Biological rhythms - Infradian and Ultradian

Question 1

define infradian as a biological rhythm

Answer 1

has a periodicity of MORE than 24 hours

Question 2

give an example of a infradian cycle

Answer 2

menstrual cycle

Question 3

define ultradian as a biological rhythm

Answer 3

has a periodicity of LESS than 24 hours

Question 4

Give an example fo an ultradian cycle

Answer 4

heartbeat or the sleep cycle

Question 5

Briefly describe the menstrual cycle

Answer 5

The menstrual cycle in human females is a set of changes in hormonal functioning with a periodicity of about 28 days. It regulates fertility. Women can only conceive a child at a certain point in the menstrual cycle.

Question 6

what are the endogenous pacemakers in the menstrual cycle

Answer 6

The menstrual cycle is generated by the hypothalamus, which controls the pituitary glands, which in turn controls a number of other glands situated around the body. These glands produce hormones. The 2 main hormones it stimulates is FSH (follicle stimulating hormone) and LH (leutenising hormone). Both are constant for the first 10-15 days of after menstration starts then there is a sudden increase in both just before ovulation after this they fall rapidly and are constant until menstation begins.

Question 7

define hormone

Answer 7

Hormones are chemical substances that affect the body’s functioning.

Question 8

state some research into endrogenous pacemakers and the menstrual cycle

Answer 8

Adams et al 1978

Question 9

outline Adams et al 1978

Answer 9

• aim - to show that femal sexual behaviour is linked to menstrual cycle.
• sample - sexually mature women, some who were taking birth control pills
• method - women were divided into those who were and those who were not taking birth control pills. They reported their levels of self-initiated sexual activity over a 28-day period.

Question 10

What were the findings of Adams et al 1978

Answer 10

Amongst women who were not taking the pill, there was an increase in sexual activity around the time of ovulation. Amongst women taking the pill, levels of sexual activity were constant throughout the study.

Question 11

Give a conclusion for Adams et al 1978

Answer 11

since the pill works by controlling hormone levels, there was no overall alteration in the behaviour of women taking it. However, the variations in sexual activity amongst women not taking the pill suggests that hormonal fluctuations led to an increase in sexual activity just prior to ovulation

Question 12

what are the zeitgebers in the menstrual cycle

Answer 12

there is now evidence that external factors (zeitgebers) can play a role in when ovulation and menstruation occur. It is thought that women at different stages of the menstrual cycle give off different pheromones.

Question 13

state a piece of research into zeitgebers in the menstrual cycle

Answer 13

McClintock and Stern 1998

Question 14

Outline McClintock and Stern 1998

Answer 14

• aim - to show tha the menstrual cycle is influenced by pheromonal secretions from other women
• sample - female uni students, not taking birth control pills.
• method - A control group of women wore an alcohol-soaked pad in their armpits. The fumes from these were inhaled by another group of women (the experimental group) and their menstrual cycles monitored.

Question 15

What were the results of McClintock and Stern 1998

Answer 15

when the experimental group inhaled secretions from women who were about to ovulate, their menstrual cycles became shorter. When they inhaled secretions from women who had just ovulated, their menstrual cycles became longer.

Question 16

give a conclusion for McClintock and Stern 1998

Answer 16

the experimental groups’ menstrual cycles were affected by the secretions from the control group. This explains why when a group of women live in close proximity their menstrual cycles tend to synchronise.