Lesson 10 – Circadian Rhythms

Question 1

What are biological rhythms?

Answer 1

Biological rhythms- cyclical changes in physiological systems

Question 2

Why have biological rhythms evolved?

Answer 2

Because environments in which organisms live have cyclical 🚲 changes e.g. day ☀️/🌑 night, summer🌞/❄️ etc

Question 3

What are the types of biological rhythms?

Answer 3

1) Circadian
2) Ultradian
3) Infradian

Question 4

What is a circadian rhythm?

Answer 4

Circadian rhythms- any cycle that lasts 24 hours- optimise organism’s physiology and 🏃‍♂️ to best meet varying demands of day ☀️/night 🌑 🚲

Question 5

Which organisms have a circadian rhythm?

Answer 5

Nearly all organisms possess biological representation of 24 hour day

Question 6

What are circadian rhythms driven by?

Answer 6

Circadian rhythms driven by suprachiasmatic nuclei (SCN)

Question 7

Where is the suprachiasmatic nuclei (SCN) located?

Answer 7

In hypothalamus

Question 8

What is the suprachiasmatic nuclei (SCN) and define the term?

Answer 8

A pacemaker- controls rate at which something occurs

Question 9

How does the suprachiasmatic nuclei (SCN) keep in sync with the outside world?

Answer 9

It is constantly reset so that our bodies are in synchrony with outside 🌎

Question 10

What is photoentrainment?

Answer 10

Photoentrainment- when natural light 💡 provides input to this system, setting SCN to correct time ⏰
- SCN then uses this info to coordinate activity of circadian rhythms throughout body

Question 11

When do the strongest sleep drives occur?

Answer 11

2:00- 4:00am and 1:00-3:00pm

Question 12

What is melatonin?

Answer 12

Melatonin- induces 💤 by inhibiting neural mechanisms that promote wakefulness

Question 13

How is the production of melatonin suppressed?

Answer 13

💡 supresses production of melatonin

Question 14

Where is melatonin released from and when is this release at its peak?

Answer 14

Release of melatonin from pineal gland at its peak during hours of darkness 🌓

Question 15

What are sleep and wakefulness under?

Answer 15

Homeostatic control

Question 16

How does homeostatic control work?

Answer 16

When awake for long ⏰, homeostasis tells us need for 💤 ⬆️ because energy used up during wakefulness
Homeostatic drive for 💤 ⬆️ gradually throughout day, reaching max in late evening

Question 17

What happens to the circadian rhythm without natural light?

Answer 17

Internal circadian rhythm maintains cycle of 24-25 hours even without natural 💡

Question 18

How do circadian rhythms and homeostasis work together?

Answer 18

Circadian rhythms keep us awake as long as there is daylight- prompting 💤 as it becomes dark 🌓
The homeostatic system makes us sleepier 💤 the longer we have been awake regardless of whether it’s 🌓/☀️

Question 19

What are the evaluation points of circadian rhythms?

Answer 19

👎- individual differences- 1 research study found that cycles can vary from 13 to 165 hours (Czeisler et al, 1999)
ALSO- varies when circadian rhythms reach their peak- e.g. ‘Morning people’ prefer to rise early and go to 🛌 early whereas ‘evening people’ prefer to rise late
👍- chronotherapeutics- practical application of circadian rhythms- time ⏰ patients take medication very important for treatment success- essential that right concentration of drug released in target area of body at ⏰ drug most needed- e.g. risk of ♥️ attack greatest during early morning hours after waking … medications developed that are taken before 💤 BUT ✖️ released until vulnerable time of 6:00 am
👎- Buhr et al (2010)- believes temperature controls body clock ✖️ light- SCN transforms info about 💡 levels into neural messages that set body’s temperature 🤒- fluctuations in 🤒 set timing of cells in body
👎- research on circadian rhythms hasn’t isolated people from artificial 💡, because believed only natural 💡 affected circadian rhythms
BUT recent research suggests this not true- Cziesler et al. (1999) altered pps circadian rhythms to 22 hours and to 28 hours by using artificial 💡 alone