Lecture 11 Flashcards
What is the importance of sleep?
Lack of sleep = imputes memory, reduced cognitive abilities, mood swings, hallucinations, fatal familial insomnia, inability to enter deep sleep
Slides 1-2 lecture 11
What is unihemispheric slow-wave sleep?
One hemisphere can exhibit the electroencephalographic signs of wakefulness while the other shows the characteristics of sleep
Ex: ducks often sleep in rows, the birds sleeping at the end of a row engage in USWS with the eye that faces away from the centre of the group remaining open
Slide 3 lecture 11
What is the trends of duration of sleep?
Requirements vary widely among adults, from about 5-10 hours per night
Average length is about 7.5 hours and the sleep duration of about 68% of young adults is between 6.5 and 8.5 hours
As people age, they tend to sleep more lightly and shorter times
Older adults make up for shorter and lighter nightly sleep periods by napping during the day
Slide 4 lecture 11
How do you record brain waves?
Electroencephalogram (EEG) records tiny voltage fluctuations, microvolts (μV) in amplitude
Contribution of any single cortical neuron is exceedingly small, takes thousands of underlying neurons, activated together, to generate an EEG signal big enough to see at all
Amplitude of EEG signal depends on how synchronous the activity of the underlying neurons is
Each cell receives same amount of excitation, but spread out in time the summer signals are meager and irregular
Slides 5-6 lecture 11
What are the 4 types of EEG rhythms?
EEG rhythms vary dramatically and correlate with particular states of behaviour (attentiveness, sleeping, or waking) and pathology (seizures or coma)
Beta >14 Hz activated cortex
Alpha 8-12 Hz quiet, waking states
Theta 4-7 Hz some sleep states
Delta <4 Hz deep sleep
In deep sleep, cortical neurons are not engaged in information processing, and large numbers of them phasically excited by a common, slow rhythmic input
Slide 7 lecture 11
What are the 5 stages of sleep and their EEG rhythms?
Stage 1- transitional sleep, fleeting, lightest stage EEG alpha rhythms of relaxed waking become less regular and wane, eyes make slow rolling movements
Stage 2- slightly deeper, occasional 8-14Hz oscillation sleep spindle, high amplitude sharp wave
Stage 3- EEG begins large amplitude, slow delta rhythms, eye body movements are usually absent
Stage 4- deepest stage, large EEG rhythms of 2Hz or less
Rapid eye movement (REM)- fast EEG beta rhythms and frequent ballistic eye movements
Slides 8-9 lecture 11
What is the sleep cycle?
Sleep is a readily reversible state of reduced responsiveness to the environment
Several times during night cycle REM sleep present waves similar to being awake
Decreases in muscle tone, heart rate, breathing, blood pressure, metabolic rate, and temp in non REM sleep
BP, heart rate, and metabolism return to levels almost as high as awake state in REM sleep, also has explosion of extra striate activity with no increase in primary visual cortex
Slide 10-11 lecture 11
How are dreams made?
In REM sleep
Has explosion of extrastriate activity (when we dream), with no corresponding increase in primary visual cortex
Emotional component of dreams might derive from the heightened limbic activation
Low activity in the frontal lobe suggests that high level integration or interpretation of the extrastriate visual information might not take place, leaving us with I interpreted visual imagery
Slide 11 lecture 11
How doe muscle paralysis occur in REM sleep?
Increased activation of GABA-ergic neurons in the pons inhibit spinal motor neurons
The GABA activation causes the inhibition of NE and 5HT neurons and the activation of ACh neurons in the puns
The ACh neurons excite glutamatergic neurons, the glutamatergic neurons project to the medulla, where they terminate on inhibitory neurons that release glycine onto motor neurons and hyperpolarizes them, producing motor paralysis
Slide 12 lecture 11
What is REM sleep behaviour disorder?
RBD is characterized by the dreamer acting out his or her dreams
Often involve kicking, screaming, punching, grabbing, can often sustain injuries
Lesions in pons cause a similar condition in cats
The basis for RBD seems to be disruption of the brain stem systems that normally mediate REM atonia
Slide 13 lecture 11
What is narcolepsy?
Disabling disturbance of sleeping and waking in which victims suddenly collapse into a similar state of REM sleep
Excessive daytime sleepiness, “sleep attacks”, and cataplexy (sudden muscular paralysis)
Cataplexy is often brought on by strong emotional expression such as laughter or tears
Thought to result from abnormal activation of the motor inhibition that normally occurs during periods of REM sleep
Narcoleptic person often goes from waking directly into REM
Slide 14-16 lecture 11
What are the neural circuits governing sleep and wakefulness?
The neurons most critical to the control of sleeping and waking are part of the diffuse modulatory neurotransmitter systems
These systems act like the switches of the forebrain, altering cortical excitability and gating the flow of sensory information into it
NE and 5-HT fire during waking and enhance the awake state; some ACh neurons enchanted critical REM events, others active during waking
Descending branches of the diffuse modulatory systems cause inhibition of motor neurons and paralysis during dreaming
Stim of cholinergic neurons cause sleeping cat to waken, slow stim of thalamus causes an awake cat to fall asleep
Slides 17-18 lecture 11
What is wakefulness?
Hormones, etc
Neurons of the locus coeruleus (Ne), raphe nuclei (5HT), brain stem and nasal forebrain (ACh), and the midbrain (histamine) increase their firing rates in anticipation of awakening and during various forms of arousal
These neurons synapse directly on the entire thalamus, cerebral cortex, etc.
Slide 19 lecture 11
What are the 2 states thalamocortical neurons can be in?
Thalamocortical neurons can be in 1 of 2 stable states: intrinsic bursting (or oscillatory) state; of a tonically active state
Tonically active is generated when the thalamocortical neurons are depolarized, when input of ascending modulatory systems generates wakefulness
Slide 20 lecture 11
What do GABA-ergic neurons in the thalamic reticular nucleus hyperpolarize?
GABA-ergic neurons in the thalamic reticular nucleus hyperpolarize thalamic cells which stabilizes the bursting state
When neurons in reticular nucleus undergo a burst of activity, they cause thalamocortical neurons to generate short bursts of APs, seen as spindle activity in the cortical EEG recordings
Slide 21 lecture 11
