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As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon. In response to a signal from another neuron, sodium- (Na +) and potassium- (K +)–gated ion channels open and close as the membrane reaches its threshold potential.
An excitatory synapse is a synapse in which an action potential in a presynaptic neuron increases the probability of an action potential occurring in a postsynaptic cell. Neurons form networks through which nerve impulses travels, each neuron often making numerous connections with other cells of neurons.
The slope of phase 0 on the action potential waveform (see figure 2) represents the maximum rate of voltage change of the cardiac action potential and is known as dV/dt max. In pacemaker cells (e.g. sinoatrial node cells ), however, the increase in membrane voltage is mainly due to activation of L-type calcium channels.
Therefore, the postsynaptic potential attenuates by the time it reaches the neuron cell body. The neuron cell body acts as a computer by integrating (adding or summing up) the incoming potentials. The net potential is then transmitted to the axon hillock, where the action potential is initiated. Another factor that should be considered is the ...
An impulse (action potential) that originates from the SA node at a relative rate of 60–100 bpm is known as a normal sinus rhythm. If SA nodal impulses occur at a rate less than 60 bpm, the heart rhythm is known as sinus bradycardia. If SA nodal impulses occur at a rate exceeding 100 bpm, the consequent rapid heart rate is sinus tachycardia ...
The stimulus is automatically decreased in steps of a set percentage until the response falls below the target (generation of an action potential). Thereafter, the stimulus is stepped up or down depending on whether the previous response was lesser or greater than the target response until a resting (or control) threshold has been established.
When an action potential arrives at an axon terminal (A), the neurotransmitter is released and diffuses across the synaptic cleft. If the postsynaptic cell (B) is also a neuron , neurotransmitter receptors generate a small electrical current that changes the postsynaptic potential .
In neuroscience, an excitatory postsynaptic potential (EPSP) is a postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential. This temporary depolarization of postsynaptic membrane potential , caused by the flow of positively charged ions into the postsynaptic cell, is a result of opening ligand-gated ion ...