1. Ultradian Rhythms, Endogenous Pacemakers and Exogenous Zeitgebers

2. Lesson 3 – Ultradian Rhythms
BATs
A01 -Define REM and NREM sleep and the BRAC
Describe the different stages of sleep
A02 - Analyse evidence related to BRAC and the stages of sleep
Starter
What does REM stand for?

3. List 3 differences between Circadian and Infradian Rhythms
ovulation LH
FSH
Hormone Levels

4. Ultradian Rhythms The sleep-wake cycle takes one day (circadian)
Whilst asleep another rhythm exists – ULTRADIAN (less than a day)
Lasts for 90 minutes
Involves 2 types of sleep NREM and REM sleep within the 90 min cycle.
Repeats several times throughout sleeping period

5. Basic Rest-Activity Cycle
The 90 minute ‘clock’ seems to be ‘ticking’ when asleep and throughout the rest of one day.
Known as Basic Rest-Activity Cycle
(BRAC)
Read about BRAC on p4
What evidence is there that the
BRAC exists?
2. Why is the BRAC thought to be
important?

6. The Stages of Sleep 1-4 = NREM
Thanks to Eric H Chudler, University of Washington, Seattle USA
1-4 =
NREM
Stage 1 & 2 – relaxed state, easily woken, heart
rate slows, temperature drops
Stages 3 & 4 – Slow Wave Sleep (SWS),
Metabolic rate slows, growth hormone released
REM sleep – paradoxical sleep – brain and eyes
active, but body paralysed.

7. The stages of sleep as shown on an EEG
Electroencephalograph (EEG) in operation

8. Awake A 1 2 3 4 R C

9. Stage 1 A 1 2 3 4 R C

10. Stage 2 A 1 2 3 4 R C

11. Stage 3 A 1 2 3 4 R C

12. Stage 4 A 1 2 3 4 R C

13. REM Sleep A 1 2 3 4 R C

14. A
REM
St1
St2
St3
St4 A 1 2 3 4 R C

15. These lines represent the EEG (electroencephalogram) which shows a record of brain activity; the EMG (electromyogram) shows muscle activity; the EOG (electroculogram) shows eye movements. Look at the differences in the EEG, EMG and EOG during waking, REM sleep (Rapid Eye Movement Sleep) and NREM sleep

16. MRI scan, showing brain activity during different stages of sleep

17. 4-7 Hz Occasional "sleep spindles" Occasional "K" complexes
Stage
EEG Rate (Frequency)
EEG Size (Amplitude)
Awake
8-25 Hz
Low 1
6-8 Hz 2
4-7 Hz Occasional "sleep spindles" Occasional "K" complexes
Medium 3
1-3 Hz
High 4
Less than 2 Hz
REM
More than 10 Hz

18. Plenary Stage & type State of body Brain waves 1 & 2 NREM 3 & 4 REM
Match the number cards to the stage of sleep it represents.
Stage & type
State of body
Brain waves
1 & 2
NREM
relaxed state, easily woken, heart rate slows, temperature drops
Medium frequency
Low - medium amplitude
3 & 4
Slow Wave Sleep (SWS),
Metabolic rate slows, growth hormone released
Low frequency
High amplitude
REM
brain and eyes active, but body paralysed.
Higher frequency
Low amplitude

19. Lesson 4 – Endogenous pacemakers and Exogenous Zeitgebers
BATs
A01 - Define and compare endogenous pacemakers and exogenous zeitgebers
A02 - Analyse and evaluate evidence of endogenous pacemakers and exogenous zeitgebers
Starter

20. Endogenous Pacemakers
Internal biological clocks
Darlington et al 1998 – clock ‘ticking’ created by the interactions between certain proteins in the nucleus.

