Neuro Exam 3.4
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Neuro Exam 3.4
review of neuro lecture 4 for exam 3
diffuse nuclei of tegmentum of brainstem; primary integrating area of brainstem relating to consciousness
elongated gray mass that extends b/w medulla and midbrain
What is the primary global integration area of the brainstem?
What are the 3 zones/columns reticular formation?
Which zone/column of the reticular formation is closest to midline?
Which zone/column of the reticular formation is the middle part?
What is the median zone/column of the reticular formation responsible for?
inhibition of pain perception
What structure is found in the median zone/column of the reticular formation?
What is the median zone/column of reticular formation's primary neurotransmitter?
Where does the median zone/column of the reticular formation project to?
Why does the median zone/column of the reticular formation project to the spinal cord?
to modulate pain transmission to conscious centers
Is the median zone/column of the reticular formation important in ARAS?
Where is the medial zone/column of the reticular formation found?
primarily in medulla and pons
What is the function of the medial zone/column of the reticular formation?
makes sense of input
What is the function of the efferent component of the medial zone/column of the reticular formation?
influence basic activities of body:
What is contained in the medial zone/column of the reticular formation?
Where can nuclei of the medial zone/column of the reticular formation project to?
other tegmental nuclei
cranial nerve nuclei
Which tracts terminate with LMN of the medial zone/column of the reticular formation?
rubrospinal and reticulospinal tracts
What does the medial zone/column of the reticular formation add to ARAS?
What does the lateral zone/column of the reticular formation add to ARAS?
primary afferent component
What is the function of the lateral zone/column of the reticular formation?
recieves input from collaterals, neurons associated w/ major ascending pathways
Is the lateral zone/column of the reticular formation an important part of ARAS?
What does ARAS stand for?
ascending reticular activating system
What does ARAS control?
various states of arousal
What is ARAS?
functional system of reticular formation
What makes ARAS?
medial and lateral zones/columns
Where does ARAS recieve input from?
cranial nerves and CNS
ascending sensory systems from spinal nn
cerebral areas of cortex
What are the functions of ARAS?
if ARAS is not working right, then cortex is not getting information:
What is the clinical significance of ARAS?
anesthesia acts by hyperpolarizing neurons in ARAS to decrease output, thus deactivating nuclei in reticular formation by competing for binding sites
What makes up the afferent input of ARAS?
lateral column of reticular formation
What makes up the efferent component of ARAS?
What are the outcomes of ARAS?
What is a conscious experience?
you are aware of feelings, ideas, dreams, and thoughts
What are the states of consciousness?
What level is normal consciousness?
What is speech like at the normal consciousness state?
spontaneous (voluntary) speech at a normal rate
What is motor activity like at the normal consciousness state?
normal voluntary and reflex somatic motor activity
What are the eyes like in the normal consciousness state?
open, normal oculomotor activity
What levels is lethargy?
What is speech like in level 2 lethargy?
spontaneous sentences, spoken slowly
What is motor activity like at level 2 lethargy state?
decreased speed of voluntary motor activity
What are the eyes like in level 2 lethargy state?
open, decreased oculomotor activity
What is speech like in level 3 lethargy?
spontaneous words, spoken infrequently
What is motor activity like at level 3 lethargy?
decreased speed and coordination of voluntary motor activity
What are the eyes like in level 3 lethargy?
open or closed; decreased oculomotor activity
What are the levels of the stupor state of consciousness?
What is speech like in level 4 stupor?
vocalization only to stimuli that cause pain
What is motor activity like at level 4 stupor?
marked decrease in spontaneous motor activity
What are the eyes like in level 4 stupor?
generally closed, some spontaneous eye movement
What is speech like in level 5 stupor?
What is motor activity like in level 5 stupor?
appropriate defensive movements (generally flexor) to movements that cause pain
What are the eyes like in level 5 stupor?
What is speech like in level 6 stupor?
