Reticular formation/sleep/wakefulness and Cortex1 Flashcards
what is special about the reticular formation?
it is the oldest part of our nervous system phylogenetically
- It is present throughout the midbrain, pons, and medulla
where can the reticular formation be found? What does it look like?
regions of the brainstem between clearly defined nuclei and tracts
- It is groups of neurons embedded in a seemingly disorganized mesh of axons and dendrites
how many groups of neurons related by function and connections are identified in the reticular formation?
over 100
what brain regions does the reticular formation send information to and get information from?
the reticular formation receives input from all parts of the nervous system ⇒ every sensory system
- locus coeruleus
- cortex
- spinal cord
- motor nuclei
- hippocampus
- periaqueductal gray
- thalamus
- hypothalamus
- cerebellum
- superior colliculus
- amygdala
what do many of the neurons look like in there reticular formation
large, highly branches dendrites to receive diverse information
what regulation roles does the reticular formation play? (5)
- Motor control
- Sensory attention
- Autonomic nervous system
- Eye movements
- Sleep and wakefulness
Reticular formation (RF)
in the lower pons and medulla receives motor information from premotor cortex, motor cortex and cerebellum as well as proprioceptive and vestibular sensory information
- RF sends axons to cranial nerve motor nuclei and to ventral horn of the spinal cord via the reticulospinal tracts
- RF initiates accompanying movements
Accompanying movements
subconscious and are needed in support of a consciously initiated movement ⇒ these movements are often needed to maintain balance
what precedes conscious movement? What is required for this type of movement?
accompanying movements; reticular formation is required
connections to the RF are mono, bi, multi lateral?
bilateral
how does RF influence motor neuron activity?
through interneurons
how does RF influence somatic motor neuron activity?
integrates visceral sensory information to influence somatic motor neuron activity
- Ex: breathing is regulated by axons from RF to cervical spinal cord
what other roles does RF play? through what connections?
essential roles in regulating blood pressure and heart rate largely through connections with brainstem and spinal cord autonomic preganglionic neurons
Reticulo-thalamic neurons
helps in filtering sensory information
- Can help to reduce irrelevant stimuli
what senses do reticule-thalamic neurons involve?
Touch, temp, pain, auditory, and visual stimuli
which autonomic functions doe the RF affect? (3)
- Breathing
- Heart rate and blood pressure
- Vomiting, gagging, and coughing
what are efferents of the RF to help with autonomic functions? (2)
- glossopharyngeal nerve (9)
- vagus nerve (10)
how does vomiting work?
- Vomiting center in medulla
- Activated by different stimuli
- Chemical ⇒ no blood brain barrier (area postrema)
- Vestibular
- Cortical ⇒ emotions, smells, visual stimuli
- Visceral ⇒ pharynx, GI tract
- Increased intracranial pressure - efferents are nucleus of solitary tract and dorsal nucleus of X
- Complex series of coordinated actions
how does RF affect eye movements?
it influences horizontal eye movements because PPRF gets input from the frontal eye fields or cortex and sends information to the abducens and oculomotor pathways to contract the eye muscles
- The medial longitudinal pathway sends things to oculomotor
- The abducens nucleus contracts the abducens related muscles
T/F sleep and wakefulness are active processes? How are these influenced by RF?
True
- Sleep and wakefulness are controlled by areas of the reticular formation in the midbrain and upper pons
Reticular activating system (+ 2 parts)
from midbrain and pons is required for wakefulness
- locus coeruleus => NE
- raphe nucleus => SER
how does wakefulness work?
Noradrenergic neurons in the locus coeruleus and serotonergic neurons in the raphe nucleus of the reticular formation project to cortex and are required for wakefulness
what wakefulness network molecules make you awake? (5)
- Acetylcholine
- histamine
- norepinephrine
- orexin
- serotonin
for sleep and wakefulness where does the RF project? (3)
- Nonspecific thalamic nuclei ⇒ cortex
- Specific thalamic nuclei ⇒ cortex
- Norepinephrine and serotonin ⇒ cortex
what 2 molecules take turns having high/low doses for circadian rhythm?
cortisol and melatonin
- Melatonin peaks in dark
- Cortisol peaks in light
suprachiasmatic nucleus
an intrinsic pacemaker
- Synchronizes rhythms to the light/dark cycle
- Sends output to many brain regions (including pineal)
what is the suprachiasmatic nucleus projection pathway to release melatonin?
suprachiasmatic => paraventricular nucleus => IML => SCG => pineal gland releasing melatonin
what is light from the eyeball as a pathway via the suprachiasmatic nucleus?
input from the retinal ganglion cells (primary visual pathway from optic nerve ⇒ chiasm ⇒ LGN ⇒ visual cortex)
melatonin
first released at about 3 months of age, which correlates with the onset of a regular sleep/wake cycle
- Released at night, so some people take melatonin to help induce sleep
- Melatonin sometimes taken to help treat jet lag, particularly when flying eat
where does the suprachiasmatic nucleus project to (2) aside from the paraventricular nucleus?
- pre optic area
- reticular formation
5 stages of sleep
- Non rem sleep: first 4 stages are characterized by progressively decreasing frequency and increasing amplitude of EEG cortical activity
- Rapid eye movement (REM): 5th stage characterized by high frequency and low amplitude EEG cortical activity, similar to the awake state
how long do stages 1-4 of sleep take? What about REM?
about 1 hour and REM lasts about 10 minutes before the cycle repeats
what processes are slowed during non REM sleep? What about REM?
- physiological processes slowed in non REM but increased during REM
- Somatic muscle activity is reduced during REM sleep
- Most dreaming takes place during REM sleep
when does tossing and turning occur?
during non-REM sleep
- tend to have deeper sleep the longer we go and then become closer to awake as you get toward morning
characteristics of non REM sleep (5)
slow wave sleep) ⇒ SWS
- Muscle activity
- Little dreaming
- Few eye movements
- Slowing of breathing
- Reduced BP
what is non REM sleep characterized by?
inactive brain in an active body
characteristics of REM sleep (5)
- Reduced muscle activity
- Frequent dreaming
- Increased eye movements
- Enhanced breathing
- Increased BP
how is age and REM sleep related?
the amount of REM sleep a person gets per night decreases with age
- 8 hours at birth
- 2 hours at 20
- 45 minutes at 70
what inhibits thalamocortical axons during REM sleep?
cholinergic axons from the reticular formation to thalamus activate GABAergic neurons in thalamus
what inhibits the activity of spinal motor neurons during REM sleep?
Pontine reticulospinal axons
what does the pontine RF project to? What is this required for? (non nerve proj.)
projections to the superior colliculus and is required for the rapid eye movements during REM sleep
what does lack of sleep result in?
mental and physical fatigue, poor decision making, impaired learning, emotional irritability, and an increased risk of migraine and epileptic seizures
- Chronic insomnia results in death
T/F the mechanisms for understanding restorative sleep is well understood?
False => poorly defined
what happens to extracellular space in the brain for awake mammals vs sleep?
extracellular space in the brain of an awake mouse accounts for 14% of the brain volume ⇒ during sleep this increases to 23%
- the brain shrinks
how much does CSF increase/decrease during sleep?
increases 95%
what neurotransmitter is responsible for the loss of extracellular space when awake?
noradrenaline
- Lack of sleep makes your brain look older
