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SF2 - Test 3 > 3 - Reticular System > Flashcards

3 - Reticular System Flashcards

1
Q

Reticular System:

Definition

Target

A

Diffuse collection of >110 nuclei; extends from medulla to the forebrain

Projectiosn to thalamus and cortex

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2
Q

What does the Reticular System intregrate?

A

Integrates information from all senses (EXCEPT OLFACTION) to modulate brain functions

Ex: Pain, Motivation, Respiration, Sleep, REM sleep

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3
Q

Ascending Reticular Activating System (ARAS)

A

Consciousness, Arousal, Attenion, Wakefullness

Allows purposeful interaction with your environment

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4
Q

Reticular Formation Divisions: Rostral vs Caudal

A

Rostral: Supplies cerebral cortex with excitatory inputrs for consciousness/wakefullness/arousal/attening (ARAS SYSTEM)

Caudal: Modulates motor function via medial and lateral reticulospinal tracts (descending tracts)

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5
Q

Major Functions of the Ascending Reticular Activating System (ARAS)

Prime

Filter

Shunt

A

Primes - the corect and othe rbrain regions allowing incoming sensory information to be proessed (focuses attention)

Filters - out information that is unimportant

Shunts - information that is life-threatening or fearful directly to amygdala

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6
Q

Reticular Formation Divisions: Telencephalon

A

Nucleus Basalis of Meynert

Major source of cholinergic (ACh) neurons for the cortex and amygdala (w/out thalamic relay)

Clinical: Substantial neurodegeneration is always associated with cognitive dysfunction, decline, dementia, AD

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7
Q

Reticular Formation Divisions: Diencephalon

Reticular Nucleus of the Thalamus

A

Wide variety of thalamic and hypothalamic nuclei strongly associated with reticular formation

Retocular Nucleus of the Thalamus: Only thalamic nuclei to have no projections outside of the thalamus

Integrates incoming information from cortex, thalamic relay and other ARAS inputs; may control when information is sent to various cortical areas

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8
Q

Telencephalon - Nucleus Basalis of Meynert

A

Major source of Cholinergic (ACh) Neurons for cortex and amygdala (without thalamic relay)

Degeneration can be associated with cognitive dysfunction, dementia, AD

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9
Q

Diencephalon - Reticular Nucleus of the Thalamus

A

Only thalamic nuclei to have no projections outside the thalamus

Integrates information incoming from cortex, relay, and other ARAS inputs

May control when information is sent to various areas (coordination role)

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10
Q

Midbrain Pathways

A

Two (PAG, Dorsal Raphe Nucleus) main pathways that carry nociceptive signal to somatosensory cortex with collateral going to reticular formation

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11
Q

Midbrain - Periaqueductal Gray (PAG)

A

Modulation of descending pain transmission

Determines whether pain will be transmitted; contains high desnity of Opiod receptors

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12
Q

MIdbrain - Dorsal Raphe Nucleus

A

Primary site of serotonergic neurons (5HT) in reticular formation

Modulates pain transmission; no thalamic relay

Modulates consciousness, attention, and mood (ARAS)

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13
Q

Midbrain - Ventral Tegental Area (VTA)

A

Mesolimbic (DA) and mesocortical pathways

Critical in reward circuitry, memory, attention, and motivation

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14
Q

Midbrain - Substantia NIgra Pars Compacta (SNc)

A

Nigrostriatal (DA) pathways; modulation of basal ganglia

Parkinson’s Disease

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15
Q

Pons - Nucleus Locus Coeruleus (blue nucleus)

A

Majority of Norepinephrine (NE) input in CNS

Ascending / Descending projections to the limbic structures, dorsal horn, and cortex (without relaying in the thalamus)

Modulates ARAS - arousal, selective attention, stress response, pain modulation, and mood

Clinical: Degenerates in both AD / Parkinsons

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16
Q

Pons - Pedunculopontine Nucleus and Lateraldorsal Tegmental Nucleus

A

Largest sites of Acetylcholine (ACh) production in brain

Involved in ARAS / REM sleep; part of indirect arousal system

**Must be inhibited for sleep to occur**

17
Q

Medulla - Nucleus Raphe Magnus (5HT) and Rostral Ventral Medulla (RVM-Glutamate)

A

Regulate whether information will be transmitted higher in the brain; modulates transmission of pain to the dorsal horn

18
Q

Medulla - Nuclei of the Medullary Reticular Formation

A
  • Critical in vital functions; cardiovascular and respiratory center regulation

- Death can occur from tonsillar herniation compression of these structions

  • Opiod abuse results in depression of respiratory centers
  • SIDS possibly factor here
19
Q

How does the ARAS Prime?

