Biological rhythms

Question 1

Biological rhythms

Answer 1

Regular patterns of physiological, behavioral or cognitive activity. They are divided into: circadian rhythms, infradian rhythms and ultradian rhythms.

Question 2

Circadian rhythms

Answer 2

Biological rhythms with a cycle length of 24 hours. Examples include sleep-wake cycle, body temperature cycle

Question 3

Infradian rhythms

Answer 3

Biological rhythms with a cycle length of more than one day. Examples include hibernation, the menstrual cycle, migration, breeding

Question 4

Ultradian rhythms

Answer 4

Biological rhythms with more than one cycle in 24 hours. Examples include alternation of REM&NREM sleep during the night, blood circulation, pulse, heart rate, blinking

Question 5

Exogenous zeitgebers

Answer 5

They are defined as external stimuli important in the control of biological rhythms. Eg. temp, light, food availability

Question 6

Endogenous pacemakers

Answer 6

In the absence of external stimuli, there are internal ‘clocks’ that help regulate biological rhythms. These are called endogenous pacemakers.

They are defined as internal body ‘clocks’ that regulate biological rhythms. Eg. suprachiasmatic nucleus (SCN), pineal gland

Question 7

Nocturnal

Answer 7

Animals that are active at night and rest during the day.

Question 8

Diurnal

Answer 8

Animals that are active during the day and rest at night.

Question 9

Seasonal Affective Disorder (SAD)

Answer 9

A form of depression that regularly affects vulnerable people during the winter months. It may be associated with abnormalities of biological rhythms.

Evidence to support this includes light therapy or treatment with melatonin.

Question 10

Melatonin

Answer 10

A hormone made by the pineal gland that plays an important role in many aspects of biological rhythms. The presence of light decreases melatonin levels therefore it increases in darkness.

Question 11

Effects of SAD on people

Answer 11

Usually less reactive to the effect of light which means their melatonin system is disrupted.
Exposure to bright light first thing in the morning may help to resynchronize the melatonin system and reduce SAD.

Question 12

Suprachiasmatic nucleus (SCN)

Answer 12

A group of neurons in the hypothalamus of the brain. It is the most important endogenous pacemaker and controls the pineal gland and the release of melatonin.

Question 13

Pineal gland

Answer 13

A small structure in the brain, controlled by the SCN, that releases melatonin which in turn regulates many biological rhythms.