Wakefulness and Sleep Flashcards
Name some internal mechanism that operate on a 24 hour cycle.
Sleep, frequency of eating and drinking, body temperature, secretion of hormones, urination and sensitivity to drugs.
Explain circannual rhythms.
Internal mechanisms that operate on an annual or yearly cycle, like birds migratory patterns, or animals storing food for the winter.
What is the purpose of the circadian rhythm?
To keep our internal workings in phase with the outside world.
Explain the concept of zeitgeber.
Meaning time-giver, referring to the stimulus that resets the circadian rhythm.
Give some examples of zeitgeber.
Sunlight, tides, exercise, meals, and temperature of the environment.
Give three examples of the effect of using something other than sunlight as a zeitgeber.
Depression, irritability, and impaired job performance.
What is jet lag?
The disruption of the circadian rhythms due to crossing time zones.
Travelling west phase-____ our circadian rhythms.
Delays.
Travelling east phase-____ our circadian rhythms.
Advances.
How do people adjust best to night work?
If they sleep in a very dark room during the day and work under bright lights.
Give three mechanisms of the circadian rhythms.
The suprachiasmatic nucleus, genes that produce certain proteins, and melatonin levels.
What is the suprachiasmatic nucleus?
The main control centre of the circadian rhythms of sleep and temperature.
Where is the suprachiasmatic nucleus (SCN) located?
Above the optic chiasm and part of the hypothalamus.
What does damage to the SCN result in?
Less consistent body rhythms that are no longer synchronised to environmental pattern of light and dark.
How is the SCN reset?
Via a small branch of the optic nerve called the retinohypothalamic path, travelling directly from the retina to the SCN.
What does the retinohypothalamic path consist of?
Specialised ganglion cells that respond directly to light and require no input from rods or cones.
Name the two genes that are responsible for generating the circadian rhythm.
Period and timeless.
What proteins do period genes produce?
PER
What proteins do timeless genes produce?
TIM
What do mutations of the PER gene result in?
Odd circadian rhythms or decreased alertness if deprived of a good night’s sleep.
What do PER and TIM proteins increase the activity of?
Certain neurons in the SCN that regulate sleep and waking.
What does the SCN regulate?
The pineal gland.
Where is the pineal gland located?
Posterior to the thalamus.
What does the pineal gland secrete?
Melatonin.