Sleep- Biological Rhythms

Question 1

What is a biological rhythm?

Answer 1

This is a cyclical activity (characteristic of all animal life).

Question 2

What is the study of biological rhythms called?

Answer 2

Chronobiology

Question 3

What is a circadian rhythm?

Answer 3

Internally generated rhythms with a period close to 24 hours.

Question 4

What is a diurnal rhythm?

Answer 4

This is a circadian rhythm that is synchronised with a day/night cycle.

Question 5

What is an ultradian rhythm?

Answer 5

These are biological rhythms (feeding cycle) with shorter period (higher frequency) than circadian.

Question 6

What is an infradian rhythm?

Answer 6

These are biological rhythms with a cycle with more than 24 hours (human menstrual cycle)

Question 7

How do you internally control bio. rhythms?

Answer 7

Controlled through endogenous pacemakers (body clocks)-SCN.

Question 8

How do you externally control bio. rhythms?

Answer 8

Controlled through exogenous Zeitgebers- rhythmically occurring natural phenomenon- act as a cue to regulate circadian rhythms.

Question 9

What is the purpose of internal and external controls?

Answer 9

They ensure physiology and behaviour are coordinated with the outside world.

Question 10

What is the result with the plant experiment with circadian rhythm?

Answer 10

Plant in darkness continued to open and close flowers

Question 11

Outline experiment of spending 32 days underground?

Answer 11

2 people spent 32 days underground in a cave and measured body temp, urine output, eating habits and sleeping patterns.

Question 12

What are the results of the 32 day underground experiment?

Answer 12

They maintained regular sleep- wake cycle (body temp, urine output etc).
Therefore, humans have an endogenous circadian rhythm (and 24 hours).

Question 13

What is the PER gene?

Answer 13

This is the period gene discovered in drosophila.
The length of rhythm depends on this gene.

Question 14

What did research show was the length of natural cardiac rhythm?

Answer 14

Found to be 25 hours, not 24 as expected.
Other research- 23.5-24.5

Question 15

What do we know is the average endogenous circadian rhythm?

Answer 15

24 hours and 15 minutes.

Question 16

What would happen if we couldn’t correct our circadian clock to 24 hours?

Answer 16

The endogenous circadian clock differences and differences between individuals would be disastrous for individual survival and society.

Question 17

What is the meaning of a person’s CHRONOTYPE?

Answer 17

This is where individuals have the propensity to sleep at different times during the day.
Can give evolutionary advantages.

Question 18

What is the meaning of zeitgeber?

Answer 18

This is a time giver or time cue.

Question 19

What is the most important zeitgeber?

Answer 19

Light- synchronise internal body clock with external time.

Question 20

How does sunlight help our circadian rhythm?

Answer 20

Sunlight adjusts our internal clock every day to exactly 24 hours.

Question 21

What is our SCN?

Answer 21

This is the suprachiasmatic nucleus that’s located close to optical nerves and in good position to be adjusted by sunlight.

Question 22

What are the features of the SCN?

Answer 22

-located in hypothalamus
-has intrinsic activity rhythm even if isolated from rest of brain
-lesion of SCN- circadian rhythms disrupted

Question 23

What is the experiment with mutant hamsters?

Answer 23

-removed SCN from hamsters with natural sleep-wake cycle of 21 hours
-implanted into non-mutant with 24 hr cycle
-hamsters with implanted SCN changed to 21 hours
-therefore, SCN is dominant endogenous pacemaker

Question 24

What is the purpose of melatonin?

Answer 24

This is stored and released by pineal glands.
Production increases steadily after dusk and reduces during sleep, signals the start of the sleeping process (melatonin tablets can help in jet lag).

Question 25

What are the effects of intermittent shift work?

Answer 25

-disruption (occasional-result in daytime tiredness)
-frequent changes in shift patterns
-insufficient time for the body to adjust (difficult to maintain concentration and attention to detail)

Question 26

What are the effects of permanent shift work?

Answer 26

-body clocks adjust (not perfectly)
-difficult to sleep during day due to noise, light, family awake
-reduction in social and family life

Question 27

Example of controls in jetlag for 1pm USA time and 7pm UK time- what will endogenous pacemaker do?

Answer 27

This body clock will prepare body for sleep at 11pm UK time (7pm USA time).

Question 28

What will the exogenous zeitgebers do with jet lap example?

Answer 28

The light present and melatonin will try and correct but can only make a gradual change of about 1 hour a day.

Question 29

What are the symptoms of jet lag?

Answer 29

-daytime sleepiness
-headaches
-insomnia
-restless sleep (frequent waking up)
-difficulty concentrating
-impaired judgement
-upset stomach (nausea)

Question 30

Which direction of travel is easier for your body to adjust?

Answer 30

East to west- biological clock is ahead of time.

Question 31

Which direction is harder for your body to adjust?

Answer 31

West to east- biological clock is behind local time.