(I'm not sure if this answer is correct)
Here's the correct answer in better detail:
a. Generation of an action potential involves a transient increase in Na+ permeability, followed by restoration of Na+ impermeability, and then a short-lived increase in K+ permeability.
b. Propagation, or transmission, of an action potential occurs as the local currents of an area undergoing depolarization cause depolarization of the forward adjacent area.
The potential is generated like usually at the axona hillock, just as with any other neuron.
Look up saltatory conduction to understand how it is propigated in a myelinated neuron. First you need to understand that a myelinated neuron is not covered with meylin along the hole length of the axon. Myelin exists as a covering in sections, looking something like sausage links strung up together. The spaces between the myelin covering are called the nodes of Ranvier. Saltatory conduction is the process by which an action potential "jumps" from one node to the next, speeding up the conducting process.
Neurons, or nerve cells, are stimulated when the polarity across their plasma membrane changes. The polarity change, called an action potential, travels along the neuron until it reaches the end of the neuron.
An action potential is capable of traveling long distances. If a depolarizing graded potential is sufficiently large, Na+ channels in the trigger zone open. In response, Na+ on the outside of the membrane becomes depolarized . If the stimulus is strong enough additional Na+ gates open, increasing the flow of Na+ even more, causing an action potential, or complete depolarization (from -70 to about +30 millivolts).
This, in turn, stimulates neighboring Na+ gates, farther down the axon, to open. In this manner, the action potential travels down the length of the axon as opened Na+ gates stimulate neighboring Na+ gates to open. The action potential is an all-or-nothing event.
When the stimulus fails to produce depolarization that exceeds the threshold value, no action potential results, but when threshold potential is exceeded, complete depolarization occurs.
The action potentials are generated and transmitted along the nerve cell as a result of the stimulus produced.
It is called saltatory conduction. This describes the "jumping" of an action potential from node to node on a myelinated axon.
sensory neurone --> enters spinal cord --> relay neurone --> brain(is not a reflex action) or motor neurone(if action is reflex)
Unmyelinated tissue is substantially slower in conducting impulses along the axon. With myelinated axons, the action potential (impulse) jumps from node to node greatly increasing the speed of the impulse.
Gap Junctions in the cell spread the action potential to nearby cells.
Myelin sheath does several things that affect the speed of an action potential.It acts as an insulator around a neuron axon, thereby focusing the propagation of the action potential along the axis of the axon.The action potential "leaps" from one node of Ranvier (the node in between two myelinated segments) to the next, and to the next, and to the next, and so on, faster than the action potential can propagate as a wave along an unmyelinated axon of the same diameter.The regions along a myelinated axon depolarize locally and successively, thus allowing an action potential to travel along an axon using less energy, which in turn allows the neuron to repolarize more quickly, and thus be ready to conduct the next action potential sooner, thereby increasing the overall speed of information transmission.
It is called saltatory conduction. This describes the "jumping" of an action potential from node to node on a myelinated axon.
When a stimulus stimulates a neuron above the threshold, the action potential is generated.
a small myelinated axon
myelinated, large diameter fibres
Myelinated axons with the largest diameter
TRUE. Neurons with myelin (or myelinated neurons) conduct impulses much faster than those without myelin.
axon hillock
Potassium.
it contracts
sensory neurone --> enters spinal cord --> relay neurone --> brain(is not a reflex action) or motor neurone(if action is reflex)
A.P. propagation consists of the movement of the action potential along the axon, axon terminals and dendrites. A.P. propagation is non-decremental meaning that the amplitude of the A.P. remains constant throughout the propagation. Action potentials are also follow the principle of all-or-none fashion. Meaning if there is not enough summation(adding of EPSPs and mEPPs) to bring the stimulus to threshold, then no AP will be elicited
Myocardial contraction