Dr. Oddo's BIO 467 Week 2 Notes
Dr. Oddo's BIO 467 Week 2 Notes BIO 467
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This 5 page Class Notes was uploaded by Mikayla Huber on Tuesday August 23, 2016. The Class Notes belongs to BIO 467 at Arizona State University taught by Dr. Oddo in Fall 2016. Since its upload, it has received 7 views. For similar materials see Neurobiology in Biology at Arizona State University.
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Date Created: 08/23/16
BIO 467 Neurobiology: Dr. Oddo; Aug 23 & 25 Aug 23 Know these four scientists Cell Theory The cell is a fundamental unit of structure, function, and organization in all living organisms. Robert Hooke ~ 1665 Reticular Theory The nervous system is a single, continuous network. Camillo Golgi Neuron Doctrine The nervous system is composed of many individual units. This was proven to be correct by electron microscopy. Santiago Ramon Sir Charles Sherrington came up with the term synapse. The nervous system has two classes of cells: Neurons and Glial (Neuroglia or Glia) Neurons – neurons have many different shapes depending on where they are and what their job is. Components Description Function Cell body Main part of cell. Basic cell functions Contains nucleus and organelles Dendrites Short, branched extensions Receive input from other neurons Axon One per neuron, but it can Send information branch Axon hillock Site where axon originates Where action potentials originate Synaptic terminal End of axon Contains and releases neurotransmitters BIO 467 Neurobiology: Dr. Oddo; Aug 23 & 25 Know these morphological specializations: The cell body (Soma or Perikaryon) The axon Carries information away from the cell body Can be micrometers or meters long If many axons lead away from a body and attach to multiple post-synaptic neurons, the neuron diverges. The dendrite Delivers information to the cell body Has a high content of ribosomes If many dendrites attach to a single cell body, the neuron converges. Neurons generate and carry electrical signals They create action potentials and have specialized parts for synaptic communication They are post-mitotic After they are formed they do not replicate or reproduce themselves Neurons can be classified by: 1. Anatomical location 2. Shape or morphology 3. Neurochemical properties 4. Electrophysiological parameters 5. Connectivity 6. Gene Expression BIO 467 Neurobiology: Dr. Oddo; Aug 23 & 25 Glial – Supports the neurons 1. Provides structural support for the neurons 2. Insulation – limit the spread of neural activity 3. Myelinate Myelin a lipid rich coating axons. Increases the speed of transmitted information. Nodes of Ranvier are gaps in the myelination of axons. 4. Modulate neurotransmitter levels 5. Regulate metabolic components and ion levels 6. Immune function – destroys and clears debris and forms scars 7. Some populations act as stem cells Astrocytes Supportive environments for neurons Regulates ion homeostasis, metabolic support, blood flow, synaptic transmission Oligodendrites Form myelin sheaths around CNS fibers Microglia Mediates immune responses Actively probes and senses the environment Clears debris following an injury Secretes signaling molecules that modulate inflammation and influence cell survival or death Schwann Cells Can myelinate a single axon or create a Remak Bundle (many axons bundled together). Unlike neurons: Glia cells retain their ability to divide Glia cells don’t have axons, dendrites and don’t create action potentials Neuronal tracing Anterograde Following a cell from the body to the termination point. Retrograde Following a cell from the termination point to the body. BIO 467 Neurobiology: Dr. Oddo; Aug 23 & 25 Aug 25 Nernst Equation – Used to calculate the electrochemical equilibrium and resulting membrane potential when only one ionic species is present. At room temperature Ex = the equilibrium potential for any ion X R = the gas constant = 8.314 Joules per Kelvin per mole T = the absolute temperature in degrees Kelvin (K = °C + 273.15) z = the valence (electrical charge) of the permeant ion F = the Faraday constant (the amount of charge in one mole of a univalent ion) = 96485 C.mol (Coulombs per mole) Goldman Equation – The dependence of membrane potential (Vm) on ionic permeability and concentration Vm = membrane potential For Dr. Oddo’s class you do NOT need to memorize these two equations, they will be provided. Electrical Signals By regulating the flow of ions across the plasma membrane, neurons generate a negative potential, the resting membrane potential. At rest the membrane is mostly permeable to potassium ions. During an action potential the membrane’s charge changes to positive and become permeable to sodium ions. BIO 467 Neurobiology: Dr. Oddo; Aug 23 & 25 Types of electrical signals Resting membrane potential Neurons generate a constant voltage across the membranes at rest It’s typically between -40 Vm and -90 Vm (hyperpolarized) Receptor potential Becomes activated due to outside sensory information (touch, smell, etc.) They are graded, the size of the potential is determined by the size of the stimulus Synaptic potential Communications between neurons at synapses They are graded just like receptor potentials Action potential Generated by receptor or synaptic potentials They are self-sustaining and do not decay as they travel They are all-or-none Once the stimulus passes the threshold an action potential occurs and the size is unaffected by the size of the stimulus. If the size of the stimulus increases the size of the action potential does not change, but the number of action potentials increases. Ohm’s law V = IR V = voltage, V Potential energy I = current, Ampleres Movement of ions R = resistance, Ohms Resistance of ion movement Passive electrical signals – small currents that decay as they travel because axons are not good conductors. Ions produce electrical signals through: Chemical forces Diffusion through a permeable membrane Electrical forces As ions diffuse a change in the charge is created Only a small number of ions are needed The change in the charge causes the ions to be pulled back across the membrane Net movement across the membrane will stop when the electrical and chemical forces are balanced (Electrochemical equilibrium)
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