reticular formation Flashcards
what are the charecteristics of the functions of the reticular formation
Tasks involve nervous system as a
whole
Functions are integrative
intergrative fucntions of the reticular formation
Sleep, wakefulness, alertness, consciousness
Coordination of visceral functions
(homeostasis)
Responses to pain; pain modulation
Body posture
Mental stat
what is the defintion of the reticular formation
Defined as the gray matter that composes the
core of the brain stem (excluding cranial nerve
nuclei and ascending and descending tracts)
what does the RF consist of
Consists of networks of branched neurons
reticu.ar foramtion is related to ___ ____ ____ ____ in the nervous system
so many other parts
how are the nuclei of the RF defined histologically
not as well defined as other nuclei
what are the afferetn connections of the RF
All sensory systems (not specific)
Many other areas
efferent connections of the RF
- widespread
RF has a ____ function
intergrative
where is RF located in the brain
gray matter in core of brainstem
what size cells does the RF have
- what is the organixation of the dendritic web
Large and small cells
Dendritic web of large cells is oriented
perpendicular to axis of brain stem
what are the charecteristics of the axons of the RF?
- where do they travel
- how many branches?
- how many synaptic connections
- Output neurons have long axons. -
- The axons ascend all the way to the cortex, or descend to the spinal cord.
- They’re wide
spread and have numerous collaterals (branches) along the way. - These axons make a huge number of synaptic connections, and so there are many pathways throughout the body.
what are orientation of of these dendrites
- axons are traverse ( perpenducular) to the long axis of the brainstem
- RF axons/dendrites are picking up info from ascending and descending tracts
Serotonergic pathways
raphe nuclei
- location
- what do they produce
- where do efferent branches reach
- do they have topographic organization ?
Midline of medulla, pons, midbrain
Serotonergic
Efferent branches reach many parts
of nervous system including spinal
cord
Little topographic arrangement
noradrenergic pathways
locus coerulus is located in the causal midbrain and sends projections all over the brain
locus coeruleus
- location
- what does it release
- where fo effernt branches reach
- waht is the arrangement
Near mesencephalic V, under
superior cerebellar peduncle
Noradrenergic
Efferent branches reach many parts
of nervous system
Little topographic arrangement
dopaminenergic pathway
- what releases dopamine
- substantia nigra and tegmentum release dopamine
- they project muptiple places in the brain
Electroencephalogram (EEG)
- sleep conciousnes
- important in understadning sleep and wakefullness
- electrodes record electrical activity og the brain
- pick up corticol actvity and the electrical filter out spikes so youre left with the synaptiv activity of the brain
categories of the EEG waves
beta waves - awake state when the cortex is bust
alpha waves - if you close eyes and relax you get alpha waves
theta waves- falling asleep
Delta- deep sleep
realtionship of EEG frequency waves
- as you fall asleep you get higher amplitude slow frequency and more sychronixationtion and high voltage
- when you are awake they are high frequency and desychranized with low voltage
EEG waves during sleep and
wakefulness
Awake state- high frequency, low
amplitude
Sleep state- low frequency, high
amplitude (synchronized)
rapid eye movement / REM sleep
-a few times during the nigh you go from sychrnized to desycronized and “wake up”
- as it becomes desychrnoized you get REM sleep and dream
-
how deoes REM sleep look like in a EEG
desychronized as if youre awake
reticular acitivating system
wakes up the brain by going through the thalmus
- there aslo other passages that go through the hypothalmus
what is Arousal
Reticular network receives
collateral inputs from all
ascending sensory pathways
what happens when there are lesions to th RF
Lesions of reticular formation
(upper brain stem) result in coma
what can coma also be the result of
Coma can also be the result of
extensive thalamic or cortical
damage
sleep inducing system :
where fo arousal system originiate from
- what does sleepromoting neuronsdo to the hypothalmus
- what does the mutual inihibition produce
Ascending arousal system
originates in pons
Sleep promoting neurons in
hypothalamus inhibit the arousal
areas
Mutual inhibition produces a flipflop switch
what do the pontine RF contain
Pontine reticular formation
contains neurons that generate
REM sleep
other uses of EEG
Detecting and localizing seizures
Identifying brain dea
where are the reticulospinal tracts
what do the reticulospinal tracts act on
- how does it effect soindles
- act mainly on extensors and gamma motor neurons
- Controls sensitivity of spindles
gamma motor system
Gamma motor system: gamma motor neuron (blue star, Ay) goes to polar ends of spindle, increases spindle stretch, makes
whole reflex more sensitive.
Control of the ANS
RF sends descending pathways down to the spinal cord to the intermediolateral cell column and influence sympathetic activity
or autonomic activity in general
cardiac and vascular centers
Medulla controls BP and respiration
respiratiory centrs
in the medulla that controls rate of breathing
lesions can cause death bc cant breathe
Other autonomic centers of the
medullary and pontine reticular
formation
Swallowing
Vomiting
Gagging
Coughing
Sneezing
Shivering
Micturition
Crying
Pain modulation:
spinoreticular tract
- other projections that go the RF instead of the VPK
and oroject to nonspecifc nuceli of the thalmus - this sense of pain is not as precise
pain modulation
What is the source in the rf that is responsible for this
- periaquaductal gray is a source of descedning patheay to the RF and inhibit pain impulses from periphery
Periaquaductul gray is a source of a descending pathway to the raphie nuclei which secrete serotonin and inhibit pain
reactions to noxius stimuli
Reflexes (e.g., jaw opening)
Vocalization
Sweating
Pupillary dilation
Heart rate increase
Blood pressure changes
Behavioral changes
mood disorders:
monoamine hypothesis of depression
- mono aminie nuclei ascend projections to the cortex and transmitters affect mood
