Biological Rythms

• The sleep-wake cycle is an example of a circadian rhythm.
• Circadian rhythms last about 24 hours (e.g. the sleep-wake cycle) and are controlled by an endogenous pacemaker.
• Body temperature is a circadian rhythm. Human body temperature is at its lowest in the early hours of the morning and at its highest in the early evening.
• Biological rhythms are regulated by endogenous pacemakers, which are the body’s internal biological clocks.
• Biological rhythms are also determined by exogenous zeitgebers, which are external cues, including light, that help to regulate the internal biological clocks.
• Although endogenous pacemakers are internal biological clocks, they can be altered and affected by the environment.
• One endogenous pacemaker is the suprachiasmatic nucleus (SCN), which is closely linked to the pineal gland, both of which are influential in maintaining the circadian sleep/wake cycle.
• The SCN sends signals to the pineal gland, which leads to an increase in the production of melatonin at night, helping to induce sleep.
• The suprachiasmatic nucleus (SCN), which lies in the hypothalamus, is the main endogenous pacemaker.