Rhythms

Question 1

Biological rhythms

Answer 1

Cyclical changes in physiological systems - adapted because environments have cyclical changes

Question 2

Circadian rhythm

Answer 2

any cycle landing 24 hours - all types of organism have some bio representation of 24hr day - optimise based on physiology and behaviour to meet demands
Driver by suprachiasmatic nuclei (SCN) in hypothalamus - pacemakers constantly resets so bodies synchronise with outside world - natural light inputs to this system to calibrate SCN by photoentrainment

Question 3

Sleep wake cycle

Answer 3

Light and darkness e externally signal when to sleep and wake up - but rhythm dips and rise at different points of day so strongest sleep drives during 2-4am and 1-3pm
Most melatonin from pineal gland during darkness (light inhibits production) which induces sleep
Homeostasis control - awake for long time then homeostasis tells us we need to sleep as lots of energy has been used - increases gradually and max at evening
Keeps awake as long as daylight and prompts to sleep upon darkness - internal rhythm will maintain 24-25hr cycle though

Question 4

Circadian Rhythms eval

Answer 4

+ Chronotherapeutics - optimises time that meds are taken e.g risk of heart attack greatest upon waking around past 6am so drugs designed to take at night but release after 6am
+ Important to understand as essential to survive
- Research doesn’t account for artificial light but study has shown altering artificial light changes cycle length to 22-28hrs
- Individual differences - between 13-165 hrs, also differences in when rhythms peak - ‘morning’ people vs ‘evening people’
- People in arctic regions have somewhat normal sleeping patterns despite prolonged light exposure so EZ of light has little impact
+ Siffre locked himself in a cave for 3 months, for a month sleep was normal but long term had some changes until returning to normal again near the end - mixed impacts

Question 5

Ultradian vs Infradian Rhythms

Answer 5

Ultradian Span period of less than 24 hours
Infradian is more than 24 hrs

Question 6

Sleep stages

Answer 6

Ultradian rhythms - NREM 4 stages then REM sleep (non rapid or rapid eye movement) - analysed using eeg patterns
light sleep + activity slow (will say awake if awoken) , then breathing and heart slow, then deep sleep begin, then very deep sleep, then rapid eye movement with dreaming
Kleitman referred to as Basic Rest Activity Cycle which continued throughout day - state of alertness to fatigue - e.g can focus for 90 mins until resources run out so fatigue and hunger/ concentration loss

Question 7

Ultradian Rhythms eval

Answer 7

+ Elitist violinists studied - they limited practice sessions to 90 mins and often napped to recover, better violinists napped more - similar patterns with athletes, writers etc fitting with BRAC
- Individual differences - maybe biological determinism - participants stayed in lab for 11 days and studied for sleep duration, time taken to fall asleep and stage time - differences in all characteristics

Question 8

Menstrual cycle

Answer 8

Infradian rhythm - about a month but individual differences of 23-38 but average 28 days. Regulated by hormones e.g ovulation when oestrogen peaks and progesterone either decreases or stays high to allow implantation, or FSH which helps eggs mature

Question 9

Infradian Rhythms eval

Answer 9

+ Have effects on behaviour - women express preference for feminine male faces when choosing partners, but masculine faces during ovulation
- evolutionary basis e.g progesterone maintained to allow implantation and reproduction
- other factors, e.g sweat from one rubbed onto lips of others then cycles synchronise so pheromones (chemical substances which affect other organism behaviour)

Question 10

Endogenous pacemakers

Answer 10

Internal maintainer of rhythms - SCN esp which is master clock to link brain regions and sleep/arousal. Neurons synchronise so other areas of body receive time signals - only SCN can continually maintain circadian rhythms - but SCN can reset or shift in response to light
Also regulates melatonin in pineal glands - more produced at night to induce sleep

Question 11

Endogenous pacemakers eval

Answer 11

+ Kate Aldcroft spent 25 days in lab with no light to reset SCN - at the end core temp rhythm still at 24hrs so EZ not affect
- but sleep wake cycle extended to 30hrs with sleep up to 16hrs so EZ needed
- chipmunks had SCN removed, lost sleep wake cycle then high activity at night so more death
+ Evolutionary basis (chipmunks?)
+ hamsters trained to have 20hr circ rhythm then SCN transplanted to those with damaged SCN, then they developed similar 20hr cycles

Question 12

Exogenous zeitgebers

Answer 12

Environmental events to maintain bio clock - mostly light which resets SCN cycle for 24hrs cycle, melanopsin is retina protein which detects natural light
when people e.g have night shift or time zone change then endogenous pacemakers try to impose built in rhythm but out of synchrony so disturbed sleep and follow on factors

Question 13

Exogenous zeitgebers eval

Answer 13

+ Most blind people with minimal light perception have normal circ rhythms but those with no light at all have abnormal circ rhythms so EZ very important
- In arctic regions people have normal sleep despite prolonged light exposure
+- Link to Siffre
+ Exposure to light before East-West flight decreases time taken to adjust to local time
+ Same with preadapting to local times of eating and sleeping before travelling
- Individual differences of adjustments to e.g night shifts and time zones