Biopsychology: Endogenous Pacemakers Exogenous Zeitgebers

Question 1

Endogenous pacemakers

Answer 1

Mechanisms within the body that govern the internal, biological bodily rhythms

Question 2

Suprachiasmatic nucleus

Answer 2

Main endogenous pacemaker ‘master clock’
Located within hypothalamus
controls other biological rhythms in body
links to other brain regions responsible for sleep/ arousal
generate circadian rhythm
relies on info from outside world to stay synchronised with the outside world
can be reset by presence or absence of light

Question 3

How does light affect SCN?

Answer 3

Receptors in retina send melanopsin via optic nerve

SCN Communicates with penial gland, which will either release or inhibit melatonin production

Question 4

Effect on melatonin when lights increases (morning)

Answer 4

Decreases melatonin, decreases tiredness

Question 5

Effects on melatonin when light decreases

Answer 5

Increase melatonin, increased tiredness (night)

Question 6

What does melatonin do?

Answer 6

Induces sleep by inhibiting the brain mechanisms that promote wakefulness

Question 7

Exogenous zeitgeber

Answer 7

And environmental cues such as light that helps to regulate the biological clock in an organism

Question 8

What is melanopsin?

Answer 8

A protein sensitive to light which carry signals to SCN to set daily body cycle

Question 9

What are receptors in the SCN sensitive to?

Answer 9

Changes in light levels

Use light level info to synchronise the activity of the body’s organs and glands

Question 10

Social cues

Answer 10

A social stimuli such as mealtimes and social activities

Question 11

Examples of exogenous zeitgebers

Answer 11

Light

Social cues

Question 12

Klein and wegmann

Answer 12

Found circadian rhythm of air travellers adjusted more quickly if went outside at destination (less jetlag)
being exposed to social cues of people in new timezone acted as zeitgeber

Question 13

Social cue: Circadian rhythm in blind people

Answer 13

Circadian rhythm in blind people no different to sighted people bc both groups exposed to same social cues

Question 14

Light: blind people

Answer 14

Majority of blind people still on train circadian rhythm in response to light despite non-functioning rods and cones

Question 15

Light: blind people. Suggests

Answer 15

suggests pathways from retinal cells containing melanopsin, to SCN, are still intact

Question 16

Light + Blind people researchers

Answer 16

Skene and Arendt (2007)

Question 17

Endogenous pacemakers - researcher

Answer 17

Importance of SCN - Morgan et al (1995)

Question 18

A03: Morgan et al procedure

Answer 18

Bread hamsters to have abnormal circadian rhythm of 20 hours (rather than 24)
SCN neurons From abnormal hamsters transplanted into brains of normal hamsters

Question 19

A03: Morgan et al findings

Answer 19

Subsequently, normal hamsters displayed abnormal circadian rhythm of 20 hours
Suggests transplanted SCN imposed its pattern onto recipients brain

Question 20

A03: Morgan et al further confirmation

Answer 20

Reverse experiment
SCN neurons transplanted from normal hamsters to brains of abnormal hamsters
Recipient hamsters changed to circadian rhythm of 24 hours

Question 21

A03: Morgan et al. SO what?

Answer 21

Demonstrates significance and how endogenous pacemaker is are important for biological circadian rhythm is