W6 211 L11 Flashcards
Ironically sex and eating are our biggest motivators but we spend the most time of our life
Sleeping
Brain highly active during sleep and
Efforts physical and mental health
Sleep is actually a
Behaviour. Not just an action or a resting period.
Electrophysiological Measurement of Sleep
§ Sleep research is conducted in a sleep laboratory.
§ Electrodes are attached to the subjects scalp to record electrical activity of the brain. The amplifier records an electroencephalogram (EEG).
§ Electrodes are also attached to the subjects chin to record muscle activity recorded as an electromyogram (EMG).
§ Electrodes placed around the eyes monitor eye movements recorded as an electro - oculogram (EOG).
Brain activity when we’re are awake and at rest
When we are awake, our EEG shows two basic patterns:
Alpha activity consists of regular, medium frequency waves (8-12 Hz).
Beta activity is generally associated wave forms that are irregular at an amplitude of 13-30 Hz.
Beta activity is desynchronous; it’s a reflection of different neural circuits actively processing information at the same time.
Stage 1 of Sleep
When we get drowsy, we show theta activity (3.5-7.5 Hz). This is the transition between wakefulness and sleep.
Muscle activity slows down
Stage 2 of Sleep
After about 10 minutes, the EEG becomes irregular with mixture of theta activity, sleep spindles and K complexes.
- Sleep spindles are short bursts of waves (12-14 Hz) which occur between 2-5 times a minute during sleep stages 1-4.
- Older people show more K complexes. K complexes are sudden, sharp waveforms. They are found during stage 2 only. They occur spontaneously at approximately 1 per minute and can be triggered by unexpected noise.
Both seem to keep ppl asleep.
Older ppl fewer sleep spindles, but more k complexes.
If woken up, during this stage, feel grooggy.
Breathing slows and body temp decreases a little.
Stages 3 and 4 of Sleep
aka slow wave sleep.
Stages 3 and 4 are characterised by high-amplitude delta waves (less that 3.5 Hz). They occur more frequently in stage 4 (deep sleep).
More delta activity in stage 4.
During decent of waveform as sleeping, inhibitory. Biphasic
REM Sleep
Finally, about 90 minutes after the beginning of sleep, we enter REM sleep characterised by Rapid Eye Movements.
The activity in REM sleep is desynchronised, sprinkled with theta and beta activity.
The EMG becomes silent (no muscle tone). Infact, apart from occasional twitching, muscles are totally inactive during REM sleep.
Sleep Patterns
§ Stages 1-4 are referred to as non-REM sleep.
§ Stages 3-4 are referred to as slow-wave sleep because of slow, high
amplitude delta waves.
§ At stage 4 you’re usually in deep sleep. Can’t be awakened by noise.if awoken are confused, irritated and grumpy.
Cerebral blood flow and oxygen consumption decrease.
§ During REM you don’t react to noise but you can be aroused by meaningful stimuli. Like name. Wake up alert and aroused.
§ Dreaming occurs during REM sleep. Cerebral blood flow and oxygen consumption increase. In REM sleep, muscles are inactive.
Wet dreams and orgasm possible. Absence of sexual arousal.
90-minute sleep state
Sleep alternates between REM and non-REM patterns of sleep.
§ Each sleep cycle is about 90 minutes long (20-30 minutes of REM sleep). 2.5-3h during 8h cycle.
Amount of rem sleep increases as night goes on.
Mental Activity During Sleep
§ People who report their dreams are ‘conscious’ during sleep.
§ There is high cerebral blood flow to the visual association cortex which may account for the visual hallucinations that occur during dreams.
§ There is low blood flow to the primary visual cortex (because the retina is not receiving any light) and the prefrontal cortex (which makes dreams temporally disorganised).
“… the dreamer often has no feeling of striving for long-term goals but rather is carried along by the flow of time by circumstances that crop up in an unpredictable way.”
All ppl dream, few ppl remember them. Unless awoken during rem.
All have visual hallucination,
Comparative Analysis of Sleep
When lions have gorged themselves on a kill, they may sleep continuously for three days!
In bottle nosed dolphins, the two hemispheres sleep independently so they remain behaviourally alert.
see cute lion sleep on back Photo. ^o^
Only birds and mammals exhibit rem sleep.
Sleep is universal though.
Obviously flamingo leg does not go limp.
Sleep dependant, on vulnerability to predator attack. And how much they need to eat to survive.
Functions of Slow-Wave Sleep (I)
Note cannot defy urge to sleep.
§ Effects of sleep deprivation: human studies
- Lack of sleep affects cognitive abilities rather than physical abilities. Does not seem to be to rest physically that we sleep. Really for brain.
- You never regain lost sleep after sleep deprivation.
Though it appears you make up a bit more of stage 4 and REM sleep and brain will try to accomplish this. Compared to stages 1-2. Like 50% vs 7%. Anecdote of boy who stayed up for 1 consecutive days. - Presence of delta activity and low levels of physiological activity (i.e. low cerebral metabolic rate and cerebral blood flow) during slow-wave sleep indicates that the brain is resting.
- The brain must restore the effects of oxidative stress. Free radical, highgly reactive oxygen species atoms. O2
-Damages cells! Free radicals and antioxidants.
