Reticular Formation and Sleep (Exam 3)

What is the reticular formation (RF)?

A network of neurons in the brainstem (midbrain, pons, medulla)

Why is it called 'reticular'?

Because it is a mesh-like, disorganized network of neurons

Evolutionarily, what is the RF?

The oldest part of the nervous system

Where is the reticular formation located?

Throughout the midbrain, pons, and medulla

What does the RF receive input from?

ALL major systems including sensory systems, motor systems, cortex, thalamus, hypothalamus

What is special about RF neurons?

They have large, highly branched dendrites that integrate lots of information

List the 5 main functions of the RF.

Motor control, sensory attention, autonomic control, eye movements, sleep & wakefulness

What are reticulospinal tracts?

RF pathways to spinal cord motor neurons

What are 'accompanying movements'?

Subconscious movements that support voluntary movement (balance/posture)

When do accompanying movements occur?

Often before or during voluntary movement

What is the nature of RF connections?

Bilateral

What autonomic functions does the RF control?

Breathing, heart rate, blood pressure, vomiting, gagging, coughing

Which cranial nerves are important for RF autonomic control?

CN IX (glossopharyngeal) and CN X (vagus)

Where is the vomiting center located?

Medulla

What can trigger vomiting?

Chemical (area postrema), vestibular, cortical (smells, emotions), visceral (GI tract)

What does RF do for sensory input?

Filters out irrelevant stimuli

What pathway helps RF filter sensory input?

Reticulo-thalamic pathway

What role does RF play in eye movement?

Controls horizontal eye movements

Are sleep and wakefulness passive processes?

No — both are active processes

What system is required for wakefulness?

Reticular Activating System (RAS)

Which neurotransmitters are involved in wakefulness?

Norepinephrine (locus coeruleus) and serotonin (raphe nuclei)

What is circadian rhythm?

~24-hour biological cycle

What happens to circadian rhythm in total darkness?

Rhythm shifts to ~25 hours

What is the SCN?

The body's internal clock (pacemaker)

What does SCN receive input from?

Retina (light signals)

What does SCN control?

Sleep-wake cycle + melatonin release

When is melatonin highest?

At night

When is cortisol highest?

During the day (light)

How many sleep stages are there?

5 total

What happens to EEG in non-REM sleep?

Lower frequency, higher amplitude

What are characteristics of non-REM sleep?

Less dreaming, slower breathing, lower BP, more muscle activity

What is REM sleep EEG like?

High frequency, low amplitude (like awake)

What are key features of REM sleep?

Dreaming, rapid eye movements, muscle paralysis, increased BP + breathing

How long is one sleep cycle?

~70 minutes, with ~60 min non-REM and ~10 min REM

Why are muscles paralyzed in REM?

RF inhibits spinal motor neurons

What causes eye movements in REM?

RF projections to superior colliculus

How does REM sleep change with age?

High in infants (~8 hrs) and decreases with age (~45 min in elderly)