January Exam Flashcards
(32 cards)
What is consciousness? What are its two components?
awareness of environment and oneself components are: 1. content i.e. memory, perception, attention cerebral cortex 2. level i.e. awake alert, asleep brainstem
What is the ascending reticular activating system?
info goes up to the thalamus and then projects to other areas of the cortex
What were some pioneering experiments done in the field of consciousness?
stimulating certain areas in the brainstem wakes up a sleeping animal
bilateral lesion in the upper rostral brainstem (decerebration) makes animal unconscious
What are descending projections?
reticulospinal axons send post synaptic inhibition to alpha motor neurons of proximal (postural) muscles during REM sleep
What are the components of the ascending arousal system?
they are areas in the brainstem
all send arousal info to the cortex and are involved in modulation of conscious states by changing the excitability of cortical neurons
- noradrenergic neurons (from locus ceruleus control cortical attention)
- serotonergic neurons (raphe nuclei, failure to cause arousal with low CO2 in SIDS?)
- dopaminergic neurons (reward-based learning, addiction)
- histaminergic neurons (anti-histamines cause drowsiness)
- cholinergic neurons (involved in Alzheimer’s disease)
In what 2 ways can a coma be caused?
bilateral lesions of rostral brainstem ie decerebration (arousal pathways in upper pons/caudal midbrain)
bilateral lesions of cerebral cortex ie hypoxia, hematoma can cause pressure and damage cerebral cortex
What is locked in syndrome?
lesion in the mid pons, below the level of ascending arousal pathways
descending speech motor pathways are destroyed
forebrain is awake and conscious thought but patients can only interact with external world via eye movements (oculomotor cranial nerve intact)
What is the persistent vegetative state?
usually due to forebrain damage (hypoxia)
chronic
partial arousal- eyelid movement, saccades, swallowing, moaning
sleep-wake cycle occurs but no outward sign of consciousness
***they may be conscious- tennis/walking experiment, changing cortical blood flow
What is a primary evoked potential?
a change in voltage (recorded on an oscilloscope)
results from the summation of extracellular currents associated with postsynaptic potentials
is NOT due to local currents associated with action potentials
Name 3 primary evoked potentials
sciatic, median- somatosensory cortex (20 ms)
visual flash- visual cortex (80ms)
sound- auditory cortex
What is the EEG when someone is in a meditative state?
alpha rhythm (synchronized) 10 Hz
What is an EEG when you open eyes and do mental arithmetic etc?
beta rhythm (desynchronized)
13-30 Hz
lower amplitude, higher frequency
Where do the currents used for EEG come from?
EEG is the summation of cortical post-synaptic potentials occurring in neurons of the neocortex, particularly pyramidal cells
What are some theories for why we need sleep?
memory consolidation
recalibration of neural networks
restorative
energy conservation
What happens as a result of lack of sleep?
impaired memory
decreased cognitive ability and judgement
fatigue
How many sleep cycles do you have per night?
4-6 per night
slow wave sleep and then REM
Describe slow wave sleep
70-80% of sleep
different stages seen in EEG
last stage is deep sleep with large slow delta waves (1-2 Hz) and strong synchronization
children: sleep walking, sleep talking, night terrors, nightmares
dreams can occur- shorter, less visual, less emotional
decrease in blood pressure, HR, respiratory rate, temperature
Describe REM sleep
20-25% of sleep desynchronized EEG
inhibited muscle tone due to spinal inhibition from pons
deep sept
vivid dreams- longer, primarily visual, somewhat emotional
rapid eye movements, finger twitches, middle ear muscles, whiskers in animals
genital response associated with sexual arousal
large fluctuations in HR, BP, respiratory rate
Describe REM behaviour disorder
some ppl are not paralyzed during REM
appear to be acting out their dreams
about 50% of Parkinsons patients have it
too little brainstem descending postsynaptic inhibition to alpha motor neurons
What is the limbic system?
a ring of phylogenetically primitive cortex around the brainstem and its interconnecting structures
concerned with emotion, certain motivational states and behaviours (homeostatic and instinctual drives) and memory
Name 4 structures of the limbic system
cingulate cortex
hypothalamus
amygdala
hippocampus
Name some motivational states and behaviours associated with the limbic system
hunger - feed thirst - drink feel hot/cold - clothes feel tired - sleep rage/fear - attack/defense sexual arousal - mate pain - avoidance
What happens to patients infected with the rabies virus?
(attacks limbic cortex)
show profound changes in emotional state, including bouts of terror and rage
Explain what parts of the limbic system are involved in pain
somatosensory cortex (not limbic system) is responsible for the location, intensity and timing cingulate cortex is responsible for the emotional component
