lecture 8: what is sleep

Question 1

circadian rhythm

Answer 1

the physical, mental and behavioural changes an organism experiences over a 24hr cycle
cira = about
dian = day

Question 2

wake maintenance zone

Answer 2

feeling more alert just before the period where you are feeling sleepy (6-9pm)
- this was advantageous many yrs ago, as if they were alert just before dark they could find shelter/warmth

Question 3

melatonin

Answer 3

a natural chemical which is being modulated across the sleep/wake cycle
- it peaks in the middle of the night

Question 4

free-running sleep-wake cycle

Answer 4

occurs when an individual’s circadian rhythm drifts later each day, resulting in a sleep schedule that is not synchronized with the 24-hour day

Question 5

suprachiasmatic nucleus of the hympthalamus (SCN)

Answer 5

• a small region in the hypothalamus that acts as the body’s central circadian pacemaker, regulating sleep-wake cycles and coordinating various biological rhythms with the 24-hour day-night cycle
• this is where our internal clock is located
• this location is vital, if it is damaged it impairs the sleep wake cycle

Question 6

pineal gland

Answer 6

releases hormone melatonin at night

Question 7

zeitgeber

Answer 7

• any external or environmental cue which acts as a cue in the regulation of the bodys circadian rhythms
• light is the primary zeitgeber (time giver)

Question 8

how do melanosopin receptors work

Answer 8

• melanosopin receptors in the eye respond to the presence of light by transmitting signals to the SCN
• light induced activation of the SCN prevents the pineal gland from producing melatonin, a hormone that otherwise signals “biological night”
• light dark entrainment of the SCN synchronises ‘peripheral oscillators’ throughout the body, although these can subsequently be shifted by factors such as eating, exercise and body temp

Question 9

phase delay

Answer 9

• wake up later
• a phase delay means your internal clock shifts to later times

Question 10

phase advance

Answer 10

• wake earlier
• phase advance means it shifts to earlier times

Question 11

inactivity theory

Answer 11

sleep at night = less likely to be eaten and most likely to have offspring, conserve energy
limitation = sleep forces us to remain quiet during periods of vulnerability
- it is always safer to remain conscious in order to be able to react to an emergency. thus there does not seem to be any advantage of being unconcious and asleep if safety is paramount

Question 12

energy conservation theory

Answer 12

• sleep forces us to conserve energy at times when we would be relatively inefficient at searching for food
• energy metabolism is reduced by 10% during sleep in humans, decreased body temp and caloric demand

Question 13

recuperation/repair explanations of sleep

Answer 13

a. sleep deprivation should produce physiological and psychological disturbances
b. these disturbances should get worse as deprivation continues
c. after deprivation much of the sleep debt will be recovered
- sleep is crucial for the body and brain to rest, repair, and restore physiological functions, including muscle repair, tissue growth, and hormone release

Question 14

peter tripp and randy gardener

Answer 14

peter tripp (1959) = 201 hours (98 days)
- psychosis
Randy Gardner (1964) = 264 hrs (11 days)
- moodiness, problems with concentration and short term memory, paranoia and hallucinations
- only 6 hrs of extra sleep during the following week

Question 15

what was the impact of sleep deprivation on animal studies

Answer 15

after 2 weeks unable to thermoregulate, lost weight, infections
after 4 weeks = death

Question 16

what beneficial things happen during sleep

Answer 16

muscle growth, tissue repair, protein synthesis and growth hormone release occur mostly during sleep

Question 17

what are the impacts of poor sleep

Answer 17

• sleep disruption eg: shift work is linked to cancer, diabetes, cardiovascular risks, obesity, mood disorders and age related macular degeneration
• poor sleep is linked to several psychiatric disorders and Alzheimer’s disease

Question 18

glymphatic system involvement

Answer 18

• slow waves of neural activity, as occur during sleep, are associated with changes in vasodilation in the brain
• these changes are thought to pump cerebrospinal fluid (CSF) around the brain
• the CSF interacts with interstitial (extracellular) fluid and picks up the waste products of metabolism so that they can be transported out of the brain via the glymphatic system

glymphatic system = a waste clearance pathway in the brain