NEUR 334: Brainstem III (Reticular Formation)

What is the reticular formation

Its the central core of diffuse nuclei that runs through the entire brainstem

Which structures does the reticular formation join rostrally and caudally

Joins rostrally with some of the nuclei in the diencephalon

Joins caudally with intermediate gray matter of the spinal cord

The reticular formation has rostral and caudal divisions, what does each division consist of

Rostral reticular formation

• Mesencephalon

• Rostral Pons

Caudal reticular formation

• Caudal pons

• Medulla

What structure does the rostral reticular fromation work with and what does this maintain

Rostral reticular formation works with diencephalon

• Maintains conscious and alert state (awake and alertness)

• wakefulness

• Pain perception (I “feel pain”) [not the same as NOCICEPTION)

What structure does the caudal reticular formation work with and what does this interaction allow

Works with cranial nerve nuclei and spinal cord

• Carry out somatic motor, reflex, and autonomic function

• sleep!!

• respiration and cardiovascular

• Nociception

What are central pattern generators in the caudal reticular formation?

Neural circuits in the caudal pons and medulla that generate automatic, rhythmic motor patterns (chewing, swalloing, respiartion) without constant cortical input

Where is the reticular formation located

Tegmentum of the brainstem

Some of the well characterized nuclear groups in the RF are for neurotransmitters, specifically, which neurotransmitters?

• Ach

• DA

• NE

• 5-HT

• Ha

What are the other nuclei/systems associated with (but not part of) the RF

• Periaqueductal gray matter = controlling pain

• Chemotactic trigger zone (medulla) = nausea

• Some cranial nerve nuclei

In COMAS, what systems are affected

• Disruption / lesions of the rostral reticular formation within the ARAS

• Bilateral lesions involving

  • Intralaminar nuclei

  • cerebral cortical areas

What are the three levels of consciousness?

1. Alertness = without alertness → coma

2. Attention = allows person to focus. Damage here → neglect, inattention but not coma

3. Awareness = 3 with 2 and 1 is FULL conscious experience

What neural strucutres are required for alertness

Reticular formation (ARAS)

Thalamus

Cortex

What additional brain regions is required for attention beyond alertness

• Everything needed in alertness

• frontoparietal association cortex

Alertnes + frontoparitetal network = attention

What additional processes are required for awareness beyond attention

• Everything needed for alertness and attention

• Emotional, sensory and motor information

What system in the caudal reticular formation is involved in modulating and inhibiting pain transmission

Widespread neurotransmitter system for Serotonin

How does the caudal reticular formation modulate pain transmission?

Neurons located in the raphe nuclei and periaqueductal grey send thier axons into the spinal cord to regualte activity of the anterolateral system (pain and temperature pathway)

Do non-REM and REM sleep involve the same or different pathways

Different pathways

True or False: Sleep in an active rpocess and is very similar to being “unconscious”

False!

Sleep is an ACTIVE process and is very DIFFERENT to being “unconsious”

Is sleep simply the abscence of wakefulness

No. Sleep is an active,neurologically distinct process involving specific neural circuits.

Wakefulness and sleep are not opposites but coordinated active states.

What additional brain strucutre plays a significant role in sleep

The hypothalamus

Why can excessive sleepiness or drowsiness be clinically signicant

Because drowsiness can result from multiple neuroanatomical disruption, some of which may indicate a meidcal emergency

There are many regions in the medulla that generate rhythms for homeostatic respiration functions, give an example

Prebotzinger complex

• pattern generator for inspiration / expiration function

Mesencephalon

Rostral Pons

Caudal Pons