Today’s post is on Biological Psychology and an Introduction to Sleep.
This is an extract from my new Biological Psychology 2nd Edition.
CHAPTER 18: INTRODUCTION TO SLEEP
I thought that I would end this book looking at sleep because we all need sleep but:
How does it work?
Why do we need sleep?
Why do we dream?
These are all interesting as well as important questions that we need to answer to be able to understand the whole point of sleep.
Because let’s face it, sleep can be inconvenient as sometimes I would rather be doing something than sleeping.
However, as you will find out throughout this next section sleep is vital so it shouldn’t be taken lightly.
What is sleep?
Personally, I always find these sorts of questions to be great because ‘what is sleep?’ is one of those annoying questions as we know what sleep is but it’s almost impossible to put into words.
Nonetheless, three definitions include:
· “Sleep is a readily reversible state of reduced responsiveness to, and interaction with, the environment.”
· “Sleep is a naturally recurring state characterised by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles.”
· Sleep represents an altered state of consciousness (Mutz, Javadi, 2017)
Although, regardless of how you define sleep it must be noted that sleep is a universal behaviour that is displayed by higher vertebrates (all mammals and birds), and some cold-blooded vertebrates.
The Circadian rhythm:
As I read these slides and passages for my university lecture I was immediately interested in the whole sleep concept but then this strange word kept popping up.
This word or phrase was the ‘Circadian Rhythm’
Which come on is a nice word to say.
So, before we continue, we need to define it.
A circadian rhythm can be defined in simple terms as a circular rhythm that the body goes through.
In terms of sleep, the circadian rhythm is our melatonin; more on than later; drops during the day as we wake up and remains low during the day and increase as we get closer to bedtime and remains high during the night.
Before it comes full circle and drops back down to lower levels in the morning.
Circadian rhythms for the entire body:
Many bodily functions follow a circadian rhythm and these are the product of endogenous influences; influences that originate from inside the body; and exogenous influences; influences from outside the body.
Some examples of exogenous influences include:
The purpose of endogenous rhythms is to keep the working of our internal body in sync with the outside world.
This is important as the human circadian clock generates a rhythm that is longer than 24 hours when it has no external cues to refer to.
As supported by Kelley et al (1999) who studied naval officers on 18-hour shifts.
Exogenous or external cues:
These cues rely on a stimulus to reset the circadian rhythm. This is called a Zeitgeber. (time trigger)
Although, out of all the stimulus that the human body encounters light is crucial for resetting the rhythm.
Overall, the human body runs on a biological clock that needs to reset itself and we need stimulus in order to do that.
Mechanisms of the biological clock:
There are 3 mechanisms involved in the biological clock and these include:
· Genes that produce certain proteins
· The Suprachiasmatic nucleus (SCN)
The SCN is part of the hypothalamus and it’s the main centre of the circadian rhythm for sleep and temperature.
If the SCN is damaged then this results in less consistent body rhythms that aren’t synchronised to the environmental patterns of light as well as dark.
In addition, cells in the SCN fire their action potentials in a very specific rhythm that are generated by the SCN are genetically controlled.
Additionally, light resets the SCN via a small branch of the optic nerve called: the retinahypothalamus path. That travels directly from the retina to the SCN.
The way how the SCN affects sleep is because the SCN controls activity in other areas of the brain. Like the pineal gland.
The pineal gland is important as it secretes melatonin; a hormone that regulates the circadian and circannual rhythms as well as it increases 2-4 hours before bedtime.
The genetic basis of circadian rhythms:
There are two genes that are involved in circadian rhythms and thy are:
· Timeless- this gene produces proteins called TIM.
· Period- this gene produces proteins called PER.
When TIM and PER are in high concentration, they interact with a protein (clock) to induce sleepiness.
However, if the clock gene is damaged then this can result in a reduced sleep as well as erratic sleeping pattern.
Furthermore, mutations in the PER gene can result in strange circadian rhythms.
So now that we’ve looked at the basics of sleep and the circadian rhythm, what happens to us when it gets disrupted?
I hope that you’ve enjoyed today’s Biological Psychology post and if you want to learn more then please consider checking out my book Biological Psychology 2nd Edition.
Have a great day everyone.