Sleep wake cycle and the Exo/Endogenous Pacemakers Flashcards
What is an endogenous pacemaker
Endogenous pacemakers are internal mechanisms that govern biological rhythms, in particular, the circadian sleep-wake cycle.
Can Endogenous pacemakers be altered and affected by the enrivonment
Yes
What is an example of an endogenous pacemaker
The suprachiasmatic nucleus (SCN), which is closely linked to the pineal gland, both of which are influential in maintaining the circadian sleep/wake cycle.
Pineal Gland
Homeostasis
Biological rhythms
Where is the suprachiasmatic nucleus located
It is located in the hypothalamus
What does the SCN do
It controls other biological rhythms, as it links to other areas of the brain responsible for sleep and arousal.
The SCN also receives information about light levels (an exogenous zeitgeber) from the optic nerve, which sets the circadian rhythm so that it is in synchronisation with the outside world, e.g. day and night.
How do the SCN and Pineal gland work together
The SCN sends signals to the pineal gland, which leads to an increase in the production of melatonin at night, helping to induce sleep. The SCN and pineal glands work together as endogenous pacemakers; however, their activity is responsive to the external cue of light.
What is an exogenous zietbeger
these can be described as environmental events that are responsible for resetting the biological clock of an organism.
Give examples of Exogenous zietgebers
They can include social cues such as meal times and social activities
But the most important zeitgeber is light, which is responsible for resetting the body clock each day, keeping it on a 24-hour cycle.
How does light affect the SCN
The SNC contains receptors that are sensitive to light and this external cue is used to synchronise the body’s internal organs and glands.Melanopsin, which is a protein in the eye, is sensitive to light and carries the signals to the SCN to set the 24-hour daily body cycle.
What is the role of the sleep-wake cycle?
The role of the sleep-wake cycle is to regulate our sleep at night and keep us awake during the day.
-The sleep-wake cycle has a recurring pattern, as it oscillates between wakefulness and asleep in a 24-hour clock. On a healthy sleep-wake rhythm, humans spend approximately eight hours sleeping and sixteen hours awake.-
How does homeostasis act as an endogenous pacemaker
When people are awake for a long time, the homeostasis sleep pressure sends negative feedback to the body—signalling the need for sleep to reset the energy levels.
What does homeostasis do (In broader terms)
Homeostasis maintains the internal bodily environment in constant equilibrium through a series of dynamic interactions in physiological and biochemical systems.
Homeostasis along with what else works together to determine the sleep wake cycle
Biological rhythms
Which hormones are involved in the sleep-wake cycle?
Cortisol and neurotransmitters, like norepinephrine and serotonin, are released to keep the brain awake and alert.
Adenosine and Melatonin
What happens if there is damage to the SCN
Damage to the SCN causes people to sleep erratically throughout the day because their circadian rhythms don’t match with the light-dark cycle.
However, most blind people maintain some ability to sense light and are able to modify their sleep-wake cycle.
How does adenosine and melatonin affect the sleepwake cycle
As the day progresses, a chemical called adenosine accumulates in the bloodstream, signalling the feeling of tiredness. As the daylight shifts to the dark, melatonin levels rise, making you feel sleepy. During sleep, while melatonin hormones rise, adenosine levels decline.
How is serotonin involved in the sleep-wake cycle?
Serotonin is released to signal to the body that it needs to sleep or ‘homeostatic sleep pressure’. Circadian rhythms and homeostatic sleep pressure are necessary for a healthy sleep-wake cycle.
What does serotonin do
balances our mood, well being and happiness.
How is cortisol involved in the sleep-wake cycle?
it stimulates wakefulness in the morning and by continuing to support alertness as the day goes by. It is progressive in allowing the internal body rhythms, sleep drive and other chemicals, such as adenosine and melatonin.
What is cortisol
A stress hormone that regulates our sleep and other physiological functions.
It is produced by the HPA system, which is the body’s response to chronic stress.
