Lecture 15-Reticular Formation Flashcards
Where is the reticular formation found in the brainstem? What is it continuous with in the spine?
Found in all heights of brainstem → continuous w/ intermediate zone (Lamina VII) in spinal grey matter
What are the four main columns of the reticular formation? What are they based on?
Based on distance from reticular midline
1. Median
2. Paramedian
3. Medial
4. Lateral
What do the neurons in the MEDIAN zone of the reticular formation do?
Many neurons in the Median Zone synthesize serotonin.
What are the functions of ascending projections from the median zone in the brain?
The ascending projections from the Median Zone target higher brain centers associated with sleep, contributing to the regulation of sleep.
What are the functions of the descending projections from the Median Zone?
Descending projections to trigeminal spinal nucleus & dorsal spinal areas to modulate/suppress pain
Where does the PARAMEDIAN zone of the reticular formation receive inputs from?
Inputs from cerebral cortex, spinal cord, dentate & fastigial nuclei of cerebellum, & vestibular nuclei
What is the paramedian zone project to?
Project to vermis, uvula, and fastigial nucleus of cerebellum
Function of paramedian zone:
Coordination of intricate movements
What are the characteristics of the projections in the Medial Zone?
The Medial Zone is characterized by long ascending and descending projections.
What do the ascending projections of the MEDIAL zone of the reticular formation go through? What two structures do they terminate at & for what functions?
Goes through central tegmental tract & terminates in hypothalamus (autonomic functions) & intralaminar nuclei of the thalamus (arousal)
What do the descending projections of the MEDIAL zone of the reticular formation join?
Joins (lateral & medial) reticulospinal tracts for motor control of axial, trunk, & proximal limb muscles
What two motor tracts originate in the medial zone? Where does each fibre group terminate at?
- Origin of reticulobulbar & reticulospinal tracts
- Reticulobulbar fibres termiate in cranial nerve sensory & motor nuclei
- Reticulocerebellar fibres terminate in cerebellum
What is the MEDIAL zone of the reticular formation referred to as? What kind of cells are present
Output/motor/efferent zone → large (magno) cells
What is the LATERAL zone of the reticular formation referred to as? What kind of cells are present?
Sensory/afferent → small (parvus) interneurons
Where do the ascending & descending axons of the lateral zone terminate in? What tracts does the LATERAL zone contribute to? For what functions?
- Axons terminate in medial zone of reticular formation
- Contributes to reticulobulbar & reticulospinal tracts → modulate sensory info & maintain alertness
Where does the parvocellular nucleus of the LATERAL zone of the reticular formation receive sensory info from? Where does it project this info to?
Receive sensory info from cerebrum, cerebellum, cranial nerves, & spinal cord → integrates & projects to medial zone of reticular formation
Where does the reticular formation receive inputs from? What specific fibres descend down the corona radiata to terminate at the reticular formation? On what zone?
Inputs from all sensory systems, sensory cortex, MI, prefrontal cortex, cerebellum, hypothalamus, amygdala
Corticoreticular fibres descend down corona radiata to terminate at MEDIAL zone of reticular formation
What modality processes go through the solitary tract to eventually project to the reticular formation?
GVA (general visceral afferent) processes go through solitary tract, terminate at solitary nucleus, then project to reticular formation
In context to efferents of the reticular formation, what two tracts are associated with the reticular formation? What are they responsible for?
- Lateral corticospinal tract for fine distal limb movement
- Reticulospinal (lateral & medial) for balance, posture, structural movements
Where does the pontine medial zone of the reticular formation project to? For what role?
Project to oculomotor & abducens nuclei for modulating horizontal eye movement
Where do the corticoreticular fibres & the central tegmental tract terminate at in the reticular formation? For what function?
Terminate at medial zone of pontine & medullary reticular formation → modulate activity of reticulospinal & reticulobulbar neurons
Where does the medial (pontine) reticulospinal tract terminate at in the reticular formation? For what function?
Terminates at ipsilateral spinal cord to synapse w/ interneurons, motoneurons, & 1st-order muscle spindle afferents → excite extensors & inhibit flexors of trunk & proximal limb muscles
Where does the lateral (medullary) reticulospinal tract terminate at in the reticular formation? For what function?
Terminates at (ipsilateral) spinal cord to synapse w/ interneurons & motoneurons → inhibit extensors & excite flexors of trunk & proximal limb muscles
List the projection pathway of the ascending reticular activation system (ARAS). What is it involved in?
Substantia nigra → thalamus → hypothalamus → cortex
Involved in sleep/wake cycle, control of consciousness, coordinating arousal in different areas
In context to projections to the autonomic system, what tracts project to various autonomic nuclei? For what autonomic functions?
Reticulospinal & reticulobulbar tracts project to various nuclei → heart rate, breathing, blood pressure
In context to modulating cranial nerve activity, differentiate between a Duchenne smile & a pyramidal smile.
Duchenne smile: has reticular activation involved to crinkle corners in eyes, makes smile seem more genuine
Pyramidal smile: doesn’t have crinkled eyes to make smile seem genuine
How does the reticular formation modulate the endocrine system?
Has hypothalamic projections to pituitary gland
What are the functions of each of the four zones?
Median Zone: sleep regulation/modulation and supression of pain
Paramedian Zone: Motor coordination.
Lateral Zone: Sensory processing, mediates modulation of sensory afferents, and maintenance of alertness
Medial Zone: influence the autonomic nervous, level of arousal and motor control of axial and proximal limb musculature
The reticulobulbar tract (RBT) function:
Helps regulate various functions involving cranial nerves in the head and neck, including reflexes, facial expressions, speech, swallowing, and autonomic processes, by connecting the brainstem reticular formation to motor neurons in the cranial nerve nuclei.
