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Neurobiology > Reticular Formation > Flashcards

Reticular Formation Flashcards

1
Q

What is the reticular formation?

A
  • Central core of nuclei embedded in the tegmentum of the brainstem
  • Runs the length of the brainstem
  • Continuous with diencephalon nuclei and the intermediate zone of the spinal cord
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2
Q

Describe the structure and function of the rostral reticular formation

A
  • Consists of nuclei in the midbrain, upper pons, diencephalic nuclei
  • Maintains alert conscious state in the forebrain
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3
Q

Describe the structure and function of the caudal reticular formation

A
  • Consists of nuclei in the pons, medulla, cranial nerve nuclei, and spinal cord
  • Carries out important motor, reflex, and autonomic functions
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4
Q

What are the three levels of consciousness?

A

Alertness
Attention
Awareness

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5
Q

Describe pathway of the pontomesencephalic reticular formation

A
  • Will receive inputs about pain from sensory pathways, about cognition from the association cortex , and about emotion from the limbic system
  • Will send output to the thalamus, hypothalamus, and basal forebrain
  • Information transmitted via glutamate
  • Function: alertness
  • Bilateral lesions can cause a coma
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6
Q

Describe the pathway of the basal forebrain that communicates via acetylcholine

A
  • Basal forebrain sends acetylcholine to the cerebral cortex and hippocampus
  • Effects attention, memory, and learning
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7
Q

Describe the pathway of the pontomesenphalic region that communicates via acetylcholine

A
  • Pontomesenpahlic region sends acetylcholine to the thalamus and then the cortex to influence arousal
  • Also sends Ach to cerebellum, basal ganglia, and brainstem to influence locomotion
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8
Q

Describe the mesostriatal pathway

A

Dopamine from SNc and ventral tegmental area is sent to the caudate and the putamen for basal ganglia functions

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9
Q

Describe the mesolimbic pathway

A

Dopamine from the SNc and ventral tegmental area is sent to limbic structures to influence reward and addiction

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10
Q

Describe the mesocortical pathway

A

Dopamine from the SNc and ventral tegmental area is sent to the prefrontal cortex to influence working memory and attentional aspects of movement intiation

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11
Q

Describe the norepinephrine pathway in the reticular formation

A
  • Neurons located in the locus ceruleus and lateral tegmental area send norepinephrine to the thalamus (excitatory), cortex (excitatory/inhibitory), and cerebellum, brainstem, spinal cord
  • Influences attention, sleep-wake cycles, mood, and sympathetic BP
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12
Q

Describe the serotonin pathway involving the rostral raphe nucleus

A
  • The rostral raphe nucleus sends serotonin to the cortex, basal ganglia, and thalamus
  • Plays a role in some psychiatric symptoms
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13
Q

Describe the serotonin pathway involving the caudal raphe nucleus

A
  • The caudal raphe nucleus sends serotonin to the cerebellum, medulla, and spinal cord
  • Plays a role in pain modulation, breathing, temperature regulation, and motor control
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14
Q

Describe the histamine pathway in the reticular formation

A
  • Neurons in the posterior hypothalamus send histamine to the thalamus (excitatory), and the cortex (excitatory/inhibitory)
  • Helps maintain alert state
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15
Q

Describe the orexin pathway in the reticular formation

A
  • Neurons located in the posterior lateral hypothalamus send orexin to the cortex and all brainstems arousal systems
  • Promotes staying awake
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16
Q

Describe the GABA pathway in the reticular formation

A
  • Neurons in the basal forebrain, thalamic reticular nucleus, and anterior hypothalamic ventrolateral preoptic area sends GABA to the cortex, thalamus, brainstem reticular formation, and hypothalamus
  • Influences alertness and regulation of sleep
17
Q

Describe the stages of sleep

A
  • Non-REM: consists of three stages (N1, N2, N3) that get progressively deeper
  • REM: low muscle tone, dreaming, EEG is similar to wakeful state
18
Q

Which neurotransmitters are active during wakefulness?

A

Acetylcholine, serotonin, norepinephrine, dopamine, and orexin are all rapidly firing

19
Q

Which neurotransmitters are active during non-REM sleep?

A

GABA is rapidly firing and serotonin, norepinephrine, and dopamine are slowly firing

20
Q

Which neurotransmitters are active during REM sleep?

A

Acetylcholine and GABA are rapidly firing

21
Q

What is occurring during non-REM sleep?

A
  • VLPO releases GABA
  • Posterior hypothalamus is inhibited which decreases orexin, histamine, and glutamate activity
  • Brainstem ascending activating system is inhibited which decreases serotonin, norepinephrine, dopamine, and acetylcholine
22
Q

What is occurring during REM sleep?

A
  • Norepinephrine and serotonin levels decrease which decrease inhibition to brainstem cholinergic neurons and increase release on acetylcholine
  • Ach acts on thalamus and cortex to increase arousal
  • Ach acts on ponto-geniculo-occipital waves to induce visual imagery of dreams and rapid eye movement
  • Ach acts on cells in pontine reticular formation to decrease muscle tone
23
Q

How does the anterior hypothalamus contribute to sleep?

A
  • Ventral lateral pre-optic area inhibits arousal systems in the posterior hypothalamus and brainstem to promote REM sleep
  • Lesion = insomnia, cannot inhibit arousal systems
24
Q

How does the posterior hypothalamus contribute to sleep?

A
  • Glutamate, histamine, and orexin help maintain alert state
  • Lesion = hypersomnia, no alert state
25
Q

What is narcolepsy?

A

Abnormal tendency to easily enter REM sleep directly from waking

26
Q

What are the four classic presentations of narcolepsy?

A
  • Excessive daytime sleepiness
  • Cataplexy: sudden loss of muscle tone from the away state, often in response to an emotional stimulus
  • Dreamlike hallucinations when falling asleep or awakening
  • Sleep paralysis: awaking, but remaining unable to move for several minutes
27
Q

Describe the symptoms of a REM sleep behavioral disorder

A
  • Complex motor activity during dreaming (re-enacting dreams, ranges in severity)
  • Lack of descending inhibition to LMN (muscle tone does not decrease like it is supposed to)
  • Can be a precursor of parkinsonism
28
Q

What does a coma look like?

A
  • Unarousable
  • No purposeful response by cortex
  • Brainstem reflexes may be present
  • Eyes closed
  • Minimum duration 1 hour
  • EEG shows abnormal activation patterns
  • Cerebral metabolism is less than 50%
29
Q

What does a vegetative state look like?

A
  • No purposeful response by cortex
  • Can open eyes and arouse in response to stimulus
  • Sleep-wake cycles intact
  • Primitive orienting responses mediated by the brainstem and diencephalon
  • Cerebral metabolism is less that 50%
30
Q

What does a minimally conscious state look like?

A
  • Some responsiveness (may be minimal or variable)
  • No reliable communication (verbal/non-verbal)
  • No functional use of objects
31
Q

What does brain death look like?

A
  • Extreme and irreversible form of coma
  • No evidence of forebrain or brainstem function
  • No brainstem reflexes
  • Spinal reflexes may be present
  • EEG is flat
  • Cerebral metabolism 0%
32
Q

The caudal reticular formation is involved in what functions?

A
  • Control of respiration
  • Control of HR and BP
  • Abnormal posturing
  • Cranial nerve reflexes
  • Behaviors (coughing, hiccupping, sneezing, yawning, shivering, gagging, vomiting, swallowing, laughing, crying)
  • Sphincter control

Neurobiology (15 decks)

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