Deck 10: Biological Rhythms

Question 1

Infradian rhythms refer to those rhythms with a period

A) of 24 hours.
B) that is less than 24 hours.
C) that is more than 24 hours.
D) of one year.

Answer 1

C

Question 2

What is the single-most defining characteristic of a true biological rhythm?

A) It can be entrained by environmental cues.
B) It is self-sustaining.
C) It requires a zeitgeber.
D) All true biological rhythms are circadian.

Answer 2

B

Question 3

Which region of the mammalian brain is viewed as the master clock that organizes all circadian rhythms?

A) Suprachiasmatic nucleus (SCN)
B) Hippocampus
C) Pineal gland
D) Preoptic area (POA) of the hypothalamus

Answer 3

A

Question 4

Which list of biological rhythms is ordered from most frequent to least frequent?

A) Ultradian, circannual, circadian, infradian
B) Circannual, infradian, circadian, ultradian
C) Infradian, circadian, ultradian, circannual
D) Ultradian, circadian, infradian, circannual

Question 5

Photoperiodism is the

A) ability of light to entrain circadian rhythms.
B) ability to use day length to time annual cycles.
C) stimulation of the pineal gland of birds by light reflecting through the skull.
D) ability of light to entrain ultradian rhythms.

Question 6

A male and female rat each has free-running circadian rhythms shorter than the normal 24 hours. Their offspring will most likely have a

A) shorter cycle (less than 24 hours) as well, indicating that circadian rhythms have a strong genetic component.
B) normal cycle (24 hours), indicating that zeitgebers have the strongest influence on cycle length.
C) longer cycle (greater than 24 hours), indicating that circadian rhythms have a strong genetic component.
D) longer cycle (greater than 24 hours), indicating that zeitgebers have the strongest influence on cycle length.

Question 7

Which statement is true?

A) Entrainment is dependent on behavioral feedback.
B) Entrainment is limited to specific ranges.
C) Biological clocks are only found in the SCN of mammals.
D) Unicellular organisms do not possess biological clocks.

Question 8

Which is evidence that the suprachiasmatic nucleus is a master clock?

A) Cells from the SCN maintain circadian rhythms of electrical activity when isolated in culture.
B) Cells from the SCN each display different free-running rhythms of electrical activity.
C) Lesioning of the SCN completely and permanently disrupts circannual rhythms.
D) Lesioning of the SCN does not disrupt circannual rhythms.

Question 9

Scalloping refers to the

A) irregular cycling of a biological rhythm in response to unchanging environmental cues.
B) regular cycling of a biological rhythm even when environmental cues are constantly changing.
C) phase advancement of activity in females during estrus.
D) phase delay of activity in females during estrus.

Question 10

Serotonin is converted to melatonin

A) by the adrenal glands.
B) in the POA.
C) by the enzyme tryptophan.
D) by the pineal gland.

Question 11

Which term is not used to describe biological rhythms?

A) Period
B) Frequency
C) Adaptability
D) Amplitude
E) Phase

Question 12

Melatonin is produced in the

A) testes.
B) parathyroid gland.
C) renal tubule.
D) pineal gland.
E) pituitary.

Question 13

Which is not one of the main components of a mammalian biological clock system?

A) Photoreceptors in the eye
B) Melatonin
C) SCN
D) Clock-controlled genes

Question 14

When the suprachiasmatic nucleus is removed

A) all cells in the body cease to exhibit biological rhythms.
B) many, but not all, cells lose their ability to exhibit biological rhythms.
C) cells continue to exhibit daily biological rhythms, and circadian rhythms are maintained.
D) cells continue to exhibit biological rhythms, but in an uncoordinated way.

Question 15

Which of the following act as negative feedback elements in a cell's circadian loop?

A) CRY-PER
B) CLOCK-PER
C) CK1-BMAL
D) CLOCK-BMAL1

Question 16

Reproductive photorefractoriness in Syrian hamsters is best characterized by

A) the spontaneous regression of the hamsters' testes.
B) long day typical behavior but short day typical physiology.
C) arrhythmic activity rhythms.
D) the spontaneous re-activation of the reproductive system.

Question 17

Lesioning of the suprachiasmatic nucleus (SCN) in a mouse followed by implantation of the SCN from another mouse will ultimately result in

A) restoration of all circadian rhythms.
B) restoration of ultradian but not circadian rhythms.
C) restoration of behavioral circadian rhythms but not endocrine rhythms.
D) the rhythm of the recipient resuming its original phase with the environment.

Question 18

List four characteristics of biological clocks.

Question 19

Describe the two ways that biological clocks allow animals to adapt to temporal fluctuations.

Question 20

List three types of nonphotic zeitgebers.

Question 21

Why are circadian rhythms referred to as having a length of "about a day"?

Question 22

Describe the neural pathway that connects the eye to the pineal gland.

Question 23

Describe the primary functions of biological clocks.

Question 24

Compare and contrast the concept of homeostasis with biological clock function (e.g., circadian rhythms). Do biological rhythms participate in homeostasis? What would be the effect of circadian clock destruction on homeostasis?

Question 25

Rats display 4-day estrus cycles and 5-day estrus cycles. Why are there no 4.5-day estrus cycles?

Question 26

Discuss the evidence that circadian rhythms are endogenous and do not require exogenous cues.

Question 27

Compare and contrast the concepts of type I and type II seasonal rhythms in rodents.

Question 28

Explain the concept of photorefractoriness and provide an example of when it may occur in nature.

Question 29

The hourglass model and the external coincidence model are two hypotheses that explain how animals respond to changes in day length. Compare and contrast these two models.