Psyc 362Class Notes for Exam 1--Chapter 22/3/15Nerve-Peripheral neural structure that contains a large number of Axons. It can be both (or just one) motor or sensory.Neuron internal structures:● organelles contained within cytoplasm [Nucleus, Endoplasmic reticulum-in charge of protein production, ribosomes-aid in protein protection, mitochondria, golgi apparatus]● Membrane-consists of lipid molecules, defies outer boundaries of cell, contained multitude of molecules that serve different functions (receptors, channels, transporter, etc).● Mitochondrial-extracts energy from nutrients and creates ATP● nucleus-contains genetic materials in the form of chromosomes (strands of DNA with associated proteins which carry genetic information) which is composed of DNA (long complex macromolecules of 2 interconnected neural strands and associated proteins. ● neurotransmitters-produced by neuron, mostly in the soma and need to be transported down the cell. Microtubules and neurofilaments are capable of such transportation down the axon.○ Axoplasmic transport-active process of propelling substances along microtubles (long strands of bundles of protein filaments arranged around a hollow core) that run the length of the axon. ● enzyme-molecule that controls a chemical rxn, combining or breaking apart a molecule.supporting cells (CNS): since neurons have high metabolic rates, they use supporting cells to supply nutrients to sustain themselves. ● Neuroglia-provide physical support, control nutrient flow, and are involved in phagocytosis (engulfing toxic/debris to remove from environment)1. Astrocytes-physical support, removes debris, becomes scar tissue and transports nutrients to neurons. May reproduce if there is an injury in order to fill space.2. microglia- phagocytosis and involvement in brain immune function3. oligodendroglia- physical support and form of myelin sheath around axons in brain (CNS)4. Schwann cells- form myelin for PNS● myelin-the layer around axon that specifically function to insulate the axon and accelerate the rate of action potential. Is formed by Oligodendroglia in CNS and Schwann cells in PNS (different formation method in these)Blood-Brain Barrier: there is a semi permeable barrier between the CNS and neural tissue thatis, in part, formed by cells in walls of the brains capillaries. It makes it so not all substances in the blood can reach the brain, which is necessary to keep certain toxins out. There are different levels of passivity throughout the barrier. ● Capillaries in body/PNS have more open gaps s opposed to those in the brain/CNSCommunicaiton within neurons: Action Potential● nerve cells are specialized for communicating with electrochemical signals/conduction. ○ Dendrites receive chemical message, chemical messengers activate receptors on dendritic membrane, and the receptors then activate the opening of ion channels which can alter membrane potential. The result can be state of A.P. andis propagated down the membrane of the Axon and causes a release of neurotransmitters from the terminal buttons.○ When the action potential reaches the terminal buttons, the release of neurotransmitters may produce an effect on the membrane of adjacent cells, connected by a synapse. This effect can be inhibitory or excitatory.● Electrical changes in cell can be measured by taking different formes of charges or potential across the membrane. Resting potential● use giant squid axon in seawater in recording chamber to measure resting potential using glass microelectrode to be inserted into axon. the voltage measures -70mV inside with respect to outside. To maintain resting p. the cell must work to maintain differences between inside and outside of cell in which the inside is more negative than the outside. ● “the wall” neuronal membrane with a number of channels inbedded into it● “the players” Ions [Na+, K+, Cl-, proteins within the cell (not ion)] are charged molecules (cations are positive, anions are negative). ○ Voltage dependent ion channels-in the wall, open or close depending on whether -70mV changes. ● to maintain RMP, (resting membranepotential) Na-K pumps must be active, Forces effecting change in charges:● Electrostatic pressure- attractive andrepulsive forces of charged particles● Diffusion- tries to even out theconcentration of molecules inside and outof membrane. ● relative ion concentration across the axonmembrane is while resting is shown →○ at rest, K+ can leave cell, causingthe exterior of the cell membraneto be slightly higher in charge than the inside○ depolarizing makes the inside of the cell less negative, which can generate an Action Potential.Action Potential--the stereotyped change in membrane potential ● if RMP moves past threshold, membrane potential quickly moves to +40mV and then returns to resting.The AP depends on ion movement across the membrane. ● AP has an ionic basis (as seen in picture above!): Na+ in upswing of spike (both forces persuade) and K+ out in response for downside of spike.● When membrane becomes depolarized and reached threshold, voltage dependent ion channels open to allow ion movement and further changes of the membrane potetial down the axon. 5 phases of AP:1. resting2. threshold3. rising (Na+ channel opens and Na+ ions enter cell)4. falling (K+ channels open next so K+ can leave the cell, producing hyperpolarization.5.