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Lecture 9

Lecture 9 - Behavior Rhythms & Sleep and Emotions

5 Pages
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Department
Psychology
Course Code
PSY290H1
Professor
Franca Placenza

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Biological Rhythms
1.Our behavior seems to occur rhythmically (circadian rhythms)
oAlso can depend on the time of day and species in question
2.Circadian rhythms - functions of a living organism that display a rhythm of about 24
hours
oEX = sleep-wake, activity, hormone levels, body temperature
3.Circadian rhythms are even maintained without external cues
oHamster is ideal animal model to study
Studied with an actogram
External cues help animal determine when to start running
We can manipulate the stimulus (light) to measure hamster's
circadian rhythm
Implies that the animal has an internal biological clock
Light an example of a zeitgeber ("time giver") >> the
cue that an animal uses to synchronize with the environment
oHumans not so much
Neurobiology of Circadian Rhythms
4.Suprachiasmatic nucleus (SCN) of the hypothalamus
oCan synchronize all the rhythms
oSuper biological clock
oLesions of this area abolish circadian rhythms in animals (no pattern
anymore)
5.When SCN is lesioned in hamsters under constant light condition, there is
absolutely no pattern in their rhythm of running
6.Transplantation of SCN restores rhythmicity
7.Hamster mutation discovered called tau mutation
oNormal hamster circadian rhythm = 25 hrs
oHamster with tau mutation circadian rhythm = 20hrs
8.After hamster with normal circadian was implanted with SCN with mutation, the
hamster's circadian rhythm reduced to 20 hrs (the same as the host's)
SCN receives input from the visual system
oCircadian rhythms are entrained by light
oIn mammals, light info goes from eye to the SCN via the retinohypothalamic
pathway
9.90% of ganglion cells send axons to lateral geniculate nucleus
10.Specialized retinal ganglion cells projecting to SCN contain the light-sensitive
pigment,
11.Blindness of any sort in animals doesn't affect their SCN and light is able to entrain
them
12.The metabolic activity of the SCN is clock-like
oDark >> low activity of SCN
www.notesolution.com
Represented by light image because not a lot of glucose is taken up by
cells
oLight >> high activity of SCN
Represented by a dark image because cells are active and take up a lot
of glucose
Molecular Clock
13.SCN is controlled by specific clock genes
oTau = Tau protein
oPer = Per protein
oCry = Cry protein
Production of these proteins is on a clock-like rhythm
14.Transcription factors tell a portion of the DNA to start transcribing into RNA and
RNA is used to make proteins
15.Clock and cycle proteins form dimer and act as transcription factors
oAble to penetrate cell nucleus
16.Per, tau, and cry for a protein complex >> inhibits transcription of per and cry
oNo new proteins are made until the first set degrades and the cycle begins
again (every 24 hrs approx)
17.Light can entrain the molecular clock
oSpecialized ganglion cells detect light and release glutamate onto SCN cells
18.Glutamate initiates a cascade of events and act as a transcription factor that allow
genes to transcribe and proteins to be produced
oProbably through second messengers
Sleeping and Waking
19.Follows circadian rhythm
20.Can be trained by the light-dark cycle
21.When time cues are provided, free-run rhythms form
oTime cues such as lights, food, jobs, and alarm clocks
22.(FINSIH LATER)
23.Physiological functions are closely related to our sleep-awake cycle
oTemperature decreases when we sleep
24.Are multiple oscillators and a master clock
Measuring brain activity during sleep and waking
25.Brain activity is measure with EEG (electroencephalography) >> measures gross
electrical activity of the cortex
26.Brain activity (waves) can vary in frequency and amplitude
Stages of Sleep
www.notesolution.com

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Description
Biological Rhythms 1. Our behavior seems to occur rhythmically (circadian rhythms) o Also can depend on the time of day and species in question 2. Circadian rhythms - functions of a living organism that display a rhythm of about 24 hours o EX = sleep-wake, activity, hormone levels, body temperature 3. Circadian rhythms are even maintained without external cues o Hamster is ideal animal model to study Studied with an actogram External cues help animal determine when to start running We can manipulate the stimulus (light) to measure hamsters circadian rhythm Implies that the animal has an internal biological clock Light an example of a zeitgeber (time giver) >> the cue that an animal uses to synchronize with the environment o Humans not so much Neurobiology of Circadian Rhythms 4. Suprachiasmatic nucleus (SCN) of the hypothalamus o Can synchronize all the rhythms o Super biological clock o Lesions of this area abolish circadian rhythms in animals (no pattern anymore) 5. When SCN is lesioned in hamsters under constant light condition, there is absolutely no pattern in their rhythm of running 6. Transplantation of SCN restores rhythmicity 7. Hamster mutation discovered called tau mutation o Normal hamster circadian rhythm = 25 hrs o Hamster with tau mutation circadian rhythm = 20hrs 8. After hamster with normal circadian was implanted with SCN with mutation, the hamsters circadian rhythm reduced to 20 hrs (the same as the hosts) SCN receives input from the visual system o Circadian rhythms are entrained by light o In mammals, light info goes from eye to the SCN via the retinohypothalamic pathway 9. 90% of ganglion cells send axons to lateral geniculate nucleus 10.Specialized retinal ganglion cells projecting to SCN contain the light-sensitive pigment, 11.Blindness of any sort in animals doesnt affect their SCN and light is able to entrain them 12.The metabolic activity of the SCN is clock-like o Dark >> low activity of SCN www.notesolution.com
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