Reticular Formation Flashcards
what is it?
network or reticulum of many neurons that comprises the core of the neuroaxis
RF
- composed of…
- consequently…
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
consequently, all levels of the CNS are interconnected either directly or indirectly by way of the reticular formation
nuclei in the reticular formation have a role in…
regulating muscle tone for postural control during voluntary and reflexive movement
modulating the sense of pain
regulating arousal, sleep, and attention
coordinating autonomic respiratory and cardiac function
which areas of the RF are we concerned with?
central division
raphe nuclei
miscellaneous nuclei
central division
- what zones?
- how large?
medial and lateral zones
largest division
raphe nuclei
- what zone?
- location
midline zone
thin column of neurons along midline of brainstem
RF miscellaneous nuclei we care about
PPRF
pedunculopontine nucleus
locus ceruleus
ventral tegmental area
central division
- where does it begin
- where does it end
begins as continuation of the central gray interneuron network of the spinal cord (Lamina X)
ends in midbrain
central division medial and lateral zones
- which is larger
- which is afferent
- which is efferent
medial zone -larger -efferent lateral -smaller -afferent
central division lateral zone neurons
- characteristic
- recieve collateral input from…
large dendrites
receive collateral input from
-all sensory and motor information carried by cranial nerves, spinal sensory pathways, and corticospinal, corticobulbar, and corticopontine pathways
central division lateral zone
-what inputs are integrated in this area
sensory and cortical
central division lateral zone
-relays integrated information to…
the medial zone also projects to the -cerebrum -cerebellum -thalamus (central median nucleus) -spinal cord
central division medial zone
-gives rise to the…
major efferent pathways from the reticular formation
central division medial zone
-major functions
vital function regulation
somatic motor activity regulation
nuclei of the medial zone receive input from…
lateral zone
variety of peripheral receptors, including the carotid body relayed through the solitary nucleus
hypothalamus
prefrontal cortex
how does the medial zone 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
-spinal cord for somatic control of motor neurons in the spinal cord that regulate inhalation and expiration
patients with lesions to the brainstem in areas involved in vital function regulation have what problems?
abnormal respiratory patterns
difficulty regulating BP with HTN
additional reticular nuclei regulate swallowing and vomiting
somatic motor activity regulation (medial zone)
- nuclei in the pons and medulla receive input from the…
- this input comes via the…
input from -cortex (corticoreticular pathway) -cerebellum -vestibular nuclei -somatosensory areas via the lateral zone
somatic motor activity regulation (medial zone)
-what do these nuclei do with the info they receive via lateral zone
influence LMNs for the purpose of regulating postural, reflexive, and voluntary muscle control
somatic motor activity regulation (medial zone)
- fibers that influence LMNs descend in…
- how do they descend?
descend in two separate pathways
both pathways descend ipsilaterally, but then can synapse on interneurons both ipsilaterally and contralaterally
thus, influence can be seen bilaterally
tracts within the medial zone
medial (pontine) reticulospinal tract
lateral (medullary) reticulospinal tract
medial reticulospinal tract
-part of which activation system
part of medial activation system
medial reticulospinal tract cell bodies
- originate in…
- descend in _____ as part of…
- end in…
originate in pontine RF
descend in ventral funiculus as part of the MLF to end in medial parts of ventral horn, primarily at a cervical level
medial reticulospinal tract
-function
facilitate tonic facilitation of axial or postural flexors along with proximal joint muscles
lateral reticulospinal tract
-part of what activation system
part of lateral activation system
lateral reticulospinal tract cell bodies
- originate in…
- descend in _____ to the _____
originate in the medullary reticular formation
descend in the lateral funiculus to the lateral side of the ventral horn at all levels
lateral reticulospinal tract
-function
assist the lateral vestibulospinal pathway in tonically facilitating LMNs of the extensors and inhibiting flexors
this tonic activity also influences the gamma motor neuron system to assist in the sensitivity of stretch reflex activity
raphe nuclei
-location
located in brainstem along the midline just anterior to the periaqueductal gray (central gray)
raphe nuclei
-many of the neurons use what neurotransmitter
serotonin (5-HT)
raphe nuclei
- receive input from…
- output consists of…
receive input from a wide variety of brainstem, cortical, cerebellar and spinal areas
output consists of ascending and descending pathways
raphe nuclei ascending pathways
- what type of neurons
- play a major role in
- projects to…
serotonergic neurons
play a major role in the reticular activating system that regulates
-arousal
-sleep
-mood
projection of the neuronal pathways is throughout the cerebrum and brainstem
raphe nuclei descending pathways
- what type of neurons
- function
serotonergic
modulate pain input at the level of the “gate” in dorsal horn of the spinal gray
modulate visceral and facial pain
raphe nuclei descending pathways
- which nerves correspond with visceral and facial pain
- modulation of these occurs where?
visceral -CN X facial -CN V occurs at -solitary nucleus -spinal trigeminal nucleus
raphe nuclei descending pathways
-what is important to activation of this system?
input from periaqueductal gray area that is receiving input from spinoreticular pathways (part of anterolateral system)
raphespinal pathway
- specific or nonspecific
- function
nonspecific
function
-provides diffuse activation of motor neurons in the anterior horn
-may be involved in influencing motor output during levels of high motivation or arousal
what do raphespinal neurons in the lateral horn influence?
cardiovascular system
miscellaneous RF nuclei
paramedian pontine RF
pedunculopontine nucleus
locus ceruleus
ventral tegmental area
PPRF
- associated with what nerves
- located at level of…
associated with CNs of extraocular eye muscles
located at level of facial colliculus, surrounding abducens nucleus
pedunculopontine nucleus
- an _____ nucleus
- located in…
- projects to..
an Ach nucleus located in caudal midbrain projects to parts of the -basal ganglia -vestibular nuclei -reticular spinal nuclei
pedunculopontine nucleus
- function
- sends rhythmic impulses to…
thought to have a role as a brainstem central pattern generator to induce walking without cerebral control
sends rhythmic impulses to caudate and putamen of the basal ganglia
locus ceruleus
- what type of system
- location
major norepinephrine system
location
-rostral pontine central gray region
locus ceruleus
- receives input from…
- sends input to…
receives only restricted input from two brainstem nuclei
sends widespread ascending and descending connections
locus ceruleus ascending connections
- ascend to…
- function
ascend to -thalamus -hypothalamus -basal forebrain -neocortex involved in ability to maintain and direct attention
locus ceruleus descending cerulospinal tract
-function
provides nonspecific activation of the motor neuron pool in the anterior horn
provides modulation of pain information in the dorsal horn
ventral tegmental area
- what type of system
- what is the other system like this?
dopamine projecting system
the othe ris from substantia nigra
ventral tegmental area
- fibers project to…
- function
project to limbic and frontal cortical areas
believed to play a role in cognition (decision making) and motivation
ventral tegmental area
- projections to the frontal lobe are balance with the _____ pathways
- disturbances in these systems play a role in ____
balanced with the serotonergic pathways
disturbances play a role in depression and other disorders of cognition and affect
