Neurophysiology Notes Exam 3 - Neurophysiology Exam 3...

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Unformatted text preview: Neurophysiology Exam 3 Circadian rhythms, EEG, Consciousness and Sleep 1. What is the function of the Zeitgeber in biological rhythms and what is a free- running rhythm? Rhythms are considered free-running when they are in the absence of a Zeitgeber. Rhythms are present in body temperature, sleep-wake cycles, body electrolytes, hormones, susceptibility to disease etc. Rhythms are entrained by one or more Zeitgebers. 2. What evidence suggests that the SCN is the master circadian oscillator in the brain? The suprachiasmatic nucleus appears to be the master oscillator. Cells maintain rhythm in culture, in absence of neural connections. Serotonergic input comes from the raphe nuclei (involved in wakefulness) . There are also some cells within the suprachiasmatic nucleus that secrete vasopressin. The number of vasopressin containing cells in SCN decrease with aging especially in Alzheimer disease patients. Vasopressin is not the oscillator for sleep-wake rhythms. FROM THE BOOK Within the eye there are receptors that lie in the outer nuclear layer of the retina and they project to the suprachiasmatic nucleus of the hypothalamus. The SCN functions as the site of circadian control of homeostatic functions generally. The most convincing evidence of the SCN as the master biological clock is that its removal in experimental animals abolishes their circadian rhythm of sleep and waking. I t also controls other functions that are synchronized with the sleep wake cycle, including body temperature, hormone secretion, urine production, and changes in blood pressure. Activation of the SCN leads to its axons that synapse onto preganglionic sympathetic neurons in the lateral horn of the spinal cord. Eventually this leads to stimulation of the pineal gland. The pineal gland synthesizes the sleep promoting neurohormone melatonin and secretes it into the blood stream. Melatonin synthesis increases as light decreases. In older individuals the pineal gland calcifies perhaps explaining why older people sleep fewer hours and are more often afflicted with insomnia. - What are some of the genes that are involved in circadian rhythms? In fruit flies you have the per mutants, instead of having 24 hour cycles, move to either 19 or 29 hour cycles depending on the mutation that they have. If you get rid of the gene altogether then fruit flies do not have a circadian rhythm. 3. Understand how melatonin is produced and understand its role in rhythms in man. Discussed in question 2. 4. What cellular mechanisms produce the EEG and how is it measured? Elect roencephalogram is the recording of elect rical activity occurring on the surface of the brain. The EEG is measured in Hz and it’s amplitude is measured in m V....
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This note was uploaded on 05/20/2008 for the course NEURO 5125 taught by Professor Bales during the Spring '08 term at Western University of Health Sciences.

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Neurophysiology Notes Exam 3 - Neurophysiology Exam 3...

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