If you're seeing this message, it means we're having trouble loading external resources on our website. Show If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. Polarization is established by maintaining an excess of sodium ions (Na +) on the outside and an excess of potassium ions (K +) on the inside. A certain amount of Na + and K + is always leaking across the membrane through leakage channels, but Na +/K + pumps in the membrane actively restore the ions to the appropriate side. The main contribution to the resting membrane potential (a polarized nerve) is the difference in permeability of the resting membrane to potassium ions versus sodium ions. The resting membrane is much more permeable to potassium ions than to sodium ions resulting in slightly more net potassium ion diffusion (from the inside of the neuron to the outside) than sodium ion diffusion (from the outside of the neuron to the inside) causing the slight difference in polarity right along the membrane of the axon. Other ions, such as large, negatively charged proteins and nucleic acids, reside within the cell. It is these large, negatively charged ions that contribute to the overall negative charge on the inside of the cell membrane as compared to the outside. In addition to crossing the membrane through leakage channels, ions may cross through gated channels. Gated channels open in response to neurotransmitters, changes in membrane potential, or other stimuli. The following events characterize the transmission of a nerve impulse (see Figure 1):
Figure 1.Events that characterize the transmission of a nerve impulse.
The following four steps describe the initiation of an impulse to the “resetting” of a neuron to prepare for a second stimulation:
What is an electrical impulse in the nervous system?An electric signal
The nervous impulse is also called 'action potential'. It refers to the electric signal produced by a neuron when stimulated. This signal is then transmitted by synapses, or connections between the cells.
How does an electrical impulse move through a neuron?A nerve impulse begins when a neuron receives a chemical stimulus. The nerve impulse travels down the axon membrane as an electrical action potential to the axon terminal. The axon terminal releases neurotransmitters that ca rry the nerve impulse to the next cell.
How would you describe a nerve impulse?A nerve impulse is the relaying of a coded signal from a nerve cell to an effector (a muscle cell, a gland cell or another nerve cell) in response to a stimulus. It is the means by which a nerve cell communicates with another cell.
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