What is motor activity like in level 6 stupor?
mass movements to stimuli that cause pain
What are the eyes like in level 6 stupor?
closed, decreased spontaneous conjugate eye movement
What level is the coma state of consciousness?
What is speech like in coma?
What is motor activity like in coma?
decrebrate posturing to stimuli that causes pain, or no response
postural change that occurs in some comatose pts consisting of episodes of axial rigidity, rigid extension of limbs, internal rotation of UEs, and marked PF of feet
What are the eyes like in coma?
eyes closed, absent spontaneous eye movements
What scale is used to grade comas?
Glasgow Coma Scale
What is a coma?
extensive damage to cerebral cortex; general sensations do not get there
In addition to damage of the cerebral cortex, where else may damage occur from a coma?
reticular formation of midbrain and upper pons, and thalamus
What part of the reticular formation is damaged during coma?
nuclei of reticular formation, not ascending pathway
What happens to information in the reticular formation during coma?
info goes up to the thalamus, but collaterals are not synapsing w/ nuclei of reticular formation, so there is no info in the brainstem
What is a toxic coma?
caused by medications, drugs
Can liver failure cause coma?
yes, build up of high levels of toxins which are toxic to neurons. Renal failure can do the same thing
What is the range of the Glasgo coma score?
What does the Glasgow coma score mean?
high is good; low is bad
What is the criteria for the Glasgow coma score?
best eye movement (4 pts)
best verbal response (5 pts)
best motor response (6 pts)
What are the cardinal signs for cerebral death?
absence of brain stem reflexes
What is the prerequisite to cerebral death?
all appropriate diagnostic and therapeutic procedures have been performed
What is the criteria to be present (from cerebral death) for 30 minutes at least 6 hours after the onset of coma and apnea?
coma with cerebral unresponsivity
absence of brain stem reflexes
state in which pt doesn't respond purposefully to externally applied stimuli, obeys no commands, and does not utter sounds spontaneously or in response to a painful stimulus
absence of spontaneous respiration, manifested by need for controlled ventilation for at least 15 minutes
papillary, corneal, oculoauditory, oculovestibular, oculocephalic, ciliospinal, snout, pharyngeal, cough, and swallowing
EEG w/ absence of electrical potentials of cerebral origin
What are the different waking states?
What is the alert wakefulness of the waking state?
awake, alert, eyes open
Beta rhythm >13 Hz/sec
What is the relaxed wakefulness of the waking state?
awake, relaxed (not alert), and eyes open
Alpha rhythm, 8-13 Hz/sec
What is the relaxed drowsiness of the waking state?
fatigued, tired, eyelids may narrow/close, head may droop, lapses of alertness and attention, and still awake but not asleep
decrease in alpha wave amplitude and some decrease in frequency--closer to the 8 Hz
Is sleep a part of ARAS?
Sleep is a form of:
What is sleep?
altered state of consciousness: the brain is still aware of the environment and still receives input and is very active processing sensory info
What is the Sleep-Wake cycle?
natural endogenous cycle/rhythm of the body
the natural physiologic processes (HR, BP) that vary throughout the day
Sleep-Wake cycle tunes your body to:
day and night (circadian cycle)
What are the parts of the circadian cycle?
What does the suprachiasmatic nucleus contain?
retinal cells sensitive to light
Where is the suprachiasmatic nucleus located?
hypothalamus, above optic chiasm
What does the suprachiasmatic nucleus do?
maintain circadian rhythm and biological clock
What does the primary biological clock allow?
the body to stay w/in cycle
What is sleep influenced by?
suprachiasmaatic nucleus (it is not dependent upon it)
Where is the sleep center located?
w/in reticular formation of pons
Is the sleep center excitatory or inhibitory in nature?
inhibitory, puts us in a sleep state
What does the sleep center interact with?
