Lecture 8 Flashcards
What type of rhythm is the Sleep wake cycle? What does this suggest?
The Sleep-wake cycle is a circadian rhythm (about 25 hour cycle in humans). This suggests an internal clock which runs a little bit slow. It is reset by light acting as a zeitgeber.
Where is the human internal clock?
The internal clock is found within many cells, but the master clock is in the suprachiasmatic nucleus of the hypothalamus. It sends out signals throughout the body, even to the secondary cells to keep them in sync, a good example is a signal to the pineal gland to secrete melanin during sleep.
What is a synchronized and free running actogram?
A synchronized actogram is one in which activity is synced to environmental cues, a free running actogram is one where there are no cues to sync to and the activity gets out of sync with the external environment.
What is sleep propensity like over time?
Sleep propensity (tiredness) is higher in the afternoon than in the evening (6-9pm ish), this zone of decreased sleep propensity is known as the wake maintenance zone. Sleep propensity is highest during sleep.
What happens when damage to the suprachiasmatic nucleus occurs?
Without the suprachiasmatic nucleus the total amount of sleep is the same, but it becomes spread out over a 24 hour period. Showing it doesn’t control the amount of sleep, but does control when it occurs.
How does light reset the suprachiasmatic nucleus?
Light activates the suprachiasmatic nucleus via:
- melanopsin recptors in the eye responding to light presence (particularly blue light, as found in electronics, causing sleep problems) and sending a signal to the suprachiasmatic nucleus.
- Light-induced activation of the suprachiasmatic nucleus prevents the pineal gland from producing melatonin (signals biological night).
- Light-dark entrainment of the SCN synchronizes peripheral oscillators throughout the body, although these can be shifted again by factors such as eating, exercising and body temperature.
is phase delay or phase advance easier?
For most people phase delay (waking up later) is easier than phase advance (waking up earlier), this is because our body clock typically runs 25 hours (longer than a typical day).
What is the two process model of sleep regulation?
The two process model of sleep regulation is circadian rhythm and homeostatic debt. This refers to the homeostatic mechanisms in our body which function during sleep, hence we build up a sleep “debt” which can be repayed by sleeping to allow these homeostatic mechanisms to occur.
Why do we sleep?
One possible reason we sleep is that sleep forces us to conserve energy at times when we would be relatively inefficient. This predicts sleep should vary based on how much time they spend gathering food and how vulnerable they are, this kind of makes sense for the most part. Another possibility is for recuperation, this predicts that sleep deprivation should produce physiological and psychological disturbances, these disturbances should get worse over time and recover with sleep, in some cases sleep deprivation led to bad effects (psychosis, 201 hours, with stress), but in others only some impairment in attention, motivation and cognition, with only 6 hours of extra sleep in the next week (264 hours, no stress). Sleep also is found to help with health (e.g cancer, diabetes, cardiovascular risk).
