PY4 - Biological Rhythms

Question 1

What are endogenous pacemakers and exogenous zeitgebers?

Answer 1

Endogenous: Internal ‘clocks’ that keep our body in rhythm.
Exogenous: External cues such as light that affects endogenous factors.

Question 2

What are infradian, circadian and ultradian rhythms?

Answer 2

Infradian: less than 24 hours e.g. stages of sleep.
Circadian: 24 hours e.g. day cycle
Ultradian: over 24 hours e.g. hibernation

Question 3

How does the pineal gland function in birds and reptiles?

Answer 3

Detects light levels and when they drop, melatonin is released to induce sleep.

Question 4

Explain the sleep/wake cycle in mammals.

Answer 4

Light enters through the retina (via optic nerve) to the SCN. This activates the pineal gland for melatonin release slowing the central nervous system and brainwaves to induce sleep.

Question 5

What did Siffre find in his study? What are two issues with this and a further supporting study?

Answer 5

He stayed in a cave and found that his sleep cycle extended from 27 to 32 hours. This proves that our internal factors do serve a purpose however need external cues