This site is 100% ad supported. Please add an exception to adblock for this site.

bales reticular system


undefined, object
copy deck
What are the boundaries of the reticular formation?
CAUDALLY: from the spinal cord intermediate zone of spinal grey matter to ROSTRALLY: the diencephalon (thalamus)

RF fills in the space left behind by the other names nuclei and tracts, forming the core of the medulla, pons, and midbrain (brainstem)
What do the reticular formation fibers represent?
dendritic trees and collateralized axons
What type of cells are the larger RF cells? Describe their axons.
Golgi type I neurons

long axons with multiple collaterals oriented in the transverse plane
Describe the anatomical correlation to function of the RF axons.
Some of the larger Golgi I RF axons project rostrally AND caudally, thus allowing for integration of the OUTPUT effects of the RF
Describe the smaller RF cells.
long DENDRITES, extedn to distant locations.

penetrate cranial n, sensory tracts and motor tracts
What do the smaller RF cells allow for?
synaptic integration of systems projecting to or through the brainstem.
Describe the axons of small RF neurons.
short axons course MEDIALLY. interact with large output neurons
What types of integration does the RF provide?
sensory and motor as well as rostrocaudal integration
What are the three main longitudinal regions of the RF?


What type of neurons are found in the raphe zone? What else is included?
small neurons staddling length of brainstem median plane

periaqueductal gray
What is included in the medial zone nuclei?
large neurons: giganto or magnocellular in the PONTINE and MEDULLARY tegmentum

OUTPUT region of RF primarily
What is included in the lateral zone of the RF?
small neurons, parvicellular, throughout the brainstem tegmentum

INPUT region of RF primarily
Where does the RF receive its collaterals from?
most ascending and descending brainstem pathways

visceral AND somatic


motor AND sensory
What are the ORIGINS of AFFERENTS?
spinal cord




cerebral cortex

Where do the afferents of the RF tend to synapse?

How are efferents distributed?
lateral parvicellular neurons which then relay to the central gigantocellular neurons which distribute much of the RF efferents
Where do the collaterals of sensory systems to the RF come from?
secondary or tertiary pathways
Which type of systems will bypass direct input to the RF? Why?
sensory systems because they must maintain one to one topographic relationships liek descriminative tough, vision, auditory
What type of secondary input involves the RF?
startle reactions to tough, light or sound

RF functions in arousal and attention
What type of spinal cord afferents are associated with the RF?
spinoreticular tract originate at all levels of the cord


spinothalamic tracts (ALS) send collaterals
What type of brainstem afferents are associated with the RF?
collaterals from secondary and tertiary cranial nerve sensory nuclei

tectoreticular tracts from superior and inferior colliculi

reticuloreticular pathways exist between parts of the tegmentum
What cerebellar afferents are associated with the RF?
deep cerebellar nuclei project to RF esp fastigial nucleus
What limbic system afferents are assoicated with the RF?
mammillary nuclei via the mamillotegmental tract
What are the four main regions of RF output?
cranial nerve nuclei--collaterals of long axons

descending reticulospinal fibers--ventral part of lateral funiculus and in anterior funciculus

Nonspecific intralaminar nuclei of thalamus--ascending axons reach the intralaminar nuc of thalamus then widespread to cortex

What are the major functional categories of the RF?
mental activity

lower motor neuron control

homeostasis and vegetative reflexes
What part of the RF is associated with mental activity?

In which direction does it travel?

What is the name given to this system?

What is it involved in?
rostral half of RF


ascending reticular activating system (ARAS)

arousal, consciousness, alertness, attention span, sleep wake cycle
What happens when the pontine RF is lesioned? What if the upper brainstem (midbrain) is lesioned?

Anasthetics may work in the ARAS

What is the name of the nucleus in the ARAS that may be involved in sleep phases?

What does it look like?

Describe its efferents.

Where is it found?
locus coeruleus

looks bluish because of melanin content

highly branched efferents reach all parts of the CNS and cortex directly

found adjacent to the PAG near the pontomidbrain junction
What is another name for the lower motor neuron control system of the RF?

In which direction does it go?
reticulospinal-reticulaobulbar system

What does the reticulospinal-reticulaobulbar system control?

What is it a relay for? Exception??

What does it regulate?
motor and visceral control

relay for ALL descending tracts EXCEPT direct pyramidal tract

regulates reflexes like hiccuping, sneezing, yawning, swallowing

Also modulates normal postural tone and reflexes

Major descending pathway in movement control
What are the homeostatic and vegetative reflexes important in?
CV and respiratory centers

breathing, HR, BP, GI motility, electrolyte balance, pupillary size, ocular movements

regulates somatic and visceral coordination: gagging, vomiting, laughing, crying
What is interesting about the raphe nuclei?

What does it modulate?

Where does it receive afferents from?

Where does input come from and where does output go? What is one hypothesis for this arrangement
use serotonin

modulate ascending sensory transmission

receives limbic, olfactory, and hypothalamic afferents

input from PAG
output to dorsal horn = possibly pain supression
How are dendrites and axon collaterals arranged?
pancake-like. parallel to one another
Does the medial zone have more dendrites than the lateral zone?
no. lateral has more dendrites while the medial has more axons
What functions are associated with the mediolateral RF?
parabrachial area - feeding (integ. of XII, VII, and V) and expiration

locus coeruleus - sleep phases

paramedian pontine reticular formation (PPRF)- eye reflexes

small cell zone - respiratory rhythm "pneumotaxic center"

superficial medullary zone - cardiac and respiratory regulation

Deck Info