Chapter 10

Question 1

What are biological rhythms?

Answer 1

Regular fluctuations in any living process

Question 2

What are circadian rhythms?

Answer 2

Physical, mental, and behavioral changes that follows a 24 hour cycle

Question 3

What is within Circadian rhythms?

Answer 3

• Hormones: Melatonin & Corticosterone
  * Sleep/Wake
  * Body Temperature
  * Aggression/Anger

Question 4

What is Ultradian rhythms?

Answer 4

Biological cycles that takes place within 24 hrs (<24). Repeats more than once a day

Question 5

What is apart of Ultradian rhythms?

Answer 5

• Feeding & related hormones release
  * Bouts of activity

Question 6

What is Infradian rhythms?

Answer 6

Repeats longer than a day

Question 7

What is included in infradian rhythms?

Answer 7

• Emotion/mood
  * Reproductive cycle
  * (menstrual/estrus cycles)

Question 8

Humans are diurnal

Answer 8

Active during the day

Question 9

What is free-running?

Answer 9

Animals deprived of external cues about time of day, maintains their own personal cycles; tend to be longer than normal circadian rhythm

Question 10

What is a free-running period?

Answer 10

The time between two similar points of successive cycles; ex, sunset to sunset

Question 11

What is phase shift?

Answer 11

A shift in the activity of a biological rhythm, typically provided by a synchronizing environmental stimulus; ex. Light

Question 12

What is entrainment?

Answer 12

The process of synchronizing a biological rhythm to an environmental stimulus; ex. A hamster synchronizing it’s wheel to the start of the dark period when subjected to periods of light and dark

Question 13

What is Zeitgeber?

Answer 13

The stimulus that entrains circadian rhythms

Question 14

What is the suprachiasmatic nucleus (SCN)?

Answer 14

Lesions of a tiny subregion of the hypothalamus and the location of the circadian clock

Question 15

What do lesions of the suprachiasmatic nucleus eliminate?

Answer 15

Circadian rhythms of drinking, locomotion, and hormone secretion

Question 16

What happens to isolated SCN cells?

Answer 16

They continue to show a circadian rhythm for days or weeks

Question 17

SCN is necessary and sufficient to produce circadian rhythm-controlled behaviors

Question 18

What does melatonin inform?

Answer 18

It informs the brain about day length (the pineal gland forms the hormone melatonin)

Question 19

Circadian rhythms entrain to light-dark cycles using different pathways; some are outside of the eye (ex.birds)

Question 20

In mammals, some retinal ganglion cells form the retinohypothalamic pathway

Question 21

What is the retinohypothalamic pathway?

Answer 21

Pathway, which Carrie’s light information from the eyes to the SCN

Question 22

What special photopigment makes mammals sensitive to light?

Answer 22

Melanopsin; that is why mammals don’t rely on traditional photoreceptors to learn about light

Question 23

What increased our understanding of the circadian clock in mammals?

Answer 23

Molecular studies in Drosophila (flies) and mice’s using mutations of the period gene (per) and cryptochrome (cry)

Question 24

What two proteins do SNC cells make in mammals?

Answer 24

Clock and Cycle

Question 25

What do Clock and Cycle proteins form by binding together?

Answer 25

Dimer

Question 26

What is a dimer?

Answer 26

a pair of proteins attached to each other

Question 27

What two genes does the Clock and Cycle dime promote transcription of?

Answer 27

Period (per) and Cryptochrome (cry); clock and cycle binds to the cells DNA to do this; takes 24 hours to complete

Question 28

What happens when Per and Cry protein bind to each other?

Answer 28

It inhibits the activity of the Clock/Cycle dimer thus slowing the transaction of per and cry genes

Question 29

What happens when Per and Cry proteins break down?

Answer 29

They release the Clock/Cycle from inhibition, allowing the cycle to start over again

Question 30

What are larks?

Answer 30

People who feel energetic in the morning; likely to carry a different version of the clock gene than night owls

Question 31

What do transplant studies provide supporting evidence for?

Answer 31

That the SCN produces the circadian rhythm

Question 32

What did hamsters with SCN lesions in constant conditions show?

Answer 32

No circadian rhythm of running wheel activity

Question 33

What happened when hamsters received an SCN tissue transplant from hamsters with a short circadian rhythm?

Answer 33

Circadian rhythms were restored but it matched the shorter period of the donor