Hormone Levels Differ During Different Parts of the Day

PsychologyName: ______

Mr.SilimperiDate: ______

CouncilRockHigh School SouthUnit: States of Consciousness

-hormone levels differ during different parts of the day

[example: melatonin (causes drowsiness)]

-disruptions in schedule => problems?

[examples: jet lag, shift work, etc.]

Biological Rhythms

•A biological clock in our brains governs the waxing and waning of

–hormone levels,

–urine volume,

–blood pressure,

–and the responsiveness of brain cells to stimulation.

•Many of these rhythms continue to occur even in the absence of external time cues; they are endogenous, or generated from within.

Circadian Rhythms

•Some biological rhythms, called circadian rhythms, occur approximately every 24 hours.

•The best-known circadian rhythm is the sleep-wake cycle, but there are hundreds of others.

The Body's Clock

•Circadian rhythms are controlled by a biological clock, or overall coordinator.

•The clock is located in a tiny teardrop-shaped cluster of cells in the hypothalamus called the suprachiasmatic nucleus (SCN).

•Neural pathways from special receptors in the back of the eye transmit information to the SCN and allow it to respond to changes in light and dark.

•The SCN then sends out messages that cause the brain and body to adapt to these changes.

•Other clocks also exist and some may operate independently of the SCN.

•For most circadian rhythms, the SCN is regarded as the master pacemaker.

When the Clock Is Out of Sync

•Under normal conditions, the rhythms are synchronized, just as wristwatches can be synchronized.

•Their peaks may occur at different times, but they occur in phase with one another.

•If you know when one rhythm peaks, you can predict when another will do so.

•When your normal routine changes, your circadian rhythms may be thrown out of phase with one another.

•Such internal desynchronization often occurs when people take airplane flights across several time zones.

•Sleep and wake patterns usually adjust quickly, but temperature and hormone cycles can take several days to return to normal.

Moods and Long-term Rhythms

•In human beings, long-term cycles have been observed in everything from the threshold for tooth pain to conception rates.

•Folklore holds that our moods follow similar rhythms, particularly in response to seasonal changes and, in women, to menstrual changes.

But do they?

Does the Season Affect Moods?

•Clinicians report that some people become depressed every winter, when periods of daylight are short, and improve in mood each spring, as daylight increases

•This pattern that has come to be known as seasonal affective disorder (SAD)

Does the Menstrual Cycle Affect Moods?

•Controversy has raged about another long-term rhythm, the monthly female menstrual cycle.

Does Testosterone Affect Moods

•The notion that hormones affect mood and performance has rarely been extended to men.

•Men’s hormones also fluctuate in a cyclical manner.

•There may be a bias to attribute women’s moods to hormones, but not men’s.