Lesson 13 - Endogenous Pacemakers And Exogenous Zeitgebers

Question 1

The SCN

Answer 1

Regulates the production and secretion of melatonin in the pineal gland via the interconnecting neural pathway. It sends a signal to the pineal gland linking it to increased production at night and decreased production in the morning.

Question 2

Endogenous Pacemakers Strengths

Answer 2

SCN Is Vital
University Student

Question 3

SCN Is Vital (+)

Answer 3

Morgen bred a strain of hamsters that had abnormal 20 hour CRs, when the SCN neurone were transported from this hamster to another hamster, they also displayed abnormal CRs showing the importance of SCN.

Question 4

University Study (+)

Answer 4

Studied a uni student who spent 25 days in a lab she had no access to light or anything to reset the SCN, but her CRs were still 24 hours showing the importance of endogenous pacemakers.

Question 5

Endogenous Pacemakers Weaknesses

Answer 5

Animal Studies
University Student Zeitgebers

Question 6

Ethical Issues (-)

Answer 6

The SCN have had unethical procedures and not met requirements e.g. breeding hamsters to have abnormal CRs. It’s also not ecologically valid because they’re animals that have been tampered with.

Question 7

University Student Zeitgebers (-)

Answer 7

Folkard discovered Kate’s sleep wake cycle had extended to 30 hours with her sleeping as long as 16 hours suggesting exogenous zeitgebers may be important.

Question 8

Exogenous Zeitgebers

Answer 8

Any environmental events that are responsible for painting the biological clock of an organism via external cues.

Question 9

Light

Answer 9

Receptors in the SCN are sensitive to light and use it to synchronise the body’s organs and glands. Light resets the SCN.

Question 10

Melanopsin

Answer 10

Is sensitive to natural light and therefore vital in the SCN.

Question 11

Clash Between Endogenous Pacemakers and Exogenous Zeitgebers

Answer 11

When there’s a change in timezone/night shift, endogenous pacemakers impose in-built sleep rhythms but EZs are out of sync with light leading to increased anxiety and decreased alertness.

Question 12

Social Cues

Answer 12

Social stimuli e.g. meal times and activities can also be EZs. Aschoff Et Al showed people can compensate for the absence of light through social cues.

Question 13

EZs In Blind People

Answer 13

Have the same CR, as the SCN has connections with the eye that don’t require sight, it’d be better described as light exposure being the EZ.

Question 14

CRs In Infants

Answer 14

Start at 6 weeks and by 16 weeks they have a sleep/wake cycle due to mealtimes/bedtimes.

Question 15

Preventing The Clash Between EPs and EZs

Answer 15

Adapting to local times by eating/sleeping is a way of beating jet lag when travelling bares.

Question 16

Strengths Exogenous Zeitgebers

Answer 16

Melapsonin Blind People
Practical Application

Question 17

Melapsonin Blind People (+)

Answer 17

Research has shown the majority of blind subjects still have some light perception and normal circadian rhthys, suggesting exogenous zeitgebers are important for everyone.

Question 18

Endogenous Pacemakers

Answer 18

Internal biological clocks i.e. SCN.