Reticular Formation Flashcards
What is known as a network of reticulum of many neurons that comprises the core of the neuroaxis?
Reticular Formation
What is composed of many well defined groups of neurons that receive collaterals from all ascending and descending systems and distribute their axons widely in caudal and rostral directions?
Reticular Formation
Are all levels of the CNS interconnected by way of the reticular formation?
YES
Role of the nuclei in the reticular formation?
regulating muscle tone for postural control during voluntary and reflexive movement; modulating the sense of pain, regulating arousal, sleep, and attention; and coordinating autonomic respiratory and cardiac function
What is the largest division of the RF?
Central Division (Lateral and Medial zone)
What nuclei of the RF involves a thin column of neurons along the midline of the brainstem?
Raphe Nuclei (Midline Zone)
What 4 nuclei are considered miscellaneous nuclei of the RF?
- paramedian ponitine RF
- pedunculopontine nucleus
- locus ceruleus
- ventral tegmental area
The central division is a continuous but diffuse column of neurons that begins as a continuation of what? and ends where?
begins as a continuation of the central gray interneuron network of the spinal cord (Lamina X) and ends in the midbrain
The central division consists of what 2 zones?
- Medial zone (efferent) - larger
- Lateral zone (afferent) - smaller
Lateral zone consists of neurons with large dendrites that receive collateral input from all sensory and motor information carried by what?
- cranial nerves
- spinal sensory pathways
- corticospinal, corticobulbar, and corticopontine pathways
The lateral zone relays this integrated information (sensory and motor) to what?
the medial zone
What other areas, besides the medial zone, does the lateral zone project to?
- cerebrum
- cerebellum
- thalamus (central median nucleus)
- spinal cord
The medial zone gives rise to what?
the major efferent pathways from the RF
Nuclei of the medial zone receive input from what three areas?
- lateral zone
- a variety of peripheral receptors, including the carotid body relayed through the solitary nucleus
- hypothalamus
- prefrontal cortex
Role of the nuclei of the medial zone?
to regulate vital cardiac and respiratory function through output to preganglionic sympathetic neurons in the lateral horn of the thoracic spinal cord and preganglionic parasympathetic neurons associated with the vagus nerve (cardiac), and to spinal cord for somatic control of motor neurons in the spinal cord that regulate inhalation and expiration
Lesions to the brainstem that involve the regulatory centers of the medial zone nuclei result in what?
abnormal respiratory patterns or difficulty regulating blood pressure with hypertension
Additional reticular nuclei regulate what?
swallowing and vomiting
Nuclei in the pons and medulla receive input from where? via what?
the cortex (corticobulbar pathway), cerebellum, vestibular nuclei, and somatosensory area, via the lateral zone
Role of the nuclei in the pons and medulla?
to influence LMNs for the purpose of regulating postural, reflexive, and voluntary muscle control
Fibers of the nuclei of the pons and medulla descend in two separate pathways. Both pathways descend ipsilaterally or contralaterally? This makes the influence bilaterally or unilaterally?
ipsilaterally; bilaterally
What are the two descending pathways from the nuclei of the pons and medulla?
- medial (pontine) reticulospinal tract
- lateral (medulla) reticulospinal tract
Which pathways is part of the medial activation system?
medial (pontine) reticulospinal tract
Pathway of the medial (pontine) reticulospinal tract? (where does it originate, descend, terminate)
cell bodies originate in the pontine RF, descend in ventral funinculus as part of the MLF to end in the medial parts of the ventral horn, primarily at the cervical level
Function of the medial (pontine) reticulospinal tract?
to facilitate axial and proximal limb muscles; tonically excites extensors and inhibits flexors
Medial (pontine) reticulospinal tract arises from neurons located where?
LATERALLY in pons and medulla
Which pathway is spontaneous and which is under more cortical control?
- medial (pontine) is more spontaneous
- lateral (medulla) is under more cortical control
The axons of the medial (pontine) RS tract run ipsilaterally or contralaterally in the ventral funiculus?
ipsilaterally
Lateral (medulla ) RS tract arises from neurons located where?
MEDIALLY in the medulla
Function of the lateral (medulla) RS tract?
inhibition of neurons to extensor muscles and excitation of of neurons to flexor muscles
Lateral (medulla) RS tract descends bilaterally in what?
the lateral funiculus (part of lateral motor system)
Which pathway can be viewed as the antagonistic system of the lateral vestibulospinal pathway and is under a great deal of cortical control?
lateral reticulospinal pathway
Which pathway is tonically active and works alongside the vestibulospinal pathways in that it facilitates extensors, primarily at the proxial joints of upper and lower extremities?
medial reticulospinal pathway
Which pathway is involved in generalized inhibition of all muscles?
lateral (medulla) reticulospinal pathway
Activation of which pathways results in inhibition of extensors and tonic facilitation of flexors?
lateral (medulla) reticulospinal pathway
Where is the raphe nuclei located?
located in the brainstem along the midline just anterior to the periaqueductal gray (central gray)
Many neurons of the Raphe nuclei use what as a neurotransmitter?
serotonin (5-HT)
The raphe nuclei receives input from where?
from a wide variety of brainstem, cortical, cerebellar, and spinal area
Output of the Raphe nuclei consists of ascending pathways, descending pathways, or both?
BOTH
Ascending pathways of the Raphe nuclei are involved in what?
Serotonergic neurons of the raphe play a major role in the reticular activating system that regulates arousal, sleep, and mood
Projection of the ascending pathways of the raphe nuclei is throughout what?
the cerebrum and cerebellum
Descending pathways of the raphe nuclei are involved in what?
Serotonergic neurons modulate pain input at the level of the “gate” in dorsal horn of the spinal gray