PSYCH 2210 1st Edition Lecture 4 Outline of Last Lecture II. Nature and NurtureIII. The Genetic CodeIV. Genes and BehaviorV. The Human Genome ProjectVI. Heredity: Destiny or Predisposition?a. Genes and Individualityb. Heredity, Environment and VulnerabilityVII. In PerspectiveVIII. Drawing ConclusionsOutline of Current Lecture I. The Neuron DoctrineII. Cells of the BrainIII. 4 Neuron Zonesa. Inputb. Integrationc. Conductiond. OutputIV. Structure of the NeuronV. Electrical SignalingVI. Reasons for differential distribution of ionsa. Selective Permeabilityb. Diffusionc. Electrostatic Pressured. Sodium-Potassium PumpVII. SummaryCurrent LectureI. The Neuron Doctrinea. (1) The brain is composed of independent cells b. (2) Information is transmitted from cell to cell across synapsesc. Neurons (nerve cells) are the most important part of the nervous systemd. Glial cells provide support for neurons and also participate in information processing.II. Cells of the Brain (Roles) These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Astrocytes: scar tissue, line capillaries of blood-brain-barrier, provide nutrients, source of stem cells, neurotransmitter uptakeb. Microglia: immune function, phagocytosisc. Oligodendrocytes: provide myelin around axons in the CNS (spinal cord and brain) and appear white because of the surrounding myelind. Schwann cells: provide myelin around axons of peripheral nervous system (other regions of the body besides the spinal cord and brain, similar to oligodendrocytes)III. 4 Neuron Zonesa. Input zone: receives info from other cells through dendritesb. Integration zone: cell body (soma) region where inputs are integratedc. Conduction zone: single axon (nerve fiber) conducts output info away from the cell body as an electrical impulse. d. Output: axon terminals at the end of the axon communicate activity with the other cells. e. *note: neurons classified by shapes will NOT be on the testIV. Structure of the Neurona. Despite some variation, neurons have the same basic structureb. Consist of cell body, axon & dendrites, myelin sheath, axon terminals (terminal buttons), and nodes of Ranvierc. Cell body (soma): contains the nucleus and cellular organelles for production of proteins, macromolecules. d. Axons: carry electrical signals (action potential) away from the somae. Dendrites: carry electrical signals towards somaf. Myelin Sheath: provides insulation for axong. Nodes of Ranvier: unmyelinated sections of axonh. Axon terminals: (terminal buttons) contain vesicles filled with neurotransmitters. V. Electrical Signalinga. Resting membrane potential, action potential, post-synaptic potential b. Signal processing: neurons send and receive electrical and chemical signals. It is always unidirectional. c. Resting membrane potential—difference in electrical charge across the membrane when the neuron is at rest. d. Hodgekin & Huxley (1952)—developed a mathematical model fro how electrical signals (action potentials) are produced and transmitted down the axon. i. Won the Nobel Prize. ii. Described the flow of ions. iii. Results= the inside of a neuron is negatively charged. iv. Differential distribution of ions (electrically charged particles are present here) e. Important Definitionsi. Polarized: difference in electrical charge between the inside and the outside of the cell (can become more or less polarized) ii. Ion: electrically charged molecules1. Anion: negative charge, cation: positively charged. iii. Ions are dissolved in intracellular fluid, or cytoplasm, and are separated from the extracellular fluid by the cell membrane, a lipid bilayer. iv. Electrons: negative charged, protons: positively charged.VI. Reasons for Differential Distribution of Ionsa. Selective permeabilityi. Potassium ions (K+) more freelyii. Sodium ions kept outsideiii. Why??--> iv. Ion channels: open for K+ and closed for Na+ for resting v. Potassium ions do not eventually even outvi. **ION CHANNELS REGULATE FLOW OF IONS1. Gated channels: sodium ions (Na+) kept outside2. Selectively permeable channels: Potassium ions (K+) concentrated inside (we’ll see why)3. Nodes of Ranvier: location of channels on unmyelinated parts of axon. *NOT ion channel, just where they’re located. b. Diffusioni. Ions move from high concentration to a low concentration in order to create equilibriumii. Na+: concentrated outside, cant diffuse inside because the channels are closed. iii. K+: concentrated inside, moves outside, but the other force moves K+ right back in. c. Electrostatic Pressurei. Ions of similar charges repelii. Ions of opposite charges attractiii. Na+ attracted to the inside of the neuron but cannot enter due to the closed channels. iv. K+ attracted to the center and can enter freely but monitored by diffusion. d. Sodium-Potassium Pumpi. “Leaky” channels: permit a few Na+ ions to enterii. Na+/K+ pump: exchanges 3Na+ ions from inside for them for 2K+ ions from inside (keeps the inside negative at all times)VII. Summarya. Na+ ions under pressure to move inside due to i. Diffusion (concentration gradient), electrostatic