| How does sleep work? | animals have rhythms that correspond to functional activity of animal |
| Biological clock | rhythm is a response to an external stimulus
animals have an internal mechanism |
| what is the Endogenous circadian rhythms? | internally controlled cycles that last about a day |
| Evidence for circadian rhythms: | if you stay up all night, you feel sleepier as it gets later but perk up a bit in the morning
animals kept in total darkness still keep to a 24h cycle
humans kept in an environment with a 28hr cycle cannot synchronise, and go back to 24hr cycle
blind and deaf animals have normal circadian rhythms |
| what does the SCN brain area do? | damage to SCN = damage to circadian rhythms
remove SCN and keep tissue culture and it continues to produce 24hr rhythm of action potentials
hamsters who had a 20hr SCN implanted started to live a 20hr cycle |
| How does SCN control circadian rhythms? | controls the pineal gland = endocrine hormone behind thalamus
releases melatonin = hormone makes us sleepy |
| upsetting the biological clock | internal clock but responds to environment
feedback system between world and clock allows adaptation
stimulus that changes the clock is called 'zeitgeber'
good for changes in seasons |
| what is the zetigeber? | means 'time giver'
for most land mammals = zeitgeber is light
but also respond to exercise, noise, temp, meals
some marine mammals respond to tides |
| how does jet lag disrupt rhythms? | disruption by crossing time zones
sleeping at wrong times, depression, lack of concentration, nausea
mismatch between bio clock and external stimuli |
| what is a phase delay and phase advance? | phase delay: delaying your sleep - easier
phase advance: sleeping earlier |
| how does shift work disrupt rhythms? | even after years of shift work, people still have disruptive sleep patterns
feel fatigued
can't sleep well during the day
don't adjust well to working at night |
| why is light so important? | small branch of optic nerve goes straight to SCN
comes from special ganglion cells
special photopigment, melanopsin (not rods or cones)
respond directly to lights
respond slowly and turn off slowly
so SCN can gauge the time of day |
| how can stages of sleep be detected? | with an EEG
eeg can detect electrical signals of spontaneous brain activity |
| describe the 4 stages of sleep: | stage 1 and 2: irregular activity, high but declining, bursts of activity in stage 2, cortex still receiving sensory light
stage 3 and 4: slow wave sleep (SWS) = neuronal activity is highly synchronised, sensory input reduced |
| what is REM sleep? | 90min cycles
rapid eye movement
also called paradoxical sleep
neither light nor deep sleep
light because lots of brain activity
deep because muscles are relaxed |
| what is the brain doing during REM? | lateral geniculate nucleus in the thalamus (limbic system) = emotions
Pons (brainstem) = 'bridge' axons from cortex to spinal cord = movement (inhibits) |
| what happens when you lesion the pons? | did this to cats
cats still had REM sleep
but muscles not relaxed
chased prey |
| What is the insomnia sleeping disorder? | stress, anxiety, depression
shifting circadian rhythms
dependence on sleeping pills |
| what is sleep apnea sleeping disorder? | inability to breathe while sleeping
due to obesity or old age? |
| what is narcolepsy sleeping disorder? | attacks of sleepiness during the day
REM during the day? |
| What is the periodic limb movement disorder? | involuntary movement of the legs/arms
maybe something to do with pons? |
| function of sleep? | a form of hibernation?
conserving energy when you can't get much done - food is scarce, light is too light/low
hibernating hamsters live longer than other hamsters |
| Animals vary in how much sleep depending on: | safety from predators
how much time they need to find food
whether they need to surface for air |
| where does lack of sleep lead? | causes dizziness, hallucinations etc
eventually the immune system shuts down in severely deprived animals
more sleep enhances memory |
| facts about REM sleep | we spend 1/5 sleep in REM sleep
emotional activity during REM
if deprived, the brain attempts REM during waking hours
babies have more REM sleep than adults
mammals and birds have REM sleep
must be a biological function |
| why do we need sleep? what is it for? | to strengthen memories - weed out pointless connections
sleep overall improves memory
anti-depressant drugs (MAO inhibitors) reduce REM and people have memory problems |
| Dreaming: The activation - synthesis hypothesis: | effort to make sense of distorted info
PGO waves from Pons activate parts of cortex, which synthesises a story
but not always in REM |
| Dreaming: The clinico-anatomical hypothesis: | dreaming is thinking
senses are supressed, so brain left to own devices
motor cortex suppressed so no action
pre-frontal cortex suppressed so no working memory to piece together a believable story |
| Temperature regulation: | to regulate temperature, humans:
sweat
shiver
blood vessel constriction
blood vessel dilation
pre-optic area: near hypothalamus - changes in its own temp, and temp receptors in skin |
| thirst: | humans have flexible strategies depending on circumstances
if water is scarce - pituitary gland releases vasopressin
blood vessels constrict
raises blood pressure and compensates for the flow fluid volume
vasopressin is an antidiuretic hormone (ADH) - makes urine more concentrated |
| Why do hangovers make us thirsty? | drinking alcohol blocks production of vasopressin by pituitary gland
prevents kidneys absorbing water
makes urine more diluted
morning after experience massive widespread dehydration - hence very thirsty |
| Hunger: how do we know what to eat? | combination of learned and unlearned strategies
learned from peers, culture
but innate tastes are essential
likeness of sweet food, disgust for bitter/sour |
| hunger: how do we know when to eat? | hypothalamus (associated with regulating behaviours)
has neurons sensitive to hunger and feeling full
these feeding mechanisms seem to have changed very little from mammalian times
many areas involved so can make errors, but can also be compensated |
| Eating disorders: Obesity | problem in industrialised countries
huge cultural influence
social aspect of eating
in our biology - tendency to like fatty foods
some genetic disorders |
| eating disorders: Anorexia nervosa: | unwillingness to eat
0.3% of young women
perception of fatness even when thin
body deterioration, muscle wasting, death
unlikely to be genetic
serious condition |
| eating disorder: bulimia nervosa: | extreme dieting mixed with binge eating
vomit after meals
imbalance of hormones associated with feeding
but may result in erratic eating rather than cause |
| How does our sex and gender affect our behaviour - evolutionary theory: | we are the product of successful strategies, so should have inherited successful strategies
men and women were subject to different selection pressures in evolutionary history - therefore exhibit different traits |
| Reproductive behaviours: | men and women differ:
sexual strategies - reproductive behaviour
Mate choice, attitude to sexual behaviour |
| Reproductive behaviours men vs women | men: numerous mobile sperm; potential to father many offspring
more promiscuous
women: few immobile eggs; maximum 20 in a lifetime
the 'choosy' sex
'evolutionary battle of the sexes' |
| Sexual strategies: role of hormones: | men: androgens (testosterone) produced in testes and the adrenal gland
sensitises regions of the brain underlying sexual motivation
removal of the testes (i.e. cancer) results in decreased sex drive, but still some production in brain
women: oestrogen produced by ovaries
and androgens produced by adrenal gland
androgens associated with sex drive
postmenopausal women can still have high sex drive due to androgen production |
