Psychology Essay 4

Psychology Twelfth Edition

Chapter 5 Body Rhythms and

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Mental States

Biological Rhythms: The Tides of

Experience

• LO 5.1.A Define circadian rhythms, and explain

how the body’s “biological clock” works (and what

happens when it doesn’t).

• LO 5.1.B Explain why seasonal affective disorder

and premenstrual syndrome are examples of long-

term biological rhythms, and summarize the

evidence regarding the existence of both

phenomena.

Circadian Rhythms (1 of 5)

• Consciousness is the awareness of oneself and

the environment.

• Throughout the day, mood, alertness, efficiency,

and consciousness itself are in perpetual flux.

• One way to understand consciousness is to study

how it changes over time.

– Mental and physical states are intertwined.

• Examining a person’s ongoing rhythmic cycles is

like watching a video of consciousness.

Circadian Rhythms (2 of 5)

• Changing states of consciousness are often

associated with biological rhythms.

• A biological clock in our brains governs:

– the waxing and waning of hormone levels

– urine volume

– blood pressure

– the responsiveness of brain cells to stimulation

Circadian Rhythms (3 of 5)

• Biological rhythms are typically in tune with:

– external time cues, such as changes in clock time,

temperature, daylight

• Many rhythms continue to occur even in the

absence of such cues.

– endogenous, generated from within

• Circadian fluctuations:

– occur about once a day

– are governed by a biological clock in the

suprachiasmatic nucleus (SCN) of the hypothalamus

Circadian Rhythms (4 of 5)

• The SCN regulates and, in turn, is affected by the

hormone melatonin.

• Melatonin is responsive to changes in light and

dark and increases during the dark hours.

– secreted by the pineal gland, deep within the brain

– induces sleep

– helps keep biological clock in phase with light–dark

cycle

Circadian Rhythms (5 of 5)

• When our normal routine changes, we may

experience internal desynchronization.

– Example: taking airplane flights across time zones

• The usual circadian rhythms are thrown out of

phase with one another.

– Sleep and wake patterns adjust quickly but

temperature and hormone cycles can take days to

return to normal.

– Jet lag affects energy level, mental skills, motor

coordination.

Moods and Long-Term Rhythms (1 of 5)

• Some people experience depression every winter

in a pattern that has been labeled seasonal

affective disorder (SAD).

• During the winter months, SAD patients report:

– feelings of sadness

– lethargy

– drowsiness

– craving for carbohydrates

Moods and Long-Term Rhythms (2 of 5)

• The causes of SAD, which is relatively

uncommon, are not yet clear.

• SAD is not recognized as an official disorder.

– Much of the research to date has been flawed.

• Light treatments can be effective in alleviating

symptoms.

• SAD may occur in people whose circadian

rhythms are out of sync.

– In essence, they have a chronic form of jet lag.

Moods and Long-Term Rhythms (3 of 5)

• Another long-term rhythm is the menstrual cycle,

during which various hormones rise and fall.

• Well-controlled, double-blind studies have been

conducted on premenstrual syndrome.

• These studies do not support claims that

emotional symptoms are reliably and universally

tied to the menstrual cycle.

Moods and Long-Term Rhythms (4 of 5)

• How both sexes interpret bodily and emotional

changes is affected by:

– expectations

– learning

• Few people of either sex are likely to undergo

dramatic monthly mood swings or personality

changes because of hormones.

Moods and Long-Term Rhythms (5 of 5)

Figure 5.1

Mood Changes in Men and Women

(McFarlane, Martin, & Williams, 1988)

The Rhythms of Sleep

• LO 5.2.A Describe the four stages of sleep, and

explain the primary features of each stage.

• LO 5.2.B List the mental consequences of

sleeplessness and the mental benefits of a good

night’s sleep.

The Realms of Sleep (1 of 6)

• During sleep, periods of rapid eye movement

(REM) alternate with non-REM (NREM) sleep in

approximately a 90-minute rhythm.

• The REM periods last from a few minutes to as

long as an hour.

• They average about 20 minutes in length.

The Realms of Sleep (2 of 6)

• Non-REM sleep is divided into stages on the basis

of characteristic brain-wave patterns.

• Alpha waves gradually slow down, passing

through three stages, each deeper than the

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