How is a nerve impulse carried?

Answer 1

Nerve impulses are signals carried along nerve fibers. These signals convey, to the spinal cord and brain, information about the body and about the outside world. They communicate among centers in the central nervous system and they command your muscles to move.

Nerve impulses are electrochemical events. Observed as an electrical event, a nerve impulse is called an action potential (AP) because it involves a change in electrical potential that moves along the nerve cell. It can be measured as an electrical potential difference between the inside and the outside of a nerve fiber. That option has not been generally available to the beginning student. Instead, the nerve impulse has ordinarily been observed as a voltage change along the outside of the sciatic nerve of the common grass frog, Rana pipiens.

Rana pipiens and its relatives have long been favorite subjects for introducing students to the physiology of nerve and muscle. For serious investigations, use of frogs will continue to be justified, but the consumption of this resource for routine teaching ought now to be reduced, for at least three convincing reasons:

1. Computing power has become so effective and so generally available that some essential concepts of nerve electrophysiology can as well or better be conveyed by simulation and example rather than by use of live material.
2. In the frenzy of trying to make the real specimen perform properly during a student exercise, important ideas are often omitted or are lost because of equipment failure or operator ineptitude.
3. Frog populations worldwide appear to be diminishing at an alarming rate, and biologists, of all people, ought not abet this decline.

This instructional module shows, by illustrations and text, some of the essential features of nerve impulse propagation, a phenomenon that many students find especially difficult to visualize. The lesson is based on observations made during external recording from the sciatic nerve of Rana pipiens.

Topics 1-11 afford a review of some aspects of single-neurone transmembrane characteristics. With this background,the student is prepared to appreciate the whole-nerve behavior illustrated in topics 12-30. The latter are based on actual cathode-ray-oscilloscope records of the type obtained by students in a laboratory course.

this info was taken off http://www.bio.fsu.edu/easton/intro.html

Answer 2

Transmission of a nerve impulse is called an action potential and is conducted by a part of the nerve cell, or neuron, that is like a long cord and is called an axon. At the end of the axon are axon terminals that lead to a synapse. This is where neurotransmitters, chemical messengers, transfer the impulse to another neuron (interneuron), a muscle (neuromuscular junction), or a gland (target cell).

Yes, it is True that there are some neurons that extend from the hip to the toe that are one meter in length - while at the same time maintaining the standard Cell size in the order of microns. This means that these Cells are a million times longer than they are 'around'.

Answer 3

A neural impulse is transmitted via neurotransmitters, which are chemicals which move from the end of one neuron to the beginning of the next one.

This happens as follows: there is a gap between neurons called a SYNAPSE (a very small space between the end of one neuron and the beginning of another). An impulse traveling within the first (initiating) neuron (along its axon) which has reached that presynaptic neuron's axon terminal causes voltage-gated Calcium ion pores to open in that axon terminal, allowing Calcium ions into that axon terminal, which causes small bags (vesicles) of chemicals (neurotransmitters) to move to and merge with the cell membrane at the end of that axon terminal (which is the beginning of the synapse), releasing the neurotransmitters into the space between two neurons (the synaptic cleft), where they DIFFUSE quickly over to the SECOND neuron, (usually at a dendrite or dendritic spine), where the neurotransmitters bounce around in or slide into or otherwise fit into the RECEPTOR sites of ligand-gated Sodium ion PORES on the SECOND or receiving neuron (ligand-gated simply means chemically activated), causing those pores to open, allowing Sodium ions to enter the dendrites of the receiving neuron, which causes the beginning of the neural impulse as they bump into or electrostatically push sodium ions already within the neuron (which is a graded response, which means it gets smaller and smaller in strength as it travels further and further along the dendrite, and is known as electrotonic conduction). This impulse travels down the dendrite, across the soma (body of the neuron), to the axon hillock (where the axon or output of the neuron begins), where any and all such multiple inputs are summed up, and, if they yield a sufficiently high enough voltage potential in summation, trigger an action potential (the neural impulse within & along the axon) in the initial segment of the axon, which then propagates along the axon by successive openings of voltage-gated sodium ion pores which let in more sodium ions, which opens more pores, etc., in a chain reaction.

If the axon happens to be myelinated, from a succession of glial cells wrapped along it as insulation, then electrotonic conduction (which is fast, but degrades in strength over longer distances), will occur in the axon under those glial cells, which activates an action potential in the gaps between the glial cells, (known as the nodes of Ranvier), which re-strengthens the impulse, resulting in an impulse which can travel longer distances faster than it would in an un-myelinated axon purely by the action potential; such impulse conduction in a myelinated axon is called saltatory-conduction.

Un-myelinated neurons in the cortex of the brain (grey matter) are tightly packed and their axons run much smaller distances from one to another than the white mattermyelinated axons which connect to more distant parts of the brain, so the neurons in the cortex don't need the 'speed improvement' provided by myelination.

Read more: http://wiki.answers.com/Q/How is nerve impulse transmitted#ixzz1Hmd2WU5s

Answer 4

A nerve impulse is carried along a nerve cell (neuron) through a process called action potential. This involves the movement of ions across the cell membrane, causing an electrical signal to propagate down the length of the neuron. Once the impulse reaches the end of the neuron, neurotransmitters are released to communicate with the next neuron or target cell.

Answer 5

Nerve impulse transmitted through the nerve cells to a muscle.

Answer 6

Neurons