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Functional Neuranatomy > Reticular Formation > Flashcards

Reticular Formation Flashcards

1
Q

reticular formation “evolutionary age” and general functions

A
  • phylogenetically old part of brainstem
  • has over 100 loosely distributed nuclei that functionally link higher brain centers with the spinal cord, maintain vegetative functions and regulate states of arousal and consciousness
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2
Q

describe the architecture of the reticular formation

A

-the cytoarchitecture consists of large and small cells intermixed with bundles of ascending and descending myelinated fibers

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3
Q

how are the dendrites of the reticular formation oriented with respect to the neuroaxis?

A

-perpendicular

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4
Q

Describe the general afferents of the reticular formation

A
  • ascending sensory information both visceral and somatic

- descending motor signals from the cortex, superior colliculus, and cerebellum

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5
Q

the main efferents of the reticular formation include

A
  • spinal cord controlling/modulating: postural control, visceral motor, and crude voluntary motor
  • cranial nerve nuclei (eye movements)
  • cerebellum
  • and thalamus
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6
Q

the reticular formation gains access to widespread areas of cortex via the ____ nuclei through which it can regulate conscious state.

A

-intralaminar thalamic nuclei

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7
Q

How do monoamine neurons in the reticular formation project to the cortex?

A

-directly!! No need to go through the thalamus

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8
Q

let’s play a game:
Neurotransmitter, location, effect
serotinin

A
  • raphe nuclei

- mood

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9
Q

let’s play a game:
Neurotransmitter, location, effect
norepinephrine

A
  • locus coeruleus

- vigilance and attention

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10
Q

let’s play a game:
Neurotransmitter, location, effect
acetylcholine

A
  • pedunculopontine/laterodorsal tegmentum –> sleep/wake cycles and behavioral salience
  • basal forebrain–> attention and memory
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11
Q

let’s play a game:
Neurotransmitter, location, effect

histamine

A
  • tuberomammillary hypothalamus

- alertness

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12
Q

let’s play a game:
Neurotransmitter, location, effect

Dopamine

A
  • ventral tegmental area

- motivated behavior and cognition

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13
Q

peptide containing cells in the lateral hypothalamic area

A
  • widespread projections to cortex and thalamus and regulate arousal
  • orexin and melanin-concentrating hormone
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14
Q

Experimental Investigation of Conscious State:
during the 1930’s-50s, researchers performed different brainstem lesions. Describe their methods and some of their results

A

-if they lesioned ONLY major ascending sensory pathways, but NOT the reticular formation than sleep-wakefulness was not disrupted
—-BUT—–
IF they lesioned the reticular formation, but not ascending sensory pathways they produced a permanent coma

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15
Q

describe a way to waken a sleeping animal

A

-stimulate the midbrain reticular formation

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16
Q

Reticular Activating System

A

-nickname of the reticular formation since it is necessary for maintaining conscious awake states

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17
Q

EEG

A

electroencephalogram was developed by Hans Berger in the 1920’s

  • electrodes are placed on scalp and grounding position like the ear
  • EEG records waves of electrical activity conducted from the cortex through the head; these reflect the activation of the cortex by the thalamus
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18
Q

The EEG represents ___ activity. When groups of cells fire in a ___ manner, they produce a large amplitude electrical signals

A
  • summed

- synchronized

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19
Q

EEG: alpha waves

A
  • Stage 1
  • a person at rest with eyes closed
  • cortical activity is described as being moderately synchronized in slow, small amplitude a waves
20
Q

Beta waves

A
  • when a person is alert and concentrating on a task
  • these waves are describes as lower amplitude waves that occur with a higher frequency. these reflect desynchronized firing
21
Q

The first definitive EEG sign of sleep state is the ___

A

sleep spindle. This occurs in stage 2

22
Q

describe stage 4 EEG patterns

A

-amplitude of synchronous EEG increases dramatically while the frequency declines

23
Q

Delta sleep (slow wave)

A
  • occurs in stage 4

- the sleep is deep and the body exhibits low BP, low HR, and slow respirations

24
Q

AFTER an episode of slow-wave sleep

A
  • the EEG reflects an awake pattern called rapid eye movement (REM)
  • this is paradoxical sleep
25
Q

describe the physiological events associated with REM sleep

A
  • EMG will show muscle atonia
  • EOG shows rapid eye twitches
  • increased BP, HR, respiration, and the brain will consume more O2

** most dreaming occurs during REM :)

26
Q

Animals and humans will die if __ sleep is prevented

A

REM

-within 12-16 days for humans

27
Q

What are the causes of death in animals that have been deprived of sleep?

