Biological Rhythms and Sleep
- Circadian
- Infradian
- Ultraduan
- endogenous pace makers and exogenenous zeigebers
- What happens if you dissrupt these
- Created by: Annabelle
- Created on: 13-01-11 18:07
Bio Rhythms
- •The term refers to regular variations in biological activity. •It includes changes in levels of brain chemicals, increases and decreases in body temperature and the shift between sleeping and waking
Types of rhythm
Because of the variety of rhythms they need to be put in different types such as: Circadian Infradian Ultradian
What controls these rhythms?
Light – we go to sleep when dark and wake up when it is light
Food scarcity – birds migrate and squirrels hibernate when food is scarce
Exogenous Zietgeber
This suggests that biological rhythms are controlled by environmental factors such as:
Light
Temperature
Availability of food
These are called exogenous zietgebers (German for external time givers)
AO2
However, many studies have shown that it is not that simple.
If beach living algae are kept in a laboratory in controlled conditions they still burrow into the sand and come out at times in time with the tides.
e.g.
Squirrels kept in controlled conditions still prepare for hibernation as winter approaches in the world outside by putting on weight and decreasing body temperature.
Clock
So there must be some sort of internal clock that regulates rhythms when there are no zeitgebers.
These internal clocks are called endogenous pacemakers
Circadian
This word comes from the Latin for ‘about a day’.
The sleeping waking cycle involves one period of each in 24 hours
Our body temperature has one peak (in the afternoon) and one trough (in the early morning) in the same period
This is a 24 hour rhythm
What are four things which have some variation over 24 hours?
Answer
1. heart rate
2. breathing
3. metabolic
4. body temperature
All the above reach maximum values in late pm/early evening and minimum values in the early hours of the morning
Why?
Answer
We are active during the day and inactive at night
These rhythms persist if we suddenly reverse our activity patterns.
Hormones
These also vary in concentration over the day.
Why would this happen?
This is so energy is provided when needed so for example is makes sense for the body temperature to dip in the middle of the night when we are inactive i.e. asleep
The rising body temperature in the day allows for increased activity and energy expenditure
Approaches, Issues and Debates
Approaches, Issues and Debates
Which of these link to this topic so far?
Answer
Approach – biological
Debate – reductionist
Issues – use of animals coming up
Menstruation #
These have a rhythm of more than a day.
What do you think has been most researched under this?
Answer
Menstrual cycle
Hibernation
Every 28 days female bodies have several changes with two possible outcomes
What are they?
Answer
Conception
Menstruation
The menstrual period is the end of the cycle not the beginning. The womb has prepared to house and nourish a fertilized egg
Pre menstrual syndrome – PMS
Five days before a period women may have:
Mild depression
Headaches
Decrease in alertness
Irritation
A day of energy followed by lethargy
AO2 #
PMS occurs in all cultures which indicates a physiological cycle rather than a pattern of behaviour because of the culture
Primates also suffer similar effects AO2
Light
In lighter months of the year conception increases so light levels may have an influence on the pituitary gland – this gland controls the menstrual cycle
SAD
Seasonal Affective Disorder is a form of depression that affects certain people in the winter months.
These people tend to eat and sleep more.
If sufferers are exposed to bright light first thing in the morning this can help combat SAD
Ultradian Rhythms #
These are rhythms of less than a day’s length. i.e. sleep
During the night we move into different stages of sleep - light slow wave sleep to deep slow wave sleep. And into REM
One cycle takes about 90 minutes
This cycle is controlled in the brain using neurotransmitters.
The key elements are suprachiasmatic nucleus (SCN) and the pineal gland
Other examples
There are other examples of ultradian rhythms.
Some studies of alertness in humans show that it can vary within 90 minute periods
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