Sleep and Circadian Rhythms

Question 1

what are the two main processes that control sleep?

Answer 1

homeostatic - sleep debt

circadian - 24hr cycle

Question 2

what is the best way of measuring sleep?

Answer 2

polysomnography - recordings of electrical activity from multiple sources:
EEG: measures neurons in the brain
EOG: measures movement of muscles around the eyes
EMG: measures body muscle movement

Question 3

describe brain activity during wakefulness

Answer 3

irregular activity of beta waves

Question 4

describe brain activity during sleep

Answer 4

there are 4 patterns of activity:
stage 1 - the transition between sleep and wakefulness, theta activity
stage 2 - sleep begins, k complexes (big jumps in waves of activity)
stage 3 - high amplitude & low frequency delta activity, regular waves
REM sleep - increase in brain activity and muscle atonia

Question 5

what are the two hypotheses on dreaming?

Answer 5

activation-synthesis hypothesis - hobson 2004
bottom up, brainstem is activated during REM and sends signals to the cortex which creates images with actions and emotions from memory. because the frontal cortex is less activated during dreaming there is no logical order to the timing

clinico-anatomical hypothesis - valli and revonsuo 2009
top down, we dream about things that we find our threatening in our lives. dreaming is a form of problem solving

Question 6

describe adenosine

Answer 6

a chemical that accumulates throughout the day and promotes sleep

Question 7

which area of the brain promotes sleep?

Answer 7

ventro-lateral preoptic area - contains inhibitory neurotransmitter GABA

Question 8

which area of the brain promotes arousal?

Answer 8

reticular formation (reticular activation system)
comprised of several nuclei in the brainstem and extends to forebrain: locus coeruleus releases melatonin, raphe nucleus releases serotonin, raphe nucleus releases serotonin, TMN releases histamine, nucleus basalis of maynert releases ach

Question 9

what is the flip flop switch concept?

Answer 9

saper 2001 - systems that promote sleep inhibit arousal systems and vice versa

Question 10

describe orexion

Answer 10

a peptide released from the lateral hypothalamus, highly responsible for wakefulness

Question 11

describe a study which supports the presence of circadian rhythms

Answer 11

aschoff 1965 - no cues, still developed an endogenous biological clock

Question 12

what is the name given to external cues that serve to set our biological clock?

Answer 12

zeitgebers

Question 13

what is a chronotype?

Answer 13

refers to the different circadian rhythms that vary between people

Question 14

what is the biological clock of the hypothalamus?

Answer 14

suprachiasmatic nucleus

Question 15

what are PRGCs?

Answer 15

photosensitive retinal ganglion cells - communicate with SCN have their own photopigment (melanopsin), are most responsive to blue light

Question 16

what are the 4 hypothesis as to why we need sleep?

Answer 16

adaptive, restorative, development, learning and memory

Question 17

describe sleep being adaptive

Answer 17

it is thought that originally we slept in order to conserve energy: whilst we sleep there is a decrease in muscle activity and body temperature

Question 18

describe sleep being restorative

Answer 18

sleep removes free radicals and prevents damage from oxidative stress as a result from activation during the day

Question 19

describe stress being for development

Answer 19

infants sleep more than adults, during slow wave sleep growth hormone is released

Question 20

describe sleep being for learning and memory

Answer 20

sleep enhances and regulates memories
REM stage enhances non declarative tasks
SWS(stage 3) enhances declarative memories
synaptic homeostasis hypothesis - tononi and cirelli 2014 - synaptic pruning occurs during sleep which helps to reinstate the brain so that it can function and learn more the next day

Question 21

what are symptoms of chronic sleep deprivation?

Answer 21

problems with attention, increase in negative emotions, inability to handle stress, maintaining focus, decrease in problem solving abilities