REM sleep and dreaming
we spend one-third of our lives asleep.our need for sleep is related to our state of mind. at a party, it is easier to stay awake whereas if you are at home and board than it is easier to go to sleep.people who are depressed will sleep more than they normally would.we vary in the amount of sleep we need throughout our lives:
- when we are babies, we sleep and wake many times during the course of the day.
- as we get older, we only sleep once at night, although people from hot countries may well have a siesta during the day when the sun is at its highest in the sky.
- we seem to need less sleep when we are in our teens and twenties, yet as we get older we need more sleep
- when we are much older, our need for sleep decreases again.
how is sleep investigated?
most of the work undertaken on sleep has been carried out in sleep laboratories. which is normally in a small room with a bed in it. it must be hard enough going to sleep in a lab and on top of that knowing that you are connected to wires and someone is observing you, while writing things down or video recording you.there are three types of machines that participants can be wired up to to measure the nervous system;
- an EEG electroencephalograph measures brain activity;the electrodes are placed over the head to record the electoral activity of the underlying neurones.
- an EMG electromyogram measures muscle activity;facial and jaw muscle activity is monitored by electrodes placed on the jaw area
- an EOG electro-oculogram measures eye movements; the electrodes are placed around the eye socket.
the sleep cycle
stage one- sleep is the first drifting stage that we go through on our way to deep sleep. it can occur when the natural light fades, as this information is transferred through the eyes to the pineal gland in the brain, which starts to produce a hormone called melatonin.melatonin directly makes us feel sleepy and therefore, when it gets dark, we begin to feel drowsy.
stage two-this stage is deeper than stage one but we can still be woken up easily.the heart rate, breathing and brain activity are slower than at stage one.
stage three- is deeper still, with more long slow delta waves.we are difficult to wake at this point.and the heart rate, blood pressure and temperature dropping
stage four- is known as delta or quite sleep.this is the stage where it is hard to wake us, unless the stimulus is very relevent, such as an alarm clock or a baby crying. this sleep lasts for appro 30mins burts.during this stage we are able to toss and turn our limbs as neccassary.
a whole sleep cycle lasts for about 90mins and involves us moving down through all four stages and moving up again. this 90 minute cycle is present in infants who are fed on demand, and has also…