Lecture 5: Action Potential Propagation & Nerve Conduction Flashcards
1. Define the necessary condition for an action potential to propagate along a membrane. 2. List 2 examples demonstrating the importance of refractoriness to organized action potential propagation. 3. State the role of pacemaker potentials for action potential generation. 4. State the effect of nerve fiber size on the rate of action potential propagation. 5. State the effect of nerve fiber myelination on the rate of action potential propagation. 6. Define saltatory conduction.
What conditions are necessary to allow an action potential to propagate along the membrane?
Local circuit currents causing a graded potential and suprathreshold potentials allowing for an action potential. And also, the refractoriness of the membrane
Why is the refractoriness of the membrane important?
The refractoriness of the membrane following an action potential directs the action potential in the direction of membranes that are not refractory. By doing so it prevents antidromic conduction in nerve fibers (action potential moving the wrong direction) and prevents circus rhythms from developing in the heart (fibrillation)
How do biologic pacemakers work within the body in regards to regulating action potentials?
Spontaneous pacemaker potentials are usually a result of rhythmic changes in K+ permeability. This can be seen in the digestive system.
T/F. The larger the diameter of nerve fibers the greater/faster the current flows.
TRUE. Action potential propagates more quickly in a large diameter fiber because the graded potentials decrements more quickly in smaller diameters (smaller = weaker). Action potentials are brought to threshold further along, also allowing the current move more rapidly.
Why do we love myelin?
We don’t, but our nerves do. Myelin allows the current to jump from node to node increasing the speed of the depolarization and allowing it to be felt further from the axon. It also prevents the leakage of charge from node to node.
What are this “Saltatory Conduction”?
Saltatory conduction is when the action potential jumps from one Node of Ranvier to the next due to the myelin sheaths thus increasing the velocity of the action potential.
