Wakefulness & Sleep Flashcards
what is an endogenous rhythm?
internal mechanisms that operate on an approximately 24 hour cycle
What two measures are circadian rhythms assessed by?
Physiological and Behavioural
What is the infradian rhythm? name an example
Biological rhythm lasting over 24 hours e.g a menstrual cycle (approx. 28 days)
What is a circannual rhythm?- give example
Biological rhythm that lasts over a year- e.g. hibernation or SAD
What is ultradian rhythm? give example
A rhythm that lasts shorter than a cicardian rhythm- e.g. hunger fluctuations
3 types of endogenous biological rhythms discussed in chapter
circannual
ultradian
infradian
what evidence indicates that humans have an internal biological clock?
people who have lived in an environment without light-dark scedhule much different from 24 hours fail to follow that schedule and instead become wakeful and sleepy on an approx. 24 hour basis
What is stimulus Zeitgeber?
a stimulus that rests the circadian rhythm
What is the primary Zeitberger for humans? Name some secondary ones as well
Sunlight- primary
secondary- exercise and social interaction
Why does jet lag occur?
A mismatch between internal circadian clock and external time
What is it to phase-delay sleep?
To delay sleep- go to sleep a little later than what we are used to
What is it called when we sleep earlier and awaken earlier? Opposite of phase-delay
Phase-advance
People in big cities surrounded by bright lights are more likely to stay up late than people in rural areas. T/F?
T
What is the concept developed by Richer that says the brain generates its own rhythms?
Biological clock
How to blind people maintain a circadian rhythm?
Meal times, noise, temperature, activity, etc.
What is the main driver of rhythms for sleep and body temperature?
suprachiasmatic nucleus (scn)
where can you find the scn?
it is a part of the hypothalamus- above the optic chiasm
What happens if you damage the SCN?
the body’s rhythm becomes erratic
an isolated SCN cell can maintain a circadian rhythm although _______.
interactions among cells sharpen the accuracy of the rhythm
Which gland does the SCN influence?
the pineal gland, which then produces melatonin
What evidence strongly indicates that the SCN produces the circadian rhythm itself?
SCN cells produce a circadian rhythm of activity even if they are kept in a cell culture isolates from the rest of the body.
What is the retinohypothalamic path?
A small branch of the optic nerve
consisting of a special path of ganglion cells that extend from the retina to the SCN.
What is special about the retinohypothalamic ganglion cells?
They have their own photopigment- melanopsin that don’t require input from rods & cones
People who are blind because of cortical damage can still synchronise their circadian rhythm, why?
if the retina is intact, melanopsin-containing ganglion cells can still send messaged to the SCN, resetting its rhythm.
Proteins & the SCN- explain the mechanism (4 steps)
- SCN makes two proteins called CLOCK & CYCLE from DNA, RNA with help from ribosomes
- CLOCK & CYCLE bind to DNA in the nucleus of SCN cells to transcribe the proteins: PER & TIM.
- PER & TIM proteins inhibit the expression of CLOCK & CYCLE genes (stop from making more PER & TIM)
- PER & TIM proteins are slowly broken down by an enzyme to ensure that the loop can begin again & we can synthesise CLOCK & CYCLE.
at night PER & TIM concentrations are at their ______.
highest
How do the SCN & pineal gland work together?
The SCN controls the pineal gland to release melatonin
Where can I find the pineal gland?
posterior to the thalamus