L11 - Ultradian and Infradian Rhythms

Question 1

what are ULTRADIAN RHYTHMS?

Answer 1

ULTRADIAN RHYTHMS span a period of LESS THAN 24 HOURS.

An example is the FIVE SLEEP STAGES. Human sleep follows a PATTERN alternating between RAPID EYE MOVEMENT (REM) SLEEP, which is STAGE 5, and NON RAPID EYE MOVEMENT (NREM) SLEEP, which consists of STAGES 1-4 - the cycle REPEATS ITSELF EVERY 90 MINUTES

Each stage shows a DISTINCT EEG PATTERN. As the person enters DEEP SLEEP, their BRAINWAVES SLOW and their BREATHING and HEART RATE DECREASES. During the FIFTH STAGE, the EEG pattern resembles that of an AWAKE PERSON, it is during this stage that DREAMING OCCURS

Question 2

what did KLEITMAN propose?

Answer 2

KLEITMAN referred to the 90 MINUTE CYCLE found during sleep as the BASIC REST ACTIVITY CYCLE (BRAC)

He suggested that this 90 minute cycle CONTINUES WHEN WE ARE AWAKE. During the day, rather than moving through the SLEEP STAGES, we move PROGRESSIVELY from a STATE OF ALERTNESS into a STATE OF PHYSIOLOGICAL FATIGUE.

STUDIES SUGGEST that the HUMAN MIND can FOCUS for about 90 MINUTES, and towards the END OF THOSE 90 MINUTES the BODY BEGINS TO RUN OUT OF RESOURCES, resulting in LOSS OF CONCENTRATION, FATIGUE and HUNGER

Question 3

+ ERICSSON ET AL (EVALUATION OF ULTRADIAN RHYTHMS)

Answer 3

+ ERICSSON ET AL found SUPPORT for the ULTRADIAN RHYTHMS. They studied a GROUP OF ELITE VIOLINISTS and found that among this group, PRACTICE SESSIONS WERE LIMITED TO 90 MINUTES AT A TIME.

VIOLINISTS FREQUENTLY NAPPED to RECOVER FROM PRACTICE, with the BEST VIOLINISTS NAPPING MORE. The SAME PATTERN was found AMONG ATHLETES, CHESS PLAYERS and WRITERS. This FITS WITH THE BRAC

Question 4

• TUCKER ET AL (EVALUATION OF ULTRADIAN RHYTHMS)

Answer 4

• TUCKER ET AL suggests that there are INDIVIDUAL DIFFERENCES in ULTRADIAN RHYTHMS which are BIOLOGICALLY DETERMINED and may even be GENETIC IN ORIGIN

Pps were STUDIED OVER 11 CONSECUTIVE DAYS and NIGHTS in a LABORATORY ENVIRONMENT.

The researchers ASSESSED SLEEP DURATION, TIME TAKEN TO FALL ASLEEP and the AMOUNT OF TIME IN EACH SLEEP STAGE. They found DIFFERENCES IN ALL OF THESE CHARACTERISTICS

Question 5

what are INFRADIAN RHYTHMS?

Answer 5

INFRADIAN RHYTHMS span a period of LONGER THAN 24 HOURS; they MAY LAST WEEKS, MONTHS or EVEN A YEAR

One example of an INFRADIAN RHYTHM is the MENSTRUAL CYCLE, which LASTS FOR ABOUT A MONTH.

There are CONSIDERABLE VARIATIONS in the LENGTH OF THIS CYCLE, with SOME WOMEN EXPERIENCING A 23 DAY CYCLE and others a 36 DAY CYCLE. The AVERAGE is 28 DAYS

Question 6

how does the MENSTRUAL CYCLE WORK?

Answer 6

HORMONES REGULATE the MENSTRUAL CYCLE. OVULATION occurs ROUGHLY HALFWAY through the menstrual cycle, when OESTROGEN LEVELS are at THEIR PEAK, and USUALLY LASTS FOR 16-32 HOURS.

After ovulation, PROGESTERONE LEVELS INCREASE in PREPARATION for the POSSIBLE IMPLANTATION of an EMBRYO in the UTERUS.

Question 7

+ PENTON VOAK (EVALUATION OF INFRADIAN RHYTHMS)

Answer 7

+ INFRADIAN RHYTHMS CAN AFFECT BEHAVIOUR. PENTON VOAK found that WOMEN EXPRESS a PREFERENCE for FEMINISED MALE FACES when CHOOSING A PARTNER FOR A LONG TERM RELATIONSHIP. However, they showed a PREFERENCE for MORE MASCULINE FACES DURING OVULATION

Question 8

• PHEROMONES (EVALUATION OF INFRADIAN RHYTHMS)

Answer 8

• The MENSTRUAL CYCLE is NOT ONLY GOVERNED by INFRADIAN RHYTHMS. When SEVERAL WOMEN of CHILDBEARING AGE LIVE TOGETHER, and DO NOT TAKE ORAL CONTRACEPTIVES, their MENSTRUAL CYCLES SYNCHRONISE

In one study, SAMPLES OF SWEAT were COLLECTED FROM ONE GROUP OF WOMEN and RUBBED ONTO THE UPPER LIP of ANOTHER GROUP OF WOMEN, their MENSTRUAL CYCLES BECAME SYNCHRONISED.

This suggests that the SYNCHRONISATION is AFFECTED BY PHEROMONES. PHEROMONES are a CHEMICAL SUBSTANCE PRODUCED and RELEASED INTO THE ENVIRONMENT by an ANIMAL, which AFFECTS THE BEHAVIOUR OF OTHERS OF THE SAME SPECIES