Consciousness, Evoked Potential, EEG, Sleep

imissyou419's version from 2017-01-29 20:34

Section 1

Question Answer
Define consciousnessaware of environment and oneself
what are the 2 components of consciousness?content (memory, perception, attention) - cerebral cortex; level (awake, alert, asleep, coma) - brainstem (rostral pons/caudal midbrain)
Ascending Reticular Activating System Pioneering ExperimentsPioneering Experiments: stimulate certain areas in brainstem - wakes up a sleeping animal/conscious, bilateral lesion rostral brain (decerebration) - unconscious animal [cut into ascending reticular activating system]
Ascending Reticular Activating System Descending ProjectionsReticulospinal axons send post synaptic inhibition (IPSPs) to alpha motor neurons of PROXIMAL (postural) muscles during REM sleep
Where does the Ascending Arousal System arise?in the brainstem (rostal pons/caudal midbrain)
What are the 5 types of neurons/NT systems of the Ascending Arousal System? KNOW THIS1. Noradrenergic (those from locus ceruleus control cortical attention).
2. Serotonergic (raphe nuclei, failure to cause arousal with low CO2 in Sudden Infant Death syndrome? - enfants with underdeveloped serotonergic neurons).
3. Dopaminergic (reward-based learning, addiction).
4. Histaminergic (anti-histamines cause drowsiness).
5. Cholinergic (Alzheimer's Disease)
These come from rostral pons/caudal midbrain
What does the Ascending Arousal System do?widespread projections, some to virtually every part of CNS.
Function in modulation of conscious states (including sleep/awake) by acting as neuro-modulators that alter the membrane potential of thalamo-cortical and cortical neurons (depolarization when producing awake state)
What is coma?state of prolonged unconsciousness with no response to stimuli
what are the 2 causes of coma?1. bilateral lesion of rostral brainstem (arousal pathways in rostral pons/caudal midbrain),
2. bilateral lesion of cerebral cortex e.g. decreased oxygen (hypoxia), hematoma (blood clot) produces pressure and damages to cerebral cortex
Locked-in syndromelesion mid/caudal-pons (below level of Ascending Arousal pathways) by brainstem stroke, etc.
Descending limb and speech motor pathways destroyed (cannot move arms, legs, or speak),
Forebrain awake and conscious but patient can only interact with external world via eye movements (oculomotor cranial nerve [cranial nerve III] intact moving extra ocular muscles)
Persistant vegetative statedue to forebrain damage (hypoxia), chronic (long term), partial arousal (eyelid, saccades, swallowing, moaning), sleep-wake cycle occurs but no sign of consciousness
Are some persistant vegetable state patients conscious?Adrian Owen using fMRI and simple Yes/No questions -> Yes - imagining plaing tennis (activates motor areas), No - imagine walking own home (hippocampal area), ~15% patients could answer by changing cortical blood flow in specific areas i.e. they were conscious

Section 2

Question Answer
Primary evoked potentialsevoked by stimulation of the sciatic nerve (somatosensory).
1. change in voltage (AVERAGING LOTS OF NEURONS b/c currents small + noise) (recorded on oscilloscope)
2. results from summation of extracellular currents associated with postsynaptic potentials. (lots of neurons)
3. It is not due to local currents associated with APs (from afferent neuron)
What are the 2 properties of primary evoked potential?1. has short latency e.g. 20ms (visual is 80 ms because it takes 60 ms to get out of retina due ion channels cascade).
2. is only recorded over somatosensory cortex if electrode is on surface of correct part of cortex

Section 3

Question Answer
Alpha rhythm8-12 Hz (synchronized), meditative state
Beta rhythm13-30 Hz (desynchronized) i.e. low amplitude, fast frequency, mental arithmetic or opening the eyes
Delta waves1-2 Hz (synchronized) i.e. large amplitude, low frequency, non-REM sleep (slow wave)
What is the origin of electrical current associated with EEG?summation of cortical post synaptic potentials occuring in neurons of neocortex, particularly pyramidal cells. Not due to currents associated with APs. Uses: location of epileptic focus, location of cortical tumors, diagnosis of sleep disorders, brain machine interface
Why sleep?No consensus but many theories: memory (learning) consolidation, recalibration of neural networks such as VOR, restorative (flushing out toxins around neurons), energy conservation
Lack of sleepimpaired memory, decreased cognitive ability, decreased judgement, fatigue (driving)
What causes sleep?not just a decrease in neural activity. Results from cooperative interplay of many brainstem neural components in Ascending Arousal System. In awake state and REM sleep, some certain groups of brainstem neurons increase their activity whereas others decrease (in a cyclic fashion during sleep)
What are the 6 characteristics of Non-REM (slow wave) sleep? KNOW THESE1. 70-80% of sleep.
2. Different stages seen in EEG.
3. Last stage deep sleep with large slow waves (delta 1-2 Hz) strong synchronization.
4. Children: sleep walking, sleep talking, night terrors, nightmares.
5. Dreams can occur (shorter, less visual, less emotional).
6. Decrease in BP, HR, respiratory rate, temp.
What are the 8 characteristics of REM sleep? KNOW THESE1. 20-25% sleep (4-6 periods/night).
2. desynchronized EEG (similar to awake activation).
3. inhibited muscle tone due to spinal inhibition from pons.
4. deep sleep.
5. vivid dreams (longer, primarily visual, somewhat emotional).
6. rapid eye movements, finger twitches, middle ear muscles, whiskers in animals.
7. genital responses associated with sexual arousal.
8. large fluctuations in HR, BP, respiratory rate
What is paradoxical about REM sleep?brain awake (desynchornized EEG), body asleep (inhibited postural muscle tone due to spinal inhibition from pons)
Which sleep do you have large fluctuations in HR, BP, respiratory rate?REM sleep
Which sleep do you have different types of muscle contractions?REM sleep
Which sleep do you have vivid dreams?REM sleep
Which sleep are you in deep sleep?REM
How many sleep cycles are there per night?4-6 sleep cycles (non-REM/REM)
Which sleep are children more likely to sleep walk, and get nightmares?Non-REM sleep
REM behavior disordera specific brainstem region in Arousal System (if stimulated, get REM sleep & muscle atonia - descending inhibition) but with lesion - no muscle atonia (no postsynaptic inhibition) so animals appear to act out their dreams during REM sleep
REM behavior disorder is present in what disease?50% of patients with Parkinson's because there is too little brainstem descending postsynaptic inhibition to alpha motorneurons

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