Reticular formation Flashcards
What is the Reticular Formation?
An ill-defined diffuse network of neurons signaling via the medulla, pons, and midbrain.
What types of neurons surround the Reticular Formation?
Motor, sensory, and visceral (autonomic) neurons.
What are the characteristics of dendrites in the Reticular Formation?
Long, straight, dorsal-ventral.
What is the structure of axons in the Reticular Formation?
Very long, bifurcated into descending and ascending, with numerous collateral branches.
What is the function of the Locus coeruleus?
Contains norepinephrine-secreting neurons.
What are the three subdivisions of catecholamines?
- Dopamine
- Norepinephrine
- Epinephrine
What is the precursor for catecholamines?
Tyrosine.
What are the functions of the Reticular Formation?
- Alertness
- Sleep process
- Inhibit pain
- Regulate muscle tone and movement
- Regulate vital signs against heart and lung
What are the three functional zones of the Reticular Formation?
- Lateral zone
- Median (raphe) zone
- Medial zone
What is the role of the Ascending Reticular Activating System (ARAS)?
Essential for regulating arousal, consciousness, and attention.
How does the Parvocellular nucleus contribute to ARAS?
Processes signals from various sources and releases glutamate.
What neurotransmitter does the Pedunculopontine nucleus release?
Acetylcholine (Ach)., glutamate, GABA
What is the first step in the ARAS process?
Sensory input from the lateral zone.
What happens in Step 2 of ARAS?
Connection to the medial zone (arousal center).
What does the medial zone activate in ARAS?
The thalamus.
What is the final step of ARAS that leads to behavioral arousal?
Cortical response and activation of cortical neurons.
What are the four pathways involved in maintaining alertness?
- Noradrenergic pathway (Locus coeruleus)
- Serotonergic pathway (Raphe nucleus)
- Histaminergic pathway (Hypothalamus)
- Orexin pathway (Hypothalamus)
What is the role of the noradrenergic pathway?
Sends signals to locus coeruleus to release norepinephrine, maintaining alertness.
What is the function of the serotonergic pathway?
Parvocellular neurons send signals to the median zone (raphe nucleus), which releases serotonin to promote alertness.
What does the histaminergic pathway do?
Releases histamine from the tuberomammillary nucleus to promote alertness.
What is the role of the orexin pathway?
Involved in wakefulness and preventing sudden sleep.
What tools are used to assess consciousness?
- Electroencephalogram (EEG)
- Glasgow Coma Scale (GCS)
What does a Glasgow Coma Score (GCS) of 8 or below indicate?
Severe impairment of consciousness.
How does sleep differ from coma?
Sleep is a state of unconsciousness that can be aroused by stimuli; coma is unconsciousness that cannot be aroused.
What are the stages of sleep?
- Stage I
- Stage II
- Stage III
- REM sleep (paradoxical sleep)
What happens to deep sleep as the night progresses?
Less deep sleep is recurred as the night goes on.
What is the nature of sleep?
It is a cyclical phenomenon with initial awake periods, non-rapid eye movement sleep, and rapid eye movement sleep.
Fill in the blank: The medial preoptic area and the _______ nucleus are involved in regulating the sleep cycle.
[suprachiasmatic]
What is the duration of a typical sleep cycle?
90-100 minutes for non-REM and 10-15 minutes for REM sleep.
True or False: Sleep is considered a passive phenomenon.
False
What are the characteristics of deep sleep?
Associated with slow wave activity and is restorative.
What system inhibits pain transmission?
Descending Pain Control System
This system is involved in modulating pain signals before they reach the brain.
What areas of the brain are involved in regulating muscle tone and movement?
Area 3,1,2
These areas are part of the somatosensory cortex involved in processing sensory information related to muscle control.
What are the two types of reticulospinal tracts?
- Medial reticulospinal tract (MRT)
- Lateral reticulospinal tract (LRT)
These tracts originate from the reticular formation and influence motor control.
Where does the medial reticulospinal tract (MRT) originate?
Pons RF (ipsilateral)
MRT primarily influences extensor muscles.
What is the function of the lateral reticulospinal tract (LRT)?
Modulates flexor muscles
LRT also originates from the reticular formation and affects anterior horn cells in the spinal cord.
Which part of the brain participates in lateral gaze?
Paramedian pontine reticular formation (DPRF)
DPRF is crucial for coordinating eye movements.
What is the role of the medullary reticular formation?
Regulation of vital visceral responses
It plays a key role in cardiovascular and respiratory centers.
What centers are regulated by the medulla and pons reticular formation?
- Cardiovascular center
- Respiratory center
These centers are essential for maintaining homeostasis in vital functions.
What is the connection between the reticular formation and lower motor neurons?
Hippothalamus & Brainstem
The reticular formation interacts with these areas to influence motor control.
What nucleus is involved in controlling medial eye movements?
Oculomotor nucleus
This nucleus works with the paramedian pontine reticular formation.
Fill in the blank: The medial reticulospinal tract primarily affects _______.
Extensors
True or False: The lateral reticulospinal tract primarily affects extensor muscles.
False
The lateral reticulospinal tract primarily modulates flexor muscles.
