L1: Rhythms of Waking and Sleeping

Self-generated

Our body spontaneously generates its own rhythm of wakefulness and sleep or in other terms it is _____.

Mid-1900s

Year that many psychologists believed that every behavior could be traced to external stimuli such as light or temperature.

Self-generated rhythms

The idea of this was a major step toward viewing animals as active producers of behaviors.

1. Endogenous Circannual Rhythm

2. Endogenous Circadian Rhythm

Two Kinds of Endogenous Cycles

Endogenous Circannual Rhythm

Generation of rhythm preparing for seasonal changes.

Endogenous

“generated from within”

Circannual

From Latin word circum, and annum, for “year”

Internal Mechanisms

Animals’ readiness for change in seasons come partly from this

Endogenous Circadian Rhythm

Changes and alternation to our body on a daily basis.

Carcadian

Circum for “about” and dies for “day”

Wake-sleep Rhythms

Humans generate ____.

True

True or False: We have circadian rhythms in our eating, drinking, urination, secretion of hormones, sensitivity to drugs and other variables.

False; Circadian Rhythms differ among individuals

Circadian Rhythms are the same among individuals.

Morning People (Larks)

Awakes early, quickly become productive, and become less alert as the day progresses.

Evening People (Owls)

Warm up more slowly and reaching their peak in the late afternoon or evening.

True

True or False: Humans have internal biological clock.

Approximately 24 hours

Amount of hours the brain generate wake-sleep cycle even in an unchanging environment.

About age 20

The mean preferred time of going to sleep gets later and later until about this age and then starts a gradual reverse.

Readjust or Misadjust

Our circadian rhythms generate a period close to 24 hours, but they are not perfect— we tend to _______ our internal workings depending on our lifestyle.

Light

Critical for resetting circadian rhythms. It is also a dominant zeitgeber for land animals and humans.

Zeitgeber

German term referring to stimulus that resets circadian rhythm, meaning “time-giver”

1. Exercise

2. Arousal of any kind

3. Meals

4. Temperature of environment

Other Forms/Sources of Zeitgeber

Social Stimuli

Effect of other people; weak zeitgebers; these are everyday activities that do not affect zeitgeber that much.

1. Noise

2. Temperature

3. Meals

4. Activity

Some set circadian rhythms through the following:

Jetlag

Disruption of circadian rhythms due to crossing time zones.

Internal circadian clock and External time

Travelers complain of sleepiness during the day, sleeplessness at night, depression, and impaired condition, which stems from mismatch between these

Going West

Phase-delay circadian rhythms

Going East

Phase-advanced circadian rhythms

Cortisol

Stress elevates blood levels of this adrenal hormone.

Hippocampus

Studies shown that prolonged elevations of cortisol damage neurons in this area resulting to memory impairments.

Shift Work

Individuals with irregular sleep patterns often experience variations in their sleep duration depending on the time they go to sleep.

TRUE

True or False: Night shift workers have more accidents than day shift workers.

TRUE

True or False: Working at night does not reliably change the circadian rhythm.

150-180 lux

Amount of artificial lighting most buildings use for moderate effect in resetting the rhythm.

Curt Ritcher

In 1967, he introduced that brain generates its own rhythms— a biological clock.

Biological Clock

insensitive to most forms of interference and a hardy, robust mechanism.

Suprachiasmatic Nucleus

Provides main control of the circadian rhythms for sleep and body temperature; above the optic chiasm.

Erratic

After damage to SCN, the body rhythms become _____

genetically controlled, unlearned

SCN generates circadian rhythms itself in a _____ manner

Single isolated SCN cell

Can maintain circadian rhythms although interactions among cells sharpen the accuracy of the rhythm.

TRUE

True or False: Rhythm followed the pace of donors, not the recipients.

Retinohypothalamic Path

Small branch of the optic nerve, extends directly from retina to SCN. Axons of that path alter the SCN’s settings.

Melanopsin

Special population of retinal ganglion cells that have their own photopigment that receive some input from rods and cones, but even if they do not receive the input, they respond directly to light.

Melanopsin-containing ganglion cells

Send input to the posterior thalamus, a part of the pathway producing pain in migraines.

Alternations of sleep schedules

Mutation in the genes producing PER proteins lead to ______.

Shorter than 24 hours

People with a particular PER mutation have been found to have circadian rhythm ______.

Pineal Gland

Secretes melatonin mostly at night, making is sleepy at that time. SCN regulates waking and sleeping by controlling activity levels in other brain areas including this which is an endocrine gland located just posterior to the thalamus.

Melatonin

A type of hormone that influences both circadian and circannual rhythms

Night

Time of the day when pineal gland secretes melatonin mostly, making us sleepy at that time.

Pineal Gland Tumors

People with this condition sometimes stay awake for days at a time.

2-3 hours before bedtime

When do melatonin secretion starts to increase?