Exam 4 Study Guide Sleep Circadian rhythms there are many circadian rhythms for many processes in the body and the brain o Awareness o Body temperature o Hormone levels Growth hormones Cortisol a glucocorticoid how awake you are Activity is very easy to monitor especially in rodents that like to run at night Revolutions of the wheel produce a mark on a strip of paper to show when the animals run Analysis of activity shows that there is a free running or endogenous rhythm that is entrained by light or some other cue o The endogenous rhythm last a little longer than 24 hours Jet lag traveling from west to east can induce a jet lag your international clock does not match the external zeitgeber o Takes a while to resynchronize o Traveling from east to west there is less jet lag o Internal clock tends to run long o Easier to stay up late and sleep in late Two major brain structures control circadian rhythms o Superchiasmatic nucleus in hypothalamus Receives input directly from retina The retinal ganglion cells do not receive input from rods or cones but contain their own photopigment melanopsin o Pineal gland which secretes melatonin Controlled by the sympathetic portion of the autonomic nervous Secretes melatonin at night Affects seasonally breeding mammals as the hypothalamus becomes very sensitive to the negative feedback from gonad hormones In humans may play a role in the timing of sleep Circadian rhythm involves a feedback loop in which proteins are first made and then combine Combined protein called a dimer for two proteins inhibits the production of its component proteins Dimer degrades and process begins anew Ultradian rhythms less than a day Circannual rhythms follow the course of a year Different stages of sleep use electrodes on surface of scalp to measure electrical potentials generated by brain o EGG electroencephalogram o REM rapid eye movement o SWS slow wave sleep Young adults show a progressive lengthening of REM sleep while older adults often are awakened during sleep Four areas for sleep and arousal o Basal forebrain Generates slow wave sleep Releases GABA in tuberomammilary nucleus in the hypothalamus GABA in an inhibitory neurotransmitterreduces brain activity Anesthetics work by making GABA receptors more sensitive o Brainstem System that controls wakefulness Reticular formation runs the length of the medulla and projects to most of the rest of the brain Responsible for maintaining alertness and arousal orienting response Locus coerulus involved in vigilance Raphe Nuclei inhibit the reticular formation and promotes sleep or drowsiness o A region of the pons that controls REM sleep Part of reticular formation in the pons Record PGO waves in the EEG These waves of electrical activity during REM sleep begin in the Pons travel to the lateral geniculate then on the occipital cortex REM sleep inhibited by activity of the raphe nuclei o Hypothalamus Neurons that use the neuropeptide hypocretin are found in the lateral hypothalamus and project into other brain areas involved in sleep The hypocretin neurons may act as a switch that controls whether we are awake in SWS or in REM sleep Narcoleptics lose their hypocretin neurons Sleep disorders o Insomnia inability to sleep a normal amount of time Onset inability to get to sleep Maintenance inability to stay asleep o Sleep apnea stop breathing during sleep o SIDS have infants sleep on back instead of stomach reduce SIDS by 44 Stages of sleep o Awake medulla o Slow wave basal forebrain o REM Pons o Cortical hypothalamus Eating 70 of calories go to basal metabolic rate About 14 of caloric intake is used by the brain Rate increased with weight but decreases with age o Performance increases glucose level until glucose gets too high then performance decreases junk food Glucose is the only fuel for the brain The rest of the body can use glucose for fatty acids Insulin is needed for the body both use glucose and to store it as glycogen o Insulin is created by the pancreas hypothalamic nuclei involved in eating behavior o Ventromedial hypothalamus don t eat o Lateral hypothalamus says eat Feedback pathways for eating Gherlin Growth releasing hormone apatite stimulant If Leptin is high you want to turn on ventral medial hypothalamus it signals fat opposite of Ghrelin When Leptin is on want to turn off Ghrelin and vice versa Stress plays a role in hypothalamus Stress increases glucocorticoids Fluid in the body o Most of the fluid is within cells o Some fluid is between cells and in the blood o A little fluid is in the cerebral ventricles Sports drinks add salt to compensate for the loss during sweating Hyponatremia from too much water o Nausea headache confusion lethargy fatigue loss of appetite restlessness and irritability muscle weakness spasms or cramps seizures Hypovolemic thirst baroreceptors in major blood vessels detect any pressure drop from fluid loss Osmosensory osmosensory neurons in the brain detect any increased osmolality of extracellular fluid Three key components o Hypothalamus o Pituitary o Adrenal glands Vasopressin released pituitary acts on kidneys Kidneys release rein to constrict blood vessels activate adrenal and provide feedback to subfornical organ Adrenals lease aldosterone to retain sodium Brain Development Zygote undifferentiated single egg Development specification genes Layer formation outer layer ectoderm Become specialized by turning genes on and off Stages of neural development o Proliferation cell division o Migration neuroblasts eventually distorts into ventricles o o Differentiation dendrites axons synapses becomes a neuron Growing axon CMA cell adhesion molecules Target neurotrophic factors NGF nerve growth factors BDNF brain derived neurotrophic factor Pruning and cell death Ends functional cell or not This stage overlaps with three Myelination doesn t occur until connections are made o Timing o Early spinal cord reflexes o Late proliferation Cerebellum 2 yrs Olfactory bulb life Dentate gyrus of hippocampus life o Differentiation Cerebral cortex visual to prefrontal o Early synapses between motor neurons and muscles Neurons stop peliferating forever Visual cortex develops first year Prefrontal cortex develops through adolescence Rats loss of neurons between puberty and adulthood in medial prefrontal cortex and in amygdala Both rats and humans synapses are lost in prefrontal cortex myelination increases Adult brain changes o Proliferation in 2 brain areas only o No long axon growth o Grow and