IPSP & EPSP Synapse PDF

We will focus on:  Criteria for a chemical transmitter  Graded potential  Events in the Post-Synaptic Neuron (PSP).  Identify the nature of excitatory and inhibitory Postsynaptic Potentials - EPSP and IPSP  SYNAPTIC INTEGRATION  Spatial and Temporal Summation  The neurotransmitters then...

We will focus on:  Criteria for a chemical transmitter  Graded potential  Events in the Post-Synaptic Neuron (PSP).  Identify the nature of excitatory and inhibitory Postsynaptic Potentials - EPSP and IPSP  SYNAPTIC INTEGRATION  Spatial and Temporal Summation  The neurotransmitters then bind to specific receptor proteins that are part of the postsynaptic membrane  Receptor proteins have high specificity for their neurotransmitter, which is the ligand of the receptor protein. The term ligand in this case refers to a smaller molecule (neurotransmitter) that binds to and forms a complex with a larger protein molecule (receptor) Ligand-molecule that binds to another molecule  Voltage-regulated and Chemically regulated Two broad categories of gated ion channels  Voltage-regulated channels are found primarily in the axons; Voltage-regulated channels open in response to depolarization;  Chemically regulated channels are found in the postsynaptic membrane. They open in response to binding of postsynaptic receptor proteins to their neurotransmitter ligands. AXON voltage-regulated & What is this in membrane? chemically regulated The synapse - Transport where the action protein happens The next cell’s plasma membrane When the chemically regulated ion channels are opened, they produce a graded change in the membrane potential, also known as a graded potential- Depolarization produced by channels must spread decrementally to axon hillock, where the first action potentials are produced Events in the Post-Synaptic Neuron (PSP). Neurotransmitters released from pre-synaptic neurons binds to receptors on postsynaptic membrane. Some post-synaptic membrane receptors can act as ligand (chemically) gated ion channels, that is, they open in response to being bound by signal molecules. Ex. many ligand gated channels allow both Na+ & K+ to diffuse down their concentration gradients. Others allow CI- ions to travel down its concentration gradient.  Integration of input (EPSPs & IPSPs) generally occurs in dendrites & cell body, with axon serving to conduct action potentials Positive voltage shift – Negative voltage shift– excitatory PSP inhibitory PSP Excitation Inhibition Graded potentials(GP) because the magnitude of the change in membrane potential varies with the strength stimulus. The graded nature of excitatory postsynaptic potentials- EPSP The stronger triggering event, the stronger the graded potential. The spread of a GP is decremental Make a working nervous system, only two forces necessary: are excitation and inhibition. SYNAPTIC INTEGRATION The summation of EPSPs helps to determine if the depolarization that reaches the axon hillock will be of sufficient magnitude to generate new action potentials in postsynaptic neuron. Summation of graded potentials can occur in two ways: Temporal and Spatial.. Graded Potential vs Action Potentials EPSP Magnitude varies with All or none triggering event Propagated Decrement throughout (can’t perpetuate itself) membrane Triggered by stimulus Triggered by depolarization to threshold No refractory period Refractory period Occurs in specialized Occurs where there are Regions lots of Na+-gated channels