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35 Cards in this Set
- Front
- Back
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What are the boundaries of the reticular formation?
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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) |
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What do the reticular formation fibers represent?
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dendritic trees and collateralized axons
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What type of cells are the larger RF cells? Describe their axons.
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Golgi type I neurons
long axons with multiple collaterals oriented in the transverse plane |
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Describe the anatomical correlation to function of the RF axons.
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Some of the larger Golgi I RF axons project rostrally AND caudally, thus allowing for integration of the OUTPUT effects of the RF
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Describe the smaller RF cells.
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long DENDRITES, extedn to distant locations.
penetrate cranial n, sensory tracts and motor tracts |
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What do the smaller RF cells allow for?
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synaptic integration of systems projecting to or through the brainstem.
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Describe the axons of small RF neurons.
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short axons course MEDIALLY. interact with large output neurons
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What types of integration does the RF provide?
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sensory and motor as well as rostrocaudal integration
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What are the three main longitudinal regions of the RF?
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raphe
media lateral |
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What type of neurons are found in the raphe zone? What else is included?
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small neurons staddling length of brainstem median plane
periaqueductal gray |
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What is included in the medial zone nuclei?
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large neurons: giganto or magnocellular in the PONTINE and MEDULLARY tegmentum
OUTPUT region of RF primarily |
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What is included in the lateral zone of the RF?
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small neurons, parvicellular, throughout the brainstem tegmentum
INPUT region of RF primarily |
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Where does the RF receive its collaterals from?
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most ascending and descending brainstem pathways
visceral AND somatic AND motor AND sensory |
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What are the ORIGINS of AFFERENTS?
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spinal cord
brainstem cerebellum diencephalon cerebral cortex RECEIVE THE MOST HETEROGENEOUS INPUT OF ANY NEURONAL SYSTEM IN THE CNS |
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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
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Where do the collaterals of sensory systems to the RF come from?
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secondary or tertiary pathways
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Which type of systems will bypass direct input to the RF? Why?
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sensory systems because they must maintain one to one topographic relationships liek descriminative tough, vision, auditory
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What type of secondary input involves the RF?
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startle reactions to tough, light or sound
RF functions in arousal and attention |
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What type of spinal cord afferents are associated with the RF?
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spinoreticular tract originate at all levels of the cord
AND spinothalamic tracts (ALS) send collaterals |
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What type of brainstem afferents are associated with the RF?
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collaterals from secondary and tertiary cranial nerve sensory nuclei
tectoreticular tracts from superior and inferior colliculi reticuloreticular pathways exist between parts of the tegmentum |
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What cerebellar afferents are associated with the RF?
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deep cerebellar nuclei project to RF esp fastigial nucleus
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What limbic system afferents are assoicated with the RF?
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mammillary nuclei via the mamillotegmental tract
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What are the four main regions of RF output?
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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 cerebellum |
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What are the major functional categories of the RF?
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mental activity
lower motor neuron control homeostasis and vegetative reflexes |
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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
upward ascending reticular activating system (ARAS) arousal, consciousness, alertness, attention span, sleep wake cycle |
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What happens when the pontine RF is lesioned? What if the upper brainstem (midbrain) is lesioned?
Anasthetics may work in the ARAS |
insomnia
coma |
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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 |
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What is another name for the lower motor neuron control system of the RF?
In which direction does it go? |
reticulospinal-reticulaobulbar system
downward |
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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 |
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What are the homeostatic and vegetative reflexes important in?
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CV and respiratory centers
breathing, HR, BP, GI motility, electrolyte balance, pupillary size, ocular movements regulates somatic and visceral coordination: gagging, vomiting, laughing, crying |
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What is stored in the rostral half of the RF? The caudal half? @ midpons transection
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Rostral: mental activity (ARAS)
Caudal: lower motor neuron control and vegatative reflexes |
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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 |
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How are dendrites and axon collaterals arranged?
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pancake-like. parallel to one another
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Does the medial zone have more dendrites than the lateral zone?
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no. lateral has more dendrites while the medial has more axons
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What functions are associated with the mediolateral RF?
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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 |
