer 10

• superiorly: thalamus
• rostrally: optic chiasm
• cadually: mamillary bodies

Question 11

what major nuclei make up the hypothalamus?

what is the role of each nucleus?

Answer 11

• tuberomamillary nulceus (histamingergic center): stimulates arousal - by directly cholinergic axons into cerebral cortex
• lateral hypothalamus: stimulates arousal - by exciting the tuberomammillary nucleus
• ventrolateral preoptic nucleus: promotes sleep - by sending inhibitory signals to brain centers that promote alertness

Question 12

which hypothalamic nucleus is the histaminergic center of the brain?

what does it do?

Answer 12

tuberomamillary nucleus

stimulates arousal by sending axons directly into cerebral axons

Question 13

what it the role of the lateral hypothalamus in mediating arousal?

Answer 13

promotes arousal - by sending excitatory signals to the tuberomammillary nucleus, which then sends ACh through its cholinergic axons into the cerebral cortex

Question 14

what is the role of the ventrolateral preoptic nucleus in mediating arousal?

Answer 14

“the masters switch for sleep”

inhibits arousal and promotes sleep - does so by inhibits brain centers that promote cortical arousal (i.e., tuberulomammillary & lateral hypothalamus)

Question 15

the reticular formation

• is located where?
• has which key nuclei? with what characteristics?
• has what general role?

Answer 15

• located: from spinal cord to thalamus - esp in medulla & pons
• nuclei:
  
  • dorsal tegmenal - cholinergic
  • paramedian reticular - dopaminergic
  • locus coeurleus - adrenergic
  • nucleus raphe pontis & magnus - serotonin
  • pontine reticular (oral and caudal) - GABA
• characteristics: highly stellate with long axonal processes
• role: interacts extensively with cranical nerves

Question 16

dorsal tegmental nucleus releases?

Answer 16

reticular formation nucleus

cholinergic

Question 17

the paramedian reticular nucleus releases?

Answer 17

(reticular formation nucleus)

dopamine

Question 18

the locus coreulus releases?

Answer 18

(reticular formation nucleus)

adrenergic NTs

Question 19

which reticular formation nuclei release serotonin?

Answer 19

• nucleus raphe pontis
• nucleus raphe magnus

Question 20

which reticular formation nucleus releases GABA?

Answer 20

• oral pontine reticular nucleus
• caudal pontine reticular nucleus

Question 21

which basal forebrain, thalamus and reticular formation release acetylcholine?

Answer 21

• basal forebrain: basal nucleus of meynert
• thalamus: tuberomammillary nucleus
• reticular formation: dorsal tegmental nucleus

Question 22

the brainstem is in charge of what major visceral functions?

Answer 22

• hearbeat
• ventilation
• digestive processes

Question 23

describe the mediation of ventilatory rhythm

Answer 23

• mediated by the brainstem via the following reticular formation nuclei:
  
  • solitary nucleus: mediates inspiration
  • nucleus amgiguus: mediates exhalation
  • nucleus parabrachialis: mediates transition from inhalation to exhaation

Question 24

the solitary nucleus

• is located where?
• has what role?
• is regualted how?

Answer 24

• location: reticular formation
• role: stimulates inspiration - by projectiing to phrenic & intercostal nerves
• regulation: is self excitatory (i.e., excited by I neurons)

Question 25

the nucleus ambiguus * is located where? * has what role? * is regulated how?

Answer 25

* location: reticular fornation * role: stimulates exhalation -\> projects to intercostal nerves * regulation: is inhibited by I (inspiratory) neurons, which are: * inhibited by nucleus parabrachialis medialis

Question 26

the nucleus parabrachialis medialis * is located where? * has what role? * is regulated how?

Answer 26

* location: reticular formation * role: mediates transition from exhalation to inhalation, by * exciting E neurons in nucleus ambiguus * inhibited I neurorons in solitary nucleus, * which also inhibits inhibition of E neurons

Question 27

the reticular formation _ascending pain pathway_ * involves what reticular formation nuclei? * that recieve what signals? * that send their projections where? * leads to what type of pain perception?

Answer 27

* nuclei: * **the "central group"** * lateral reticular nucleus * subnuclear reticularis dorsalis * gigantocellular nucleus\* * receive signals from ascending fibers in the spinal cord * send projects that disperse _widely throughout the cerebral cortex_ * thus, producing non-locazalized pain that is perceived as general "awareness"

Question 28

reticular formation _pain modulation_ * involves what nuclei? * that receive what sigals? * that send their projections where?

Answer 28

* nuclei: * th**e caudate raphe nuclei** * nucleus raphe obscurus * nucleus raphe magnus * nucleus raphe pallidus * receive signals from the **periaqueductal gray matter** * send projections to the * **substantia nigra:** **​**dosral horn 2nd order nueoron in spinothalamic tract * **lateral reticular & gigantocellular**: reticular formation neurons in ascending pain path * spinal trigeminal * **results in modulation of pain**

Question 29

the reticular formation is involved in pain transmision in what two general ways?

Answer 29

* **as part of an ascending pain path**: leads to general "pain awareness" without localization * **via modulation of other ascending pain paths:** spinothalamic, spinal trigeminal, reticular formation

Question 30

which reticular fomation nuclei are involved in the sleep cycle? which are involved in: * maintaining arousal * promoting REM sleep

Answer 30

* arousal * nucleus raphes - pontis, dorsalis * pedunculopontine * laterodorsal tegmental * locus coeruleus * transition to sleep * sublateral dorsal nucleus

Question 31

what are the roles are the sublateral dorsal nucleus?

Answer 31

* transition to REM sleep * promotion of atonia

Question 32

ascending reticular activating system (ARAS) * includes what nuclei * has what role?

Answer 32

* includes * several same nuclei has the arousal nuclei * nucleus raphe - dorsalis, pontis * pedunculopontine * oral pontine reticular nucleus * parabrachial nucleus * **serve to maintain consciousness**

Question 33

the ARAS projects to what two parts of the brain?

Answer 33

two rostral projections 1. hypothalamus (subthalamic) 2. thalamus: intralaminar nucleus of the thalamus

Question 34

disruption of the ARAS can lead to?

Answer 34

* depends on which brainstem level reticular formation disrupted: * medulla: brain death * pons, midbrain: coma

Question 35

the the reticular formation has motor functions via what two pathways? * reticulospinal * reticulocerebellar

Answer 35

* reticulospinal * reticulocerebellar

Question 36

the reticulopinal pathway * involves what reticular formation nuclei? * innervate what targets? * have what actions:

Answer 36

* two _extrapyramidal pathways_ that innervate _postural muscles_ * medial (pontine) reticulospinal * origin: **oral & caudal pontine reticular nuclei** * action: **LE extension** (+ flexion inhibition) * lateral (medullary) reticulospinal * origin: **gigantocellular nucleu**s * action: **UE flexion** (+extension inhibition)