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Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system.
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.
Summation is the adding together of these impulses at the axon hillock. If the neuron only gets excitatory impulses, it will generate an action potential. If instead the neuron gets as many inhibitory as excitatory impulses, the inhibition cancels out the excitation and the nerve impulse will stop there. [10]
Nerves that exit from the brain are called cranial nerves while those exiting from the spinal cord are called spinal nerves. The nervous system consists of nervous tissue which, at a cellular level, is defined by the presence of a special type of cell, called the neuron .
In the nervous system, a synapse [1] is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons.
Nerve conduction studies are performed as follows: [8] Two electrodes are attached to the subject's skin over the nerve being tested. Electrical impulses are sent through one electrode to stimulate the nerve. The second electrode records the impulse sent through the nerve as a result of stimulation.
A neuron, neurone, [1] or nerve cell is an excitable cell that fires electric signals called action potentials across a neural network in the nervous system. They are located in the brain and spinal cord and help to receive and conduct impulses.
The two main types of cells in the brain are neurons, also known as nerve cells, and glial cells, also known as neuroglia. [1] There are many types of neuron, and several types of glial cell. Neurons are the excitable cells of the brain that function by communicating with other neurons and interneurons (via synapses ), in neural circuits and ...