ARAS (excitatory) as a feedback loop
What does the sleep center involve?
a slow accumulation and dissipation of transmitter substances (NT/NM)
Why is sleep an active process?
sleep is not the absence of wakefulness; the brain is not inactive
What happens during sleep?
there is not an overall massive inhibition of neuronal activity
neurons continue to fire and some areas of the brain are more active than others
blood flow and oxygen demand do not decrease
What is the purpose of sleep?
important in long-term chemical and structural change that brain must undergo to make learning and memory possible
purposes of adaptations of organisms
What does it mean that sleep is "catch-up time"?
represents a period of rest for specific elements, during which time they can replenish substrates important for generation of AP (upregulation and downregulation of genes)
What is an example of the purposes of adaption of organisms that occur during sleep?
animals are asleep in burrows, nothing will eat you
What are the different EEG frequencies (rhythms)?
What is the range for beta EEG rhythms?
13 Hz and up
What is the range for alpha EEG rhythms?
What is the range for theta EEG rhythms?
What is the range for delta EEG rhythms?
Does slow wave sleep involve REM sleep?
no, non-REM sleep
How does one enter slow wave sleep?
from one of the stages of wakefulness
What are the characteristics of slow wave sleep?
no complex dreams
primarily used for rest
muscle tension is reduced but not eliminated
movement minimal but possible
How many stages are there in slow wave sleep?
How long does it take to go through all 4 stages of the slow wave sleep?
What are the characteristics of the stages of slow wave sleep?
each stage is repeatable and has an EEG pattern characterized by slower frequency and higher amplitude than previous stage
Describe stage I of slow wave sleep:
light sleep, easily aroused by moderate stimuli
alpha-rhythm reduced to partial theta rhythm (4-8 Hz/sec)
Describe stage II of slow wave sleep:
further lack of sensitivity to activation and arousal
primarily theta-rhythm (4-8 Hz/sec)
Describe stage III of slow wave sleep:
deep sleep, activation and arousal requires vigorous stimulation
theta wave (4-8 Hz) activity, as well as delta wave (about 2 Hz/sec)
Describe stage IV of slow wave sleep:
true/deep sleep; arousal requires vigorous stimulation
predominantly delta rhythm (2 Hz)
When does REM sleep occur?
after one cycle of slow wave sleep, but can occur at every stage of sleep
What is eye activity like during REM sleep?
burst eye movement activity superimposed over slow, rolling eye movement
How often does REM sleep occur?
every 90 minutes and last about 20 minutes (at 13+Hz/sec)
Why is REM sleep a paradox?
because EEG resembles that of a person who is awake, and oxygen use is higher than when you are awake
Why is REM sleep a deeper state of sleep?
based on criteria for external arousability
--takes immense external stimuli to wake up; noise/movement
What is the lightest state of REM sleep based on?
criteria for internal arousability
--little internal stimuli required to wake up; dream/heartburn/full bladder, etc
What happens to muscles during REM sleep?
profound loss of muscle tone (hypotonia/flaccidity/paralysis) throughout the body
Which muscles do not have hypotonia during REM sleep?
mm of respiration
mm of eye movement
mm of inner ear (stapedius mm)
What is the function of the stapedius mm?
modulate sound--modulates eardrum (dampens activity of sound transmission)
When do dreams occur?
only in REM sleep
When are penile and clitoral erection common during sleep?
What are some problems of sleep?
REM sleep behavior disorder
pathological conditions which interrupt ARAS
obstructive sleep apnea
manifest REM; unintentional sleep episode w/ REM (amphetamines)
REM sleep behavior disorder:
excessive, vivid dreams w/ movement
usually occurs during stage IV of non-REM sleep; body wakes up before mind does; not usually during REM sleep
wake up screaming (Stage IV)
may occur at any stage; becomes a problem if continues after age 16
any stage; generally occurs w/ obesity b/c oropharynx has lost space
defect of ARAS; often age-related
Obstructive sleep apnea:
blockage of airway; common in obese
stop breathing for 20-30 seconds, and then take a deep breath
can't die b/c respiratory reflex will take over
really never reach stage IV, so people are always tired
intentional absence of sleep