Reproduction: Biological Clocks

Question 1

What are the types of biological rhythms?

Answer 1

Infraradian: period longer than 24 hours (ex. estrous cycle)

Ultradian: period less than 24 hours (ex. respiration, heart rate)

Circadian: period of about 24 hours (ex. sleep/wake)

Question 2

What happens to the biological clock in the absence of environmental cues?

Answer 2

Continues to run under constant conditions
Produces rhythmic patterns (free running)
Can be reset by external environment, photoperiod, temperature, and social clues

Question 3

What are the components of the biological clock?

Answer 3

1. Suprachiasmatic Nucleus: central master circadian oscillator (pacemaker) that generates the rhythm
2. inputs that detect external environmental cues (zeitgebers) and entrain the oscillator
3. outputs that translate the rhythm from oscillator into overt rhythms

Question 4

What are the two levels of regulation of the oscillator?

Answer 4

1. Negative feedback: protein products of gene act on gene itself to downregulate expression
2. Post-transcriptional control: protein degradation and translational control

Question 5

What is the predominant zeitgeber?

Answer 5

Light

Question 6

What role does melatonin play?

Answer 6

Communicates info about environmental lighting to various parts of body

Entrains biological rhythms

Roles in sleep, seasonal rhythms, and body temperature regulation