Sleep & Dreaming Flashcards
What is sleep?
Reversible state
Recurring
Reduced responsiveness to the environment
Reduced or absent consciousness
Suspended sensory activity, inactivity of nearly all the voluntary muscles
What are endogenous and exogeneous influences?
Endogenous influences: are influences originating from inside the body, specifically from the nervous system
Exogenous influences: are influences originating from outside the body e.g. light, temperature, environment
What are circannual rhythms?
e.g. animals story food for winter
animals can’t rely on external cues only
e.g. animals need to start storing food before it gets too cold
What are circadian rhythms?
Regulates the frequency of eating and drinking, body temperature, secretion of hormones, urination, sensitivity to drugs
Are there any cues for endogenous rhythms? What is the purpose of these rhythms? How long are they?
Purpose: keep our internal workings in phase with the outside world
Rhythm is slightly longer than 48 hours
No exogenous cues
What are zeitgebers? What is the most important zeitgeber?
Zeitgeber: stimulus that resets the circadian rhythm
Light is crucial to reset this
Other zeitgeber: exercise, noise, temperature. These are less effective than light
In the study by Roenneberg et al (2007) what was the procedure and results for the ‘sun time’ in Western and Eastern Germany?
The whole of Germany is on the same time zone
But the sun rises 30 mins earlier in the East
People from both sides reported the times they were waking up and going to bed
The midpoint was calculated
East Germans midpoint was 30 minutes earlier than West Germans
How does melatonin and cortisol fluctuate during the day and night?
High cortisol during the day, with low melatonin
More active
High melatonin during the night, with low cortisol
Sleeping
What are examples of disruptions to circadian rhythms? Why is there a disruption? Can everyone adapt to these disruptions?
e.g. monday morning blues, daylight savings in spring, jet lag, shift work
Mismatch between internal circadian clock and external time
Easier for some, more difficult for others
What is jet lag? What are phase delays? What are phase advances? How does this affect sleep and body temperature?
Sleepiness during the day but sleeplessness at night
Travelling west: phase delays (late to go to bed and late to get up) Difficulty going to sleep
Travelling east: phase advances (go to bed earlier and wake up earlier) Difficulty staying asleep
Facilitated by body temperature, lowest temperature when asleep
Is it easier to fly west or east? Why? How long are our endogenous cycles, so how can this help with phase delays and phase advances?
Easier to adapt to jet lag when flying west because the day of the travel is lengthened
This is shortened when travelling east
Endogenous cycle is 25 hours, so we can cope better with phase delay than phase advance
How can shift work be an example of phase delay and phase advance? Why is disrupting a worker’s sleep cycle bad?
Rising early or retiring to bed earlier is a phase advance
Going to bed late or getting up late is a phase delay
Accidents can happen when a worker’s sleep cycle is disrupted by a night shift
e.g. more lorry accidents between 4am and 7am, chernobyl occurred between 1am and 4am
How does sleep change as an infant newborn and during adulthood? What is the duration? Is it disrupted? When do they sleep?
In adulthood you can sleep throughout the night with no disruptions. This duration of sleep of sleep is shorter
Newborn infants need a longer duration of sleep. This is more disputed. they sleep throughout night and day on and off.
How does sleep change in old age? How long is it, is it broken up, when do they wake up? Why?
Amount of sleep decreases
More fragmented
Shifts earlier
More occasional wake ups
But is this due to a reduced need of sleep or decreased capacity of sleep mechanisms?
Where is the Suprachiasmatic nucleus located? How does it help circadian rhythms? If it is damaged, what happens?
Parts of the hypothalamus located above the optic chiasm
The main control centre of circadian rhythms of sleep and temperature
Damage to the CSN results in less consistent body rhythms that are no longer synchronised with environmental patterns of light and dark
How does the SCN help circadian rhythms? What happens regarding action potentials and genetics?
Cells in the SCN fire their action potentials in a particular rhythm
The circadian rhythm generated by the SCN are genetically controlled
How does the SCN receive light information? What is the optic nerve, the retinohypothalamatic path and melanopsin?
Light resets the SCN via a small branch of the optic nerve (the retinohypothalamatic path)
Travels from retina to the SCN
The retinohypothalamatic path comes from a special population of retinal receptors that have their own photopigment called melanopsin.
These cells respond directly to the light and do not require any input from the rods or cones
Are blind mole rats able to follow sleep/wake cycles? Why is this the case in regards to melanopsin cells?
Blind mole rats
There are eyes but no muscles to lift the lids nor lenses
Able to follow steady sleep and wake cycles
The melanopsin cells are fully functional in the absence of functioning rods and cones
Where is the pineal gland located? How does the SCN regulate the pineal gland? What hormone does the pineal gland secrete? How does this help circadian and circannual rhythms?
The SCN regulated waking and sleeping by controlling activity levels in other areas of the brain such as the pineal gland
Located posterior to the thalamus
Secretes melatonin, a hormone that increases sleepiness
Melatonin also regulates circadian and circannual rhythms
There are 2 proteins which generate the circadian rhythm. What is the period and timeless protein? What happens to the sleep/wake cycle when they are high or low?
Period: produces proteins called PER
Timeless: produces proteins called TIM
When they’re high they induce sleepiness, low induces wakefulness
What is an actigraph?
Actigraph watch is a recording device with an accelerometer (movement sensor)
What is polysmonography?
Uses multiple methods to look at brain, heart, muscle and eye movement activity
What are some advantages of using an EEG?
Equipment is cheap
Low invasiveness
Can be used to study the brain activity over an extensive period of time
Can be used on a wider range of patients e.g. babies and dogs
How does an EEG detect brain activity? How does it work in regards to neurons?
Record electrical activity in the brain
Measures the changes in the potential of the postsynaptic neurons
Groups of neurons firing at the same time
Electric activity is detected by placing electrodes on scalp and amplifying them and displaying them on a screen