PSYCHOLOGY 0505 LECTURE OBJECTIVES AND OUTLINE Spring 2014 LECTURE CELLS AND COMMUNICATION IN THE NERVOUS SYSTEM Objectives Terms and concepts to learn glial cells astrocytes oligogendrocytes glucose lactate satellite cells Schwann cells self propagation all or none response principle spatial summation temporal summation diffusion electrostatic pressure dendrites and cell body soma axon and terminals myelin nodes of Ranvier synapse presynaptic membrane events synthesis and storage neurotransmitter release exocytosis neurotransmitters synaptic vesicle reuptake enzymatic breakdown autoreceptors types of receptors postsynaptic membrane events depolarization hyperpolarization repolarization refractory periods resting potential excitatory postsynaptic potentials inhibitory postsynaptic potentials action potential sodium ions Na potassium ions K ion channels sodium potassium pump threshold would temnd ot be 155 mv but vaianrcy amond guerens is big I SUPPORTIVE CELLS sometimes are forgotten cells as a lot more to nervous system that just neurons even estimates say hat ten times as many supportive cells as neurons within the nervous system called glial cells these magic supportive cells as glue cells A Glial Cells central nervous system 1 Astrocyte looks like a large star shaped cell in place like a skeletal framework to hold all these neurons in place want them stationary as want to prevent accidental contact between neurons also deliver nutrients to neurons and remove waste products as it is the astrocyte and not neurons themselves is what is connected to blood vessels serve to thus feed and care for the neurons in this way in the past thought glucose was the critical factor for maintaining cells within nervous system but more recently even though important glucose it not the main one glucose absorbed by astrocyte and then secreted as lactate which is finally what is essential nutrient for the neurons one astrocyte can interact with several neurons in its vicinity 2 Oligodendrocyte cell that produces myelin there are two types that do this to help speed up communication within nervous system this is the myelination cell of the central nervous system as a large multi projection cell and each section of projection ends in the myelin one arm goes and wraps around a section of axon and another arm goes out and can do myelination to another neuron axon just goes at whatever is close in proximity thus segments of myelin not continuous but go in little sections B Satellite Cells Peripheral Cells peripheral nervous system Schwann cell myelination cell of peripheral nervous system that is an individual cell making every section of myelin its own individual cell with a cell body and all other normal cellular processes too II THE NEURON some types of neurons don t have to memorize most shapes are multipolar neurons most abundant most common and have dendrites extent right off the cell body unipolar neurons have cell body project off axon and has two ends as one receiving dendritic and one sending axon end bipolar neurons has a cell body in the middle and a dendrite and an axon end interneurons have more connecting function then being in path small or no dendrites across different types and locations the may they exactly function and how quickly will change a little bit A Structure of the Neuron all leads to one way communication as an electrical signal 1 Dendrites as branches on tree off of Cell Body Soma other neurons release neurotransmitters that go on to dendritic spines little bulges docking stations for the neurotransmitters one multipolar neurons probably communicates with hundreds of other neurons 2 Axon long single extension that is covered in myelin 3 Terminal Buttons Terminals the very end of the axon going out which release all the neurotransmitters comes extremely close to touching the dendritic spine without actually touching it forming small little gap between as we do not like physical content between at point where we see dendrites release neurotransmitter B Conduction of Electrical Charge Within Neuron 1 Resting Potential 2 Action Potential a all or none action potential either occurs or does not occur stimulation occurs through the entire length of the axon as a polar shift of ions from negatively charged to positively charges and back to negatively charged b polarization c self propagation once the positive charge occurs in one section of the axon this triggers the positive channels to open in the next section of axon and continues the signal down the axon C Chemical Communication Between Neurons 1 Synapse made up of three parts as the pre synaptic membrane membrane that is at the end of the axon where the terminal button terminal is the synaptic gap synaptic cleft the little space in between where chemical substances neurotransmitters released and the post synaptic membrane membrane on the dendrite often part of dendritic spine neurotransmitters released by the terminal then bind to receptors on dendrite to initiate a number of changes within that membrane that hopefully initiate an action potential down the road if enough excitatory neurotransmitter input an action potential is likely other neurotransmitters are inhibitory and their job is to hyperpolarize make more negatively charged to decrease the chances of an action potential of happening 2 Presynaptic Membrane Events a synthesis of neurotransmitters smaller neurotransmitter molecules made within terminal itself and larger neurotransmitter molecules made further put the axon within the cell body transported via microtubules down axon to terminal where they are deposited to be ready for release b storage all neurotransmitters are inside an synaptic vesicle same lipid membrane property as cell membrane itself that now encircles neurotransmitter wrapped in vesicles to aid in quick release by exocytosis and to keep from breaking down of the neurotransmitter as degradation by other enzymes in the terminal c release when action potential reaches the terminal the vesicles carrying neurotransmitters moves toward the pre synaptic membrane where they doc on a calcium channel on the membrane and the influx on calcium at the terminal is what opens a channel allowing the neurotransmitter to be released into the synaptic cleft vesicle then simply becomes a part of the membrane itself partially to keep the membrane of the cell from having a hole cell does not grow exponentially larger as the membrane begins to pinch off higher up on