W5 - RETICULAR ACTIVATING SYSTEM (RAS)

WHAT ARE THE LOCATION OF

extend from midbrain to medulla oblongata

what are the major regulation role of RAS

• Motor control

• Sensory attention

• Eye movements

• Autonomic nervous system

• sleep and wakefulness

explain the Anatomy Reticular Formation

Lateral reticular formation

• Small neurons

• Positioned close to the motor nuclei of the cranial nerves

• Interneurons - Coordinate autonomic reflexes & simple behavior mediated by cranial nerves.

Medial reticular formation

• Large neurons

• Source of most of the long ascending & descending projections of reticular formation.

• Projection neurons modulate motor responses & posture, pain sensation, autonomic functions, & arousal.

Raphe nuclei

• Thin plates of neurons - in & adjacent to the sagittal plane.

• Cells - Modulate the action of neurons involved in motor responses, pain, autonomic functions, & arousal.

what are the NEUROTRANSMITTERS IN THE RAS and their function

1. Noradrenergic

   • cardiovascular and endocrine functions,

   • autonomic reflexes and pain sensation,

   • maintaining vigilance and it enhances responsiveness.

2. Adrenergic

   • GIT functions

3. Dopaminergic

   • Emotion and cognition

4. Serotonergic

   • wake-sleep cycles

5. Cholinergic

   • Wake-sleep cycles

DEFINE SLEEP

“Sleep is a readily reversible state of reduced responsiveness to, and interaction with, the environment.”

Why sleep is necessary??

1. Recovery time for the brain

2. Restoration

   • Sleep to rest and recover, and prepare to be awake again

3. Adaptation

   • Sleep to keep out of trouble, hide from predators

NEURAL MECHANISMS OF SLEEP

1. Critical Neurons and Brain Systems

   • use different neurotransmitter to send messages.

2. Noradrenergic and Serotonin:

   • keep us awake and alert.

   • also help in switching between different sleep stages.

3. Acetylcholine

   • active when we're awake and especially during REM sleep

   • might even start REM sleep.

4. Thalamic Rhythms and Sensory Input

   • When these rhythms slow down, they block external signals from reaching our brain, making it easier to sleep.

5. Impact on Muscle Control:

   • During REM sleep, these brain systems stop our muscles from moving so we don't act out our dreams.

explain the 3 states of electrophysiology of sleep

1. Wakefulness Awake

2. Slow-wave sleep - NREM

   • Non-Rapid Eye Movement

   • characterized by EEG

   • divided in four stages

   • first NREM lasts about 90 min

   • NREM: 75-80% of sleep ‘

3. Paradoxic sleep - REM

   • Rapid Eye Movement

   • characterized by EEG

   • dreaming occurs

   • REM: 20-25% of sleep

explain the 4 stages of sleep

Stage 0: Awake Stage

Stage 1: dozing

Stage 2: Unequivocal Sleep

Stage 3: deep sleep transition

Stage 4: Cerebral Sleep

Sedatives & hypnotics works on reducing the time to transition into stage 4—immediate sleep

explain the TECHNIQUES USED TO STUDY SLEEP

1. Electroencephalogram (EEG)

   • monitors electrical brain activity

2. Electromyogram (EMG)

   • permits electronic monitoring of head and neck muscles

3. Electro-oculogram (EOG)

   • electrodes placed around the eye, the EOG records eye movement

explain what happen when RAS decreace and increase

RAS decrease

• Under-aroused cortex

• Difficulty in learning

• Poor memory

• Lack of consciousness

• Coma

RAS increase

• Over aroused cortex

• Hyper-vigilance (sensory sensitivity )

• Touching everything

• Talking too much

• Restless

• Hyper active

explain Sleep - Promoting Factors

• Muramyl dipeptide

  • facilitates non-REM sleep

  • Isolated from the CSF of sleep-deprived goats

• Interleukin-1

• Adenosine

  • may have inhibitory effects of diffuse modulatory systems

• Melatonin

  • released at night- inhibited during the day (circadian

    regulation)

  • initiates and maintain sleep

  • treat symptoms of jet lag and insomnia

explain jet lag

• is caused by a mismatch between a person’s normal daily rhythms and a new time zone

• a temporary sleep problem that usually occurs when you travel across more than three time zones

• can affect anyone who travels across multiple time zones

• affect your mood, your ability to concentrate, and your physical and mental performance.