Disrupting Biological Rhythms

• Write down all you know about the disruption of biological rhythms

• Add your name and then swap papers

• Mark the work based on the following success criteria

Success criteria = Max 80 marks

Mentions jet lag = 5 pointsExplains jet lag = 10 points

Mentions shift work = 5 pointsExplains shift work = 10 points

Key terms = 5 points each

(Circadian rhythm, oscillators, SCN, melatonin, phase delay, phase advance, desynchronisation)

Objectives

I can describe some effects of jetlag

I can explain why jetlag affect us using ideas about circadian rhythms.

I can evaluate theories using AIDS

E

C

A

The Big Question….Discuss the disruption of biological rhythms (8+16)

Disruption of biological rhythms

• So far we have found out that biological rhythms are controlled by endogenous pacemakers or oscillators.

• Some of these oscillators can easily be reset by exogenous zeitgebers, whereas others are more resistant.

• This means that sometimes, our oscillators can become desynchronised – out of time with each other.

How are our circadian rhythms disrupted?

• Our circadian rhythms can be subject to;– Phase advance (West to East) – e.g. having to get

up earlier than usual – Phase delay (East to West) – e.g. going to bed

later than usual

• Which do you think is easiest to deal with?

• Why?

Does the direction of travel make a difference to jet lag?

East to WestPhase delay. Easier to cope

with – like going to bed

laterWill be ready for

bed earlier, but biological clock will wake us up

earlier too

West to East

Phase advance – harder – like getting up earlier

Trying to adjust to a shorter day so disruption to circadian rhythm is more pronounced

Daylight, social zeitgebers and clocks tell us it is morning when we may still be wanting to sleep

Recht et al 1995 – jet lagged baseballers p8

Watch the Video

• http://www.tv.com/shows/the-early-show/watch/explaining-jet-lag-2921920/

• http://www.youtube.com/watch?v=POpHfe3i0S0

Jet Lag News Report

UK breakfast TV want to do a similar piece but wish to take a more 'expert approach'. Use your knowledge to make a script or video for the TV

Objectives

I can describe some effects of shift work

I can explain why shift work affects us using ideas about circadian rhythms.

I can evaluate theories using AIDS

E

C

A

The Big Question….Discuss the disruption of biological rhythms (8+16)

The causes of the accident are still described as a fateful combination of human error and imperfect technology.

Chernobyl nuclear disaster. 25-26th April 1986. 1.42am

The Exxon Valdez oil tanker struck Bligh Reef, off the coast of Alaska, at around 12:04 am March 24th, 1989. The accident resulted in the discharge of approximately 11 million gallons of oil 20% of the cargo, into Prince William Sound.

The third mate failed to properly manoeuver the vessel, possibly due to fatigue and excessive workload

What do these 2 disasters have in common?

• Both happened in the early hours of the morning.

• Both were thought to be caused by human error caused by disrupted biological rhythms!

Shiftwork (shift lag)

• Can have a harmful effect on health and well being.• Major cause is disruption of circadian rhythm• Body trying to function in complete opposite

way to the instructions by Endogenous pacemakers and exogenous zeitgebers.

• Be alert at night and sleep during the day against the cues from zeitgebers.

Circadian Trough

• Boivin et al 1996 - Night workers experience decreased alertness (at around 6am) – Circadian ‘trough’

• Core body temperature takes even longer to re-set, which may affect performance (below optimum temperature for body functions e.g. enzymes)

• Artificial lighting only slightly effective in re-setting rhythm

Poor quality of sleep, partial sleep deprivation

More difficult to sleep in day:• Body clock doesn’t adjust completely• More noise and disturbances in the day• Daytime sleep 1-2 hours shorter than at night• REM particularly affected (Tilley and Wilkinson,

1982)

Consequence is sleep deprivation – makes circadian trough worse!

Effects on health

Knutsson (1986) – many studies show significant relationship between shiftwork and heart disease.

Those who worked shifts for over 15 years 3x more likely to develop heart disease

Martino et al (2008) shift work is linked to all types of organ disease.

Commentary on ShiftWork

Shiftwork has negative effects

Individual differences – Reinberg etal 1984 Some workers are able tocope with shifts because theirrhythm changed Less

Shift workers also experience socialdisruption – can’t spend time withfriends and family

Gold et al 1992 - More problems with rotating shifts than fixed shifts (all nights)

Harmful effects can be reduced

1. If rotating shifts are unavoidable Phase delay (get up and go to bed later) is less disruptive than phase advance (get up and go to bed earlier)

2. Czeisler et al 1986 Bright lights can mimic the effect of daylight and re-set body rhythms (temp and cortisol) in 3 days (usually takes 9 days to adjust to a phase advance of 6 hours).

The strong light entrains all rhythms not just the sleep wake cycle

Applying this research

Read ‘Reducing the harmful effects’ section on p9

Use this and what you have learned about the effects of

shiftwork to write a letter or an info sheet for a new company about to employ shift workers

(15-20mins)

Objectives

I can describe some effects of shift Work

I can explain why Shift Work affect us using ideas about circadian rhythms.

I can evaluate theories using AIDS

E

C

A

The Big Question….Discuss the disruption of biological rhythms (8+16)

Homework

Plan and write the essay!

Discuss research relating to the disruption of biological rhythms (24 marks)