Sleep and Dreaming Flashcards
sleep represents…
an altered state of consciousness
two definitions of sleep
‘sleep is a naturally recurring state characterised by or absent consciousness, relatively suspected sensory activity and inactivity of nearly all voluntary muscles’
‘sleep is a readily reversible state of reduced responsiveness to, and interaction with, the environment’
endogenous influences
influences originating from inside the body, specifically from the central nervous system
exogenous influences
influence originating from outside the body, e.g. light, temperature or environment
circadian rhythms are the product of…
both endogenous and exogenous influences
what type of rhythm do most physiological functions follow daily
circadian rhythm
high cortisol =
active
high melatonin =
sleep
examples of exogenous influences
-light
-temperature
-environment
how often do circannual rhythms occur
annual (yearly)
how often do circadian rhythms occur
daily
what do circadian rhythms regulate
regulates the frequency of eating and drinking, body temperature, secretion of hormones, urination and sensitivity to drugs
what is the purpose of circadian rhythms
to keep our internal workings in phase with the outside world
zeitgeber
a stimulus which resets the circadian rhythm
examples of zeitgebers
-light - light is critical for resetting the circadian rhythm
-exercise
-noise
-meals
-temperature of the environment
however every zeitgeber is less effective than light
examples of common disruptions to circadian rhythms
-jet lag
-shift work
-daylight savings time in spring
sleep for a newborn infant
16-18 hours per day
throughout the day
on/off sleep rather than a long one
sleep for a 16 week old baby
14-15 hours per day
diurnal pattern
longer night sleep but regular day naps
sleep for a 3-5 year old infant
10-12 hours per day
biphasic pattern
long night sleep plus afternoon nap
sleep for an adolescent
~8 hours per day
monophasic pattern
increased need for daytime naps
sleep in old age
amount of nocturnal sleep decreases (6-7 hours)
more fragmented
more occasional night wake ups
biological mechanisms for resetting the circadian rhythms
-the superchiasmatic nucleus (SCN)
-genes that produce certain proteins
-melatonin levels (a hormone regulating sleepiness)
superchiasmatic nucleus (SCN)
part of the hypothalamus located above the optic chiasm
the main control centre of the circadian rhythms of sleep and temperature
damage to the SCN results in less consistent body rhythms that are no longer synchronised to environmental patterns of light and dark
how does light reset the SCN
through a small branch of the optic nerve (the retinohypothalamic path) - travels directly from the retina to the SCN
