Reticular Formation

Question 1

what is it?

Answer 1

network or reticulum of many neurons that comprises the core of the neuroaxis

Question 2

RF

• composed of…
• consequently…

Answer 2

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

Question 3

nuclei in the reticular formation have a role in…

Answer 3

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

Question 4

which areas of the RF are we concerned with?

Answer 4

central division
raphe nuclei
miscellaneous nuclei

Question 5

central division

• what zones?
• how large?

Answer 5

medial and lateral zones

largest division

Question 6

raphe nuclei

• what zone?
• location

Answer 6

midline zone

thin column of neurons along midline of brainstem

Question 7

RF miscellaneous nuclei we care about

Answer 7

PPRF
pedunculopontine nucleus
locus ceruleus
ventral tegmental area

Question 8

central division

• where does it begin
• where does it end

Answer 8

begins as continuation of the central gray interneuron network of the spinal cord (Lamina X)
ends in midbrain

Question 9

central division medial and lateral zones

• which is larger
• which is afferent
• which is efferent

Answer 9

medial zone
-larger
-efferent
lateral
-smaller
-afferent

Question 10

central division lateral zone neurons

• characteristic
• recieve collateral input from…

Answer 10

large dendrites
receive collateral input from
-all sensory and motor information carried by cranial nerves, spinal sensory pathways, and corticospinal, corticobulbar, and corticopontine pathways

Question 11

central division lateral zone

-what inputs are integrated in this area

Answer 11

sensory and cortical

Question 12

central division lateral zone

-relays integrated information to…

Answer 12

the medial zone
also projects to the
-cerebrum
-cerebellum
-thalamus (central median nucleus)
-spinal cord

Question 13

central division medial zone

-gives rise to the…

Answer 13

major efferent pathways from the reticular formation

Question 14

central division medial zone

-major functions

Answer 14

vital function regulation

somatic motor activity regulation

Question 15

nuclei of the medial zone receive input from…

Answer 15

lateral zone
variety of peripheral receptors, including the carotid body relayed through the solitary nucleus
hypothalamus
prefrontal cortex

Question 16

how does the medial zone regulate vital cardiac and respiratory function

Answer 16

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

Question 17

patients with lesions to the brainstem in areas involved in vital function regulation have what problems?

Answer 17

abnormal respiratory patterns
difficulty regulating BP with HTN
additional reticular nuclei regulate swallowing and vomiting

Question 18

somatic motor activity regulation (medial zone)

• nuclei in the pons and medulla receive input from the…
• this input comes via the…

Answer 18

input from
-cortex (corticoreticular pathway)
-cerebellum
-vestibular nuclei
-somatosensory areas
via the lateral zone

Question 19

somatic motor activity regulation (medial zone)

-what do these nuclei do with the info they receive via lateral zone

Answer 19

influence LMNs for the purpose of regulating postural, reflexive, and voluntary muscle control

Question 20

somatic motor activity regulation (medial zone)

• fibers that influence LMNs descend in…
• how do they descend?

Answer 20

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

Question 21

tracts within the medial zone

Answer 21

medial (pontine) reticulospinal tract

lateral (medullary) reticulospinal tract

Question 22

medial reticulospinal tract

-part of which activation system

Answer 22

part of medial activation system

Question 23

medial reticulospinal tract cell bodies

• originate in…
• descend in _____ as part of…
• end in…

Answer 23

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

Question 24

medial reticulospinal tract

-function

Answer 24

facilitate tonic facilitation of axial or postural flexors along with proximal joint muscles

Question 25

lateral reticulospinal tract | -part of what activation system

Answer 25

part of lateral activation system

Question 26

lateral reticulospinal tract cell bodies - originate in... - descend in _____ to the _____

Answer 26

originate in the medullary reticular formation | descend in the lateral funiculus to the lateral side of the ventral horn at all levels

Question 27

lateral reticulospinal tract | -function

Answer 27

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

Question 28

raphe nuclei | -location

Answer 28

located in brainstem along the midline just anterior to the periaqueductal gray (central gray)

Question 29

raphe nuclei | -many of the neurons use what neurotransmitter

Answer 29

serotonin (5-HT)

Question 30

raphe nuclei - receive input from... - output consists of...

Answer 30

receive input from a wide variety of brainstem, cortical, cerebellar and spinal areas output consists of ascending and descending pathways

Question 31

raphe nuclei ascending pathways - what type of neurons - play a major role in - projects to...

Answer 31

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

Question 32

raphe nuclei descending pathways - what type of neurons - function

Answer 32

serotonergic modulate pain input at the level of the "gate" in dorsal horn of the spinal gray modulate visceral and facial pain

Question 33

raphe nuclei descending pathways - which nerves correspond with visceral and facial pain - modulation of these occurs where?

Answer 33

``` visceral -CN X facial -CN V occurs at -solitary nucleus -spinal trigeminal nucleus ```

Question 34

raphe nuclei descending pathways | -what is important to activation of this system?

Answer 34

input from periaqueductal gray area that is receiving input from spinoreticular pathways (part of anterolateral system)

Question 35

raphespinal pathway - specific or nonspecific - function

Answer 35

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

Question 36

what do raphespinal neurons in the lateral horn influence?

Answer 36

cardiovascular system

Question 37

miscellaneous RF nuclei

Answer 37

paramedian pontine RF pedunculopontine nucleus locus ceruleus ventral tegmental area

Question 38

PPRF - associated with what nerves - located at level of...

Answer 38

associated with CNs of extraocular eye muscles | located at level of facial colliculus, surrounding abducens nucleus

Question 39

pedunculopontine nucleus - an _____ nucleus - located in... - projects to..

Answer 39

``` an Ach nucleus located in caudal midbrain projects to parts of the -basal ganglia -vestibular nuclei -reticular spinal nuclei ```

Question 40

pedunculopontine nucleus - function - sends rhythmic impulses to...

Answer 40

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

Question 41

locus ceruleus - what type of system - location

Answer 41

major norepinephrine system location -rostral pontine central gray region

Question 42

locus ceruleus - receives input from... - sends input to...

Answer 42

receives only restricted input from two brainstem nuclei | sends widespread ascending and descending connections

Question 43

locus ceruleus ascending connections - ascend to... - function

Answer 43

``` ascend to -thalamus -hypothalamus -basal forebrain -neocortex involved in ability to maintain and direct attention ```

Question 44

locus ceruleus descending cerulospinal tract | -function

Answer 44

provides nonspecific activation of the motor neuron pool in the anterior horn provides modulation of pain information in the dorsal horn

Question 45

ventral tegmental area - what type of system - what is the other system like this?

Answer 45

dopamine projecting system | the othe ris from substantia nigra

Question 46

ventral tegmental area - fibers project to... - function

Answer 46

project to limbic and frontal cortical areas | believed to play a role in cognition (decision making) and motivation

Question 47

ventral tegmental area - projections to the frontal lobe are balance with the _____ pathways - disturbances in these systems play a role in ____

Answer 47

balanced with the serotonergic pathways | disturbances play a role in depression and other disorders of cognition and affect