Neuronal potentials excitatory postsynaptic

Figure 5.2 Temporal summation. Multiple excitatory postsynaptic potentials (EPSPs) produced by a single presynaptic neuron in close sequence may add together to depolarize the postsynaptic neuron to threshold and generate an action potential.

Figure 5.3 Spatial summation. Multiple excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs) produced by many presynaptic neurons simultaneously may add together to alter the membrane potential of the postsynaptic neuron. Sufficient excitatory input (A and B) will depolarize the membrane to threshold and generate an action potential. The simultaneous arrival of excitatory and inhibitory inputs (A and C) may cancel each other out so that the membrane potential does not change.

Imon, H., Ito, K., Dauphin, L. McCarley, R. W. (1996). Electrical stimulation of the cholinergic laterodorsal tegmental nucleus elicits scopolamine-sensitive excitatory postsynaptic potentials in medial pontine reticular formation neurons. Neuroscience 74, 393-401. 

FIGURE 6-1 Path of excitation in a simplified spinal reflex that mediates withdrawal of the leg from a painful stimulus. In each of the three neurons and in the muscle cell, excitation starts with a localized slow potential and is propagated via an action potential (a.p.). Slow potentials are generator potential (g.p.) at the skin receptor the excitatory postsynaptic potentials (e.p.s.p.) in the interneuron and the motoneuron and end-plate potential (e.p.p.) at the neuromuscular junction. Each neuron makes additional connections to other pathways that are not shown. 

Activation of ionotropic mechanisms creates postsynaptic potentials. An influx of cations or efflux of anions depolarizes the neuron, creating an excitatory-postsynaptic potential (EPSP). Conversely, an influx of anions or efflux of cations hyperpolarizes the neuron, creating an inhibitory-postsynaptic potential (IPSP). Postsynaptic potentials are summated both... 

Fig. 4. Electrophysiological traces from a prefrontal layer V showing the response to nearby electrical stimulation of corticocortical afferents. Stimulus artifact appears as a vertical line. (1) The fast evoked excitatory postsynaptic current (evEPSC) follows immediately, as depicted by the arrow. Under normal conditions, stimulation at 0.1 Hz evokes only a fast evEPSC. (2) However, after the application of a psychedelic hallucinogen (3 pMDOI, 15 min), stimulation at this frequency almost always evokes both a fast evEPSC and a late evEPSC, as depicted by the arrows. The neuron is voltage-clamped close to its resting potential and was not directly depolarized by DOI. It is not known what type of glutamate release accounts for the late evEPSC. Traces are averages of 10 sweeps taken during each of the conditions.

Neurotransmitters can be classified as excitatory or inhibitory, depending on the nature of the action they elicit. Stimulation of excitatory neurons causes a movement of ions that results in a depolarization of the postsynaptic membrane. These excitatory postsynaptic potentials (EPSP) are generated by the following (1) Stimulation of an excitatory neuron causes the release of neurotransmitter molecules, such as norepinephrine or acetylcholine, which bind to receptors on the postsynaptic cell membrane. This causes a transient increase in the permeability of sodium (Na+) ions. (2) The influx of Na+ causes a weak depolarization or excitatory postsynaptic potential (EPSP). (3) If the number of excitatory fibers stimulated increases, more excitatory neurotransmitter is released, finally causing the EPSP depolarization of the postsynaptic cell to pass a threshold, and an all-or-none action potential is generated. [Note The generation of a nerve impulse typically reflects the activation of synaptic receptors by thousands of excitatory neurotransmitter molecules released from many nerve fibers.] (See Figure 8.2 for an example of an excitatory pathway.)... 

Agonist binding modifies the state of the neurons through two main mechanisms. First, movement of cations through the chaimel causes a depolarisation of the plasma membrane (which results in an excitatory postsynaptic potential in neurons), as well as the activation... 

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