biopsych part 2

Question 1

what is a biological rhythm

Answer 1

Periodic biological fluctuations in an organism that corresponds to, and is in response to, periodic environmental change

Question 2

what are the three types of biological rhythm

Answer 2

circadian, infradian and ultradian

Question 3

what is a circadian rhythm

Answer 3

A type of biological rhythm which completes one full cycle every 24 hours e.g. the sleep-wake cycle. Like other biological rhythms, it is affected by both endogenous pacemakers and exogenous zeitgebers

Question 4

what are examples of circadian rhythms

Answer 4

sleep wake cycle
body temperature
hormone production (cortisol and melatonin)

Question 5

what is the sleep wake cycle

Answer 5

within a 24-hour period, we have one period of wakefulness and one period of sleep. This is controlled by our suprachiasmatic nucleus (SCN), which has its own cycle but can be affected by light

Question 6

what is the body temperature cycle

Answer 6

we cycle between our lowest temperature (36°) at 4.30am and highest (38°) at 6pm. Our body temp. lowers as our body prepares for sleep

Question 7

what is the hormone production cycle

Answer 7

melatonin makes us sleepy and is at its highest at midnight and lowest at 6am. Cortisol keeps us alert and is on an opposite cycle (highest at 6am, lowest at midnight)

Question 8

strengths of circadian rhythms

Answer 8

• Siffre – lived in a cave, away from time cues, for several months. Found that even without light, social cues etc. he still kept to a fairly routine daily cycle (25 hours, tho it did differ to as high as 48hours). Demonstrates the existence of a natural circadian rhythm.
• Real world application – knowledge of these circadian rhythms can help, for example with medicine (chronotherapeutics). For example, heart attacks are more common in the morning, so prevention medicine should be taken at night as sleep must involve regulatory functions

Question 9

limitations of circadian rhythms

Answer 9

• Extraneous variables – a problem with research such as Siffre’s cave study is the impossibility of ruling out time cues. For example, he used artificial lighting. Czeisler was able to entrain participant rhythms from 22-28 hours using artificial lighting.
• Individual differences – not everyone’s circadian rhythms are the same. Czeisler found cycle length varied from 13-65 hours across people. Also, some people nap or have a siesta – so their sleep/wake cycle is not the same as everyone else.

Question 10

what is an infradian rhythm

Answer 10

with a frequency of one complete cycle occurring less than once every 24 hours. Such rhythms are entrained by endogenous pacemakers and exogenous zeitgebers

Question 11

examples of infradian rhythms

Answer 11

menstrual cycle and SAD (seasonal affective disorder).

Question 12

what is the menstrual cycle

Answer 12

lasts roughly 28 days, though cycle lengths vary from person to person (and for many
people, from month to month). During each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it (this is known as ovulation). After ovulation, the hormone progesterone helps the womb lining to grow thicker, readying the womb for pregnancy. If pregnancy does not occur, the womb lining leaves the body as menstrual flow.

Question 13

what is seasonal affective disorder

Answer 13

Depressive condition common in winter months, brought about by lack of sunlight causing an excessive amount of melatonin (causing fatigue)

Question 14

strengths of infradian rhythms - menstrual cycle

Answer 14

Cycle may be controlled externally rather than only by these hormones – McClintock effect (menstrual cycles of women synchronised to a donor if exposed to sweat from the donor). Other factors can also affect it, such as diet and stress.

Question 15

limitations of infradian rhythms - menstrual cycle

Answer 15

However, the McClintock Effect could be explained through inconsistent cycles. Eventually two cycles of differing lengths will synchronise anyway.

Question 16

strengths of infradian - seasonal affective disorder

Answer 16

Phototherapy (exposure to bright light) is a more effective treatment for symptoms of SAD than placebo (Miller)

Question 17

limitations of infradian - seasonal affective disorder

Answer 17

Could be other seasonal factors, such as social support. People tend to spend more time indoors during the winter, so SAD could be explained by social isolation rather than melatonin.

Question 18

what is an ultradian rhythm

Answer 18

with a frequency of one complete cycle occurring more than once every 24 hours

Question 19

what is an example of ultradian rhythm

Answer 19

stages of sleep, where a full sleep cycle takes 90 minutes to complete

Question 20

what is the sleep stages

Answer 20

During sleep we experience 5 stages of sleep, in 90-min cycles (see diagram).
Stages 1 & 2 – light sleep
Stages 3 & 4 – deep, Slow-Wave Sleep (SWS). This is where protein synthesis happens, helping the body to recover.
REM stage – dream sleep. The brain is very active and EEG waves look similar to a waking brain.

Question 21

what is the brac

Answer 21

Basic Rest Activity Cycle - Just as with sleep stages, we have 90 minute cycles of alertness and fatigue throughout the day
(see diagram).

Question 22

strengths for sleep stages

Answer 22

Dement & Kleitman woke people during REM or Non-REM (stages 1-4). 89% woken during REM recalled dreaming. Only 7% recalled dreams if woken during NREM.

Question 23

limitations for sleep stages

Answer 23

Sleep cycle varies throughout your life. 50% of REM and 50% SWS as an infant; in old age, you have very little of either and mostly stages 1 & 2.

Question 24

strengths for brac

Answer 24

• Ericsson – observed high-performing individuals (e.g. violinists) and noticed consistent 90-min cycle patterns, with the best performers the ones who napped most frequently
• Explains and helps to create workplace and school schedule (roughly 90-120 minutes between breaks)

Question 25

what is an endogenous pacemaker

Answer 25

internal cues to regulate rhythms

Question 26

example of endogenous pacemakers

Answer 26

Includes Suprachiasmatic nucleus (SCN) – Found in the hypothalamus. This has its own protein life cycle that lasts 24 hours, which helps to dictate the organism’s circadian rhythms.

Question 27

what are exogenous zeitgebers

Answer 27

external cues to regulate rhythms

Question 28

what are examples of exogenous zeitgebers

Answer 28

Light – is received by the photoreceptors in the retina, which inhibits melatonin levels to keep us alert Social cues – other people’s actions affect our rhythms (e.g. noise in the house; alarm clock to make it to school on time)

Question 29

strengths of eps and ezs

Answer 29

• Morgan – bred hamsters with 20 hour rhythms and implanted their SCN in newborns, who adopted 20-hour rhythms. Shows power of the SCN.
• Siffre – spent 6 months in a cave away from all exogenous zeitgebers. Still kept to a regular 25 hour rhythm, despite having no exogenous zeitgebers.

Question 30

limitations of eps and ezs

Answer 30

• Czeisler - Artificial light was able to entrain participants’ circadian rhythms from 22-28 hours. This shows the power of artificial light to override the SCN.
• Siffre – the fact that he kept a 25-hr rhythm suggests that we need exogenous zeitgebers to keep us in line with the world’s 24-hour clock.