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Lecture 15

Lecture 15 - Mar 15.doc

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PSYC 342
Jens C Pruessner

PSYC 342 Lecture 15 - Mar. 15 Definition of a Rhythm: • Movement or variation characterized by the regular recurrence or alternation of different quantities or conditions Terminology: • The Mesor • The Period (Frequency) • The Amplitude • The Atrophies • The Acrometron Endogenous Biological Rhythms: • Circadian Rhythms • Occur about every 24 hours • Infradian Rhythms • Occur less often than once a day • Circavigintan, Circatrigintan rhythms • Ultradian Rhythms • Occur more frequently than once a day (e.g., pulsatile release of corticosterone) More Examples For Circadian Rhythms: • Many of these rhythms are controlled by the SCN in the hypothalamus Rhythms and Hormones: Which hormones have what type of rhythm? • • Melatonin → circadian rhythm • Cortisol → circadian rhythm • Growth hormone → circadian rhythm • Estrogen, Testosterone, LH/FSH → infradian rhythms But all of these can have other rhythms superimposed! (e.g., seasonal cortisol secretion) • • One main structure in the CNS responsible for the circadian rhythms: The suprachiasmatic nucleus • If you take out the SCN in one animal = no more biological rhythms • If you transplant to this animal the SCN of another animal = restoration of biological rhythms • But most importantly, the rhythm is restored with the rhythm of the donor, showing that the clock is present inside the SCN Circadian Rhythms: How can this internal clock coordinate the biological rhythms with the local time in the environment. The answer lies in light • SCN and Circadian Rhythms: • Light reaches the retina • Presence of cels that are responsive to light because they contain a pho- topigment called melanopsin • These melanopsin-containing cells project to the SCN through the Retino- hypothalamic (RHT) path • The SCN projects multisynaptically to the pineal gland • Activation of the pineal gland results in the inhibition of melatonin (light) • Melatonin acts on behaviour (seasonal variations of behaviour) Darkness: • • Important production of melatonin • Daily light • Inhibition of melatonin • Melatonin is thus very sensitive to “photoperiod” (i.e., the amount of daylight in a given day) Why We Sleep: • The exact function of sleep is uncertain but sleep appears to provide time for: • The body to eliminate waste products from muscles • Repair cells • Strengthen the immune system • Restore neural function • Sleep patterns change over the life span Why Do We Dream: • Fundamental process in all mammals Analyzes and consolidates information with personal significance or survival value • Freud: Dreams are a disguised form of Wish Fulfillment, to satisfy unconscious urges or satisfy conflicts • • Activation-Synthesis Theory: meaningless random signals from hindbrain to cortex during REM • Problem Solving theory: dreams give people a chance to address and review problems of the day Dreams as Reflections of Current Concerns: • Dreams may reflect ongoing conscious issues such as concerns over relationships, work, health, children • Dreams are more likely to contain material related to a person’s current concerns than chance would allow for Dreams as By-product of Mental Housekeeping: • Unnecessary neural connections in the brain are eliminated and important ones are strengthened • The brain divides new information into “wanted” and “unwanted”
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