In neuroscience, an excitatory postsynaptic potential (EPSP) is a temporary increase in postsynaptic membrane potential caused by the flow of positively charged ions into the postsynaptic cell. They are the opposite of inhibitory postsynaptic potentials (IPSPs), which usually result from the flow of negative ions into the cell. A postsynaptic potential is defined as excitatory if it makes it easier for the neuron to fire an action potential. EPSPs can also result from a decrease in outgoing positive charges, while IPSPs are sometimes caused by an increase in positive charge outflow. The flow of ions that causes an EPSP is an excitatory postsynaptic current (EPSC). Neuroscience is a field of study that deals with the structure, function, development, genetics, biochemistry, physiology, pharmacology, and pathology of the nervous system, consisting of the myriad nerve pathways running throughout the body. ... Membrane potential (or transmembrane potential or transmembrane potential difference or transmembrane potential gradient), is the electrical potential difference (voltage) across a cells plasma membrane. ... An ion is an atom, group of atoms, or subatomic particle with a net electric charge. ... Inhibitory Postsynaptic Potential is commonly abbreviated to Impulses are transmitted from neuron to neuron by the release of a chemical transmitter across synaptic clefts from the synaptic vesicles along the axon to the postsynaptic receptors of another neuron. ... Postsynaptic potentials are changes in the membrane potential of the neuron that receives information at a synapse. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ...

EPSPs, like IPSPs, are additive. When multiple EPSPs occur on a single patch of postsynaptic membrane, their combined effect is the sum of the individual EPSPs. Larger EPSPs result in greater membrane depolarization and thus increase the likelihood that the postsynaptic cell reaches the threshold for firing an action potential. A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ...

Overview

EPSPs in living cells are caused chemically. When an active presynaptic cell releases neurotransmitters into the synapse, some of them bind to receptors on the postsynaptic cell. Many of these receptors contain an ion channel capable of passing positively-charged ions either into or out of the cell (such receptors are called ionotropic receptors). At excitatory synapses, the ion channel typically allows sodium into the cell, generating an excitatory postsynaptic current. This depolarizing current causes an increase in membrane potential, the EPSP. Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. ... Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cells plasma membrane, but also in the membranes of some subcellular compartments and organelles. ... Another, unrelated ion channeling process is part of ion implantation. ... Ionotropic receptor (also ligand gated ion channel) are a subclass of transmembrane receptors. ...

Excitatory molecules

The neurotransmitter most often associated with EPSPs is the amino acid glutamate, and is the main excitatory neurotransmitter in the central nervous system. Its ubiquity at excitatory synapses has led to it being called the excitatory neurotransmitter. In the neuromuscular junction, EPSPs (called end-plate potentials, EPP) are mediated by the neurotransmitter acetylcholine. However, classifying neurotransmitters as such is technically incorrect, as there are several other synaptic factors that help determine a neurotransmitter's excitatory or inhibitory effects. An amino acid residue is what is left of an amino acid once a molecule of water has been lost (an H+ from the nitrogenous side and an OH- from the carboxylic side) in the formation of a peptide bond. ... Glutamate is the anion of glutamic acid. ... A diagram showing the CNS: 1. ... A neuromuscular junction is the junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscles surface. ... The End-plate potential is a chemically induced change in electric potential of the motor end plate (the portion of the muscle-cell membrane that lies opposite the terminal of a nerve fibre at the neuromuscular junction). ... The skeletal structure of acetylcholine The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ...

Spontaneous EPSPs

The release of neurotransmitter vesicles from the presynaptic cell is probabilistic. In fact, even without stimulation of the presynaptic cell, vesicles will occasionally be released into the synapse, generating EPSPs. Bernard Katz pioneered the study of these spontaneous EPSPs (often called miniature end-plate potentials^[1]) in 1951, revealing the quantal nature of synaptic transmission. In a neuron, synaptic vesicles, also called neurotransmitter vesicles, store the various neurotransmitters that are released during calcium-regulated exocytosis at the presynaptic terminal into the synaptic cleft of a synapse. ... Sir Bernard Katz (March 26, 1911 - April 20, 2003) was a German-born biophysicist, noted for his work on nerve biochemistry. ... 1951 (MCMLI) was a common year starting on Monday; see its calendar. ... A quantum is the smallest increment into which many physical properties are subdivided. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ...

Notes

• ↑  Functionally, EPSPs and miniature end-plate potentials (mEPPs) are identical. The name end-plate potential is used since Katz' studies were performed on the neuromuscular junction, the muscle fiber component of which is commonly called the motor end-plate.

A neuromuscular junction is the junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscles surface. ... A top-down view of skeletal muscle A muscle fiber (American usage) or muscle fibre (British usage) (also technically known as a myocyte) is a single cell of a muscle. ... ...

External link

• Quantal transmission at neuromuscular synapses