A
  • autonomic and immune system failures

- disrupted weight control, body temp, and cardiovascular function and sepsis secondary to immunodeficiency

28
Q

REM rebound

A

-since REM is the most crucial component of sleep a person who is deprived of REM sleep one night will spend double the time in REM the following night

29
Q

Newer research indicates that sleep is necessary for

A
  • optimum removal of brain metabolites and contaminant s

- this happens thanks to an increase in interstitial space and a greater perfusion of brain tissue by CSF

30
Q

Through its diffuse projections to the intralaminar nuclei, the ____ RF is positioned to control conscious states

A

-mesencephalic

31
Q

In the ALERT state, the excitatory projections of the MRF to the intralaminar nuclei cause thalamic and cortical activity to _____

A

-desynchronize

32
Q

Under what conditions can the thalamus and cortex process meaningful sensory information

A
  • alert state

- excitatory projections of the MRF to the intralaminar nuclei cause the thalamic and cortical activity to desynchronize

33
Q

When a person enters sleep, cells of the ___ begin to slow down. A process which is facilitated by reducing sensory input. As the __ drive to the ___ circuitry falls below a certain threshold, the thalamic and cortical cells begin to fire in a ___, oscillatory manner

A
  • mesencephalic RF (MRF)
  • MRF
  • thalamocortical
  • synchronized
34
Q

As a person falls asleep, the termination in the EEG peak is due to inhibition from the ___

A

-reticular thalamus

35
Q

The onset of non-REM sleep is correlated with increased activity in the

A
  • ventrolateral preoptic area of the hypothalamus

- these are GABA neurons

36
Q

Stimulation of the VLPO induces ___ in animals

A

sleep

37
Q

VLPO cells project to the:

A
  • histamine cells in the tuberomammillary hypothalamus
  • orexin neurons in the lateral hypothalamic area
  • cholinergic cells in the PPT/LDT
  • norepinephrine cells in the locus coeruleus
  • serotonin cells in the raphe nuclei
38
Q

lesions of the tuberomammillary hypothalamus histamine cells leads to

A
  • somnolence

- this is why anti-histamine drugs can make one sleepy

39
Q

Brainstem cholinergic cells are known to fire before EEG evidence of REM. This activation _____ the _____ and prevents rhythmic firing of thalamocortical circuits. This leads to the EEG becoming ____

A
  • depolarized the thalamus

- desynchronized

40
Q

Timing trigger

A
  • talking about the REM timing trigger

- thought to lie at the midbrain-pons junction

41
Q

What accounts for the muscle atonia during REM

A

-result of the inhibition of motor neurons

42
Q

Describe the circuit for inhibition of motor neurons during REM

A
  • Glutamate neurons in the sublaterodorsal nucleus of the pons are activated by cholinergic PPT/LDT. The SLD neurons project directly to the spinal cord and indirectly to glutamate neurons in the supraolivary medulla which also project to the spinal cord!
  • the glutamate projections activate GABA/glycine interneurons in the spinal cord that then inhibit motor neurons
43
Q

REM behavior disorders

A
  • can occur from lesions in the pons or medulla which would release the motor inhibition during REM
  • Humans with this lesion will act out their dream
44
Q

Patients with narcolepsy have

A
  • excessive daytime sleepiness suggesting REM intrusion into the wake cycle
  • cataplexy (loss of muscle tone) suggestion intrusion of REM atonia into then wake cycle
  • hypnagogic and hypnopompic hallucinations at sleep onset and offset, respectively
45
Q

Sleep paralysis

A
  • represents the inappropriate intrusion of cortical sensory processing and consciousness into the REM sleep state
  • people suddenly become aware of muscle atonia and are unable to move despite sending urgent motor commands
46
Q

a strain of Dobermans suffer from narcolepsy because of a mutation in the gene coding for

A

orexin receptor

Functional Neuranatomy (12 decks)

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