BIO 251 1nd Edition Lecture 5Outline of Last Lecture I. Membrane potentialII. Action potentialsIII. Neuron and the conduction of action potentialsIV. Graded PotentialOutline of Current Lecture I. IntroductionII. Synapse structureIII. Synaptic functionIV. Result of synaptic functionCurrent LectureI. IntroductionA. How is information transferred from neuron to neuron?1. The electrical signal that moves down a neuron must be passed to the next neuron2. The junction between two neurons is called a synapseII. Synapse Structure (Fig 8.2)A. Axon terminals of presynaptic neuron junction with dendrites & cell body of postsynaptic neuronB. Synapse is area of communication between neurons, with information moving from presynaptic neuron to postsynaptic neuron only.C. The postsynaptic neuron may receive input from thousands of presynaptic neurons.III. Synaptic Function (Fig 8.2; IPCD Nervous System 2, Synaptic Transmission 6)A. Action potential reaches the axon terminal of the presynaptic neuronB. which triggers the opening of voltage gated Ca++ channels and the subsequent entry of Ca++ into the presynaptic neuron.C. The entry of Ca++ into presynaptic neuron causes synaptic vesicles inside the synaptic knob to release neurotransmitters into the synaptic cleft through the process of exocytosis.D. After diffusing across the synaptic cleft, the neurotransmitters bind to receptor sites onthe membrane of the postsynaptic neuron.E. Neurotransmitters are quickly removed from synapse by1. inactivation by enzymes or by beingThese 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.2. actively taken back into synaptic knob or by simply3. diffusing away.4. This occurs to ready the postsynaptic membrane to receive another messageIV. Result of synaptic function (IPCD Nervous System 2, Synaptic Potentials 7, 8, 9)A. Excitatory Postsynaptic Potential (EPSP) occurs at an excitatory synapse (Fig 8.4a)1. Excitatory pre-synaptic neuron releases neurotransmitter2. Neurotransmitter binds to receptor on the postsynaptic membrane3. Na+ and K+ channels on postsynaptic membrane open4. Lots of Na+ flow into cell, a few K+ move out of cell5. With this net influx of positive ions into the cell, the membrane depolarizes a little, so that it is closer to thresholdB. Inhibitory Postsynaptic Potential (IPSP) occurs at an inhibitory synapse (Fig 8.5)1. Inhibitory pre-synaptic neuron releases neurotransmitter2. Neurotransmitter binds to receptor on membrane3. K+ channels on membrane open4. K+ leaves cell5. Net result is inside of cell becomes more negative relative to the outside of the cell, which is a6. hyperpolarization of the membrane so that membrane is further from thresholdC. Grand Postsynaptic Potential (GPSP) Fig 8.81. Within entire postsynaptic neuron, the sum of all EPSP and IPSP = GPSP2. Multiple rapid excitatory firings of a single presynaptic neuron can result in TemporalSummation, which causes an action potential in the postsynaptic neuron3. Simultaneous excitatory firings from multiple presynaptic neurons can result in Spatial Summation, which causes an action potential in the postsynaptic