Biological Rythms Flashcards
What are biological rhythms?
Changes that systematically recur in organisms
They involve periodic fluctuations in an organism.
Define biological rhythms.
Patterns of repeated activities associated with environmental cycles of day and night
List some regulated functions of biological rhythms.
- Hormone secretion
- Sleep-wake cycle
- Core temperature
- Mood
- Mental alertness
- Seasonal cycles of fertility in mammals
- Reproductive cycle
- Migration schedule
What are the three types of biological rhythms?
- Ultradian
- Infradian
- Circadian
What is an ultradian rhythm?
Short periods: < 24hrs with higher frequency
Examples include feeding cycle, cardiac cycle, breathing cycle, hormone release from the pituitary gland.
Define infradian rhythm.
Longer period: > 24 hours with lower frequency
An example is the menstrual cycle.
What does ‘circadian’ mean?
Coined by Franz Halberg, meaning ‘around the day’
Also known as diurnal rhythms, synchronized with the day & night cycle, approximately 24 hours.
List examples of circadian rhythms.
- Sleep-wake cycle
- Body temperature
- Cardiovascular functioning
- Hormone secretion
What are the two main types of factors that control biological rhythms?
- External (exogenous)
- Internal (endogenous)
What are exogenous factors in biological rhythms?
Environmental components such as temperature changes and light-dark cycles
The main external zeitgeber is bright light which affects the SCN.
What is the role of melanopsin in biological rhythms?
Melanopsin-containing retinal cells sense light stimuli which are conducted to the SCN via the retinohypothalamic tract.
What are endogenous factors in biological rhythms?
Factors within the organism that are independent of the environment, including biological ‘clock’ genes.
What is the central clock in biological rhythms?
Suprachiasmatic nuclei
What are some clinical correlates of disrupted biological rhythms?
- Bipolar disorder
- Heart attack
- Asthmatic attack
True or False: Jet lag is a transient sleep disorder.
True
What is delayed sleep phase syndrome?
Inability to fall asleep in the evening & wake up in the morning; total sleep time is normal.
What mutation is associated with advanced/chronic sleep phase syndrome?
Mutation in the ‘period’ gene
This syndrome is peculiar to an extended family in Utah and is also observed in fruit flies & golden hamsters.
What is light therapy used for?
Treatment of disturbance in the circadian cycle
What is melatonin used for?
Treatment of jet lag and insomnia in the elderly
What is ramelteon?
Melatonin receptor agonist used for treatment of insomnia
What class of drug is zolpidem?
Sedative hypnotic
It promotes sleep onset by slowing brain activity.
What is modafinil used to treat?
Daytime sleepiness due to shift work and delayed sleep disorder syndrome