A

Focuses attention, increase general alertness

20
Q

How does the ARAS filter?

A

Bottom-Up control; removes conscious awareness of information perceivd to be unimportant

Modulates how information is represented to the cortex

21
Q

How does the ARAS shunt?

A

Sends information that is life-threatening or fearful directly to the amygdala

22
Q

Where are major ARAS nuclei clustered?

A

Ponto-mesencephalic diencephalic regions of reticular formation

23
Q

ARAS facilitated learning

A

ARAS ACTIVATES the cortex (entorhinal/hippocampus)

Cortex tells ARAS what is important allowing filtering of extraneous information

Memory formed

24
Q

Clinical: Amnestic Agent

A

ARAS Depression produces state of unconsciousness; still allows activity in the thalamic and cortical areas, but there will be no arousal = NO formation of memory

Ex. Midazolam (Versad)`

25
Q

Clinical: Bilateral lesion of Ponto-mesencephalic-diencephalic region of Reticular Formation?

A

Critical for maintaining consciousness

Bilateral Lesion = Coma

26
Q

What are the two pathways of consciousness?

A

Direct - Aminergic Contributions

  • Direct Cortical Projections (no Thalamic relay)
  • Activated only during waking state/regulating overall activity of the brain

- - -

Indirect - Cholinergic Contributions

  • Indirect projection to cortex VIA thalamic relay

- Activated during waking state and REM sleep

27
Q

What are the two parts of consciousness?

A

Content and Level

Content: Sensory, Motor, Memory, Emotion

Level: Attention, Alertness, Awareness

One side can not maintain consciousness alone!

28
Q

Clinical: Bilateral lesion of upper brainstem affecting ARAS nuclei and pathways, or bilateral thalamic lesion?

A

Loss of consciousness

29
Q

Clinical: Bilateral compromis or destruction of the hemispheres?

Causes?

A

Toxic insult, metabolic, anoxia, drug or alcohol overdose, barbiturates, encephalopathy/increased brain pressure

30
Q

Clinical: Focal or Unilateral lesion of the thalamus (as long as the RAS projectings to at least one hemisphere and thalamus are intact)

A

Generally–do not generate coma directly, but can indirectly via tonsillar herniation

31
Q

Clinical: Locked in Syndrome

A

Bilateral Ventral Pontine Lesion

Prevents Corticospinal (trunk/limb) / Corticobulbar (non-oculomotor face, head, neck) motor output

Symptoms: Quadriplegia, Aphonia (can’t speak)

Preserved: ARAS is unaffected = fully conscious, sensory function, vertical eye movement, and blinking

32
Q

Clinical: Akinetic Mutism, Abulia, Catatonia

A

Distinct constellationof psychomotor disturbances; bilateral medial frontal lobe lesion with intact ARAS

Symptoms: Apathy, Deficits in response initiation, No spontaneous movement, Purposeful response some aversive stimuli, intact reflexes, normal sleep wake cycles

Staring, Mutism, Refusal to eat, abnormal posture, grimace

33
Q

Clinical: Minimally Conscious State

A

Impaired function of cortex and ARAS due to widespread cerebral damage

Cause: Diffuse cerebral hypoxia or trauma

Symptoms: Periods of responsiveness or wakefullness with minimal and variable awareness, visual tracking intact, sleep/wake cycle intact, highly variable EEG

34
Q

Clinical: Vegetative State

A

> Month = Persistent vegetative state

Severe impaired cortical function; some ARAS may be preserved

Symptoms: Periods of wakefulness, no period of awareness; NO visual tracking, may react to pain

  • Small number of patients can activate parts of brain by thinking of an activity; return of visual tracking may indicate + sign patient is recovering
35
Q

Clinical: Coma

A

Severe impairment of cortical function and ARAS; prolonged loss of consciousness

Symptoms: Unresponsive, no reaction to sensory input, no awareness, no sleep wake cycle, som primitive reflex activity is present

36
Q

Clinical: Brain Death

A

All cortical, subcortical, brainstem function is lost

Only spinal cord function may be preserved

37
Q

What occurs if the reticular system does not prime an area to receive information?

A

The sensory information will not be processed

38
Q
A

SF2 - Test 3 (25 decks)

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