Sleep and conscious Flashcards
Discuss sleep state.
Subjective:
Recumbent
unconscious
dreams and nightmares
quality, deep/light, great or poor.
objective:
a might relate to immobility, arousal thresholds and a range of physiological variables like heart rate, respiration, temperature
Discuss the state of wake.
the quality of which is often described by the terms alertness, sleepiness and fatigue
What is sleep inertia?
quality of wakefulness immediately following sleep, during which time it might take the brain some time to transition from sleep and to reach full waking performance
Which 2 oscillatory processes regulate sleep?
Circadian rhythms and sleep homeostat.
Discuss the circadian rhythms.
24HR- SCN Hypothalamus
Adjusted to the environment by external cues,
known as zeitgebers- synchronize an organism’s internal biological rhythms with the external environment.
they can be entrained into these zeitgebers, such as daylight
this regulates sleep and wakes cycles and other systems, Melatonin increased at night.
Discuss the sleep homeostat.
Hourglass oscillator
* Tracks the history of sleep and wakefulness and thereby tracks sleep
debt
* Sleep pressure increases during wakefulness and dissipates during sleep (sleep debt)
* Maintains duration and intensity of sleep
Which factors increase the drive for sleep (sleep pressure)?
- Sleep deprivation
- Immune response to an infection
(cytokines) - Cognitively or physically demanding
tasks
Discuss the marker of sleep pressure- adenosine.
- Adenosine is released as a by-product of metabolism (ATP is used for
energy) - An increase in adenosine (basal forebrain) increases sleep pressure
- The sleep drive helps the body maintain sleep-wake homeostasis (i.e.
the right amount of sleep and wakefulness over time) - The longer a person stays awake, the more energy is used at a cellular
level, the greater the accumulation of adenosine, the stronger the
sleep drive becomes - During sleep, adenosine that accumulated throughout the day is
removed
How does caffeine work?
adenosine antagonist blocks the receptors in the basal forebrain
What are the benefits of sleep?
Waste removal
Period of reduced caloric use
restore brain energy stores
Immune support- adaptive
Reverse performance loss associated with wakefulness
Enhance neural connections
How is the sleep and wake cycle balanced?
When the alerting areas are most active – they inhibit activity in the sleep-promoting areas
When the sleep-promoting areas are most active – they inhibit areas of the brain responsible for wake
Describe the Wake-promoting pathways.
Dorsal:
* innervates the hypothalamus
* enables thalamic processing of signals related to sensation, motor responses and cognition; facilitates transmission of sensory information to the cortex
* Necessary for the ”content” of consciousness by enabling proper thalamocortical
signalling
Ventral:
* innervates the hypothalamus, basal forebrain and other forebrain structures
* excite the cortex
* Essential for the behavioural sate of wakefulness
Discuss the wake-promoting neurons.
Monoaminergic neurons (light green) in the rostral brainstem and caudal hypothalamus directly innervate the cortex.
* noradrenergic neurons of the locus coeruleus
* serotonergic neurons of the dorsal and median raphe nuclei
* dopaminergic neurons of the ventral tegmental area
* histaminergic neurons of the tuberomammillary nucleus
parabrachial nucleus and cholinergic regions (dark
green with hatching), including the pedunculopontine and laterodorsal tegmental nuclei and
basal forebrain.
How do orexin neurons facilitate the wake-promoting pathway?
Hypocretin (orexin) neurons in the lateral hypothalamus help to facilitate the wake-promoting process in a synergistic manner through exciting neurons in the cortex, midline thalamus, and all wake-promoting regions
Discuss the sleep-promoting neurons.
Sleep generation is initiated within the ventrolateral preoptic nucleus (VLPO) of the anterior hypothalamus.
Acts to inhibit the arousal regions of the brain:
* tuberomammillary nucleus
* lateral hypothalamus
* locus coeruleus
* dorsal raphe
* laterodorsal tegmental nucleus
* pedunculopontine tegmental nucleus
Describe the flip-flop switch.
the areas of the brain that maintain wakefulness by activating the cortex also inhibit VLPO neurons.
Conversely, when VLPO neurons fire rapidly and induce sleep, they also inhibit activity in the arousal centers such as the tuberomammillary nucleus.
Describe how the brain wakes.
Neurons in the upper pons produce ACh, which activates areas of the thalamus responsible for channeling signals to the cerebral cortex, the site of consciousness.
NT including NE, serotonin, histamine, and dopamine are produced in the pons, hypothalamus, and other nearby regions. They prime the cerebral cortex to receive signals from thalamus
Orexins: these peptides produced in the lateral hypothalamus reinforced the arousal system.
Describe what happens when the brain tires.
Homeostatic control: as the ATP breaks down, ADP builds up and triggers neuron activity in the VLPO
Circadian control: SCN is the brain’s master clock, containing neurons that fire in a 24-hour cycle to influence the VLPO. it is controlled by signals from the retina during the day and by melatonin from the pineal gland at night.
the brain sleeps, and shut down: when VLPO neurons are activated, they release GABA and galanin. these bind to receptors in the hypothalamus and pons to inhibit the ascending arousal pathway.
How do we measure sleep?
Polysomnography
Brain activity (EEG), heart activity (ECG), eye movements (EOG), muscle activity
(EMG), respiration, oxygen saturation
Describe the alpha blockade.
The alpha wave rhythm is blocked by higher frequency B waves, especially when the eyes open.
this is due to a stimulus and allows for cognition to occur.
Define EEG and discuss its principles.
An electrophysiological technique for the recording
of electrical activity arising from the human brain
Primarily measuring spontaneous brain
activity for sleep
generated by cortical pyramidal neurons in
the cerebral cortex that are oriented
perpendicularly to the brain’s surface
the summation of the excitatory and
inhibitory postsynaptic potentials of
relatively large groups of neurons firing
synchronously
differential amplification: recording voltage differences between pairs of electrodes – i.e. one active exploring electrode site and another
neighboring or distant reference electrode
EEG waveforms are generated by measuring differences in electrical potential between electrodes
Outline the different waveforms.
Alpha: awake but resting, eyes closed, not mentally concentrating on any subject or task, 8-13Hz
Beta: Receiving sensory stimulation or engaged in concentrated mental activity. 14-60 Hz
Theta: Drowsy or sleepy state in adults, common in children. 4-7.9 Hz
Delta: Deep sleep. <4Hz
What is the best site to view slow waves?
F4-M1
What is the best site to view spindles?
C4-M1
