Biological Rythms

Question 1

How many times do circadian rhythms repeat?

Answer 1

approximately once every 24 hours

Question 2

What is an example of a circadian rhythm?

Answer 2

the sleep wake cycle, which typically follows a regular 24-hour cycle

Question 3

what controls the sleep/wake cycle?

Answer 3

Endogenous pacemakers (internal body clocks) such as neural mechanisms and hormones from the brain

Question 4

What is the regularity of the cycle maintained by?

Answer 4

exogenous zeitgebers (external time givers), for example light or alarm clocks, which entrain (reset) the sleep/wake cycle.

Question 5

What is the regularity of the cycle maintained by?

Answer 5

exogenous zeitgebers (external time givers), for example light or alarm clocks, which entrain (reset) the sleep/wake cycle.

Question 6

How do studies investigate the free running of endogenous endogenous pacemakers?

Answer 6

through the use of isolation studies which involve participants having no access to external cues such as regular daylight

Question 7

What does free running mean?

Answer 7

regular activity in the absence of exogenous zeitgebers

Question 8

How long are infradian rhythms?

Answer 8

longer than 24 hours, so repeat less than once every 24 hours

Question 9

What is an example of an infradian rhythms?

Answer 9

the human menstrual cycle, which has a typical duration of 28 days.

Question 10

What is the menstrual cycle internally controlled by?

Answer 10

endogenous pacemakers such as hormones, coordinated by the pituitary gland.

Question 11

What can the menstrual cycle also be influenced by?

Answer 11

by external zeitgebers such as pheromones, which are biochemical substances that are released into the air

Question 12

What may pheromones do?

Answer 12

facilitate the synchronisation of menstrual cycles between different women.

Question 13

What may pheromones do?

Answer 13

facilitate the synchronisation of menstrual cycles between different women.

Question 14

How long are ultradian rhythms?

Answer 14

shorter than 24 hours and so repeat more than once every 24 hours.

Question 15

What is an example of an ultradian rhythm?

Answer 15

the cycle of sleep stages which involves NREM (non-rapid eye movement) and REM (rapid eye movement).

Question 16

Whilst sleep what do we usually experience?

Answer 16

5 sleep cycles, each lasting about 90 minutes

Question 17

During each cycle (of sleep) what does each person undergo?

Answer 17

a period of NREM sleep lasting approximately 80 minutes, followed by a period of REM sleep lasting around 10 minutes

Question 18

What is the brain stem (ultradian)?

Answer 18

is the endogenous pacemaker that acts as a switching mechanism between REM and NREM sleep whilst exogenous factors such as alcohol, caffeine and exercise are external factors that can influence the timing of the cycle.

Question 19

what is an endogenous peacemaker?

Answer 19

an internal, biological clock within an organism that regulates it’s biological rhythm

Question 20

What the the supra-chiasmatic nucleus of the hypothalamus?

Answer 20

the main endogenous pacemaker in mammals and is responsible for internally controlling the sleep/wake cycle

Question 21

Where is the SCN located?

Answer 21

above the optic chiasm, which is the point where the optic nerve from each eye crosses over

Question 22

What does the position of the SCN mean?

Answer 22

it can receive neural
chiasm signals about the amount of light

Question 23

How does the SCN work?

Answer 23

-Neural signals from the SCN are transmitted to the pineal gland, located just behind the hypothalamus.
-The pineal gland secretes melatonin, which is a hormone that inhibits neural mechanisms that promote wakefulness. -When it is dark the pineal gland increases the production of melatonin and a person will start to sleep.
-In the morning when it is light, secretion of melatonin from the pineal gland decreases so a person feels more awake.

Question 24

What is an exogenous zeitgeber?

Answer 24

an external cue that can/entrain an organism’s biological rhythms.

Question 25

What is the dominant exogenous zeitgeber in humans?

Answer 25

light

Question 26

What has research shown about bright light?

Answer 26

bright light can slow down melatonin production.

Question 27

How does light work?

Answer 27

-SCN receptors are sensitive to neural signals about changes in light levels and use this information to synchronise the internal activity of the body’s organs and glands with the external environment.
-Light therefore resets the biological clock each day, keeping it on a 24-hour activation cycle.

Question 28

What serve as additional exogenous zeitgebers?

Answer 28

Social cues such as set meal times- -evident when travelling long distances across time zones; if an individual adopts the meal times of their destination in the days prior to departure, this can help entrain their biological clock and lessen the symptoms of jet lag upon arrival.