Chapter 9- Wakefulness and Sleep Flashcards
True or False?The body generates its own rhythm of wakefulness and sleep?
True
What is an Endogenous circannual rhythm?
A Rhythm that prepares an animal for season changes.
Ex. Animals storing food for the winter or migratory birds
What do Endogenous circannual rhythm operate on?
internal mechanisms on a yearly patterns
What is an Endogenous circadian rhythm?
Rhythms that last about a day.
True or False? Endogenous circadian rhythm only controls our wakefulness and sleep patters?
False. It also regulates the functions of eating, drinking, body temperature, secretion of hormones, urination and sensitivity to drugs
True or false? Every human has the exact same ECR cycle?
False. Cycles can differ between people and lead to different patterns of alertness
The human circadian clock generates a rhythm slightly..
longer than 24 hours
True or False. Sometimes the ECR needs to be reset?
True.
What is a Free-running rhythm?
a rhythm that occurs when no stimuli reset or alter it
What is a Zeitgeber?
The stimulus that resets the circadian rhythm “ time giver” . Light is the dominant one for land animals, others can include exercise, noise, meals, temperature of environment
What are some symptoms of using something other than sunlight as a zeitgeber?
Depression, irritability and impaired job performance
Circadian rhythms in blind people..
Still generate, just more slowly
What is jet lag?
A disruption of circadian rhythms due to crossing time zones. It is caused when there is a mismatch between our internal circadian clock and external time
When we travel east to west it results in…
Phase Delay, gaining time..it’s easier for us to adjust to
When we travel west to east it results in…
Phase advance, losing time
What happens to circadian rhythms when there is no environmental cue indicating the time of day?
They remain consistent
What is the Suprachiasmatic Nucleus ( SCN)?
Part of the hypothalamus; provides the main control of the circadian rhythms for sleep and body temperature .
Generates rhythms in genetically controlled, unlearned manner. Various cells communicate with each other to sharpen the circadian rhythm
Where is the SCN located?
above the optic chiasm
Damage to the SCN results in…
less consistent body rhythms that are no longer synchronized to environmental patterns of light and dark
A Mutation in one gene causes hamsters’ SCN to…
produce 20-hour instead of 24- hour rhythm
What resets the SCN?
Light from the retina
What is the retinohypothalamic path?
A small branch of the optic nerve that extends directly from the retina to the SCN
True or False? Most of input from the retinohypothalamic path does not come from normal retinal receptors?
True.
For all mammals, retinohypothalamic path to SCN comes from a special population of…
Retinal ganglion cells
They respond directly to light, not rods or cones , the overall average of the light that changes from one level to another
They are located mainly near the nose, and respond to light slowly and turn off slowly when light ceases
What is Melanopsin?
the name of the photopigment that cells have
True or False? The SCN regulates waking and sleeping by controlling activity levels in other brain areas?
True, including the pineal gland - an endocrine gland that is located behind the thalamus that releases melatonin
What are the two genes that generate circadian rhythms?
Period ( Per) and Timeless (tim)
How do Per and Tim interact with the body to generate rhythms?
The proteins start in small amounts in the morning and then increase during the day, reaching high levels by evening, interact with a protein called Clock which induces sleepiness.
High level feeds back to the genes to shut them down. Genes are dormant at night. Cycle starts again in the morning.
What happens when there is a pulse of light during the night ?
Inactivates Tim protein and resets biological clock, decreasing sleepiness
Mutations of the Period gene in humans …
Results in odd circadian rhythms or decreases alertness if sleep deprived