21. Endogenous Pacemakers
1. CLOCK and CYCLE bind together in the morning
24 hrs
4. PER-TIM levels fall CLOCK-CYCLE increases ready to begin the next cycle
2. Increased production of PER and TIM during the day
3. As PER-TIM levels increase, levels of CLOCK-CYCLE production decrease

22. The Suprachiasmatic Nucleus (SCN)
In mammals, the main endogenous pacemaker is a pair of tiny clusters of nerve cells called the SCN, which lie in the hypothalamus, just above the optic chiasm (where the optic nerves from each eye cross over)

23. Melatonin Secretion Melatonin Level Time of Day asleep
7 am pm 7 am
Time of Day

24. Endogenous Pacemakers
Even when our eyes are shut the SCN gets info on light from the optic nerve. Light can penetrate the eyelids and special photoreceptors in the eye transfer light signals to the SCN.
If our endogenous clock is running slow – the morning light automatically shifts the clock ahead so it is in synchrony with the world outside
See: Psyonline – PYA4

25. Campbell and Murphy (1998)
Found that when light was shone on the back of participants’ knees many were able to shift the circadian rhythms of body temperature and melatonin secretion, suggesting that light can reach the brain without passing through the eyes!

26. Light, the pineal gland and melatonin regulate the sleep-wake cycle
Another endogenous pacemaker that works with the SCN is the Pineal Gland.
Contains light sensitive cells.
When light is sensed melatonin production is inhibited.
When light level falls melatonin production increases
This induces sleep by inhibiting brain mechanisms that promote the awake state.
Light, the pineal gland and melatonin regulate the sleep-wake cycle

27. Read p 64-65 and do the following tasks
Why is the pineal gland especially important in birds and reptiles?
Copy a diagram of the biological clock idea put forward by Darlington et al in 1998
Bullet point sources of evidence that endogenous pacemakers exist.

28. Exogenous = outside the organism Zeitgeber = time-giver
Exogenous Zeitgebers
Exogenous = outside the organism
Zeitgeber = time-giver
The biological-clock is reset each day by cues in the environment – like the light cues of sunrise and sunset.
This process is called entrainment, (the opposite of free-running where the biological clock works free of any exogenous cues, including social cues like clocks).

29. Which are more important exogenous zeitgebers social cues or light?
Until recently biologists believed that daily rhythms were entrained by social convention (set meal and bedtimes), not internal biology.
Since the discovery that exposure to bright light suppresses melatonin production it is now recognized that light is the dominant zeitgeber in humans (Wever et al 1983).

30. Light as an exogenous zeitgeber
Daylight resets the biological-clock, but dim light is less effective.
Hall (2000), found that proteins called cryptochromes found throughout the body can detect changes in light.

31. What if you are blind?
Lack of info about light messes up sleep patterns.
Miles et al (1977) – young man, blind from birth had a circadian rhythm of 29.4 hours. Even with the help of clocks and social cues he was unable to reduce the pace of his biological rhythm.
He had to take stimulants in the morning and sedatives at night.

32. Temperature as a zeitgeber
Bio-rhythms can also be entrained by temperature:
Leaves fall from deciduous trees in autumn because of changes in temperature as well as day length.
A factor in the onset of hibernation.
No evidence that it affects human bio-rhythms

33. Read p 6-7 and do the following tasks
How could the discovery of cryptochromes give support to the study by Campbell and Murphy (1998) and explain why some blind people have normal bio-rhythms?
Outline evidence that zeitgebers exist.
3. In a table show the advantages and disadvantages of having both endogenous pacemakers and exogenous zeitgebers.

34. Writing essays
Discuss the role of endogenous pacemakers and exogenous zeitgebers in biological rhythms. (25 marks)
AO1 – general but accurate description of the role of endogenous pacemakers and exogenous zeitgebers in bio-rhythms.
Describe the brain mechanisms underlying endogenous pacemakers and/or the interaction with zeitgebers e.g. light
base answers on studies e.g. isolation (Siffre), role of pheromones and menstrual cycle, Morgan (95) – hamsters expt - suprachiasmatic nucleus

35. Both endogenous pacemakers and exogenous zeitgebers must be discussed.
Writing essays
Discuss the role of endogenous pacemakers and exogenous zeitgebers in biological rhythms. (25 marks)
AO2 – Do not just describe the studies.
- Use them e.g the implications of Sifrre’s work.
How relevant are the studies to the role of endogenous pacemakers and exogenous zeitgebers
How has the use of electric lighting in the last 100 years affected biological rhythms
Issues and debates – use of non-human animals e.t.c