PSYC 220 Week 4 Notes
PSYC 220 Week 4 Notes PSYC 220
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This 6 page Class Notes was uploaded by Lynde Wangler on Monday February 1, 2016. The Class Notes belongs to PSYC 220 at University of North Carolina - Chapel Hill taught by Meghan Jones in Spring 2016. Since its upload, it has received 10 views. For similar materials see Biopsychology in Psychlogy at University of North Carolina - Chapel Hill.
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Date Created: 02/01/16
PSYC 220 Week 4 Notes 2/1/16 Chapter 2 Synapses Clarification: food does not directly cause neurotransmitter release – amino acids that come from you diet can influence the supply of different types of neurotransmitters Ionotropic – fast, shorter-lasting effects, one effect, activated by smaller neurotransmitters Metabotropic – slower, longer-lasting effects, can have many effects, activated by larger neuropeptides (through G-protein and secondary messengers) Gap Junctions – at electrical synapses, very quick, direct flow of ions across a very small space between cells, needed in areas where synchrony is necessary (brain in early development has many of these junctions to synchronize growth and neural circuitry formation) Features of Neuropeptides: Neuropeptides Other Neurotransmitters Synthesized in the cell body Synthesized in the pre-synaptic terminal Released from dendrites, cell body, and Released from axon terminal sides of axon Released by repeated depolarization Released by single action potential Diffuse to wide area Effect on receptors of adjacent post- synaptic cell Duration of effect: minutes Duration of effects: less than a second to a few seconds Acetylcholine (Ach) – chemical from Otto Loewi’s frog heart experiment (basis of proof for chemical communication between cells); diffuse modulatory system: cholinergic originates in basal forebrain; loss of cholinergic neurons is noted in individuals with Alzheimer’s disease, which suggests that this neurotransmitter is important for learning and memory Dopamine (DA) – diffuse modulatory system: dopaminergic; 2 main pathways Mesostriatal Pathway: origin is substantia nigra and projects to the striatum; DA important for movement and motor control (Parkinson’s patients have loss of dopamine producing cells) Mesolimbocoritcal Pathway: origin is VTA (ventral tegmental area) and projects to the limbic system and cortex; abnormalities of this pathway are associated with schizophrenia and addiction; important for reward and motivation Norepinephrine (NE): diffuse modulatory system: noradrenergic; important for mood, arousal, sexual behaviors; sympathetic fibers of the body use this transmitter; 2 main pathways – Locus Coeruleus – in the pons Lateral Tegmental Area – in the midbrain Serotonin (5-HT): diffuse modulatory system: serotonergic; origin in the Raphe Nuclei; important for sleep, mood, anxiety, and sexual behavior; used in anti-depressants (SSRIs) Neurotransmitter Reuptake: neurotransmitters will either be inactivated or taken back up and recycled; transporters are membrane proteins that collect neurotransmitters for reuse; COMT – enzymes that convert excess into inactive chemicals o Serotonin – taken back up into presynaptic terminal by transporter proteins o ACh – broken down by acetylcholinesterase into acetate and choline o Excess dopamine is converted into inactive chemicals Negative Feedback from the Postsynaptic Cell: accomplished in one of two ways – o Autoreceptors – detect amount of transmitter released and inhibit further synthesis and release o Postsynaptic Neurons – respond to simulation and send retrograde transmitters to the presynaptic terminal where they inhibit further release Neuropeptides: Neuropeptide Y – anxiogenic (anxiolytic = antagonist); Substance P – pain; Orexin – hunger Hormones: chemicals secreted by endocrine glands and transported via the bloodstream to target organs where they alter activities; responsible for triggering long-lasting changes in multiple parts of the body (think puberty, for example); hypothalamus secretes releasing and inhibiting hormones that control different endocrine glands; endocrine glands can send inhibitory messages (negative feedback) to the hypothalamus to regulate hormone concentrations in the blood o Pituitary Gland (“The Master Gland”) – attached to hypothalamus; secretes releasing and inhibitory hormones that regulate anterior pituitary hormone production; synthesizes vasopressin and oxytocin which migrate to posterior pituitary o Anterior Pituitary: Growth Hormone (GH) – body growth Adrenocorticotropic hormone (ACTH) – increases steroid hormone production by the adrenal glands Thyroid Stimulating Hormone (TSH) – stimulates thyroid gland Follicle Stimulating Hormone (FSH) – promotes ovum maturation and sperm production for respective sexes Luteinizing Hormone (LH) – stimulates ovulation Prolactin – increases milk production o Posterior Pituitary: neural tissue, releases vasopressin and oxytocin (hormones synthesized in the hypothalamus) Oxytocin – uterine contractions, milk release, sexual pleasure Vasopressin – raises blood pressure, decreases urine volume o Adrenal Gland: part of HPA axis (hypothalamus-pituitary-adrenal axis); hypothalamus synthesizes and secretes CRH (corticotrophin releasing hormone) stimulates anterior pituitary to release ACTH stimulates adrenal glands to release cortisol (in rodents called corticosterone); important in stress response mechanisms, sympathetic nervous system activation o Ovary: estrogens and progesterone female sexual characteristics and pregnancy o Testis: testosterone male sexual characteristics o Kidney: Renin regulates blood pressure, contributes to hypovolemic thirst (thirst due to loss of blood volume) Endogenous – substances that are made within an organism Exogenous – substances that do not originate from within the body Drug Effects o Agonist – binds to receptor site and activates receptor like an endogenous substance would o Antagonist – binds to the receptor either at the ligand binding site or another site and blocks activation of the receptor Affinity vs. Efficacy o Affinity – the likelihood that a drug will bind with a receptor o Efficacy – the likelihood that the drug will activate the receptor o Different receptors have differing affinities for different ligands; a drug is classified as agonist or antagonist depending on the overall effect of the response Ex. How would you classify a drug with high affinity but low efficacy? – in areas where receptors are open, the drug will increase activity and in areas where the endogenous substance is not lacking, the drug will decrease activity because it will act as a competitive agonist (this will decrease activity even if all the receptors are active because the drug is less effective than the endogenous molecule would be) How Do Drugs Influence Synaptic Transmission? o Presynaptic Process: Neurotransmitter production and release, autoreceptors – limit neurotransmitter release from presynaptic terminal, neurotransmitter clearance – reuptake inhibitors o Postsynaptic Process: transmitter-receptor selective drugs (agonist or antagonist), downstream processes that regulate receptor expression or prevent cell’s ability to respond Amphetamine & Cocaine – stimulate DA synapses; increase release of DA from presynaptic terminal Methylphenidate (Ritalin) – blocks reuptake of DA at a gradual and more controlled rate; prescribed for people with ADD (we don’t know if use in childhood causes higher likelihood of drug abuse in adulthood) Some drugs of abuse have their own receptor because they are chemically similar to endogenous compounds that the human body makes and uses Cannabinoids – autoreceptors Opioids – opioid receptors 2/3/16 Chapter 4 Genetics & Evolution Is Development Shaped by Genetics or by the Environment? – Mendel (studying pee plants) was able to determine that inheritance occurs through genes, which are units of heredity with structural integrity Disposition for developing psychological disorders, weight, personality traits, success, sexual orientation What is DNA? (Basic Biology Review) o Gene – part of chromosome composed of DNA (deoxyribonucleic acid) o Chromosome – strands of DNA; exist in pairs (except XY) o Homozygous – identical pair of genes of each chromosome o Heterozygous – differing pair of genes on each of two chromosome RNA: one strand of DNA; order of bases on an RNA molecule determines the order of amino acids which then code for certain proteins regulatory functions; structure of body; enzymes that regulate chemical reaction throughout the body Dominant vs. Recessive genes – Phenylthiocarbamide (PTC) is a dominant trait for supertasters; there are dominant, recessive, and intermediate genes Sex-linked – gene is on X or Y chromosome (females: XX, males: XY); gene that controls color blindness is on the X chromosome males are more often color blind than females Sex-limited – gene is present in both sexes but active in only one; sex hormones are responsible for activation of these genes Genetic Changes: o Mutation – a heritable change in DNA (occurs through duplication or deletion) Epigenetics – the concept that genes can be turned on or off by experience; ex. rat pups born to malnourished mother show increased propensity for obesity & rat pups with low degree of maternal care show more likelihood of developing emotional stress issues How Is This Possible?? o Histones bind DNA and must be unbound from the DNA for it to be activated; epigenetic influences modify histone tails near a gene Heredity: o Heritability – degree to which a trait being passed on depends on genetics o How do we study heritability? – twin studies, adoption studies, link gene to phenotype o Environmental modification – Phenylketonuria (PKU), alter diet and there are no problems How Genes Affect Behavior – some genes control brain chemicals but other genes affect behaviors indirectly Evolution of Behavior: any gene associated with higher reproductive success will be kept in the gene pool and in greater prevalence than other genes; Artificial Selection vs. Natural Selection no evidence for Lamarckian evolution (you don’t lose it if you don’t use it; he thought that physical characteristics such as strength could be passed directly from parent to offspring); fitness (“survival of the fittest”) is measured by one’s ability to pass on genes to the next generation evolution benefits genes Brain Evolution – nutrition hypothesis; more genes active during development; study with guppies Evolutionary Psychology – study of natural selection with regards to genes that may promote certain favorable (for fitness) behaviors (ex. males have many more sexual partners than women because it takes ten minutes compared to nine months for women to pass on his/her genes) Altruistic Behavior: o Actions that benefit someone other than the person committing the action o Hard to find examples in non-human species o Kin Selection – selection for a gene that benefits the individual’s relatives 2/5/16 Chapter 4 Development of the Brain Brain Size – birth (350g), 1 year (1000g), and adult (1200-1400g) Nearly all neurons form within the first 28 weeks of conception Stages of Development: o Neurogenesis/Proliferation: cells lining the ventricles divide; either become primitive neurons or glia that migrate to other locations of remain as stem cells to continue dividing; neurogenesis in adulthood is limited to the olfactory bulb and part of dorsal hippocampus; Stem Cell Research has potential to aid Alzheimer’s and Parkinson’s diseases research o Cell Migration: chemical process guided by immunoglobulins and chemokines that guide neuronal migration; radial glia o Differentiation: axons, dendrites, and cell bodies vary in structure depending on the cell’s ultimate fate; axons grow first, during migration; dendrites and cell bodies form once the cell reaches its destination; final fate depends on what neighboring cells are doing – affects chemicals released, patterns of firing, etc. o Myelination: occurs first in spinal cord then hindbrain, midbrain, and forebrain; continues gradually throughout adolescence; vulnerable to problems introduced by experience (composed of oligodendrocytes & schwann cells) o Synaptogenesis: formation of synapses; begins before birth and continues throughout life o Neuronal Cell Death: o Synapse Rearrangement: Chemical Pathfinding by Axons: Question – Do muscles that neurons attach to determine their function or do neurons already have a predetermined function and attach to very specific regions? –Paul Weiss, 1924: regenerated a salamander limb and because it was then able to move concluded that the muscle determines the neuron (WRONG) o Roger Sperry conducted an experiment in 1943 where he cut a newt’s optic nerve and rotated its eye, but the axons still grew back to their original targets Chemoattraction – axons migrate to targets with a similar chemical gradient and then form synapses with many cells around the correct location Neural Darwinism – each target cell receives synapses from many different axons and only those that are the strongest will survive – synaptic pruning is not random o How do the Right Number of Synapses Form? Apoptosis – programmed cell death (all cells are programmed for death unless told otherwise) Nerve Growth Factor (NGF) promotes survival and activity of neurons (cancels apoptosis, periphery vs. brain) Brain-Derived Neurotrophic Factor (BDNF) – another neurotrophin that promotes survival and synaptic strength (learning and depression) Necrosis – unplanned cell death Fetal Alcohol Syndrome: condition caused by prenatal alcohol consumption characterized by hyperactivity, impulsiveness, difficulty maintaining attention, mental retardation, motor problems, heart defects, and facial abnormalities slows proliferation, inappropriate migration and differentiation, decreased synaptic transmission (possible cortical cell death) Differentiation of the Cortex – chemical gradients guide neuronal migration, but when do neurons differentiate exactly during development? – ferrets are born so immature that their optic nerve has not yet reached the thalamus SO…scientist damaged superior colliculus and occipital cortex (optical target) and auditory input on same side, leaving the other side of the brain to function normally o Results: auditory thalamus and cortex reorganized; ferret responds to a visual stimulus as if it were an auditory stimulus Fine-tuning By Experience: environmental enrichment (affects dendritic branching and overall functioning of neurons), exercise, sensory adaptations, and phantom limb
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