Circadian Rhythms

Circadian Rhythms

1. Biological Rhythms

   • Distinct patterns of change in the body activity that conform to the cyclical time periods. Biological rhythms are influenced by internal body clocks and external changes in environment.

2. Endogenous zeitgebers

   • External changes in environment

3. Exogenous pacemakers

   • Body's internal clock and natural rhythm

4. Circadian rhythms are a type of biological rhythm which lasts around 24 hours.

   • Sleep wake cycle
   • Core body temperature

5. Sleep wake cycle

   • An example of a circadian rhythm, humans and animals sleep depending on the level of light they receive.
   • Internal governing
     • Superchiasmatic nucleus
       • SCN in the hypothalamus detects the level of light presented and uses this information to co-ordinate the activity of the circadian rhythm.
   • Melatonin
     • Triggers a wake
       • Pineal gland detects levels of light go down and secretes melatonin accordingly.

6. SIFFRE (1973)

   • Deprived himself of light and sound by spending two months in a cave
     • Found that his free-running biological rhythm has settled down to one just above 24 hours but continued to sleep and wake up on a regular schedule

7. AO3

   • Research into circadian rhythms provides an understanding of adverse consequences when disrupted
     • Night workers experience a period of reduced concentration at 6 in the morning (circadian trough) so likely mistakes and accidents.
       • Relationship between shift work and poor health. Shift workers more likely to develop heart disease.
   • Used to improve medical treatment
     • The rise and fall during the course of a day has led to chronotherapeutics
       • Medical treatment that can be administered to respond to the person's biological rhythms.
         • e.g aspirin for a heart attack works best when